Category Archives: WW2

World War 2 saw the airplane rise to even greater importance than in the first World War. Air superiority became a crucial component of battlefield operations and air forces were massively expanded during the conflict.The Allied and Axis sides of the war developed enormous war machines, capable of developing and rolling out unprecedented numbers of advanced new military equipment in rapid response to changing conditions on the battlefield, as well keeping up with the technological advances of adversaries.

High altitude bombing raids and night fighting were hallmarks of the War for Europe, whilst aircraft carrier battles pitched the American and Japanese fleets against one another. The technology of the day was pushed to it’s limit with the use of superchargers in aircraft engines, the introduction of radar, and the rapid development of the jet engine by the war’s end.

The period ended as the Nuclear Age and subsequent Cold War were ushered in by the tremendous and tragic blows to Japan’s wearied people.

Messerschmitt Me 163S Habicht

Nazi flag Nazi Germany (1945)
Rocket Interceptor Trainer – 1 Built

A rear 3/4 view of the Soviet captured “White 94” Me 163S. Colorization by Michael Jucan [Yefim Gordon]
The Messerschmitt Me 163S (Schulflugzeug / Training Aircraft) Habicht (Hawk) was an unarmed two-seat training glider based off of the famous Messerschmitt Me 163 Komet. Originally designed for the purpose of training novice pilots for landing, the Habicht ultimately never saw active service with the Germans and only a single example was produced through the conversion of a serial Me 163B-1. With the sole example captured by the Russians after the war, the Habicht underwent extensive testing by the Soviet Air Force which helped them understand the flying characteristics of the Komet and prepared Soviet pilots for flying the powered Komets. The Habicht undoubtedly played a part in helping Soviet engineers understand the Komet and thus played a part in the future development of Soviet rocket aircraft.

History

A closeup view of the Me 163S showing the right wing. [Yefim Gordon]
The Messerschmitt Me 163 Komet was one of Nazi Germany’s most famous aircraft produced during the Second World War. Although bearing the title of the world’s first mass-produced rocket-powered interceptor, the Komet did have its fair share of flaws, such as the volatile and sometimes dangerous Walter HWK 109-509 rocket engine, which prevented it from becoming an effective weapon against the Allies.

As the Komet was designed to have a limited amount of fuel to engage Allied bombers, pilots were expected to glide the Komet back to friendly airfields once they disengaged from combat. With gliding landings as a potential problem for the less experienced pilots, one of the ideas proposed by Messerschmitt designers in 1944 was to introduce a dedicated trainer variant of the Komet which would have a student pilot accompanied by an instructor pilot. Designated as the Messerschmitt Me 163S (Schulflugzeug / Training Aircraft) Habicht, the trainer glider differed from the production model with the addition of an instructor’s cockpit behind the forward cockpit. This addition was accompanied by the removal of the Walter HWK 109-509 rocket engine and the Habicht would have to be towed by another aircraft in order to get airborne. Another interesting addition to the Habicht was a second liquid tank behind the instructor’s cockpit for counterbalancing. All the liquid tanks would be filled with water for weight simulation and ballast. A total of twelve examples were planned for production, but only one was produced due to wartime production constraints.

The sole example of the Habicht was built by converting an earlier Me 163B-1 production model. Due to the scarcity of information regarding the Me 163S, it is unknown exactly when the Habicht was produced and what sort of testing it may have undergone during German possession. However, it is known that the Soviet Union was able to capture the only example during the final stages of the World War II’s Eastern Front. The sole Habicht was sent to the Soviet Union along with three Me 163B Komets during the Summer of 1945 for thorough inspection and testing. In historian Yefim Gordon’s book “Soviet Rocket Fighters – Red Star Volume 30”, he claims that in addition to the three Komets, seven Habicht trainer models were also captured. This, however, remains quite dubious as there is no evidence that more than one Habicht existed, and all current photographic material, research materials, and books all suggest that only a single example was produced.

