Experimental Light Bomber – One Prototype Built
Prior to the German invasion, the Soviet air industry was in the process of developing a series of new experimental ideas and concepts. While generally unknown around the world, some of these were interesting designs, such as the Bolkhovitinov “S” experimental twin-engine fast attack bomber. Due to the German advance and the need for immediately operational planes, the development of this model was terminated.
An Unusual Idea
The S-2M-103 was designed and developed by a Soviet aircraft engineer team led by Viktor Federovich Bolkhovitinov (Ви́ктор Фёдорович Болхови́тинов). Bolkhovitinov (February 1899 – 29 January 1970) was a Soviet professor at the Zhukovsky Air Force Academy in Moscow, and also an aircraft engineer. One of his best known designs was the four-engined Bolkhovitinov DB-A bomber that was intended to replace to aging TB-3 bomber.
During 1936, Bolkhovitinov and his team were looking for a solution for the lack of a high-speed light bomber in the Soviet Air Force. Their answer would be an unusual twin-engine aircraft with a peculiar wing configuration. Instead of a conventional wing placement, the wings were mounted very low on the fuselage, and the tail was a twin fin design.
When they began working on the first calculations and drawings, their greatest concern was how to reduce drag. Usual bomber designs with wing-mounted engines slowed down the plane due to excessive drag. Fighters, on the other hand, had much better aerodynamic properties as they were designed to achieve the highest possible speeds. Bolkhovitinov and his team decided that, for their purposes, they would reuse elements from other bombers (two engines, bomb-carrying capacities, defensive armament) and a one-part fuselage.
The problem was how to position the two engines in order to reduce the drag as much as possible. They quickly came up with the idea of putting them both on the same line (one behind the other) and in the same fighter-like fuselage. While this configuration would make the new plane longer, it could be designed with much better aerodynamic properties.
The development and design of the unusual twin-engine system began in 1936, while work on the aircraft design itself began the next year. By 1938, the design was completed and preparations for the construction of a fully operational prototype began in July that year. The prototype was completed in 1939 and flight tests were scheduled to begin in July 1939 (or in early 1940 according to some sources).
The aircraft’s original designation was simply “Bolkhovitinov S” or “Sparka/Cпаренный”, which means twin. Today it is generally known under the “S-2M-103” designation, where the “2” stands for twin-engine configuration and “M-103” is the name of the engine. There were other designations used for this plane, such as “BBS-1” (Ближний бомбардировщик скоростной, fast short-range bomber), “LB-S“ (легкий бомбардировщик спаренный, light twin-engined bomber) оr “BB“ (Болхови́тинов Бомбардировщик, Bolkhovitinov Bomber). As the plane is best known as the the S-2M-103, this article will use this designation.
The S-2M-103 was designed as a low wing, all-metal construction, two-seater, two-engined fast attack bomber. The S-2M-103’s main fuselage had an elliptical cross-section. The fuselage consisted of four (bottom, top and left and right side) panels that were held in place by using four strong angled-section longerons. The S-2M-103’s structure was covered with a modern light alloy stressed-skin.
The wings were constructed using a structural box with flanged lightening holes (to save weight). The wings’ interior sheet ribs were covered on both sides (upper and lower) by metal skin and held in place by flush riveting.
The rear twin-finned tail was covered with duralumin skin. For better stability, the rudders were equipped with inset balanced hinges. For the tailplanes’ movement, an irreversible trimming motor was used. The elevator had trim tabs with a variable geared drive.
The S-2M-103 had a completely retractable landing gear that was operated electrically. The front wheels and the smaller rear tail wheel was able to retract backward 90 degrees. During the winter of 1940/41, the wheeled landing gear was replaced with fixed skis.
This aircraft had an unusual two tandem engine arrangement, placed in the same mounting in the fuselage. The rear-mounted engine’s shaft passed through the front engine’s cylinder blocks. Both engines were connected to the two propellers (with six blades in total) which, when powered, turned in opposite directions, which provided better stability during flight (at least in theory). The S-2M-103 was powered by two 960 hp (716 kW) Klimov M-103’s V-12 liquid cooled engines. This engine was based on the French Hispano-Suiza 12Y which was produced under license by the Soviet Union as the M-100.
The water radiators were placed under the fuselage and had controllable exit flaps. Two oil coolers were located on the ducts on both sides of the two engines. The fuel was stored in four fuel tanks that were placed in the wings (between the wing spars). Unfortunately, there is no information available about the capacity of these tanks.
The two crew members were positioned in an unusually large cockpit fully enclosed with a plexiglass canopy. The crew consisted of the pilot and the navigator. The navigator was also provided with a bombsight. The navigator’s position was covered with plexiglas on all sides, which provided him with an excellent all-around view, including under the plane. His additional role was to operate the rear-mounted machine gun.
The S-2M-103 lacked any forward-firing offensive armament. While it was planned to equip it with weapons mounted in the wings, this was never accomplished. For self-defense, one 0.3 in (7.62 mm) ShKAS machine gun was provided for the navigator/gunner. Due to its tail design, the rear machine gun had a wide firing arc. Later, it was planned to replace the single 7.62 mm rear gun with heavier twin 0.5 in (12.7 mm) UBT machine guns. There were also alleged plans to equip the S-2M-103 with a rear-mounted remotely controlled ShKAS machine gun. Whether this was ever implemented is unknown, as there no photographs or precise information are available. The bomb bay, which could carry 880 lb (400 kg) of bombs, was located under the pilot cockpit. The bomb bay opening doors were opened electrically.
The S-2M-103, piloted by D.N. Kudrin, made its first test flight in late 1939. More tests were carried out by the Army from March to July 1940, the plane being piloted by D.N. Kudrin and A.I. Kabanov. During these flight tests, the S-2M-103 proved to be able to achieve a maximum speed of 354 mph (570 km/h) at 15,400 ft (4,700 m). The tests also proved that the concept of installing two engines in the same fuselage had some advantages over the wing-mounted configuration. The most obvious was the reduced drag, which lead to increased speed and improved flight performance.
There were also some problems with the design. Immediately noticeable were the poor take-off and landing performance during these tests trials. Due to its high weight of 12,460 lb (5,650 kg), the S-2M-103 needed a 3,430 ft (1,045 m) long airfield. More tests were carried out by removing any extra weight. With the weight being reduced by some 1,100 lb (500 kg), the S-2M-103 now only needed a 2,800 ft (860 m) long airfield. During landing at speeds of 103 mph (165 km/h) the aircraft needed a 2,130 ft (650 m) long airfield. Some problems with the twin propellers were also noted. The rear-mounted propeller drive shaft was damaged due to strong vibrations. Unfortunately, there are no records of cruising speed, climbing speed, or maximum service ceiling.
The Single-Engine Version
In the following months of 1940 and 1941, the S-2M-103 received a number of modifications in the hope of solving the issues observed during preliminary testing. The twin-engine configuration was replaced with a single M-105P engine with a power of 960 hp (or 1,050 hp depending on the source). The area where the second engine was previously located was filled in order to maintain the stability of the aircraft. Due to the removal the second engine, the second contra-rotating propeller was no longer needed. The new engine’s oil coolers were placed in the main radiator duct. The designers had a dilemma about what to do with the extra interior space left by the removal of the second engine, but this was never solved completely. With these modifications, the weight was reduced from 12,460 lb (5,650 kg) to 8,820 lb (4,000 kg).
The wing design was also changed to one done by Z.I. Iskovich by increasing its size and using a new aerofoil shape. The previous wing design had an area of 246.5 ft² (22.9 m²), while the new one had 252 ft² (23.4 m²). The last change was made to ease testing during winter, replacing the landing gear with fixed skis.
It appears that no official designation for this version existed but, using the same logic as for the two-engine version, it could be called S-M-105, but this is only speculation at best. According to some sources, the single-engined variant was marked as the S-1.
There were plans to improve the performance of the projected fighter version by mounting two M-107 engines. The new fighter was to be designated simply as the “I” or “I-1”. Due to the later cancellation of the S-2M-103 project, the I-1 was also abandoned.
The Fate of the S-2M-103 Project
More flight tests were carried out during the first half of 1941. While there is no precise information, the newly modified single-engined version of the S-2M-103 allegedly had poor performance. Despite the modifications, the new single-engined version managed to achieve a much lower top speed of 248 mph (400 km/h) at 14,440 ft (4,400 m). The poor performance, preparation for Pe-2 production at the factory where it was built, and the German Invasion of the Soviet Union led to the cancellation of the S-2M-103 project.
TheSoviet Union – A single prototype was tested in 1940/41, but was not adopted for production.
S-2M-103 – Twin engine fast bomber
S-2M-103 (possibly S-M-105) – Single-engine version
I-1 – Improved fighter version equipped with two M-107 engines, due to cancelation of the S-2M-103 none were built.
The concept of installing two engines in the same fuselage had some advantages over the wing mounted configuration. It reduced drag, which lead to increased speed and flight performance. The S-2M-103 proved this by achieving speeds of up to 350 mph (570 km/h). However, its design had issues that were never resolved. Given enough time, those might have been solved. Alas, in 1941, the German Invasion and the need to increase production of already existing aircraft stopped all unimportant projects.
Kingdom of Italy (1935)
Fighter Plane – 774 to 791 Built
During the thirties, Fiat Aviazione was one of the most advanced aircraft manufacturers in Europe. With the advent of new technology at the time, it was obvious that the next stage in the development of the aircraft industry, especially in military aviation, would be centered around all-metal monoplanes. Fiat’s Chief Designer, Ing. C. Rosatelli, had been designing mixed-construction biplanes and even an all-metal bomber. As the demand for a modern, all-metal fighter plane was high, Fiat officials made a decision to hire a young aircraft engineer named Giuseppe Gabrielli, who would later design the Freccia, the first operational Italian all-metal fighter.
Giuseppe Gabrielli’s Work
The history of the Fiat G.50 began in 1931, when Fiat formed a new Aircraft Technical Bureau – Department 2 (Ufficio Tecnico Aviazione – Divisione II). The main purpose of this bureau was designing and building brand new types of modern all-metal planes. The same year, a young Italian engineer, Giuseppe Gabrielli, was hired by Fiat Chairman Senator Angelli to work for the Technical Bureau. Giuseppe Gabrielli had gained some experience in aircraft design while working for Piaggio. When he moved to Fiat, he immediately began working on several non-military aircraft projects. All of his projects were marked by the capital letter ‘G’, his initial. First was the G.2, an all-metal, three-engined plane, then the G.8 biplane trainer, and later the twin-engine passenger plane G.18.
During the thirties, the Italian Ministry of Aviation (Ministero dell Aeronautica) was interested in adopting a new, all-metal monoplane fighter and ground attack aircraft for the Italian Air Force. Some specifications for their request were: to use one radial engine, armed with at least two 0.5 in (12.7 mm) heavy machine guns with at least 300 rounds of ammunition and one 0.7 in (20 mm) gun or 1.45 in (37 mm) gun, and provisions for bombs on the ground attacker. A request was sent out to all domestic aircraft manufacturers. There were several proposals in response, but only the G.50 and the Macchi C.200 would be chosen for production. The others were either rejected (Ro.51 and A.U.T. 18) or built in limited numbers, like the Caproni F.5.
In order to solve the problem of the lack of an adequate fighter design, Fiat officials even considered the acquisition of a license to produce the American Seversky SEV-3, but nothing came of this. In April of 1935, Giuseppe Gabrielli began working on a new low-wing, all-metal plane named G.50. According to his first plans and drawings, it was to be armed with two machine guns, powered by a 550 hp radial engine (with a diameter of 39 in/1 m), weigh around 3,395 lbs (1,540 kg), and equipped with a retractable landing gear. At the same time, Fiat was testing a new FIAT A 74 RC 38 14-cylinder radial piston engine, so it was logical that Giuseppe Gabrielli decided to use it for his work. The A 74, in principle, was a direct copy of the American Pratt & Whitney R-1830 Twin Wasp which powered a large number of US planes, including the Douglas C-47, Consolidated PBY Catalina, Douglas TBD Devastator and Grumman F4F Wildcat. The expected speed of the G.50 with this new engine was around 285 mph (460 km/h) at 11,500 ft (3,500 m).
On 28th September, 1935, Gabrielli submitted his project to the Ministry of Aviation. Military officials were impressed by the design, but ask for some modifications. These included a wingspan of 36 ft 1 in (11 m), a weight of 4,870 lbs (2,210 kg) and a maximum speed of 280 mph (452 km/h). The offensive armament was changed to two 0.5 in (12.7 mm) heavy machine guns located in the fuselage with an additional two 0.3 in (7.7 mm) machine guns placed in the wings. In addition, the G.50 was designed to carrying a bomb load of 220 lbs (100 kg) or, if needed, extra fuel tanks with 23.5 gal (90 l) capacity.
In January 1936, the Ministry of Aviation changed its original request, choosing instead to focus only on the fighter role. The Ministry of Aviation wanted to accelerate the development of the new fighter, and the proposed ground attack role was rejected. Because of this, the bomb load was deemed no longer necessary, and the main armament was reduced to only two 0.5 in (12.7 mm) machine guns with 150 rounds each. The most important requirement was that the new fighter should have the best possible flying performance.
Despite these changes, the Fiat officials decided to proceed with the G.50 project. As Fiat’s production capacities were overburdened, work on this new project was instead moved to the CMASA works at Marina di Pisa, part of Fiat since 1931. Giuseppe Gabrielli was finishing his last drawings and the list of needed materials and equipment in June 1936. In his final drawings, the armament was reduced to two heavy machine guns without the bomb load, and the plane would be powered by the new A 74 c/n engine.
The production of the first operational prototype was scheduled to begin in late summer of 1936. The prototype was finally ready at the beginning of 1937 and was transported to the city of Turin for further testing. This prototype, under registration number MM 334, made its first test flight on 26th February, 1937. The pilot was Giovanniego De Briganti, the CMASA test pilot. During initial testing, the pilot noted several faults and possible problems with the G.50. He especially pointed out the strong vibrations during flight and the aircraft’s tendency to spin.
On 22nd June, 1937, the G.50 prototype was moved to Marina di Pisa for more testing and modifications. After these modifications were completed, the prototype was sent to the Regia Aeronautica (Italian Air Force) experimental flight center near Rome. There, the G.50 prototype was tested by several army pilots. They noted that the controls were hard to work with at high speeds and a lack of climbing ability. Before the final order for mass production, Giuseppe Gabrielli was asked to solve these problems. For this reason, another prototype was made, designated MM 335.
The second prototype made its first flight on 20th October, 1937. After a series of successful flying tests, an accident occurred. On the 11th (or 8th, depending on the source) November, 1937, while flying the second prototype at high speed, the test pilot Briganti lost control of his aircraft and crashed to the ground. He did not survive the crash. His place was taken by the new chief test pilot, Enzio Guerra.
A combination of the accident and inferior performance that did not meet expectations, along with better overall performance of the Macchi C.200 threatened to shut down the G.50 project. But as the CMASA works were already in process of producing a series of 45 G.50’s, it was deemed a waste of resources to abandon or scrap the tooling equipment needed to produced the G.50 that had already been produced. A second reason for keeping the project running was the fact that it would take too much time for Fiat to prepare for the production of the Macchi C.200. The Air Ministry decided to go on with G.50 production, but insisted that the company correct the shortcomings of the plane by the time of production. Of the 45 ordered, the first 11 were used for many more trials. Two planes, MM 3357 and 335, the salvaged and rebuilt prototype, were sent to the experimental centre in Rome. Seven were stationed at the Pisa S.Giusto airfield and tested there. Two more ,MM 3570 and 3571, were tested by pilots Guerra, Rolandi and Cus. These trials were held in Turin and the main purpose was to investigate possible changes to the design of the G.50. The preliminary tests showed that the fully enclosed cockpit had to be changed before production, and a new design was necessary. This enclosed cockpit had several drawbacks which pilots often complained about. The closed cockpit was hard to open (especially in emergency situations), was made of poor quality plexiglass which was prone to cracking, offered poor visibility and sometimes exhaust fumes accumulated in the cockpit so the pilots were forced to fly with an open cockpit. After some testing and modifications, it was decided to used a partially enclosed cockpit. This solution was not perfect and was uncomfortable for pilots. Despite this, it was decided that all future planes would be built with an open cockpit only. More modification that were deemed necessary were the installation of a new start-up system, a better undercarriage locking system and adding a new oxygen mask for piloting at high altitude.
The G.50 was first showed to the public in October of 1937 at the International Aeronautical Show held in Milan. From 1937 to 1940, when the production was changed to the improved version, some 224 G.50 were built.