The Me 163S in simulated flight configuration aided by struts. [Yefim Gordon]
As the Soviets were particularly interested in rocket propulsion aircraft, the State Defence Committee issued a resolution which called for the thorough examination of the Walter 109-509 jet engine and the Me 163 Komet along with captured German documents on rocket propulsion. The three Me 163B Komets, of which only one was airworthy, and the Me 163S Habicht were sent to the Flight Research Institute (LII), the Valeriy P. Chkalov Soviet Air Force State Research Institute (GK NII VSS), and the Central Aerohydrodynamic Institute (TsAGI). The Habicht and Komets saw extensive testing in Soviet hands, undergoing several structural, static and wind tunnel tests. During the initial flight testing period, the Komet only flew as a glider as Soviet pilots and engineers were unsure of whether or not the Walter rocket engine was ready for use since bench tests were not completed. Securing the T-Stoff and C-Stoff propellants for the rocket engine was also a problem. In order to understand the handling characteristics of the Komet, the Habicht was flown numerous times at different altitudes, as was the unpowered Komet. A Tupolev Tu-2 bomber was responsible for towing the Habicht to these altitudes. Under Soviet ownership, the Habicht was given the nickname of “Карась” (Karas / Crucian Carp) due to the glider’s distinct silhouette. The test pilot responsible for flying the Habicht was Mark Lazarevich Gallaj. In general, the Habicht was considered relatively easy to handle by the Soviet test pilots. It is unknown how many test flights the Habicht underwent, but the aircraft certainly aided Soviet pilots in understanding the handling characteristics of the Komet. The Habicht’s service came to an end once the Soviet state trials of the Komet concluded. The sole example was scrapped sometime in 1946, along with seemingly all the other Komets.

If the Me 163S was able to be mass produced and flown with the Luftwaffe, the aircraft would have been a valuable tool to train German pilots. Landing the Komet was a problem for some pilots and in some cases resulted in fatalities but, with the use of the Habicht, the number of accidents would have certainly decreased.

Design

The Me 163S hung upside down in an unspecified TsAGI workshop for static testing. [Yefim Gordon]
The Messerschmitt Me 163S Habicht was a semi-monocoque aluminum based two-seat training glider developed off the standard tailless Messerschmitt Me 163B-1 Komet. The sole example was converted from a production Komet, which meant dramatic modifications had to be made to the aircraft. The Walther HWK 109-509 rocket engine was removed and in its place was a cockpit for an instructor. The fuel tanks in the airframe were all filled with water to simulate fuel weight while another water tank was added behind the instructor’s cockpit for ballast purposes. There was no armament fitted to the glider. There was a small transparent section between the student pilot’s cockpit and the instructor pilot’s cockpit, presumably for the purpose of communication. As there are no known German documents on the Habicht and Russian documents are scarce, not much is known on the other differences the Habicht may have had. Detailed specifications of the Habicht are unknown, but theoretically it should have been identical to the standard Me 163B-1 Komet except for possibly weight, air drag and center of gravity.

Operators

  • Nazi Germany – The intended operator and producer of the Me 163S Habicht.
  • Soviet Union – The main operator of the Me 163S Habicht. A single Habicht was captured and tested by the Soviets after the war. The Habicht was scrapped in 1946.

*Editor’s note: As noted above, the exact specifications of the Me 163S Habicht are unknown. However they are presumed to be similar to that of the Me 163B-1 Komet.

Gallery

Illustrations by Haryo Panji https://www.deviantart.com/haryopanji

Me 163S Habicht “White 94” in Russian Service [Haryo Panji]
Me 163S Habicht in German Service [Haryo Panji]
 

 

Now known as the “White 94”, the Me 163S sits idly by. [Yefim Gordon]
A closeup view of the Me 163S showing the transparent section between the two cockpits. [Yefim Gordon]
The Me 163S in simulated flight configuration aided by struts. [Yefim Gordon]
A top down view of the “White 94” Me 163S. [Yefim Gordon]
A photo of the “White 94” Me 163S in flight being towed by a presumed Tupolev Tu-2. The pilot in the photo is likely Mark L. Gallaj. [Yefim Gordon]
The Me 163S inside TsAGI’s T-101 wind tunnel for testing. The struts support the Habicht and simulate its flight configuration. [Yefim Gordon]
An alternate closeup view of the Me 163S during static tests. [Yefim Gordon]

Yet another inverted static test, but this time the tail wheel strut and tire were removed from the Me 163S. [Yefim Gordon]

Sources

Akaflieg Berlin B9

Nazi flag Nazi Germany (1942)
Experimental Aircraft – 1 Prototype Built

Three-quarters view of the B9, note the large glazed cockpit. Colorized by Michael Jucan [airwar.ru]
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.

History

The SF 17 prone glider was the forerunner of the B9 powered aircraft [Akaflieg Stuttgart]
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 Design

Front view of the B9 [airwar]
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.

Operational Testing

The B9 in flight [airwar]
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.

Akaflieg Berlin B9 Specifications

Wingspan 30 ft 10 in / 9.4 m
Length 19 ft 8 in / 6 m
Height 7 ft 7 in / 2.3 m
Wing Area 128 sq ft / 11.9 m²
Engine Two Hirt HM 500 engines, with 105 hp each
Empty Weight 2,207 lbs / 940 kg
Maximum Takeoff Weight 2,458 lbs / 1,115 kg
Fuel Capacity 95 l
Maximum Speed 140 mph / 225 km/h
Range 250 mi / 400 km
Maximum Service Ceiling 13,000 ft / 4.000 m
Climb to 13,125 ft / 4,000 m 4 minutes and 12 seconds
Crew One pilot
Armament None

Gallery

Illustrations by Haryo Panji https://www.deviantart.com/haryopanji

 

Akaflieg Berlin B9 – Prototype [Haryo Panji]
B9 drawings [airwar]

Sources

Ikarus MM-2

Yugoslavia flag Yugoslavia (1939)
Prototype Advanced Trainer – 1 Built

The MM-2 prototype had an unusual color scheme with a combination of red and polished aluminum.

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.

First Steps

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.

The designer of the MM-2 trainer, Captain Dragutin Milošević.

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.

The only MM-2 prototype during its construction by Ikarus.

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.

Technical Characteristics

Captain Dragutin Milošević’s first drawing of the MM-2. Note that the engine nose design appears to be for an inline engine, different from the actual prototype.

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

MM-2 Side View

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.

Operational Service

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.

On the May 13 1942 pilot Vid Saić, he lost control of the aircraft and crashed due to inexperience. The MM-2 was deemed too complicated and expensive to repair.

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.

Production

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.

Operators

  • 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.

MM-2 Specifications

Wingspan 30 ft 6 in / 9.23 m
Length 23 ft 7 in / 7.20 m
Height 9 ft 6 in / 2.89 m
Wing Area 14.6 ft² / 13.60 m²
Engine One Gnome-Rhone K-7, 309 kW (420 hp) air-cooled 7-cylinder engine
Empty Weight 1,071 lbs / 894 kg
Maximum Takeoff Weight 2,290 lbs / 1,330 kg
Fuel Capacity 150-160 l
Maximum Speed 250 mph / 400 km/h
Cruising Speed 390 mph / 630 km/h
Range 475 mi / 764 km
Maximum (estimated) Service Ceiling 6,600 ft / 2,000 m
Climb speed Climb to 2,000 m in 3 minutes and 9 seconds
Crew Two, instructor and student pilot
Armament
  • Two Darn M30 7.7 mm machine guns in wings
  • Total bomb load around 40 kg.

Gallery

Illustration by Haryo Panji https://www.deviantart.com/haryopanji

Ikarus MM-2 Side View [Haryo Panji]
MM-2 Front View
MM-2 Rear View

Sources

Hütter Hü 136 Stubo

Nazi flag Nazi Germany (1938)
Armored Ground Attack Aircraft – 1 Replica Built

Stubo I Replica [aviationmuseum.eu]
The Hütter 136 was an interesting concept for a ground attack aircraft that employed numerous experimentations in its design. The cockpit was fully armored, the landing gear was replaced by a skid, and the entire propeller would be jettisoned off during landings. The aircraft came in two forms: the Stubo I, a short design with the ability to carry an external 500 kg bomb, and the Stubo II, a lengthened version that could carry two internal 500 kg bombs. The program never progressed as far as production and work stopped on the project shortly after the Henschel Hs 129 was ordered for production.