The G.50 Freccia, Italian for Arrow, was a single-seat, low-wing, all-metal fighter plane. The main fuselage was made from four angular shaped longerons with 17 metal frames. The wing construction consisted of a center section which was made of a steel tube connected to the lower fuselage and two metal spars connected with ribs. The four flaps were hydraulically actuated and at certain speeds they would automatically retract to their closed position. The fuselage, wing, and tail were covered with duralumin sheets. The only fabric-covered parts were the movable control surfaces in the wings and the tail.
The engine was placed in a tubular shaped mount made of chrome-molybdenum steel that was connected to the fuselage by four bolts. The engine and the cockpit were separated by a fireproof screen in order to protect the pilot from any possible fire outbreak, either due to engine malfunction or damage. The plane was powered by the 840 hp (626 kW) Fiat A 74 RC 38, 14 cylinder radial piston engine. With this engine, the G.50 could reach a maximum speed of 293 mph (470 km/h), with an effective range of 276 mi (445 km) and a service ceiling of 35,000 ft (10,700 m). An all-metal three-blade propeller produced by Fiat was used. One of major disadvantages of using a radial type of engine was the massive drag due to its large cross-section. In order for ground repair crews to have easy access to the engine and the fuselage interior, several access doors were added. The maximum fuel capacity was 83.5 gal (316 l.) There were two fuel tanks located in the wings 11.9 gal each (45 l) and two more in the fuselage, one larger with 26.4 gal (100 l) and a smaller one with 18 gal (68 l) with an additional auxiliary tank 13.75 gal (52 l) also located in the fuselage.
The first G.50 series had an enclosed cockpit design but as this created many issues, it was later changed to an open cockpit. Despite its disadvantages, the enclosed cockpit had an excellent rear view. Many different open cockpit designs were tested before the final design was chosen. The later version with the open cockpit had two smalls door installed to help entering or exiting the plane. The seat was adjustable, so it could be adapted to the pilot’s needs.
In front of the pilot, the dashboard was divided into three sections. On the upper section were the navigation instruments, reflector sight, fuel indicators and engine instruments. The middle section had the ammunition counter, warning lights, the position of the landing gear, compass and oxygen control panel. The lower section had the engine starter, cowling controls and compressed-air system indicator. The radio in the pilot’s cabin was the ARC 1, but the quality of the batteries was poor. A fire extinguisher system was also provided. There was also the possibility of installing one OMI FM62 camera gun.
The G.50 was equipped, like most modern aircraft of the time, with inward retracting landing gear, but the rear tail wheel was fixed. In the G.50 bis version, the rear tail wheel was changed to a retractable type. The landing gear could, if necessary, be manually operated. At first, it was of a Messier type, but it was later replaced with a Magnaghi design. The retracting landing gear was hydraulically operated, and pneumatically during lowering. In case both systems did not work for any reason, it could be manually operated. For easier and more pleasant landing, hydraulic shock absorbers were provided for both telescoping legs.
The main armament consisted of two forward-firing 0.5 in (12.7mm) Breda-SAFAT heavy machine guns, with some 150 rounds of ammunition for each machine gun. The guns were placed behind the engine top and both were synchronised in order not to damage the propeller. It is interesting to note that this gun used oil lubricant for faster firing and thus a lubricant tank was added on top of the engine. Some G.50 planes were armed with bomb racks and used in North Africa.
Modifications and Prototypes
As the war progressed, the Italians realized that they were lacking planes to fulfill the different necessary roles such as fast ground attack or training. In order to save time, the most obvious solution was to try to modify existing models instead of developing new ones. The G.50 would be modified in several ways, some of which demanded major changes to the plane’s design, while others were just minor variations, like the added sand filter for the G.50 S.A.
Trainer G.50 B
As the G.50 was entering production and the first operational units were formed, a trainer was needed for new pilots. As most army pilots were accustomed to flying older biplanes, retraining them for flying the monoplanes was required. For this purpose, in late 1936 the Italian Air Ministry placed an order for Fiat to developed a two seat dual control plane based on the G.50. After the mock-up was built and inspected in March 1938, it was deemed sufficient for production. By April, an order for the first prototype was placed. But due to the constant changes to the design, the production of the first prototype was frequently delayed. It was not until June 1939 when the final design with an enclosed cockpit was chosen. The plane was named G.50 B. The capital ‘B’ stands for ‘bipost,’ the Italian word for two-seater. This version was recognizable by its long glazed canopy with the rear cockpit being open from the top. The first prototype, marked 3615, would be ready in late April 1940 when it was tested by Enzio Guerra.
After only a few test flights, it was deemed adequate and was put into production. The first ten were built in 1940, with the last one built in 1943. In total, some 108 (or 100, depending on the source) G.50 B trainers were built during the war. Production by years was: 10 in 1940, 82 in 1941, 11 in 1942 and 5 in 1943.
The G.50 B was, in essence, a modified single-seat version with a new cockpit and dual controls. The front part of the cockpit was fully enclosed in contrast with the rear which was open. The main armament was removed on the G.50 B. This version was very successful, as it was easy to build and offered almost the same flying performance as the single-seat version.
These were used mostly by the Regia Aeronautica Fighter Schools. Smaller numbers were operated as liaison planes or even in some front based fighter units. After the Italian capitulation, small numbers, possible 20 or more, were used by the National Republican Air Force. At least one was given to the Croatian puppet state in the Balkans. The last G.50 B were used by the Flying School in Lecce for a few years after the war, up to 1948.
The Improved G.50 bis
The final decision for the mass production of the G.50 fighter was not based on its performance, but instead on the fact that CMASA had already begun producing it. The performance of the G.50 was poor compared to the Macchi C.200. In order to justify the production, the Italian Air Force requested that Fiat to improve the G.50’s overall performance. The sought modifications were adding extra fuel tanks, increasing capacity from 83.5 gal (316 l) to around 108.3 gal (410 l), redesigning the rear fuselage and the vertical tail surfaces, better glazing of the cockpit to protect the pilot from air turbulence, the addition of armor plates behind the pilot seat, and the tailwheel to be made retractable. The original ARC 1 radio, with its poor quality batteries, was only changed in October 1941 with the R.B.30.
The new improved version was designated the G.50 bis. According to Italian original plans, the first planes should have been ready by late 1938, but this was never achieved. The whole process was slow and the first aircraft was tested on 13th (or 9th) of September 1940 at Turin. As the main engine was not changed, despite the other modifications, the general flying performance was almost the same. The only improvements were easier maintenance and increased operational range. As these tests were completed, an order for production was given. From 1940 to 1943, around 439 of these versions were built by CMASA and Fiat.
G.50 S.A Ground Attacker
A certain number of planes that were serving in North Africa were modified by adding sand filters and a bomb rack. The landing gear was also modified for easier landing.
G.50 A Ground Attacker
The G.50 A was designed to be used as a fighter-bomber on the “Aquila” aircraft-carrier which was under construction. For this modification, the G.50 B two seater version was reused. The main offensive armament was to be increased to four 0.5 in (12.7 mm) machine guns. The problem was that the wing design did not allow the installation of the new weapons directly in the wings. The solution was to increase a part of the central section of the wings in order to accommodate these guns. Additional bomb racks were also to be added. One prototype, serial number MM 8595, was built and tested in October 1942. The whole concept proved to be problematic and the project was abandoned. The prototype would be used up to 1943 in testing new wing designs. In some sources, this model is designated as G.50 A/N.
G.50 bis “Tuffo” Dive Bomber
This was a dive bomber version designed in 1941 and 42, possibly inspired by the famous German Ju-87 “Stuka.” A bomb load of up to 990 lbs (450 kg) was planned, with two 200 lbs (100 kg) bombs placed under the wings and one 550 lbs (250 kg) under the main fuselage. For this modification, the addition of dive brakes were necessary. There is no information about prototype construction, but there is a great chance that it was never made.
G.50 B Naval Observer
One plane (MM 6548) was rebuilt for a naval observation role in 1943. It had a larger tail, different wing sections, a camera and an arrestor hook for use on an aircraft carrier. It was also equipped with a B 30T transmitter, B.G.42 direction finder and a A.R.18 receiver. Only one was built, possibly because of the impending Italian capitulation.
This version was based on the G.50 bis and the only difference was the installation of a arrestor hook for aircraft carrier use. Around 16 planes were modified for this role and were in use by the 155th Group Autonomo, mostly for training, in 1943.
Beside these, there were some minor projects that were proposed, but the majority if not all of them were not implemented. On the base of the G.50 B some project were proposed like the: night fighter, land reconnaissance or even a floatplane fighter (G.50 Idro).
Prototypes based on the G.50
During the war, in order to improve the flying performance of the G.50, many new designs and weapon loads and engines were tested.
This was a further development of the canceled G.52 project. The new project, designated the ‘G.50 ter,’ was to be equipped with the same 1000 hp (746 kW) Fiat A 76 engine as the G.52. Even before production of a prototype, the new engine was found to have a number of flaws. The first prototype powered by the new engine was ready by late July 1941. First flying tests were carried out at the Aeritalia airfield, with the plane being piloted by Agostini. During these flight tests, the engine proved to be mechanically unreliable and it could not reach expected performance. More test were held in November 1941, but in the end the project was canceled and only one plane was built.
In late 1939, the Italian Ministry of Aviation made a decision to begin negotiations with the German Daimler-Benz company for a production license of the newest liquid cooled DB 601A engine (1035 hp). It had a much lower frontal area and had much better aerodynamics than the larger Italian radial engines. The license was eventually obtained and Alfa Romeo was put in charge of the production of this engine, but it was never built in any great numbers.
In early 1940, the Italian Ministry of Aviation asked Fiat to build a modified version of the G.50 using this new engine. Two prototypes were to be built by CMASA, and these were marked as G.50 V (the ‘V’ stand for Veloce, which means fast). The first prototype, serial number MM 479, was built and tested in late August 1941 by the test pilot Ezio Guerra. Immediately, the new design proved to have some issues, such as an inefficient engine cooling system and the controls being difficult to operate. By the end of 1941, most these problems were solved and a new series of tests was scheduled.
In December 1941, more extensive flight tests were carried out by test pilot Valentino Cus in order to determine the precise flight performance, in particular the maximum speeds at various heights and the climbing rate. Maximum speed achieved was some 360 mph (580 km/h), and a maximum altitude of 16,400 ft (5,000 m) was reached in 5 minutes and 30 seconds. Mostly due to the introduction of the new FIAT G.55 and the lack of DB 601 engines, the G.50 V project abandoned.
In 1940, it was proposed to equip one G.50 with the new A 75 R engine. Nothing came of this project.
Information about this version differs significantly depending on the source.
According to Piero Vergnano, Fiat worked on improving the performance of the A 74 engine used on the G.50 for quite some time. This lead to the development of the new 1000 hp (746 kW) Fiat A 76 engine. In 1938, Fiat suggested the installation of this engine in the G.50 to the Air Ministry. At first, the request was accepted and an order for two prototypes was placed. By late 1939, the project was canceled due to the acquisition of new German DB 601A engines, and no prototypes were ever built. According to Gianni Cattaneo, the G.52 was in fact just a further development of the G.50 V. Due to the appearance of the new G.55 fighter, this project was abandoned.
This proposal was a combination of the G.50 B powered by the DB 601A engine. It was developed in 1941. It was intended to be used as a fast reconnaissance plane, but the Air Ministry never showed any interest in this proposal and nothing came of it.
First Operational Units
As CMASA began producing the first G.50 planes in late 1938, an experimental military fighter unit was formed for further testing and training. This unit was located at the Ciampino airfield near Rome. The unit was named Gruppo Sperimentale da Caccia (Experimental Fighter Unit/Group). Command of this new unit was given to Major Mario Bonzano, at that time a famous pilot ace from the Spanish Civil War (flying the CR.32 biplane). Pilot training on this new plane lasted until January 1939, when the Italian Air Force High Command decided to send a unit of 12 planes to Spain for real combat testing.
A group of 12 new G.50 fighters arrived in January 1939 in Spain, having been transported by sea. This unit was based at Escalona Airport, some 43.5 mi (70 km) from the capital of Madrid. Starting in March, this unit carried out flight patrols and fighter cover missions for bombers at altitudes between 24,600 to 26,240 ft (7,500 to 8,000 m). By that time, the opposing air force had been almost destroyed and air to air combat was rare. The only combat action that was recorded happened when a lone Soviet-built I-16, possibly flown by a Canadian pilot by the name of Dickinson, was intercepted by a G.50. The Italian aircraft was damaged and the pilot was forced to land. None of the 12 G.50 that were sent were lost in combat during the Spanish Civil War. At the end of this war, 11 operational G.50 fighters were given to the new Spanish fascist regime. These planes were used by the 27 Gruppo Caza (Fighter Group). After 1943, they were sent to Spanish Morocco, to be used by the 2. Regimento Mixto (mixed regiment) together with several German supplied He-112B.
After his return to Italy, Major Bonzano made his report of the effectiveness of the G.50. According to him, the G.50 had good maneuverability, effective armament and was easy to operate at altitude. On the other hand, he pointed out that the visibility was poor and the landing gear construction was weak and prone to malfunctioning. His conclusion about the effectiveness of the main armament would prove to have a great negative impact for the G.50 in the future.
In Finnish Service
Because of the likelihood of a Soviet attack in 1939, the Finnish government and Army wanted to equip their forces with modern equipment and weapons. As a result, a Finnish military delegation visited Turin in 1939, where the new G.50 fighters were being tested. The delegation was impressed with the aircraft’s performance, so they placed an order for 35 brand new G.50. Most of the planes sold were of the first series produced by CMASA, with serial numbers 3599 to 3614. These were supplemented by planes from the second productions series (serial numbers 4722 to 4750).
A very interesting fact is the maximum speed achieved by Finnish pilot Tapani Harmaja. As he was testing the flying performance of the G.50 at an airfield near Latina, he managed to reach a speed of 515 mph (830 km/h). He achieved this by diving from a high altitude of 11,480 ft (3,500 m) down to 1,310 ft (400 m). This was the fastest speed reached by any aircraft in Italy at that time.
Due to the outbreak of the Second World War in Europe, the transportation of the purchased aircraft was slow and complicated. The planes were disassembled and then transported by train through Italy to the north of Germany and then by ship to Sweden, and from there to Finland. As they were transported in parts, the assembly was done at Gothenburg. When they were completed, the pilots were instructed to fly them to their new stations. The first 14 G.50’s were received in February 1940 and the last in June 1940. While flying en route to their designated airfields, two planes were lost in accidents in February 1940.
The G.50 arrived too late to have any large impact on the Winter War (30 Nov. 1939 to 13 Mar. 1940) but they saw some combat during this period. The first G.50 planes were equipped with the 26th Fighter Wing (Lentolaivue 26 or just simply LeLv or HLeLv) located at Haukkajarvi. They were used to replace the older Gloster Gladiators used by this unit. By 13 March, the Finnish pilots flying the G.50 claimed to have shot down 11 Soviet planes. There is some disagreement between the sources, authors Gianni C. and David M. states that this unit did not participate in the Winter War.
Until the German and Finnish attack on the Soviet Union in June 1941, known in Finland as The Continuation War, Finnish technicians and engineers tried to improve the performance of the G.50 fighters. Most Finnish G.50s were from the first series, equipped with the enclosed cockpit. This design was not popular with the Finnish pilots and was replaced with an open cockpit. The vertical stabilizer and rudders were replaced with improved ones. Also, the Finnish tested snow skis taken from Fokker D.XXI’s, for the G.50 allowing them to better land on on frozen airstrips.
At the start of the German invasion of the Soviet Union in 1941, Finland joined the war with a much larger air force than it had in the previous conflict. LeLv 26 was stationed at an airfield near Utti, and was charged with the protection of the area around Lake Ladoga where they saw most of the action they were involved in. The G.50 proved to be an effective fighter in the hands of Finnish pilots. On 25th June 1941, six Finnish G.50 fighters managed to shoot down 10 Soviet bombers with no losses. Later in August, pilots from LeLv 26 managed to shoot down nine Soviet fighters. The most famous Finnish pilot was Oiva Tuominen, who had a total of 23 (33 or 43 according to different sources) air victories, with around 15 while flying the G.50. For his service, he was awarded the Mannerheim Cross, the highest Finnish military medal at the time. By the war’s end, LeLv 26 had around 88 air victories with the loss of 11 G.50s. Only two were shot down by Soviet planes, one was lost to AA fire, and eight more were lost either to accidents or mechanical failures. The Finnish G.50s remained in use up to June 1944, when they were moved to the rear for second-line duties. By the end of the war, there were still some 22 (the exact numbers are not known) operational G.50 fighters and they were used up to 1947.
In Italian Service
According to the Italian military program codenamed “R” (Programme R), the Italian Air Force was to be heavily reinforced with many new units and more modern aircraft designs. With the existing G.50 fighter, it was planned to form and equip one Stormo (Stormo-regiment) and one Fighter Wing/Group (Gruppo).
The first unit to receive the new G.50s was 51° Stormo located at the Ciampino airport near Rome, in November 1939. This regiment consisted of the 20th Group, with 351st, 352nd and 353rd Squadrons, and the 21st Group, with 354th, 355th and 356th Squadrons. Almost all of the squadrons were equipped with the newer G.50 with the open cockpit, and only the 351st Squadron was equipped with the first series with the enclosed cockpits. To more effectively train both experienced and new pilots, military war game exercises were often held by the Italian Army. During one of these games the 51° Stormo would earn its military emblem, a black cat with a green mouse. During one exercises, a group of different fighter planes were tasked with intercepting a group of S.M.79 bombers, marked with the green mouse emblem. The older CR.32 biplane could not fulfill this task, but the new G.50 from the 352nd Squadron accomplished this without any problem. From that point on, the pilots from 51° Stormo began painting the emblem on their planes.
Quite soon, the order was given to form a second unit, 52° Stormo. It consisted of the 22nd Group (357th, 358th and 359th Squadrons) and the 24th Group (360th, 361st and 362nd Squadrons). The 24th Group was equipped with older FIAT CR.32 planes that were soon to be replaced with G.50’s. 52° Stormo operated from two airports, Pontendera and Sarzana. Both of these groups had around 100 brand new G.50s.
By the time Italy entered the War in the West, there were some 118 G.50 planes on hand, with 97 operational, and some 21 were ready for delivery to designated units. In an attempt to profit from the fast Allied defeat in Western Europe, Italy declared war on France on the 10th of June 1940. Most G.50s saw some limited action, mostly covering SM.79 bombers during their attack on Corsica on 15th and 16th June. Subsequent attacks followed on 17th and 19th June. The center of operations then moved to the north, in the French Alps on 21st June. Due to a lack of proper training, the G.50 pilots had problems adapting to this type of aircraft, as most of them had flown only on the older biplanes. The G.50 proved to have good flying performance at low speeds, but was hard to control at high altitudes and higher speeds.
Battle for Britain
In order to support the German air raids on Great Britain, a special unit (Corpo Aereo Italiano C.A.I) was formed in late 1940 and was sent to Belgium. For this operation, the 20th Group, with 45-48 G.50’s, was selected under the command of Col. Bonzano. Despite the original planes being planned to reach their base of operations in Belgium by September 1940, this was delayed until October 1940. This delay occurred mostly due to bad weather. During the transfer from Italy to Belgium, two G.50’s were lost to accidents. The first combat actions were carried out in late October 1940, and were mostly bomber support missions. Similar missions were planned for 11th November against Great Yarmount, but they were canceled due to bad weather. From November 1940 to January 1941, the G.50 flew on many surveillance missions but there was no contact with enemy planes. By the end of January 1941, most Italian Air Force units returned home, with the exception of the 20th Group.
The C.A.I had great technical problems during this operation. The G.50 was designed for the Mediterranean rather than the cold climate of the North, and there were problems with freezing and defective instruments, unreliable batteries and fuel problems.
By April 1941, the remaining units were ordered to return to Italy. Missions conducted against Britain were unsuccessful and they did not go well for the Italian pilots, as they did not win any air victories. Italy had lost more than six aircraft with two dead pilots. This operation was a strategic failure for the Italian Air Force, mostly due to poor planning, adverse weather conditions and inefficiency of the planes used.
In the Balkans
Mussolini ordered an invasion of Greece in October 1940. For that purpose, fewer than 80 G.50 fighters based in Southern Italy (33) and occupied Albania (43) were used. Initially, because of the lack Greek air resistance, the G.50 were used as ground attack planes. But, after the arrival of the British forces in November, the first air battles started. Due to the fact that the Italian pilots had some experience during the Spanish Civil War, they managed to achieve some successes against the British. The G.50’s main opponent was the Gloster Gladiator, which had poorer flying performance in comparison. Later, however, more modern Hurricanes appeared, which were much more advanced than the G.50.
During the war in Greece, there were a number of engagements between the British and the Italian Air Forces. During one dogfight on 20th February 1941, some 10, possibly even 12, British planes were shot down in a single engagement by a group of 22 G.50s. The Italians only lost one plane. However, during the same day, British Hurricanes managed to shoot down four G.50s in a different engagement. On the 28th of February 1941, some 12 British planes were shot down at the loss of 27 Italian aircraft. In one unusual case, a collision took place between a G.50 and a Gladiator. Because of the heavy damage, the Gladiator crashed to the ground, while the pilot of the G.50, despite the damage received, managed to fly about 123 mi (200 km) back to his home base and safely land. Due to significant disagreements among sources, there is no accurate data on the losses of both sides. As the G.50 proved to be inferior to the Hurricane, they were gradually replaced with the more advanced Macchi C.200 planes.
During the attack on Yugoslavia, the so-called “April War” in April 1941, the G.50 were used in escort missions. There were very few air battles and, by 17th April, the war was over.
In the Mediterranean and North Africa
During the North African campaign, the first G.50s were stationed near Tripoli by the end of 1940 and early 1941. The first units to operate in Africa were the 151st, 152nd and 358th Squadrons with around 76 to 80 planes. Even before these units saw any action, there were great problems with the maintenance of these planes due to sand. Taking into account that North Africa is dominated by the Sahara desert, it is very strange that the Italian military leaders did not take into account the fact that the desert sand could affect the plane’s engine. Since a certain number of planes were taken out of action by this, the demand for special sand filters was high. There were also problems with the sand getting into the landing gear which caused issues. To solve these problems, the Air Ministry urged CMASA and Aeritalia to provide adequate sand filters and modify the landing gear. The G.50 planes modified in such a way were marked as G.50 A.S (A.S standing for Africa Sahariana).
The G.50 saw heavy fighting in North Africa. Depending on the combat situation, it was used in a standard fighter role, for ground attack, defence missions, or for bomber escort. As the war progressed, the G.50 was mostly used in a ground attack role by equipping them with a 220 lbs (100 kg) bomb load to increase its offensive armament. For this purpose, 50° Stormo was formed. 50° Stormo mostly operated around the Sidi Barrani sector, where it attained some success against the British P-40 and Hurricanes. The pilot Bovoli (from 50° Stormo) shot down six British Blenheim bombers in July 1941.
During 1941 and early 1942, despite reinforcements, G.50 losses were increasing. At the beginning of 1941 there were only 20 planes operational, but with reinforcements the number increased to 80 in October and then fell down to 35 in December 1941. Most planes were lost not in air combat but instead during enemy ground and air attacks on airfields, as well as accidents. For example, the 20th group suffered heavy losses when 18 G.50 were destroyed as British armored forces attacked the airfield at Martubi on 19th November 1941. By the end of 1941, the only unit operating the G.50 was the 12th Group stationed at Tripoli. By 1942, most G.50 fighters were either lost or replaced with more modern Macchi C.200 and C.202. The surviving G.50s were relocated to second line airfields in Sardinia (24th Group), Greece (151 Group) and in the Aegean (154th Group). By the time of the Axis defeat in Africa (1943), only the 358th Squadron was still using the G.50.
Despite having poorer flying performance than its main opponents, the P-40 and the Hurricane, the G.50 proved to be a formidable plane in the right hands. The G.50 also proved capable in its new role as a ground attack plane, in which it destroyed a large number of enemy planes on the ground.
The Last Stand
After late 1942, the remaining G.50 fighters that were stationed in Italy serving as trainers and for second line operations. After the defeat in Northern Africa, the Italian army was in disarray and the rapid Allied landing in Sicily in July of 1943 worsened the situation. Many surviving G.50s were used to equip the 158th and 159th Groups. These two groups suffered heavy losses attacking strong Allied positions in Sicily. In a period of only a few days, the two groups ceased to exist.
After Sicily, the Allies landed on the Italian mainland and, on 8th September 1943, Italy capitulated. By that time, there were only around 40 to 48 G.50 airplanes still in service, of which only 17 were operational. A small number of G.50 were used by the new National Republican Air Force (Aeronautica Nazionale Repubblicana/ANR) in Northern Italy until the end of WW2 as second line and training planes. A few were even used by the Italian Co-Belligerent Air Force (Aviazione Cobelligerante Italiana, or ACI) in the southern part of Italy, which had switched over to the Allied side.
In NDH Service
In the middle of 1942, in exchange for raw resources and materials, Italy delivered 10 G.50 (9 single seat and one two-seat trainer) airplanes to the NDH, the independent state of Croatia Air Force (reg. number 3501-3510). These were not newly produced planes, but instead G.50s that returned from the front and were repaired. The planes that were supplied were used alongside French-built MS.406 fighters supplied by the Germans. In 1944, six more airplanes were obtained from Italy, now under German control (reg. number 5686, 5965 and 06186, the rest are unknown) bringing the total number used to around 16 planes, possibly more as the exact numbers are not known. According to Tihomir T. and Darko Č. NDH forces acquired three G.50, after the withdrawal of Italian forces in 1943.
Their participation in the war was negligible and they saw little if any action. On 15th September 1944, only 7 were reported, with none fully operational for service. There were several cases of desertion among Croatian pilots while flying the G.50. On 2nd September 1944, pilot Andrija Arapović escaped to the island of Vis, under the control of the Yugoslav communist Partisans. A second pilot flying a G.50 fled to the Allies stationed in Italy.
Partisan forces put the captured G.50 to use during the war and it would remain in service up to 1946. An interesting fact about Andrija Arapović’s G.50 aircraft (reg. number 3505) is that it still exists today and can be seen in the Belgrade Military Aviation museum near the airport “Nikola Tesla” in Serbia. This is the only surviving example of a G.50 in the whole world, but it is in very bad condition and has been under restoration for years. By the end of the war, the Yugoslav Partisans had captured almost all of the surviving G.50s in Croatian service, but their use was limited due to a lack of spare parts.
G.50 production attempts in China
Italians were for some time trying to negotiate with Chinese authorities about opening an aviation production factory in China. After initial negotiations in June 1934, the Chinese signed a contract with the Aeronautico Italiano per la China (Aerocina). This company was owned by the Italian Government in conjunction with Caproni, Breda, Fiat and SIAI. According to this contract, the Italians were to build the SINAW (Sino-Italian National Aircraft Works) factory in Nanchang. With this agreement, the Italians were to provide tools and machines necessary for the factory to work. The head of the soon-to-be factory was the Italian Luigi Acampora and the Director was General Chu Lin. The production of the first operational aircraft was to begin from July 1937 on and all Italian personnel were to return to Italy after five years of cooperation.
The SINAW officially started production in November 1936 with six Savoia-Marchetti SM.81B bombers. Future plans included production of 30 Breda Ba.65s and 50 Fiat G.50s. The factory was slightly damaged during the Japanese bombing of Nanchang on the 20th October 1937. By November the Italian Government made a decision to discontinue any further cooperation and stopped all future deliveries of equipment and materials. This was done mostly due to Japanese military actions and the poor cooperation of the Chinese. By early December 1937, all Italian personnel returned home, and the deal with the Chinese was abandoned without a single G.50 being built.
Production and Variants
Besides the few prototype planes, a total of 791 (source Piero V.) G.50 and its variants were built during the war. Other authors give different numbers, according to Chris B. some 774 were produced and author Gianni C. quotes the figure of 778 planes. Author Duško N. give a figure of 788 planes.
The production of the G.50 fighter began in 1937 and ended in 1940, with a total 244 planes. The production totals by years were: two prototypes in 1937, 14 planes in 1938, 75 in 1939 and 153 in 1940. The improved G.50 bis was produced from 1940 to 1943 with a total of 439 planes built (421 according to some sources). 71 planes were built in 1940, some 253 in 1941, 113 in 1942 and the last 2 were built in 1943. If we compare these production numbers with other modern fighters of the time, the G.50 was built in relatively small numbers. The G.50 and its modifications and prototypes were produced by CMASA and Fiat during the war.
The Fiat G.50 was the first Italian all-metal fighter plane to enter operational service in significant numbers. In the early stages of the war, it proved to be an effective fighter, but as the war progressed, it became obvious that it was outdated in comparison with other modern fighters like the Hurricane. The G.50 was easy to control at lower speeds and had good maneuverability. The negative side was the lack of engine power and the overall design of the radial engine which affected the aerodynamics of the G.50. There were problems with cockpit visibility, but the most notorious issue was the lack of effective offensive armament, which consisted of only two heavy machine guns. Despite all this, with a good pilot the G.50 proved that it could be an effective fighter and it was responsible of downing of a significant number of Allied planes during the war.
G.50 prototype – Two prototypes built, the second was lost in an accident.
G.50 – Production aircraft.
G.50 bis – Improved version.
G.50 A.S – A number of G.50 planes that were used in North Africa were modified with sand filters and improved landing gear.
G.50 A – One plane was modified with an increased offensive armament of four 12.7 mm machine guns in October 1942. Only one was constructed and used up to 1943 for testing different wing designs.
G.50 B – Two-seat trainer version, around 100 to 108 built.
G.50 bis “Tuffo”– Dive bomber version, none built.
G.50 B naval observation – One G.50 was modified to be used by the Italian Navy in 1943.
G.50 O/R – Based on the G.50 bis, some 16 were built and used for training in 1943.
G.50 ter – Equipped with a stronger 1000 hp (746 kW) FIAT A.76 engine, only one built.
G.51– In 1940, it was proposed to equip one G.50 with the new A 75 R.C.53 engine, none built.
G.52 – Proposed project, none built.
G.50 V– Equipped with a German Daimler-Benz DB 601 engine, one built.
G.53 – Proposed project based on the G.50 B and powered by the DB 601, none built.
Kingdom of Italy – Operated around 720 G.50 aircraft, starting from the Spanish Civil War until the Italian Armistice.
Croatia (NDH) – Used at least 16 G.50 aircraft during the war (supplied by the Italians and Germans).
Finland – Operated 35 G.50’s during the Winter War and the Continuation War.
FascistSpain – Used some aircraft given to them by the Italians at the end of the Spanish Civil War and after.
SFR Yugoslavia – Captured some G.50 fighters from NDH during the war. Their use was very limited.
National Republican Air Force (Aeronautica Nazionale Repubblicana/ANR) – Operated a small number of G.50s, mostly as trainers.
Co-Belligerent Air Force (Aviazione Cobelligerante Italiana, or ACI) – Operated limited numbers.
Nazi Germany – A few were captured and saw limited use with the Luftwaffe.
China – There were plans to produce 50 G.50 aircraft in China but nothing came of this.
G.50 Freccia Specifications
35 ft 11 in / 10.9 m
26 ft 3 in / 8 m
10 ft 7 in / 3.28 m
196.5 ft² / 18.25 m²
One 840 hp (626 kW) Fiat A.74 RC.38, 14 cylinder radial piston
4,353 lbs / 1,975 kg
Maximum Takeoff Weight
5,324 lbs / 2,415 kg
292 mph / 470 km/h
267 mi / 445 km
Maximum Service Ceiling
35,100 ft (10,700 m)
Climb to 19,700 ft (6,000 m) in 7 minutes and 30 seconds
Nazi Germany (1942)
Experimental Aircraft – 1 Prototype Built
The Akaflieg Berlin B9 was a German experimental twin engine aircraft designed with the pilot placed in the prone position. It was designed to withstand extremely high g-forces. One prototype was built and tested by a glider production workshop in 1943 but it would not be adopted for mass production. The author would like to especially thank Carsten Karge from the Archiv Akaflieg Berlin for providing information on this generally unknown aircraft.
Why prone position?
During sharp up and down turns while flying an aircraft, strong g-forces appear that act on the pilot, potentially leading to loss of consciousness. Under normal flying conditions, the g-forces that appear are relatively harmless. The first effect of the g-force which the pilot notices is the difficulty of moving his body normally, as normal movements feel much heavier. Another effect of strong g-forces, which is much more dangerous, is the loss of oxygen flow to the brain. In some cases, the flow of oxygen and blood to the human brain can be greatly diminished, which can lead to the pilot losing consciousness momentarily. This effect lasts a short time, but it is enough for the pilot to lose control of the plane with a potentially fatal outcome.
While today, devices such as advanced anti-g suits help the pilot withstand strong g-forces, during the World War Two, other solutions had to be found. The Germans had noticed that, especially during sharp dive bombing actions, the pilots often lost consciousness. One way to tackle this was to put the pilot into a prone position, which in essence means to fly the plane while lying on the belly. In this position, the pilot has both his heart and his brain at the same level, which means that blood is no longer stopped from travelling to the brain during high-g maneuvers. Thus, this flying position allows the pilot to endure much greater g-forces than he would normally be able to if he would be in an ordinary sitting position. Other advantages of the prone position are the reduced aircraft size, smaller fuselage, less drag due to the smaller cockpit, and it would be easier for the pilot to operate the plane when conducting bomb sighting and ground attack, among other advantages.