History

Artist’s Impression of the Stubo I [Heinz Rodes]
During the years leading up to the Second World War, Nazi Germany found itself needing a competent air force to rival those it would soon face. Restrictions set by the Treaty of Versailles severely hindered the German military both in size and equipment in order to ensure that German power would not threaten the continent again, as it did during the First World War. History notes that the Germans broke this treaty, at first covertly and then overtly, with the Allies showing no response or protestation to the blatant violations. Germany began amassing a massive military force in preparation for war. New programs and requirements were laid down in preparation for the inevitable war. These projects included many newly tested concepts, such as dive-bombing. The Junkers Ju-87 Stuka proved the effectiveness of dive bombing in the Spanish-Civil War, with a famous example being the Bombing of Guernica, but a newer attacker was eventually needed to complement it. An order in 1938 was put out by the Reichsluftfahrtministerium (Aviation Ministry, “RLM”) to develop a new armored ground-attacker. One of the companies that would participate in this requirement would be Hütter.

2-way and cutaway of the Stubo II

The designs of Ulrich and Wolfgang Hütter are relatively unheard of when it comes to aircraft. They began their aviation career designing glider aircraft in the 1930s, such as the popular Hü 17, some of which were used post-war. The Hütter brothers built a career in designing aircraft for the Luftwaffe (German Air Force) between 1938 and 1944 under the codename of Ostmark. The two began working on the project mentioned before for an RLM request for a new ground-attacker in 1938. The requirement laid down very specific guidelines to be followed. The new aircraft needed to have good flight performance and an armored airframe for extra protection, as well as enough speed to evade fighters. In preparation for the new designs, the RLM notified designated factories that would begin to produce these airframes upon adoption into service. The Hütter brother’s response would be the Hü 136. Other competitors included the Henschel Hs 129 and the Focke-Wulf Fw 189V-1b, an armored ground attack version of their reconnaissance plane. Not all projects for a new attacker were armored at this time. Other new designs included the Junkers Ju 187 and Henschel Hs P 87.

The Hütter Hü 136 was nicknamed the Stubo, a shortened version of the name Sturzbomber (Dive Bomber). The aircraft itself would be a single-engine design. Two versions of this aircraft existed. The first, Stubo I, was meant to fill the need for a heavily armored attacker and would be used in ground-attack and dive-bombing tactics. The second was the Stubo II, a two-seater which was essentially a longer version of the Stubo I and carried twice the bomb load internally. The flight performance of the Stubo II was estimated to be the same as that of the Stubo I although, given the design characteristics, that estimation is highly doubtful. The two designs did not meet the requirements for bomb load and range. To make the aircraft more efficient, the brothers took an interesting design change. Taking a note from their glider designs, they removed the conventional landing gear and replaced it with an extendable landing skid, which made the aircraft lighter and freed more space for fuel. This, however, posed serious designs problems. The Hü 136 now had to take off using a detachable landing gear dolly, similar to how the Messerschmitt Me 163B rocket plane would take off a couple years later. Due to this, the propeller would not have enough clearing and would hit the ground during landings. To fix this, the two brothers made the propeller detachable. During landings, the aircraft would eject the propeller, which would gently parachute to the ground above an airfield for recovery and reuse. To assist in landings, a new surface brake was also added to the aircraft.

2-way and cutaway of the Stubo I

The far more conventional Henschel Hs 129 would be designated the winner of the competition. Subsequently, no construction was ever started on either the Stubo I or II. The Stubo proved to be an interesting but flawed concept. The limited visibility from the armored cockpit would negatively affect the aircraft in all operations. Dogfighting, bombing and even flying in general would be affected by the cockpit’s design. The change in landing gear design may have extended the range and lowered weight, but pilots now had to learn how to land using a skid. The fact the entire propellor evacuated the aircraft was a huge issue in itself. Once ejected, the landing could not be aborted, and if the landing attempt failed, there was no chance to loop around and try again.