During the war, the Germans would test several such aircraft designs, sush as the Henschel Hs 132 or B9, mostly for the ground attack role. Beside a few prototypes built, none were ever used operationally.
In order to test the idea of an aircraft with the pilot in the prone-position, the Aero-Technical Group (Flugtechnische Fachgruppe/FFG) of Stuttgart designed and later built the FS 17 all-wood test glider. It was especially designed to withstand forces up to 14 G. It made its first test flight on 21st March, 1938. In the spring of 1939, FFG Stuttgart made the first design drawings and calculations for a prone-piloted aircraft. This aircraft was to be powered by two Hirth HM 50 engines with an estimated speed of 250 mph (400 km/h).
FFG Stuttgart never completed this project as it was forced, for unknown but likely politicaly reasons, to hand over the project to Akaflieg (Akademische Fliegergruppe/Academic Aviator Group) Berlin. It is possible the order came from the German Experimental Department for Aerospace (Deutsche Versuchanstalt für Luftfahrt e.V. Berlin-Aldershof) DVL or even from the Ministry of Aviation (RLM – Reichsluftfahrtministerium), but precise information is lacking. Akaflieg Berlin, founded in 1920, was one of the oldest gliding clubs in Germany and it still exists today.
The RLM designation for this aircraft was “8-341” but Akaflieg used the simpler B9 designation. The technical characteristics that the new plane was supposed to have were a good field-of-view for the pilot in the prone position, a high degree of safety for the pilot, a high speed during diving, good general flying characteristics and being able to withstand forces of up to 25 G, or 22 G depending on the sources.
Akaflieg Berlin had a small number of engineers and workers and an adequately equipped workshop to complete the task given. For this purpose, a design team was formed with Theodor Goedicke, Leo Schmidt and Martin G. Winter, which was responsible for the creation of this new aircraft design. The first prototype was to be ready by August 1942 but this was never achieved, and the prototype was only completed in early 1943. It made its first test flight on the 10th April, 1943 at the Schönefeld airfield, near Berlin.
The B9 was a single-seat, low wing, mixed construction aircraft with the pilot in prone position. It consisted of a metal airframe, made of steel ribs, covered with wood and canvas. The main fuselage’s cross-section was trapezoidal shaped. As the B9 was specifically designed to withstand forces of up to 25 G, it had to have a strong fuselage.
The wings were made of wood covered with duralumin sheets. In order for the wooden wings to withstand the strong torsional forces which occur during high acceleration maneuvers, the spaces between the spars were heavily reinforced. The middle part of the wings viewed from above have a square shape and then narrow towards the wing tips. The wings were held in place by four bolts on each side. The rear tail design was a simple one, with standard rudder and elevators.
The B9 had a standard retractable landing gear copied from the Me-108, which consisted of two larger wheels and one smaller non-retractable wheel at the back. The landing gear was lowered and raised manually. The front wheels retracted into the engine nacelles, but they were not fully enclosed.
The B9 had a large 4.9 ft (1.5 m) long glazed cockpit with good all-around view. But, as the pilot was in a prone position, the above and the rear views were limited by the human body’s inability to turn the head in these directions. The glazed cockpit was made of two parts, the front windshield and the rear larger canopy that opened to the right side. The cockpit interior had to be especially designed for a pilot lying in the prone position. The usual flight controls were almost useless in this situation and, thus, certain changes were necessary. It was important to divide the controls on both sides of the cockpit, in order to avoid the pilot crossing hands, which could lead to complications in flight. On the right side were the controls for ailerons and elevation. The pilot would use his right hand to gain access to the harness and the canopy release mechanism. For controlling the rudders and brakes, the pilot would use his feet. Using his left hand, he would operate the remaining instruments, the throttles, flaps, ignition switches, emergency pump, fire warning, undercarriage control and others. Additional engine and flight instruments were located behind the pilot. These included, among others, the distance indicator, climb indicator, compass, oil and fuel pressure gauges and airspeed indicator. For the pilot to be able to see them, a small mirror was provided. There were also inclined and horizontal line markers on the inner windshield to help the pilot with orientation. For flying at high altitude, an oxygen supply system with a mask was provided to the pilot.
The aircraft was powered by two Hirt HM 500 air-cooled engines, with 105 hp each. The maximum speed was around 140 mph (225 km/h) but, according to some sources, it was as high as 155 mph (250 km/h). The four fuel tanks, with a total capacity of 25 gallons (95 l), were located between the spars on both engine sides. The B9’s effective operational range was 250 mi (400 km). Originally, the B9 was meant to be equipped with two variable-pitch propellers, but it was instead fitted with ordinary wooden fixed pitch propellers made by the Schäfer company.
As the B9 could be used as a ground attack aircraft, a bomb rack was meant to be installed, but it is not clear if this was ever implemented.
The operational prototype was ready by the summer of 1943. The first test flights were carried out by Ing. L. Schmidt and Dipl.-lng. E. G. Friedrichs. On one flight, L. Schmidt had an accident, the details of which are not known, but the plane probably suffered only minor damage.
The B9 was meant to make a series of test flights in order to ascertain if the prone position design had any merit and to test the general flying and overall structural performance. If these proved to be successful, the B9 would serve as base for future development and be put into active service. The B9 aircraft received the ”D-ECAY” marking, which was painted on both sides of the fuselage.
The tests were carried out from July to October 1943, during which time around thirty pilots had the opportunity to fly it. The test flights were conducted without any major problems and only one accident was recorded. This accident was caused not by any mechanical problems, but by a pilot mistake during takeoff. The B9 was damaged, but it was repaired and put back into service in only a few weeks.
The pilots did not have many objections to flying in the new prone position. They described it as comfortable and that it was relatively easy to adapt to the new commands. There were some issues, like fatigue and tiredness of the neck and shoulder muscles because of the constant moving of the upper arms. There were also some complaints about the chin supporter, which was deemed as unpleasant during flight but it was essential during high g-force maneuvers. During these test flights, the control panel and the controls did receive some changes in design. The large and fully glazed cockpit provided the pilot with good front and below fields of view, while the rear and upward view was somewhat problematic due to the prone position.
These tests showed that this type of aircraft was well suited for bomber, ground attack, high speed reconnaissance and possibly even in a high-speed fighter role. But it was also noticed that, due to the somewhat restricted view, the use of low speed prone pilot aircraft without air support was not recommended. Despite being designed to withstand forces of up to 25 G, the maximum achieved was only 8.5 G. One of the reasons for this was the use of low rotational speed propellers.
For 1944 and 1945 unfortunately, there is no information about the B9’s operational use. The B9 was found abandoned at the Johannisthal airfield near Berlin after the war. In what condition it was by the time of capture is not known. What is unusual is that the B9 was captured by the Americans and not the Soviets (according to author Hans J.W.). What the Americans did with the plane is unknown to this day, but it was most likely scrapped.
Only one B9 plane prototype was ever built. By 1943 and 44, a large amount of resources were invested in the production of fighters for the defense of the Reich and there were neither the time nor the resources needed to develop and test such an aircraft.
The German Air Force was responsible for several great revolutions in the development of aviation during both World Wars. While the development of jet technology in the Second World War is probably the best known, during the First World War, one of the most important such evolutions was the development of the first all-metal planes. The man responsible for this was the famous Hugo Junkers. The corrugated metalwork first seen on the D.I would become a hallmark of later Junkers aircraft.
The first all-metal projects
Aviation technology before the First World War revolved around wood as the main building material. Wood was used as it was easy to process and was easily available in great quantities and simple carpenters could be put to work on airplane construction.
One of the first persons who ever experimented with the idea of building an all-metal plane was the well-known German aviation designer and inventor Hugo Junkers (1859-1935). While working as a professor of thermodynamics at the Technische Hochschule (Technical University) in Aachen in 1907, he met a colleague, Professor Hans J. Reissner. Professor Reissner was involved in experiments with many novel ideas, such as aerodynamics in aviation. This moment would have a big impact on Hugo Junkers, as he would develop a great interest in aviation.
Hugo Junkers’ initial efforts were focused on solving the problem of poor aerodynamics of already existing aircraft. In 1912, his preliminary research showed that planes had better aerodynamics properties if they were designed to have an airfoil structure. In essence, this means that the whole plane, wing, body, and control surfaces had to have curved surfaces specially designed to give the best possible ratio of lift to drag. In order to perform even more experiments in aerodynamics, Junkers financed the construction of a wind tunnel at the Frankenberg laboratory. In the following years he continued his research, and by 1914 he had performed around 4,000 different tests and built 400 test models.
In 1914, Junkers had the first indications that an all-metal monoplane with thick wings was a feasible idea. While metals, like iron, were available in large quantities, lighter metals, like duralumin, an aluminum alloy, were more desirable for this purpose. The negative aspect of duralumin was the fact that it was difficult to work with. The techniques and technology of the day were inadequate, and the process of forming duralumin was slow and crude. As this could delay his work for years, Hugo Junkers decided to use the iron plates as a replacement, as they were much easier to work with.
After having constructed one all-metal wing prototype with a 9.18 ft (2.8 m) wingspan, Hugo Junkers made a request on the 2nd of February, 1915 to the German War Ministry for funds so he could build an all-metal prototype plane. This request was rejected, but it did not discourage Junkers from continuing his research. His second request was accepted in July 1915. With these funds, Hugo Junkers was able to construct a working prototype by December 1915.
The base of the prototype was made of iron ribs which were covered with iron sheets which were only 0.1 to 0.2 mm thick, held in place by electric welding. A second layer of sheet metal was added to reinforce the whole construction. The first prototype, designated the Junkers J 1, was ready by the end of 1915. It was powered by a Mercedes D.II 125 hp engine. After some ground testing, the new plane was shipped to Döberitz, the main German aviation training and test site in December 1915. Once there, the first test flight took place on 18 January, 1916. This was the first flight of a plane with an all-metal frame. The Idflieg (Inspektion der Fliegertruppen – Inspectorate of Flying Troops) was impressed with this prototype and ordered six more all-metal planes for future testing as a fighter plane. The J 1 design was not without problems, as there were some issues with the wing connection to the fuselage. During one test landing, one of the wings separated entirely.
Hugo Junkers began working on a second improved prototype named J 2. The problem with the wing-fuselage connection was solved by changing the internal design. The wings were divided into a couple of parts. The main section was connected directly to the fuselage and the others were affixed by screws. In only a few months, the first Junkers J 2 was ready to be tested. The J 2 was powered by a single Mercedes D.II 120 hp engine which was later changed to a stronger Mercedes D.III 160 hp. It made its first flight on 11 June, 1916. However, unlike the first prototype, the flying performance of the Junkers J 2 was poor. The speed was good, but the plane was simply too heavy at 2,480 lbs (1,160 kg) and thus useless as a fighter. Some six were ordered and built for future testing but the Idflieg lost any interest in it. Despite being rejected for operational service, it was still deemed important for testing construction methods and acquiring additional research.
After Hugo Junkers and his team analysed the Junkers J 2, they concluded that the plane could be vastly improved if lighter materials were used. Their solution was to undertake a study of how to make duralumin easier to work with. In time, specialized tooling and machines were developed and designed in the hope of producing adequate duralumin parts that could be used for aircraft construction. Despite the use of the duralumin in Zeppelin construction, the Junkers team made many improvements to these processes.
Thanks to these developments with aluminum processing, Junkers tried to build a fully operational all-metal monoplane. This was a private venture marked as the Junkers J 3. It was short lived, as the Idflieg refused to finance its development and only a single incomplete airframe was built. The Idflieg was more interested in all-metal ground attack biplanes.
The improved J 7 prototype
Hugo Junkers and his team continued to develop their own all-metal plane project. The J 4 served as a prototype for the J.I biplane and J 5 was never completed. Next in line was the Junkers J 7 as a single seat fighter and the J 8 two-seat close ground-support version. The J 8 prototype would eventually lead to the J 10 and the CL I. As the the J 7 and J 8 were developed, tests done in the wind tunnels showed that the low wing design provided good performance. One extra benefit of this design was the fact that the low wing would provide some extra protection for the pilot during a harsh landing. However, the weakest point in the design was the fuselage. Hugo and his team had significant problems designing a structure that would be strong enough to support all the necessary equipment, engine, and fuel tanks while still being light enough to maintain fighter maneuverability. They eventually reached a achieved a design that met most of the requirements.
The Junkers J 7 was constructed by using steel bars to form the structures of the plane and these were then covered in duralumin sheets. This method was copied from the J 4, with the only difference was that parts of the surface of J 4 were covered with fabric, while J 7 was all-metal. The J 7, piloted by Feldwebel Arved Schmidt, made its first test flight on 17 September, 1917. As the tests continued, Schmidt was generally pleased with how the plane behaved. In his report he said that the plane “.. made a good impression and possessed no serious fouls but the unique rotating wingtip ailerons were somewhat overbalanced…”. The J 7, despite its large front mounted radiator to accommodate the Mercedes D III 160 hp engine, managed to reach a speed of 77 mph (124 km/h). Many further trial flights were conducted, and in early October 1917 Schmidt managed to reach an altitude of 16,400 ft (5,000 m) in 17 minutes. This was a great result especially considering that the J 7 had a weight of 1,572 lbs (713 kg) and with added military equipment, the same altitude could be reached within 24 minutes.
For the next series of test flights, the J 7’s wings were equipped with conventional ailerons. These trials were held in late October 1917. The pilots were Leutnant Gotthard Sachsenberg and Theo Osterkamp. This time, the J 7 was pitted against the Albatros D.III. The J 7 proved to be a better fighter but the problems with the ailerons persisted. Both pilots gave a “green light” for the J 7 to go into production.
On 20th October, 1917 Idflieg made a decision to establish a new cooperation between Hugo Junkers and Anthony Fokker. Junkers-Fokker Werke AG was thus founded. It was hoped that the lack of production capacity of Junkers’ team would be supplemented by Fokker’s. This meant that there were two companies working on the J 7 project, Junkers (Jco) and Junkers-Fokker (Jfa). Despite the Idflieg’s hopes for good cooperation, this was never achieved as both sides sought control of the project.
In December, new modified ailerons were tested and the large nose radiator was also changed. While flying the J 7, the pilot, Tonny Fokker, had an accident upon landing. The plane was damaged but quickly repaired in time for the inspection made by Hauptmann Schwarzenberger from the Idflieg. He gave positive reviews of this plane and suggested that it should be used in the First Fighter Competition held in Germany. For this purpose, it was equipped with a new Mercedes engine and received new aerodynamically-balanced ailerons.
This competition was held from January to February 1918. Many front line pilots flew the J 7, including the famous Red Baron. He had positive comments for the J 7, in his report the plane being rated as having better climb rate and speed than other fighters in field use. However, he also noted the presence of some oscillation in the wings during sharp turns.
In January, Fokker once again had an accident during landing, but the damage was minimal. The plane was damaged again during its flight to Dessaou for wing modifications, but was repaired and ready for further testing by early February. These accidents also proved that its construction was much more robust than that of ordinary wooden planes. In March 1918, the last tests took place, with Leutnant Krohn as the pilot. His report read “.. On take-off the aircraft accelerates quickly and leaves the ground in a short time. It reacts instantaneously to the control. After ten degrees of control-stick movement, which suffices for an 80-degree bank, the control becomes very heavy. In a spiral, the aircraft reacts quickly to the controls. On the whole, the aircraft is at least as manoeuvrable as the new Albatros D.III or D.VI when diving at 155 mph (250 km/h) airspeed without any vibration in the wings..”
The ailerons were modified for the last time, which solved all previously mentioned problems with the controls. The J 7 prototype plane was used by a Fligertruppe in late March 1918. The J 7 was also used in the Second Fighter Competition held in July 1918. Despite proving to be an adequate fighter, the J 7 would never be accepted for service.
The J 9 and the D.I
At the same time as the J 7 was developed, Junkers began work on an improved model named J 9. Two prototypes were built, simply marked as J 9/I and J 9/II, the first of which was ready by April 1918. The J 9 was similar in construction to the J 7, but it was better suited for possible mass-production. By March 1918, Idflieg was negotiating with Junkers about the possible production of six planes for more testing. Hugo Junkers was disappointed with this, as he expected the signing of a major production contract. He thought it was a waste of precious time and that the plane did not need further testing. By early May, he managed to convince military officials to put the J 9 into production. A contract was signed for the production of 100 all-metal planes, including other Junkers models CL.I and the J.I, with around 20 copies of the J 9, now officially designated as the D.I. The first group was to be built by late July, with 6 in June and 14 by July.
The D.I (J 9/I) prototype made its first flight on 12 May, 1918 (Some sources incorrectly state April), piloted by test pilot Leutnant Krohn. The D.I prototype was ready to participate in the Second Fighter Competition. For this, it was equipped with the Mercedes D. IIIaü engine. During this competition, the D.I prototype presented itself well. The second D.I prototype (J 9/II) was equipped with the Benz Bz. IIIbo V-8 195 hp engine. Due to problems with this engine, it was not used in this competition. During these tests, the J 9/I was equipped with two Spandau machine guns located above the engine compartment, with one on each side. At the end of the Second Fighter Competition, several front fighter pilots were asked to test these new models. As most pilots, such as Oberleutnant Goering, thought that biplanes were the future, they marked the D.I as a complete failure.
A second commission rejected the notion that it was a complete failure, referencing its demonstrated performance. One demerit marked by this commission was the lack of downward visibility from the cockpit. This was based on the German air fighting tactics which had been adopted due to Allied air superiority. This tactic involved attacking Allied planes using high speed dives from above, and thus downward vision was deemed critical. The D.I lacked this due the to the large low-placed wings, but it compensated with the metal construction that made it more resilient to low caliber rounds.
On the 21st August 1918, Idflieg place an order for 100 more Junkers all-metal planes, including the CL.I and the J.I, of which around 20 were D.I fighters. At the beginning of August 1918, three D.Is were ready for static machine gun testing. Three more were almost completed with five more to be constructed by early September 1918. For more firing tests, two were sent to Adlershof. Due to the installation of the offensive armament, some small modifications were needed.
Despite entering production, there were still some modification that were needed. The first D.I produced had a longer fuselage and larger wings. As it was tested, there were problems with vibrations of the fuselage and maneuverability. As this could endanger the entire production, a series of quick modifications were done to the remaining four, possibly five, produced aircraft. These were built with modified, shortened fuselages and smaller wingspans. In total, around nine operational fighters and two prototypes were ready by the war’s end.
The D.I was designed as a single seat, all-metal low-wing fighter plane. It consisted of a metal airframe of steel ribs covered with corrugated duralumin sheets. Duralumin is a trade name for one of the earliest types of aluminum alloy. The corrugated surface of the duralumin offered increased strength, rigidity, and projectile resistance without a significant weight penalty. This method of aircraft skin construction would later be used in larger Junkers bombers in World War II becoming an iconic hallmark of the company, going on to inspire the look of the Citroen H van of the late 1940s. Aluminum construction low wing monoplane designs in would later come into widespread adoption, becoming the standard by World War II. In this way, the C.I’s design was truly ahead of its time.
The airframe was designed by Hugo Junkers, but it said that even he was never completely satisfied with its design. It nevertheless did its job and was robust, durable, and easier to maintain and repair. It offered the pilot a greater chance of survival during a forced landing than a wooden airframe. The D.I’s metal airframe provide good protection from most weather conditions in comparison to standard wooden built planes. The D.I could be left out in the elements and exposed to strong rain and wind without fear of damaging the plane. Due to use of lighter metals, the D.I’s total weight was 1,835 lbs (843 kg).
The main engine chosen for this plane was the BMW III water-cooled 6-cylinder inline, supplying 185 hp (138 kW). With this engine, the maximum speed that could be achieved was 118 mph (185 km/h).
The pilot was located behind the engine and had a good visibility of the to the front, sides, above, and rear, but the downwards visibility was somewhat limited due to the plane’s large and low wings. The wing’s design was similar to previous prototypes, as it was divided into a few parts. The central part of the wings was directly connected to the fuselage and the remaining were connected by fasteners. Under the pilot there were two fuel tanks. The total fuel capacity is not precisely known.
The landing gear was fixed, like on all planes of the era. The landing wheels were mounted on an axle that was connected to the plane by triangular-shaped steel bars. The main armament consisted of two Spandau (7.92 mm) machine guns mounted above the engine compartment.
Around 40 aircraft were ordered by Idflieg to be built by Junkers, 20 in May and a second group of 20 in August. Junkers completed around 27 planes before production was stopped in February of 1919.
The Junkers-Fokker joint company was also involved in the planned production of the D.I. The exact production details are not known. The Junkers-Fokker company was given an order to produce 20 more D.I, but it only produced 13. During the production run from June 1918 to February 1919, around 40 D.I fighters were built in total by both companies in addition with two prototypes..
What is interesting is the lesser known fact that Idflieg wanted to give a contract for the production of 50 D.I planes to Hansa-Brandenburg but, as the war ended in November 1918, this never took place.
The war ended before more could be produced, and thus only limited numbers were sent to the front. These were given to front line units, possibly in the Flanders sector in October 1918. Later, in early 1919, during the Entente advance after the Armistice, five D.I fighters were captured. Four were found at Hombeek in Belgium. Of these four, only one was in flying condition, two were badly damaged, and the condition of the fourth is unknown. One more was found(missing half of its parts at an airfield near Brussels. There is little information about their use in combat.
However, there is evidence that gives some indication of the D.I seeing some combat. On the plane captured at Hombeek in Belgium, there were markings behind the pilot’s cockpit that may have been kill markings, but this is at best just speculation. The aircraft captured near Brussels had machine gun bullet holes, but the origin of these is unknown.
At the war’s end, the US Air Service, after analyzing the collected data and field reports, made a report “.. no one was found who had ever seen one of these airplanes in flight …. Some of the RAF pilots, however were sure that it had been used in service..”
The Junkers D.I did see combat action after the war against Soviet Bolshevik forces in the Baltic countries. The D.I was used by Kampfgeschwader Sachsenberg (under the command of Leutnant Gotthard Sachsenberg), being mostly used in the air support role, covering the German Freikorps units that remained there after the war.
Leutnant Gotthard Sachsenberg was very impressed with the D.I’s overall performance. His report reads: ”.. The Junkers aircraft have proven themselves beyond all expectations. The weather resistance of the aircraft is so great that it was possible to allow the aircraft to stand for weeks on end in the open during snow, rain, and thaw of the March season. A tarpaulin cover over the propeller and the engine sufficed to provide protection. Since neither tents nor hangars were available, no other aircraft except the Junkers would have been able to serve in Russia at that time.. the advantage of the weather resistance, the exceptional speed and the invulnerability of the aircraft outweighed the small disadvantages. In crashes and emergency landings relatively little occurred …. the Junkers aircraft, with improvement, will without doubt, take first place as a combat type…”.
Today, only a single D.I has survived the War and can been seen at the Musée de l’Air et de l’Espace near Paris.
Junkers D.I Specifications:
28 ft 6 in / 9 m
23 ft in / 7.25 m
7 ft 4 in / 2..25 m
159 ft² / 14.8 m²
One BMW III water-cooled 6-cylinder, 138 kW (185 hp)
The Yak-23 emerged as the final step of the Yak-15 and Yak-17 development series. It made its first flight in mid-1947, powered, ironically, by a British Rolls-Royce Derwent jet-engine. By the time it entered production, the engine was changed with a Soviet-built copy. Over 300 were built, but as more advanced planes were ready for service the Yak-23s were sold to several Eastern Bloc countries. There they remained in service until replaced with the MiG-15 in the mid-1950s.
History of the Yak-23 predecessor
The Soviets began developing jet powered aircraft in the 1930s, but the process was slow with no major progress. However, by the end of World War 2, the Soviets managed to come into possession of large quantities of German war technology, engines as well as experimental and operational jet aircraft.
In April 1945, by orders of the National Defense Committee of the Soviet Union, work on a new generation of jet-powered aircraft began. In the case of jet fighters, the minimum requirement was that it had to achieve a maximum top speed of 500 mph (800 km/h). As there were a number of captured German Junkers Jumo 004B1 and BMW 003 jet engines, it was proposed to try to use them in Soviet designs. These received the new Soviet designation RD-10 Reaktinyi Dvitagatel, which is Russian for “jet engine.” The design and work on the first power plant was given to the OKB-117 Experimental Design Bureau, under the designer Vladimir Y. Klimov in late April 1945. A few months later, a second order was given to develop a new RD-20 jet engine based on the German BMW 003 jet engine. As the Soviet scientists were not familiar with this technology, the entire development ran quite slowly. The first series of these engines was ready in 1946, but the performance turned out to be limited and almost useless.
The work on the new jet fighter program was also slow and largely fruitless. Projects like the MiG-13, La-7R and Yak-3RD were built in limited numbers and proved to be unsuccessful. One of the main reasons for so many failed projects was the fact that the Soviet designers used captured and complicated German jet technology as an inspiration. There had to be a change in the way the Soviet designers and engineers approached these technologies and developments. Since time was crucial, the designers were forced to adopt simpler solutions.
Several new projects resulted from these decisions, one of which was the A.S.Yakovlev Yak-Jumo project. It was based on Yakovlev’s own analysis of German technology, especially the light weight, stepped fuselage and the forward position engine design. His first idea was to try to take advantage of the already existing piston engine-powered fighters and, if possible, install one or more jet engines on them. He reused one Yak-3 fighter and modified it to mount one rocket engine instead of the piston engine. Most parts of the Yak-3 were reused, wings, including the whole fuselage, tail surfaces, undercarriage and most in-built systems and equipment. The new engine was fitted in the forward part of the fuselage, but tilted at a 430’ angle with respect to the plane’s axis. Besides this, it was necessary to redesign the whole fuel system. A new redesigned cockpit was installed and the armament would consist of two 23 mm NS-23K autocannons each with 60 rounds of ammunition located above the engine. The German Jumo 004 engine was used and thus the project name was Yak-Jumo or Yak-3 Jumo (depending on the source).
The first prototype was completed and ready by late 1945. During its first several ground tests, many problems were reported. One of them was the excessive heating of the rear lower fuselage caused by the engine exhaust gases. A second complete and improved prototype was built in December 1945. It was equipped with the Soviet-built RD-10 which was a direct copy of the Jumo 004. Tests on the second prototype plane began during the second half of 1946. During these tests, several complaints were noted and the aircraft was returned to the factory in order to resolve these issues. By that time, this plane received a new military designation, the Yak-15.
On 12th September, 1946, an order for a limited production run was given by the Ministry of Aircraft Production. The Yak-15 and MiG-9s were first presented to the public during a military parade held in Moscow’s Red Square of that year.
Due to the rapid development of Western jet aircraft, Soviet military authorities demanded improved and more advanced jet planes. The new fighters had to be able to reach a maximum speed of 620 mph (1,000 km/h), but mostly due to lack of adequate jet engines this was only successfully implemented in later, much more improved models like the MiG-17. This was the reason why some jet fighters were put into production despite much lower top speeds.
Due to obsolescence and new problems discovered during the Yak-15’s service, most were modified to be used as advanced trainers, but some were operated as standard fighters. Yakovlev was again tasked with the development of an improved jet fighter. It was required to have a significantly better aerodynamic layout and was to be powered by an RD-10 engine. Estimated maximum speed was to be around 527 mph (850 km/h) at an altitude of 16.400 ft (5,000 m). Besides this, a novelty was the installation of an ejection seat and armored glass plate for the windscreen. By September 1946, the first Yak-17 was ready for testing. These tests were considered successful, especially by the pilots who considered it to have good flying performance. Serial production was to start in the autumn of 1947. The Yak-17 would be built in relatively small numbers as more advanced designs would replace it in the following years, designs like the Yak-23.
History of the Yak-23
Later development of new Yakovlev aircraft was characterized by several different methods of approaching development. One of the many Yakovlev design teams, lead by Leonid L. Selyakov, worked on a completely new design that would later lead to the Yak-25. The main goal of this project was to build a completely new aircraft. In addition to this team, a second team advocated for the improvement of the already existing Yak-15 and Yak-17 designs.
The second team’s design was a lightweight and with highly maneuverable jet fighter. This new fighter was to be powered by an RD-500 jet engine, which itself was based on a British Rolls-Royce Derwent 5 turbojet engine. The whole aerodynamic concept was taken from the older Yak-17, but improved with an all-metal construction. The new plane was a lightweight mid-wing monoplane, but with unswept wings and rear tail. The cockpit was placed at the middle of the fuselage and equipped with an ejection seat. To save weight, some modifications were done such as the omission of air brakes, the armor plate being removed, fuel tank capacity lowered, no pressurization fitted to the cockpit and decrease of the wing thickness. The calculated weight with these modifications was about 4,725 lbs (1,902 kg). By the time it entered production, there was a slight increase of weight. The main armament was also relatively light, as it consisted of only two 0.9 in (23 mm) cannons, with some 90 rounds for each cannon.
The work on this project began in the early 1947. Plant No.115 was tasked with the construction of the first operational prototype. On 17th June, 1947 the prototype, designated Yak-23-1 was completed. The first factory test flight was made on 8th July, 1947 by the test pilot M.I. Ivanov. The results of these first flights showed that the Yak-23-1 had a high rate of climb and excellent maneuverability. The maximum speed achieved was 578 mph (932 km/h) at low level. Some issues that were noted during these first flights were solved in time.
In September the same year, on the insistence of the Minister of Aircraft Production, Mikhail V. Khruniche, the Yak-23 was accepted for additional test trials. For this purpose, a second prototype was built, named Yak-23-2. For the series of new test flights, besides G.A.Sedov, the main test pilot, many more pilots were also chosen to test the Yak-23, such as A.G. Proshakov, Valentin, I. Khomvakov among others. By March 1948, these test flights were successfully completed. The Yak-23 displayed great maneuverability during flights. In contrast to other models, like Su-9 and MiG-9, the Yak-23 proved to have much better climb rate. But it was not without its problems: during acceleration, the forward fuselage tended to suddenly rise and the lack of air brakes made potential dog-fighting very difficult. At higher speeds it took a lot of time to slow down and the lack of a pressurized cockpit made the Yak-23 incapable of operating at high altitudes. The second prototype was lost on 14th July, 1948, during one of the many flight exercises for the planned military parade to be held at Tushino. During these exercises, an unknown object struck the wing of Yak-23-2 flown by M.I. Ivanov, which caused the wing to break and fall off. The pilot lost control and crashed to the ground. Ivanov died immediately and the aircraft was totally destroyed. A subsequent investigation found that the main culprit was a balance tab that was torn from the tail of one of the Tu-14 bombers that was flying above the Yak-23.
Despite these problems, the Yak-23 was considered a successful aircraft worthy of production. Plant No.31 was chosen for manufacturing. By mid-1949, the production began, however, at first, the process was slow due the lack of RD-500 engines. The first batch was not ready until October 1949. In the period of January to March 1950, some 20 aircraft were used to conduct more tests. These trials revealed that the Yak-23 had a few more problems to be worked out, such as smoke in the cockpit, among other small issues.. As these problems were considered minor and did not endanger the production of the Yak-23 at the time.
The Yak-23 was designed as a lightweight, all-metal, mid-wing monoplane with unswept wings and tail surfaces. The long front fuselage was designed and constructed so that it could be easily changed or removed for ease of maintenance.
The external fuselage was made of 0.039 in (1 mm) thick duralumin sheets (D16AWTL) and the inner part was made of 0.031 in (0.8 mm) sheets. To protect the main landing wheels, a special cover was installed close to the exhaust nozzle. The lower part of the Yak-23 fuselage was covered with a specially designed heat resistant plate in order to protect the plane’s inner structure from any potential thermal damage. The two unswept wings were made of 17 ribs that were covered in 0.05-0.07 in (1.3-1.8 mm) duralumin panels. At the wing’s trailing edges, ailerons and flaps were fitted. The wings were made mostly of duralumin sheet metal. The wing ends were flat and it was possible to mount two external fuel tanks that were ejectable. The rear tail had a tapered design and was made of metal covered with duralumin sheets. There were no air brakes installed and this caused the Yak-23 to have some problems with maneuvering. This would be a major problem in any potential dogfight with other fighters.
The main engine was the RD-500 turbojet engine with 3,500 lbs (1590 kg) of thrust that was fitted with a single centrifugal compressor and nine cylindrical shaped combustion chambers. The engine had a diameter of 3.58 ft (1.09 m) and 6.76 ft (2.06 m) long. It was angled downwards by 4°30’ with respect to the plane’s centerline. This was not a perfect design choice as when the pilot accelerated the plane, it tended to suddenly pitch up. The main jet fuel was kerosene, stored in five large tanks mounted in the fuselage with a capacity of 240 gallons (910 liters) and two smaller 50 gallon (190 liters) tanks located in the wings. With this fuel capacity, the maximum operational range was around 640 mi (1,030 km). The Yak-23’s flight endurance was very low, with only one hour of operational flight. With this engine, the maximum speed achieved was 606 mph (975 km/h) with a climb rate of 6,693 ft (2,041 m) per minute. The air intake was located at the front, which split into two symmetrical ducts that passed under the cockpit. There was a headlight located in the air intake to help during landings.