This, however, would not be the last project designed by the Hütter brothers for the Luftwaffe. Wolfgang would begin working on a long-range reconnaissance version of the Heinkel He 219 called the Hütter Hü 211. Another project is the rather unknown Hütter Fernzerstörer (Far Destroyer), a long-range turboprop attacker meant to be used on the Eastern Front. With the war ending, no further Hütter aircraft were designed. One would think the story of the Stubo ends with its cancellation, but the story continued rather surprisingly recently. The Military Aviation Museum in Virginia Beach, VA, acquired a full-scale replica of the Stubo I in 2017 and it is currently on display in their German Experimentals section, along with full-scale replicas of other “Luft 46” designs.

Design

The Stubo I was a single-engine armored ground attacker. In the front, it mounted a detachable propeller and a Daimler-Benz DB 601 inline engine. In the fuselage, a large gap was present between the engine and cockpit. This was most likely the fuel tank where the fuel tank was placed. Beneath the aircraft, a single 1010 Ibs bomb (500 kg) was mounted on an external hardpoint. This hardpoint most likely would be in the way of the landing skid, implying the payload had to be dropped before making an attempt at landing. For takeoff, a dolly would have to be mounted beneath the aircraft. This would be jettisoned shortly after the Stubo would be airborne. For landing, the aircraft would use an extendable skid. The wings of the aircraft had slight dihedral, which meant the wings were angled upward from the body. The Stubo I had an armored steel cockpit that was completely enclosed. For visibility, a small sight in the front and two side portholes were given. Had the aircraft been produced, peripheral vision would have been nonexistent and dogfighting would have been near impossible if it needed to defend itself. Normal operations, such as navigation and landing would have also been hindered, while combat operations such as target acquisition and attack run planning would have been exceedingly difficult. A tailfin was mounted directly behind the cockpit and not in a conventional tail design. Sources also mention the Stubo I would have mounted machine-guns, but the plans do not show exactly where or of what type these would have been.

Artist’s Impression of the Stubo II [Heinz Rodes]
The Stubo II was virtually identical to the Stubo I, aside from its extended fuselage. This lengthened design would allow the Stubo II to carry two 1010 Ibs (500 kg) bombs in a bomb bay, compared to the single bomb carried on a hardpoint by the Stubo I. Among smaller differences, the Stubo II’s wings had no dihedral compared to the angled dihedral of the Stubo I. With the lengthened fuselage, the landing skid was also extended to accommodate the longer airframe. It most likely also carried over the machine guns used on the Stubo I. The Stubo II uses nearly identical sized wings to the Stubo I, which gives the Stubo II a rather odd design, having the body lengthened but the wing size remaining the same. This would have definitely affected performance and possibly would have made the aircraft more unstable in maneuvering with the extra weight.

Variants

 

  • Stubo I – Armored ground-attacker that would carry a single external 500 kg bomb. Sources also mention machine guns, but documents don’t show where exactly they would have been located.
  • Stubo II – A lengthened version of the Stubo I, the Stubo II had an internal bomb load of two 500 kg bombs.

 

Operators

 

  • Nazi Germany – If the Hütter 136 would have entered production, Nazi Germany would have been the main operator of the craft.

Hütter 136 “Stubo I” Specifications

Wingspan 21 ft 4 in / 6.5 m
Length 23 ft 7 in / 7.2 m
Height (estimate) 5 ft 3 in / 1.6 m
Engine 1x 1,200 hp (894 kW) DB 601 Inline Engine
Loaded Weight 8,160 lbs / 3,700 kg
Maximum Speed 348 mph / 560 km/h
Range 1,240 mi / 2,000 km
Maximum Service Ceiling 31,170 ft / 9,500 m
Crew 1 pilot
Armament
  • 1x 1010 lbs (500 kg) bomb
  • At least 2 machine guns of unknown type (Most likely MG 15 or MG 17)