The landing gear was a tricycle design typical of jet planes of the era. The front nose wheel retracted forward, while the larger rear wheels retracted into the fuselage sides. A built in shock absorber mechanism with double rebound system was used for the landing gear.
The cockpit was located at the center of the upper fuselage. The cockpit was designed with a fixed windscreen with an armored glass panel and a rear sliding hood with non-armored glass. For the pilot to enter his seat, he had to climb on top of the wings. The Yak-23 was equipped with an ejection seat that could be used by the pilot in case of emergency. The ejection seat with parachute was activated with a command handle located next to the armrest of the seat’s right side. A small explosive charge was used to catapult the seat from the plane. The main command instruments were in the standard configuration. All instruments were placed ahead of the pilot and the rudder pedals were mounted at the floor. The pilot’s instrument panel was divided into three sections. In the central section were the main and most important flying instruments: M-46 Mach meter, PDK-45 compass, AGK-47A artificial horizon, and engine control indicators. Secondary controls were located at sides of the main control panel. An oxygen supply system with a capacity of 2.11 gal (8 l) with a KM-16 model mask was fitted in the cockpit. Electric power was provided by 1.5 kW GSK-1500 generator and 12A-10 type battery. For communication, a RSI-6K radio set and a RPKO-10M radio-direction finder/semicompass were used. Also, the SCh-ZM IFF (Identification Friend or Foe) system was used.
The offensive weapon load consisted of only two 0.9 in (23 mm) NR-23 cannons placed in the lower forward part of the fuselage. Available ammunition for these two cannons was limited with only 90 rounds per gun. The main weapons were aimed by the semi-automatic gyro gun sight placed above the pilot’s instrument panels. Additional offensive armament could consist of two 123 lb (60 kg) bombs attached in the place of the external fuel tanks.
Beside the Yak-23 fighter aircraft, a trainer version, the Yak-23 UTI, was developed. One Yak-23 (serial number 115001) was converted for this purpose. A second instructor cockpit was installed at the rear of the pilot’s seat. The prototype was tested from March to September of 1949, but this modification was ultimately deemed unsuccessful. A new attempt was made with the redesigned Yak-23 UTI-II. The fuselage was stretched by some 7.8 inches (200 mm) to the front, and this time the instructor was moved to the front. A special periscope was installed to allow the instructor to see what the pilot was doing in the rear seat. The armament was reduced to only one 0.5 in (12.7 mm) machine gun. Many more changes were made, which resulted in the third version, Yak-23 UTI-III. By this time, the more impressive MiG-15 UTI was entering production and so the Yak-23 UTI project was canceled.
Despite its good flying characteristics the Yak-23, also known by its NATO designation “Flora,” was built in small numbers, 310 planes in total. Its operational service life in the Soviet Union was very limited, as it was operated by only a few fighter regiments located in the Caucasus and Volga military districts. As more modern planes were becoming available, the Yak-23 would be sold off to Eastern bloc countries such as Czechoslovakia, Bulgaria, Romania and Poland.
In Czechoslovak Service
Czechoslovakia had extensively negotiated with Soviet military officials in the 1950s about the purchase of new jet-powered fighters. These negotiations had been preceded by earlier ones, from which Czechoslovakia received one older Yak-17 under designation S-100. This sole aircraft was to be used as a basis for future local production. However, since this plan went nowhere, the Yak-17 was sent to a military museum and it was never used operationally. An agreement was made in November 1950 for a possible license production of the Yak-23 under a new name, S-101, and also for the engine under the M-02 name. The first group of 12 Yak-23s arrived in Czechoslovakia in late 1950. Their first public appearance of nine planes were used in a military parade on 6th May, 1951, the anniversary of the liberation of Czechoslovakia by the Soviet Red Army in WW2. A second group of 9 Yak-23s was allegedly received, possibly in 1951 or 1952, but precise information is lacking.
The Yak’s were first used by the 3rd Fighter Division, but as the more advanced MiG-15 arrived, the Yak-23s were given to the 11th Fighter Regiment, part of the 5th Fighter Division, from June to August 1951. By early 1952, this unit had 11 operational Yak-23s in total. One Yak-23 was lost in an accident on 16 October, 1952. In 1953, all available Yaks were given to the 51st Air Regiment, which was renamed as the 7th Air Regiment in October. By early 1954, there were 12 Yak-23s reported in service, of which 11 were operational.
Due to the purchase of newer types of aircraft, the Czechoslovakian military authorities thought that the Yak-23 plane was inadequate and outdated and so the original plans for a license production were dropped. By 1956, a decision was made to withdraw all Yak-23s from operational service. Only a small number of Yak-23s where ever used by the Czech Air Force, thought to be around 21, but the exact number is unknown. Most of these were sold, 10 to Poland in 1953, possibly 7 to Bulgaria, with one given to a military museum and at least one was lost in an accident.
In Bulgarian Service
Bulgarian military officials purchased several Yak-17 UTI training variants and 12 Yak-23s from the Soviet Union in early 1951. These were used to form the 19th Fighter Regiment in March 1951. The first pilot to fly on one of the Yak-23s was Major Vasil Velichkov. On his first take-off, the engine suddenly stopped working and he was forced to land in a field near the airfield. Because it was necessary to train new pilots to fly the Yaks, some planes were supplied to the 2nd Training Combat Air Regiment, located at the Georgi Benkovski Flying School. In order to increase the number of units equipped with the Yak-23s, some 72 new planes were purchased from the Soviet Union in 1952. Around 7 Yak-23s were sold to Bulgaria by Czechoslovakia in early 1956. As in Czechoslovakia, the Yak-23 would not stay long in service, and by 1959 all were retired.
In Romanian Service
After the Second World War, the Romanian Military leadership had great plans for the revival of their shattered air force and acquiring modern jet planes. Some 60 Yak-23s were bought from the Soviet Union during the fifties, with the first 12 planes reaching Romania in early 1951. The total number of planes used is not known. As the more modern MiG-15 was received during 1953, the Yak-23 was considered obsolete and only small numbers were ever used. One Yak-23 was modified by the Romanian air engineers of the AEMV-2 (Atelierele de Reparații / Material Volant) to be used as a dual-command trainer aircraft. A new instructor cockpit was installed. This new modified plane was designated as Yak-23 DC (Dublă Comandă / double command), but only a single prototype was built.
On the 24th June, 1953, Romanian pilot Mihail Diaconu escaped to Yugoslavia in Yak-23, where he sought asylum. Not long afterwards, another pilot flying a MiG-15 flew over and later landed onto Yugoslav territory, most likely due to a navigation error. Both planes were thoroughly researched and tested. Pilots Todorović and Prebeg both flew the Yak-23 with more than 4 flight hours. Beside the flying performance, the weapon systems were also tested during 1954. According to the agreement between US and Yugoslav military officials (code name ‘Zeta’), the Yak-23 was disassembled and sent to the Wright-Patterson Air Force Base in order to test the progress of Soviet aviation technology. Test flights were conducted on 4th November and, by 25 November, it was ready to be sent back to Yugoslavia. The Yak-23 was disassembled, and loaded onto a C-124 and later flown to Pančevo airfield. The whole operation was a complete success as it remained a secret for nearly 40 years. After several months, this Yak-23 was returned to Romania, without the Soviets ever realizing where it was the whole time.
In Polish Service
After the Second World War, Poland was economically and militarily devastated. It took several years before the beginning of the renewal of Polish military power. The new Polish military leadership wanted to built up the shattered air force and, despite their plans to acquire a new jet fighter by 1948, this was not possible. The process of acquiring new jet fighters began only in the spring of 1950. The first negotiations with the Soviet Union focused on the acquisition of Yak-15s, but this was later changed to the Yak-17. Due to outbreak of the Korean war, Soviet authorities decided to supply their allies with larger numbers of newer jet fighters. On 6th January, 1951, Poland received its first Yak-23 planes. The planned production of the older Yak-17s was suspended in favor of the Yak-23 under the Polish designation G-3.
Besides the 1st Fighter Aviation Regiment (PLM for short in Polish) which had some 16 Yak-23, a second unit, the 2nd PLM was also supplied with this plane. To train the new pilots, Yak-17 UTI training planes were used. In mid-1952, all operational Yaks were used by five Fighter Regiments: 2nd PLM with 26, the 39th PLM with 19, the 40th PLM with 19, the 26th PLM with around 11 and the 29th PLM with 14 Yak-23. From 1953 onwards, according to the new Polish military strategy, the first line fighter units would be equipped with the new MiG-15, while second-line units received all available Yak-23s.
In the early fifties, the Western Allies were eager to examine and spy on the military power of the East. A simple way to do this was by using various types of balloons. They were used for propaganda, meteorological, and reconnaissance duties. The Polish Air Force was heavily engaged with shooting down these balloons.
The final fate of Polish Yak-23s was sealed by the start of licenced production of the MiG-15 (under the name Lim-1). The remaining Yak-23s were gradually phased out of service. All operational Yak planes were allocated to training units at Radom, where they were used for training new officers and pilots. Some Yak-23s were temporarily used as reconnaissance aircraft in the 21st PLZ (21st Scout Aviation Regiment). By late August 1954, all Yak-23s were moved to Radom. The ones that were not operational were cannibalized for spare parts. On 1st September, 1959, the remaining 39 Yak-23s were removed from the Polish Air Force and a few would be used as memorials. During its operational service in the Polish Air Force, several planes were lost in crashes but, in most cases, the pilots escaped without any injuries.
Albanian Air Force allegedly operated a unknown number of Yak-23. Possibly bought from Poland sometime after 1951, according to author Yefim G.
Hungary and the Yak-23
Hungary allegedly also used the Yak-17 and 23, but there is no documentation or any information to confirm this (Source Marian M.). But according to author Yefim G. an unknown number of Yak 23 were operated by the Hungarian Air Force during the 1955 to 1956. But this author does not specify the number of planes used nor describes in more detail operational service life.
Production and modifications
A relatively small number of planes of this type were ever produced. As more advanced planes were becoming rapidly available, there was no need to continue the production of the old Yak-23. Most of the Yak-23s produced would be later sold to Eastern bloc countries.
In total, 310 aircraft plus three prototypes were built by Plant No.31. The plant produced these in twelve series, with 25 to 26 aircraft in each batch. Production was stopped by the end of 1950.
Yak-23 – Main production aircraft
Yak-23 UTI – One Yak-23 was modified to be used as a fighter trainer. It did not enter production.
Yak-23 DC (Dublă Comandă) – Romanian experimental dual control trainer, only one tested.
Bulgaria – Used over 70 Yak-23s
Soviet Union – Operated only two fighter regiments equipped with the Yak-23
Romania – Some 60 Yak-23 were bought from the Soviet Union during the fifties
Poland – Used around 101 planes, under the designation G-3
Czechoslovakia – Operated around 21 aircraft (possibly more) under the designation S-101
Yugoslavia – Used one Romanian interned plane for experimenting with flying performance and weaponry
USA – Briefly tested one aircraft that was supplied by Yugoslavia
Hungary – Allegedly used this type of aircraft, but proof is lacking
Albania – Possibly operated a small numbers of Yak-23
The Yak-23, despite proving that it had good flying performance and good handling, had a rudimentary design and was produced too late to have any great impact or role in the Soviet fighter force. Due to the rapid development of jet technology, more advanced planes were soon ready for service like the La-15 or MiG-15. The Yak-23 finished its career in service with many Eastern Block air forces.
Although its operational service life was short and its significance was negligible, the Yak-23 was an example of how, with only a short time and using limited resources, a solid jet fighter could be designed and built by the Soviets.
Yakovlev Yak-23 Specifications
28 ft 7 in / 8.73 m
26 ft 7.8 in / 8.12 m
10 ft 10.3 in / 3,31 m
145.32 ft² / 13.5 m²
One Klimov 3,505 lbs/1,590 kg thrust RD-500 turbojet engine
Prototype Advanced Trainer – 1 Built
With the emergence of new fighter planes in the years leading up to the Second World War, it became necessary to replace the older biplane trainer aircraft, which were too slow, in order to efficiently train new pilots to fly the newest fighters. Thus, it was logical that more modern advanced trainer aircraft would be needed. The MM-2 was an experimental Yugoslavian solution to this problem.
At the end of the thirties, the Yugoslav Air Force was equipped with modern planes, such as the German Me-109, the indigenous IK-3, and the British Hurricane, highlighting the need for an updated trainer. There were several older aircraft in use for the role, like the FP-2 and the Rogožarski PVT, with a maximum speed of around 140 mph (230 km/h) but there was a need for a much faster and modern aircraft trainer.
To fill this gap, Air Force engineer and pilot Captain 1st Class Dragutin Milošević, on his own initiative, began to work on a new advanced trainer in 1936. The first aerodynamic calculations, choice of engine, structure, and the design were done by 1937. This new plane was conceived as a two-seater with seats one behind the other, with an enclosed cockpit and dual controls. It had a low wing, mixed construction, with a single engine and retractable landing gear. The engine would have been the Renault 6Q-02, giving 162 kW (220 hp). Milošević never gave a designation for this plane, but was later simply named the M-1.
Captain Dragutin Milošević submitted this project to the Yugoslav Department of Aviation in 1937. The Department analyzed this proposal and, while on paper it would have had great flying performance, a decision was made to reject it because the parts necessary for its construction had to be imported from abroad.
This decision did not discourage Captain Milošević, and he made attempts to improve his design. He proposed replacing the Renault with the license-built Gnome-Rhone K-7 309 kW (420 hp) air-cooled 7-cylinder engine. By adding this engine, the length of the plane would be reduced from 23 ft 7 in to 20 ft 4 in (7.2 m to 6.7 m) but the total weight increased to 2,160 lbs (980 kg). To improve the landing characteristics of the aircraft, it would have been necessary to increase the distance between two front landing wheels from 6 ft 2 in to 7 ft 10 in (1.9 m to 2.39 m). All aerodynamic and statistical calculations were finished by 1939. The second version was named M-2 and it was, in essence, the basis of the future MM-2 aircraft.
One wooden model (1:10 scale) was built by the Albatros factory in Sremska Mitrovica. This model would be used to test the aerodynamic properties and accuracy of earlier calculations. Aerodynamic properties were tested in the Paris wind tunnels on the 17th and 18th of July 1939. After these trials, the fuselage length reverted to the original 23 ft 7 in (7.2 m).
Later, Captain Milošević did new calculations that showed that certain changes to the design of the aircraft were necessary. Adding weapons and increasing fuel capacity would lead to an increase of the mass of the M-2 by 242 lbs (110 kg), some 60 lbs (30 kg) in fuel and 176 lbs (80 kg) in armament. After all the other modifications, the total mass reached 2,782 lbs (1,262 kg) compared to the initial 2,160 lb (980 kg). The wing area had to be increased from 129 to 146 sq ft (12 to 13.6 m²) and the wingspan from 27 ft 10 in to 30 ft 3 in (8.5 to 9,23 m).
Adoption of a Prototype
Captain Milošević submitted a letter, together with documents, plans and calculations, to the supreme headquarters of the Yugoslavian Air Force, notifying them of the test results of the proposed M-2 aircraft. Since he did not receive any kind of response, he asked Major Đorđe Manojlović, also an aviation engineer, for help. Although Đorđe Manojlović did not have a direct impact on the design of the M-2, his great influence and connections in the Supreme Air Force Command lead to the continuation of the project. The cooperation of these two men lead to the final approval for construction of the M-2 aircraft project.
When the Air Force Headquarters of the Army of the Kingdom of Yugoslavia accepted the M-2, construction of this project was given to the Ikarus factory. The contract was signed on the 25th March 1940. It was planned to build one prototype aircraft for testing in order to ascertain if the M-2 was fit to be accepted for serial production. The project was monitored by a team composed of engineer Sava Petrović, Air Force Major Vojislav Popović and the technician Stefan Lazić. The prototype was ready by the first half of November 1940.
Origin of the Name
In the Kingdom of Yugoslavia, there was a custom of using the initials of the names of the designers as the official designation for most of new types of aircraft in service (like the IK-2/3), and MM-2 was no exception. MM comes from the initials of the surnames of Captain Dragutin Milošević and the constructor and engineer Major Đorđe Manojlović. There is sometimes confusion about the exact name of this aircraft. It is sometimes also called MiMa-2. In some documents found after the war, it is also called M.M. 2. In this article, the MM-2 name will be used, as it is the most common.
The MM-2 was designed as an advanced two-seater trainer, with seats one behind the other, with dual controls and a fully enclosed cockpit. It was a low wing, mixed construction, a combination of wood and metal, single engine aircraft with retractable landing gear.
The wings had a trapezoidal shape with a rounded top. They were constructed by using two racks which were made of steel tubes welded together. The racks were welded to the plane’s hull and the wooden ribs were connected to them by rivets. The wings were covered with canvas, except for the central parts, which were made of aluminum sheet. This was done so that the technicians and repair crews could have easy access to the inside of the wing. The ends of the wings were made of wood that were held in place by steel fittings. The flaps were covered in canvas and operated either manually or hydraulically.
The MM-2 hull was of mixed construction. The main body was made by using welded pipes. The front part was covered with aluminum sheet and the rear with canvas. The tail was made mostly of wood and covered with canvas.
The main engine was the Gnome-Rhone K-7, which supplied 310 kW (420 hp). It was domestically built under license from Franch aircraft manufacturer Rakovica. It was hoped to use a two-bladed metal propeller but, due to the lack of resources, wood was used. The maximum estimated speed (never achieved) was around 250 mph (400 km/h), with an effective range of 475 mi (764 km) with some 40 gallons (150 l) of fuel capacity. Climbing to 6,500 ft (2,000 m) could be achieved in 3 minutes and 9 seconds, but the maximum service ceiling was never adequately tested.
The landing gear was supposed to be of the ‘Nardi’ type imported from Italy, but it was planned to domestically build the landing gears for the production version, to avoid being dependent on foreign countries. On the prototype, no radio was installed but it was hoped to equip all future production aircraft with the FuG VII radios.
The main armament consisted of two wing-mounted 7.7 mm Darn-type machine guns with 175 rounds of ammunition for each gun. The total bomb load consisted of four 10 kg bombs carried under the wings. It must be noted that the armament was never installed on the prototype, as testing was interrupted by the beginning of the war.
First Test Flights
The first test flights were made by the beginning of the 1941 at the Zemun airport. The pilot for these flights was Vasilije Stojanović, the test pilot of the Ikarus factory. By the end of March 1941, some 45 flights had been made with a total of 20 flying hours. The pilot assessed the flying performance of this plane as excellent. The results of these tests indicated that this aircraft had good flight performance. The controls were adequate, both instructor and the students cockpits had enough room with a good field of view and, during flights, the aircraft did not present any tendencies for sudden unpredictable movements. Due to its good air brakes and flaps, take-offs and landings were quite easy. There were no major objections from the test pilot about the MM-2.
The MM-2 could very easily reach speeds of up to 217 mph (350 km/h). The design maximum speed was never tested, but calculations suggested that it could be as high as 250 mph (400 km/h). This was never confirmed due to the outbreak of the war. The MM-2 prototype had an unusual color scheme with a combination of red on most of the rear fuselage and wings, and polished aluminum on the majority of the fuselage and the engine section, with a small Yugoslav flag painted on both sides of the tail.
On the 25th of March 1941, a contract was signed between Ikarus and the Air Force. According to this contract, Ikarus was to prepare for production of MM-2 trainer planes in the near future. Before the production would begin, a last series of tests was to be conducted by a test group at an airfield near city of Kraljevo. An order was given to Stojanović to fly the MM-2 from Zemun to the Kraljevo airfield. Once there, it was planned to do some more flight performance trials in order to examine the limit of the flying characteristics of the MM-2 aircraft. Stojanović completed the flight on the 4th April. Final production was never achieved due to the German invasion of Yugoslavia that started only a few days later.
The MM-2 did not see any active service in the Royal Yugoslav Army because of the beginning of the April war, the German attack on Yugoslavia in April 1941. After the defeat of the Yugoslav army, the Independent State of Croatia, or NDH, was created. In order to form the new NDH military air force, it was necessary to find and obtain planes to equip these new units. Like many other former Yugoslav planes, the MM-2 was also pressed into NDH service in a very limited role.
It seems that the MM-2 had some engine problems (possibly sabotaged) when it was captured by the Germans at airfield near Kraljevo. It is possible that it was in a bad condition since the Germans did not even bother to repair it and put it into operational use.
The MM-2, together with other Yugoslav captured aircraft, was collected and handed over to the NDH. After a while, the MM-2 was repaired under code name No. 6301, and returned to active service. Additional flight tests were conducted by Georgije Jankovski, a test pilot for Dornier-Werke. In September 1941, the plane was transferred to the Zemun airport and handed over to Croatian Major Ivan Pupis for future use. Major Pupis was the leader of the group responsible for the repair, reception and later transfer of all Yugoslavian aircraft captured during the April war. When the MM-2 was repaired and ready for active service, Pupis to keep it for his personal use rather than handing it over to the military.
The MM-2 was ‘owned’ by Pupis until March 23rd, 1942, when he received a direct order from the Croatian Aviation Command to transfer the MM-2 to the ‘Rajlovac’ airfield near the city of Sarajevo in Bosnia. The aircraft arrived at the beginning of April 1942. The MM-2 was given to the 17th Squadron (Jato) which was part of the 6th group (Skupina) under the Command of the Major Romeo Adum. The MM-2 was used mostly for limited test flights. On May 13, 1942 while piloted by Vid Saić (from the 18th Squadron), the plane crashed. The pilot survived the crash with no injuries. A commission was formed to investigate the causes of the crash and found several irregularities: The pilot did not ask for permission and had no orders to fly on the MM-2 that day, and he also did not know anything about the flying characteristics or the condition of the plane. The conclusion was that the pilot was guilty for the accident and, as punishment, Vid Saić lost his Pilot rank. The damage to the MM-2 was estimated to be around 90%. There was no point to try to rebuild it from scratch and the remaining parts were destroyed. There is no information whether it was equipped with any armament in Croatian military service.
Due to the outbreak of war on April 6th, 1941, except for the prototype, no other specimen of this aircraft was ever built. In some documents and letters found after the Second World War, it was discovered that the Ministry of Aviation planned to order around 50 copies of the MM-2 aircraft. Along with this, the Yugoslav military negotiated with Germany for the purchase of Arado Ar 96 training planes, but nothing came of this.
After the war, the new communist Ministry of Aviation and the Ikarus factory representatives were also interested in restarting the production of this aircraft but, as the chief designer had died in one of the many German prison camps and the necessary machines and tools were lost during the war, this was too difficult and was abandoned.
Kingdom of Yugoslavia – Built and tested the single prototype.
Independent State of Croatia NDH – Used the MM-2 captured during the April war, but it was lost in an accident.
30 ft 6 in / 9.23 m
23 ft 7 in / 7.20 m
9 ft 6 in / 2.89 m
14.6 ft² / 13.60 m²
One Gnome-Rhone K-7, 309 kW (420 hp) air-cooled 7-cylinder engine
Nazi Germany (1939)
Experimental Jet Plane – 2 Built
On the 27th of August 1939, test pilot Erich Warsitz made the first test flight above the Rostock-Marienehe factory airfield with the new Heinkel He 178. With this flight, the He 178 went in to history as the world’s first fully operational jet-powered aircraft.
In March 1936 Dr Hans Pabs von Ohain, a pioneer of the gas-turbine engine, and Max Hahn were hired by aircraft designer and manufacturer Ernst Heinkel, founder of Heinkel Flugzeugwerke. Their objective at Heinkel was to design and build a working turbojet engine. The concept of a jet turbine engine was not something new at the time, but no one had applied it efficiently or used its potential for the development of the future of aviation.
Other German firms also showed interest in the radical and revolutionary idea of new jet engine technology, especially Junkers Flugzeugwerke. Junkers engineers would eventually develop the first operational combat jet fighter in the world, the Me-262. Heinkel hoped to achieve building the first operational and functional jet engine before all other firms, as quickly as possible.
In September of 1937, the first prototype of the new turbo-jet engine, named HeS 1 was demonstrated. It could achieve a thrust of 551 lbf (250 kgf). The next version, the HeS 2, was deemed a complete failure, with only some 198 lbf (90 kgf) of thrust and subsequent work on this design was abandoned.
The next developmental model, the HeS 3 was ready and tested in 1938. The HeS 3 reached 970 lbf (440 kgf) of thrust, weighing 793 lbs (360 kg) and had a diameter of 3 ft 11 in (1.2 m). Heinkel used one modified He 118 plane and equipped it with this test jet engine slung under its fuselage. This was however not the first operational jet aircraft, as the testbed took off and landed under its own piston engine’s power. This flight is generally considered to be a success.
A new upgraded HeS 3b, upgraded from the earlier 3a version, with some 1,100 lbf (500 kgf) of thrust, was ready to be tested in 1939 in a specially designed aircraft, the He 178 which had been completed earlier that year.
The He 178 was a shoulder wing aircraft, made mostly of wood with a semi-monocoque metal fuselage. The He 178 was equipped with retractable landing gear. The pilot’s cabin was located well forward of the wing’s leading edge. The jet engine drew in air from the front nose inlet, with the jet exhaust emerging from a long narrow pipe at the rear of the aircraft, in the tail. Later a new HeS 6 engine was installed, with 1,300 lbf (590 kgf) of thrust.
The characteristics of the He 178 were as such: maximum speed with the HeS 3b was 580 km/h (360mph). The theoretical estimated maximum speed was much higher, up to 700 km/h (435 mph), but the question of whether it could have been successfully achieved lingers. Service ceiling was 7000m and the effective range was some 200 km.
On its first test flight the engine ingested a bird which caused some minor internal engine damage, but the pilot managed to safely land the plane. Despite this incident this first test flight was considered a success. After several more test flights were accomplished, the first He 178 (V1) was placed in the air museum in Berlin, where it would eventually be destroyed in a 1943 bombing raid. Soon after, the assembly and production of the second plane was ready with some modifications, most importantly larger wings. The second prototype (V2) never flew, and it is not known if it was ever completely built. It’s fate is unknown.
Luftwaffe officials showed little interest in jet aircraft with fuselage mounted engines, due to the increased complications involved in their design and maintenance. Fuselage mounted engines required more rigorous technical inspections, presented production complications, and were overall seen as less efficient designs. Officials instead preferred fighter aircraft with wing mounted turbojet engines, such as the later Me 262 and He 280. In the end the He 178 project as a fighter aircraft was abandoned.
The first airframe was designated V1, with the second unfinished airframe with larger wings designated the V2.
He 178 V1 – Experimental jet-aircraft
He 178 V2 – Second prototype jet-aircraft
Heinkel He 178 Specifications
23 ft 7 in / 7.2 m
24 ft 6 in / 7.48 m
6 ft 10 in / 2.1 m
86.04 ft² / 7.9 m²
One HeS 3b centrifugal-flow turbojet
3,572 lb / 1,620 kg
Maximum Takeoff Weight
4,405 lb / 1,998 kg
360 mph / 580 kmh
Estimated (theoretical) maximum possible speed up to 435 mph / 700 km/h
The Breda Ba.65 was an Italian ground attack plane that first saw action during the Spanish Civil War of the late 1930’s. It was built in both single and two seat configurations, and was exported to various nations during the buildup to the Second World War, but only saw active combat with the Regia Aeronautica in Northern Africa.
According to Italian Colonel Amadeo Mecozzi, a WWI veteran fighter ace, the best use of aerial forces was the fast neutralization of military targets rather than unnecessarily wasting resources by attacking civilians or civil industry.He placed a big emphasis on the development of attack aircraft that could perform several different roles. Per his request, the major Italian aircraft manufacturers were to present their proposed planes that would be used by the Regia Aeronautica (Italian Air Force) in the future.
Two aircraft were selected to test the Mecozzi concept. The Caproni A.P. 1 and Breda Ba.64, which were both ready for use in 1933-34. Both of these monoplanes were relatively modern in appearance. The low performance of the Caproni A.P. 1 in the Spanish Civil War led to withdrawal from the front line, with some 54 – 57 being produced.
The Ba.64 prototype was powered by a Bristol Pegasus radial engine, license-built by Alfa Romeo, but was later replaced by a better new Alfa Romeo 125 RC35 engine with 650 hp. It was armed with four 7.7mm Breda-SAFAT guns in the wings and the bomb load was around 500-550kg. But despite the stronger engine the speed was low for an fighter or an attack aircraft (350km/h). A few were tested in the Spanish Civil War in 1938 but flight performance was disappointing and it was removed from service and replaced with the Ba.65.
The Ba.65 made its first flights in September of 1935. It was designed to be a multi-role aircraft as a light bomber/attack aircraft, reconnaissance, and interceptor aircraft. Ba.65 was a cantilever low-wing monoplane with the main landing gear units retracting rearwards into the underwing fairings. The materials used on the Ba.65 was the chrome-molybdenum steel alloy tubing, covered overall with duralumin sheet, except for some parts of the wing’s trailing edges which were fabric-covered.
The engine used on the prototype was the French Gnome-Rhone K-14 700 hp (522 kW) or 900hp according to some sources. The same engine would be used to equip the first production series of some 81 aircraft. The remaining planes would be built with one 1,000hp (746 kW) Fiat A.80 RC.41 18-cylinder radial piston engine. Maximum speed with the stronger engine was 267 mph (430 km/h) with the effective range of some 342 mi (550 km) and a service ceiling up to 20,700 ft (6,300 m).
The main armament was two 12.7mm Breda-SAFAT heavy machine guns and two 7.7mm Breda-SAFAT machine guns. All were placed in the wings plus a bomb load of around 500kg, with 300kg in the fuselage bomb-bay and 200kg more on the underwing racks. Theoretically it could carry around 1,000kg of bombs, but after some heavy load tests, the result was unsatisfactory and disappointing. The pilot claimed that the plane was impossible to fly with this heavy load. So as a result of this, the weight of the payload was limited to around 500 kg. This improved the flight performance but also reduced the offensive strength and the combat potential of the Ba.65.
Besides the single-seat, a new two-seat version, the Ba.65bis had been developed mostly for export orders and for training and use by the Regia Aeronautica. Besides the pilot, a rear observer/gunner, who used the rear 7.7 machine gun, was positioned in an open cockpit above the trailing edge of the wing. Small numbers were built with a new hydraulically operated Breda L dorsal turret mounting a 12.7mm Breda-SAFAT machine gun, but it was used mostly for export.
First combat action conducted by this aircraft was in the Spanish Civil War from 1936-1939. 13 single-seat aircraft, equipped with Gnome-Rhone engine, were sent by the Italians in order to support the fascist forces. They were attached to the 65a Squadriglia Aviazione Legionaria. The Ba.65 saw heavy action in several battles during the Spanish Civil War such as the Battles of Santander, Teruel and River Ebro. Squadriglia Legionaria was reinforced with 10 new aircraft in 1938, 6 with Fiat engines, and 4 with the older Gnome-Rhone engine. Depending on the source, around 10-12 Ba.65’s survived the Civil War, and were all given to the new fascist regime. The experiences gained during the battles of the Spanish Civil War, had shown that the Ba.65 was capable only in the role of the attack aircraft, a role in which they would serve until the end of the North African Campaign.
By the start of WWII, most if not all Ba.65’s, were involved in the battle for North Africa against the British forces stationed there. The Ba.65 was not used in any other front during the war. Most of the Ba.65’s in Africa were the two-seat versions, with a relatively small number of aircraft equipped with the Breda L turret. Due to difficulty of the desert conditions, low performance and superiority of the enemy’s fighters heavy losses were suffered and almost all Ba.65’s were lost by the end of 1941. Some of the last Italian Ba.65’s were abandoned at Benghazi airfield and were captured by the British on the December of 1941. Few if any survived by the beginning of 1942. Surviving pilots were transferred either to fighter squadrons or to dive-bombing units equipped with German Ju-87B.
Due to the lack of technical capabilities to improve the flying performance of this aircraft and the failing of the Ba.88 aircraft project, Italy was left with no adequate and contemporary attack aircraft, forcing them to use the older Fiat C.R.32, some modified SM.79s, German Ju-87 and later some modified fighter planes for this role.
In addition to the combat units, several B.65 were flown for a short time in flight schools. They were utilized alongside several Ba.64 and A,P.1 to train pilots for attacking and bombing operations.
They were used by Iraq, in the Anglo–Iraqi War during May 1941. All Iraqi Ba.65’s were stationed near Baghdad in the 5thSquadron and saw some limited action against British positions and airfields. Despite some military aid from Germany and Italy, the Iraqis failed to drive the British out, who were set to invade Iraq. On the 31st of May, an armistice was signed ending the Iraqi revolt.
Production and modifications
Production of this aircraft began in 1936, running several production series. First was in 1936 with 81 aircraft produced with the 700 kW engine. The second series ended in July 1939 with a total of 137 aircraft produced, 80 by Breda and 57 by Caproni-Vizzola, equipped with the Fiat A.80 engine. Total production run was 215 operational aircraft. Of the total produced, 55 were sold to Iraq, Chile and Portugal. Few modifications to the original aircraft were ever made:
Ba.65 – Single-seat version
Ba.65 – Two-seat trainers version
Ba.65 bis – Two-seat attack aircraft version (some equipped with a rear gun turret)
Italy – Utilized mostly the two-seat version and a few with the Breda L turret.
Iraq – Bought around 25 Ba.65 two-seaters aircraft in 1938. Next to two dual-control trainers, the rest were equipped with the Breda L turret. They were used in limited combat against British in 1941.
Chile – Bought 17 single-seaters, with Piaggio PXI C.40 engine, in 1938, and 3 dual-control trainers.
Portugal – In November 1939 had acquired 10 Fiat engined two-seat versions with the Breda L turret.
China –Planned to acquire some Ba.65, but no deliveries were made.
Fascist Spain – Used all surviving Ba.65s left by the Italians after the end of the Civil War.
Fighter Bomber and Reconnaissance – 155 Built
The Breda Ba.88 Lince, Italian for Lynx, saw service with the Reggia Aeronautica during the early days of WWII. The Lince prototype was initially touted as a propaganda tool for fascist Italy with its bona fide world records for airspeed. However it’s eventual service life was cut short by drastic performance problems by the time the weight of military armaments, eventually earning it a popular reputation as one of the worst aircraft failures of all time.
On January 20th of 1936, the Italian Air Force (Reggia Aeronautica) put in a request to all Italian aviation companies for a new multi-purpose twin-engine aircraft. The new aircraft’s specification is that it should be capable of achieving a top speed of least 300 mph (470 km/h), have a service ceiling of 20,000 ft (6000 m), a flight range of 1,250 mi (2000 km), and good takeoff and landing characteristics. The armament was to consist of several 12.7 mm machine guns or a few 20mm cannons. Several companies responded to this request, with their suggestions. In the end the Breda Ba.88 aircraft was chosen.
Italian designers Antonio Parano and Giuseppe Panzeri had plans to make the Ba.88 a multi-purpose two-seat aircraft, which in essence meant that it would be suitable for long-range reconnaissance, bombing operations, and to serve as a heavy fighter aircraft similar to the German Messerschmitt Bf 110.
The Ba.88 was a twin engine all-metal high-wing monoplane. The engines on the prototype were two 900 hp (671 kW) Gnome-Rhone K-14 radials. It had a retractable tailwheel landing gear. The prototype at first had a single vertical tail assembly but it was later changed to a new modified tail unit with twin fins and rudders.
The Ba.88 prototype, designated MM 302, had its first test flight in October 1936. The first test pilot was Furio Niclot Doglio, Breda’s main test pilot. In February 1937 the Ba.88 prototype was sent to the Guidonia for more army flight tests. In April 1937 two new speed over distance world records were achieved, with average speed of 321 mph (517km/h) over 62 miles (100km) and the second of 295 mph (475km/h) over a distance of 621 mi (1000km). These records were set by Furio Niclot Doglio. Later that year he reached a top speed of 325.6 mph (524 km/h) and 344.2 mph (554km/h). The results of these test flights were more than satisfactory, and often used by the Italian fascist regime for propaganda purposes. But this string of successes did not last for long.
With the installation of military equipment and weapon armament the performance and flight characteristics fell off dramatically, which affected the operational efficiency and history of this Lince. Top speed achieved with the full military equipment and armament was much lower than that on the test flights. This gave rise to a question of its use in the role of a fighter aircraft. Italian army test pilots expressed concern over its flight characteristics, since even the simple maneuvers were hard to achieve. In order to try to fix some of these issues, a number of weight saving modification were done, such as reducing the main armament and installing two new 1000 hp Piaggio engines. Later during the war, even the rear gun position was removed in order to save weight. But these problems would be never solved completely. Despite this an order was placed for 88 new Ba.88 aircraft.
The Ba.88 production model was powered by two 1000hp (746 kW) Piaggio P.XI RC.40 14-cylinder radial piston engines. Maximum top speed with the new engines was 304 mph (490 km/h), effective range was 1000 mi (1640 km) and the service ceiling was up to 26,000 ft (8000m).
The main armament consisted of three 12.7mm Breda-SAFAT heavy machine guns plus one 7.7mm machine gun also Breda-SAFAT type, used by the rear gunner. Total bomb load was around 2,200 lbs (1000kg), in the fuselage bomb-bay or three 200kg bombs carried semi-exposed in individual recesses in the lower fuselage.
After the German attack on the Allies in France in May 1940, Italy also declared war on the Allies on 16 June 1940 and started to attack the French positions to the south. The Lince saw its first combat actions during those operations. Some 12 planes from the Regia Aeronautica 19° Gruppo Autonomo (independent group) made several bombing attacks raids on airfields in Corsica. A few days later a group of nine Ba.88 planes made a new bombing raid. But after the end of the Battle of France, Italian combat analysis of this air attacks had led to the conclusion that the Ba.88 aircraft had only limited value as a effective operational aircraft.
The next combat use of the Ba.88 was in North Africa. The Linces of the 7° Gruppo Autonomo were used in Libya against the British forces. Although they were equipped with special sand filters, the engines overheated and failed to deliver their designed power. Many planned attacks, such as the one on targets at Sidi Barrani in September 1940, had to be aborted. The Ba.88 aircraft had failed to gain sufficient altitude or even maintain formation, but the biggest problem was the inability to reach the speed that the manufacturers claimed it had.
Because of these problems, most if not all surviving Linces were been stripped of all useful equipment and armament and were scattered around major airfields mostly to act as decoys for British attacks. Ironically at that time, a further two batches of new Ba.88s were being delivered. Some 19 from Breda and 48 examples from IMAM were mostly sent straight to the scrapyard.
But the story of the Ba.88 does not end there. Three or more Ba.88 examples were modified by the Agusta aircraft plant in 1942 to be used as a improved ground-attack aircraft. Sources are not precise of how many were modified, the number of modified aircraft ranges from 3 to 14. The modification included increasing the wingspan by 6.5 feet (2m) in the hopes of alleviating wing loading problems. Two new Fiat A.74s engines were installed and the armament was increased up to four 12.7mm machine guns and dive brakes were installed. This modified Ba.88, now called the Ba.88M, were delivered and used by the 103° Gruppo Autonomo Tuffatori (independent dive-bombing group) stationed at Lonate Pozzolo on 7 September 1943. They were also used and tested by Luftwaffe pilots. Their fate is not known.
The Breda Ba.88 has a popular reputation as the “worst operational aircraft.” This is in part due to the vast difference in performance from the sleek and advanced-for-the-time prototype that was able to set world speed records, until production aircraft fitted with the weight of wartime armament drastically hampering the plane’s flight characteristics as previously mentioned. However it should be noted that by most accounts there are no prominent records of catastrophic structural failure, crashes, accidents, or combat losses. Perhaps the primary reason for this reputation is how quickly the aircraft’s operational service life was dispensed with, the marked difference in the performance of the prototype versus the fully outfitted wartime production model, and the premature relegation to the scrapyard or the duty of airfield decoy.
Production of initial production run of the Lince started in May of 1939 and ended in October of that same year. The first batch of some 80 aircraft, plus eight dual-control trainers were built by Breda. Later, by the second half of the 1940 some 67 more examples were built in small batches, 19 by Breda and 48 by IMAM. In the end total production was 155 aircraft plus the initial prototype.
Ba.88 Prototype – Initial prototype, set several world speed records, 1 built
Ba.88 Lince – Main production model, 155 built
Ba.88Trainer – Dual-control trainers, 8 built
Ba.88M – Three modified aircraft in order to improve flight performance
Breda Ba.88 Lince Specifications
51 ft 3 in / 15.6 m
35 ft 4 in / 10.79 m
10 ft 2 in / 3.1 m
358.8 ft² / 33.3 m²
Two 1000 hp (746 kW) Piaggio P.XI RC.40 14-cylinder radial piston engines.
10,250 lb / 4,650 kg
Maximum Takeoff Weight
14,900 lb / 6,750 kg
419 U.S. Gal / 1,586 L
9,843 ft / 3,000 m in 7 minutes & 30 seconds
304 mph / 490 km/h
1,000 mi / 1,640 km
Maximum Service Ceiling
26,250 ft / 8,000 m
1 pilot & 1 rear gunner
Three nose mounted 12.7mm Breda-SAFAT heavy machine guns
The Ikarus IK-2 was the first all metal, high wing monoplane fighter built designed and built in Yugoslavia, for the Royal Yugoslavian Air Force. The transition from biplane to monoplane gives this high-wing fighter a distinctive appearance, not unlike a gull in flight. The Ikarus’ powerful engine and impressive armament paved the way for Yugoslavia’s later advanced monoplane, the IK-3. Its performance in key areas gave it an advantage over the Hawker Fury. The IK-2 saw combat against Germany’s advances in the early 1940’s.
At the beginning of the 1930s, the Yugoslav Air Force was mainly equipped with the old (Czech) Avia BH-33 biplane fighters built by “Ikarus” under license. During the second half of the thirties and early forties the company “Ikarus” designed and later produced the first Yugoslav all-metal, high wing, monoplane fighter aircraft named IK-2. The IK-2 was constructed by a team led by engineers Ljubomir Ilić and Kosta Sivčevićem.
The first prototype was named IK-1L. The capital “I” is for Ilić “K” for Kosta, the “L” was for fighter, Ловац-Serb. (on some sources it was mark as IK-L1) The prototype was completed in 1934, and was ready for its first flight testing by April 1935. It had a Hispano-Suiza 860 hp engine, and it was planned be armed with a 20mm cannon, and two Darn type machine guns caliber 7.7mm.
The wing was braced with two struts on each side of the fuselage, the fixed and conventional landing gear was spatted and mounted off the wing struts. The half glazed cockpit was located behind the wing. The horizontal stabilizer on each side was braced from below with two rigid braces from the lower tailcone, and tied from above with two flying wires from the vertical stabilizer.
IK-1L had a difficult start, due to a disagreement between the manufacturer and military top brass, but also by individual pilots like Captain Leonid Bajdak who was a great supporter of biplane aircraft. Unfortunate for the constructors a decision was made, that Leonid Bajdak would be the first test pilot for the IK-1L to determine if the plane had the potential for further development and eventual production. The first test flight was conducted on 22 April 1935 at Zemun airfield near Belgrade. In these tests, which were scheduled for several days, a light fuel load was used and the plane was not equipped with any weapons.
The following day, Bajdak put the IK-1L into several aerobatic maneuvers, and at that time there were no major problems. But during the third test flight there was an accident in which Bajdak made several unplanned aerobatics and in one of them he failed to cope with the loss of power and was forced to bail out with a parachute, while the IK-1 crashed to the ground. Although he insisted the plane was unsuitable as a fighter plane, a detailed analysis of the incident revealed that the accident was a consequence of poor build quality. Despite the opposition of some pilots, including Bajka, Ikarus company decided to build a second prototype with more reinforced wings construction and with much better assembly.
Second prototype got the name IK-02 (or simply IK-2 depending on the source) and it took about ten months to be built and was completed in June 1936. The main difference from the IK-1L was that the IK-02 had wings covered with metal sheeting, leaving only the rear fuselage and tailplane fabric covered. Other changes were a radiator of reduced size and improved shape, and modified air intakes, making for a more streamlined fuselage. This prototype was armed with one 20mm cannon, and two machine guns mounted above the engine. Machine guns were initially Darn type caliber 7,7mm but were replaced with the new Browning 7,92mm.
After several tests flights, there were some minor changes, like the new improved cockpit layout. IK-02 also participated in several mock (16 to some sources) dogfights against Hawker Fury biplane which was already part of the Yugoslav Air Force. In this mock dogfights IK-2 showed complete superiority in all respects over the biplane.
The interesting fact during this tests flights, there was a fierce discussion between two pilots of the “old school” Captain Leonid Bajdak and the new test pilot 1st Lieutenant Janko Dobnikar, that resulted in a “fly duel”, IK-02 vs. the Hawker Fury. The conditions of the duel were:
Taking off and climbing up to 4000m above sea level, at Zumen Airfield,
Race on the route Belgrade-Novi Sad-Belgrade (some 140 km)
A mock dogfight above Belgrade.
The first two rounds were easy victory for the IK-02. The final round was a spectacular aerial battle over the Capital Belgrade. Despite his experience, Bajdak simply could not put his Fury in position behind the IK-02, while Dobnikar once was in position of the Fury, he kept on his nose until the end. Bajdak had to end the fight and acknowledge defeat.
Unfortunately the fate of this plane was similar to the first one. It was lost in an air accident during June of 1940 when flying in bad weather and hit by lighting. The pilot managed to save himself with the parachute, but the plane was lost.
Since additional testing and postponing the start of production took a lot of time, only a small batch of 12 aircraft were built until 1939 six were delivered in December 1938 and six more in February 1939 by the Ikarus. But while still in series production this plane was obsolete, and the planned later production was dropped, but nevertheless they saw some use in the April war German invasion of Yugoslavia 6th -18th April 1941.
Before the start of the German attack on the April 6th 1941, all available IK-2 fighters were located in the 2nd mixed Air Brigade, which consisted of the 4th Fighter Regiment and the 8th Bomber Regiment in total 20 Hurricanes, 8 IK-2s and 23 Blenheims were based in Bosanski Aleksandrovac, Bosnia. The primary mission of The 2nd mixed Air Brigade was to defend the territory of Croatia, Bosnia and Slovenia from possible enemy attacks and to provide fighter support for the 8th Bomber Regiment.
On the first day of the war, The 2nd MAB only carried out scouting missions in the direction of Austria and there were few encounters with enemy planes without losses on either side. During the following days, performing their primary task, the 4th Fighter Regiment tried to stop a German air attack on the airport of Rovina near Banja Luka, at which the 8th Bomber Regiment was based. Some eight Hurricanes and six IK-2sattacked a group of 27 German Me-109s. Although it seemed that they did not have any chance, thanks to the knowledge of the hilly terrain and the cloudy weather they managed to surprise the German fighters. In the battle that followed, three Yugoslav and two German fighter planes were shot down. For this air battle, we could say that the Yugoslav fighter emerged as winners, because the primary goal of airport security and safety of the 8th Bomber Regiment was achieved.
The same day, these bombers were sent on to carry out bombing runs on the enemy territory of Hungary. Of 13 planes that had left the airport without the support of the fighters only 4 survived.
On April 9th, the Germans launched new air attacks on the 8th Bomber Regiment Aerodrome. At first only one IK-2 intercepted German aircraft. The lone IK-2 managed to get out of the fight with no damage. Soon almost all available Yugoslav fighters joined the battle Six IK-2s and eight Hurricanes in total 14 Yugoslav vs. 27 German aircraft. The battle was somewhat chaotic, Yugoslav fighters attacked individually or in pairs, while the Germans attacked larger groups. The battle lasted around 10 minutes, as the Me-109s were running out of fuel, they left the battle. Yugoslav losses were two Hurricanes and one IK-2. German losses are unknown, but it is estimated they sustained one or two losses.
After the 9th of April, because of the bad weather, there were very few flights. In the days that followed the 4th Fighter Regiment shot down one more German plane, a Ju-88. As German ground forces approached the airport on April 14 all planes were destroyed by the ground crew.
At the end of the April War, the Germans allocated three IK-2s to the Independent State of Croatia “NDH”. In order to equip existing aircraft with spare parts and fuel, and thus extend their operative use, Croatian Air Forces with German approval tried to collect as many military materials from airports and factories located in Serbia.
IK-2s were stationed in the 6th Air Group in Sarajevo by the end of 1941. Participation of these planes in the war was limited. By the 1944 they were removed from operational use, because of the lack of any spare parts, their final fate remains unknown.
Kingdom of Yugoslavia (Kraljevina Jugoslavija) – Eight were used during the April War.
Independent State of Croatia NDH (Nezavisna država Hrvatska) – Used few planes supplied by the Germans, their service was limited.
37 ft 5 in / 11.4 m
25 ft 10 in / 7.8 m
12 ft 7 in / 3.84 m
190 ft² / 18 m²
One Hispano-Suiza liquid-cooled V-12 piston engine 860 hp (640 kW).
Maximum Takeoff Weight
4,094 lb / 1857 kg
3,311 lb / 1502 kg
16,000 ft / 5,000 m in 5’ 25’’ minutes
270 mph / 435 km/h
155 mph / 250 km/h
435 mi / 700 km
Maximum Service Ceiling
39,370ft / 12,000m
One 20mm cannon Hispano-Suiza HS.404 – fixed forward-firing cannon in an engine installation.
Two 7.92 mm Browning/FN machine guns with 250 rounds per gun.
Kratka istorija vazduhoplovstva u Srbiji, Čedomir Janić i Ognjan petrović, Beograd 2011.
Elitni vidovi jugoslovenske vojske u Aprilskom ratu. Dušan Babac.
Zrakoplovstvo nezavisne države Hrvatske 1941-1945, Vojislav V. Mikić, Target Beograd 2000,
Lovačka Avijacija 1914-1945. Zlatko Rendulić, TEOVID Beograd 2014,