Gallery

Illustrations by Haryo Panji https://www.deviantart.com/haryopanji

Stubo I Side View [Haryo Panji]
Stubo II Side View [Haryo Panji]

Sources

Martin-Baker Tankbuster

UK Union Jack United Kingdom (1942)
Anti-Tank Aircraft Design – None Built

3D artist impression of the Tankbuster in flight [candymountain.jp]
The Martin-Baker Tankbuster was a concept British anti-tank aircraft that was designed according to an order in 1942 for a specialized ground attacker. The aircraft had a twin-boom, pusher design and was only armed with a 6-pounder (57mm) cannon, most likely a Molins M-Class Gun. Compared to its competitors, the Tankbuster was strictly limited to exactly what it was named for; busting tanks, and would find itself having trouble against other ground targets or even defending itself. With the program being canceled in early 1943 and Martin-Baker working on more important projects, all work stopped on developing the Tankbuster any further.

History

Drawing of the Martin-Baker Tankbuster [British Secret Projects]
In early 1942, the Royal Air Force began seeking a new ground-attack aircraft that would replace the 40mm-armed Hawker Hurricane Mk.IID. An order was officially placed on March 7th for a specialized ground attacker that would be used against a multitude of targets including ground units, enemy aircraft, transports/shipping, and a main focus on destroying tanks. To accomplish the destruction of the aforementioned targets, the aircraft was meant to use more heavier guns than the Hurricane Mk.IID. Alternative weapon arrangements included: three 40mm Vickers S cannons, four 20mm Hispano Mk.V cannons, a combination of two 20mm with two 40mm cannons, six unguided rocket (RP) racks with two 20mm cannons or one 47mm Vickers gun with two 20mm cannons. Two 500Ibs bombs could also be added. The expected speed for the design had to reach at least 280mph (450 km/h) at 3,000ft (900 m). Visibility was also a necessity and forward view had to be unobstructed and clear. Full production was to be expected by 1944. The programs would be overseen by the Air Staff.

Over 10 different designs by several aircraft companies were subsequently created for this program. A majority of them were of unorthodox design. Armstrong-Whitworth (AW.49) and Boulton-Paul (P.99) both created twin boom designs. Boulton-Paul also submitted a canard design labelled P.100 and a biplane design labelled P.101, the latter being seen as a safe alternative to the radical canard and twin boom designs prevalent through the program. Perhaps the most interesting of the designs was the submission by Martin-Baker.

3D artist impression of the Tankbuster [candymountain.jp]
At the time of its submission, Martin Baker had been working steadily on their MB.5 project, which would eventually become one of the best performing piston aircraft built by Britain, but this wouldn’t be completed until 1944. Their design for the ground attacker was submitted several months after the order was given by the Air Staff and was only named the “Tankbuster”. Martin Baker’s concept was for a twin boom design that deviated extensively from the given requirements. The aircraft was armed with a single 6-pounder (57mm) cannon, and the aircraft would be completely encased in 1/2-inch armor. The armor itself weighed 4,900Ibs (2,200kg).

The project wasn’t very impressive nor reasonable in the eyes of the Air Staff, especially compared to the other designs in the program. Its single large-caliber gun extremely limited its target range and it would only have been able to attack one of six predicted target types the program requested. The aircraft lacked any other offensive or defensive armament and would rely on its armor alone to protect itself, a gambit that other designs in the program resolved by following the armaments listed by the Air Staff. Attempts to add more ordnance such as additional guns, rockets or bombs to the wings would have added too much stress on the airframe. The main feature of the aircraft was the root of its problems, its gun. The gun itself couldn’t be removed from the airframe and an aircraft going into battle with a single weapon would be inefficient for resources. The Tankbuster didn’t meet the armament expectations and fell under the expected speed by 10mph (16 km a h). On April 15th, 1943, Air Marshall F J Linnell (who was a good friend of James Martin, a founder of the company) advised Martin-Baker to drop development of the Tankbuster in favor of continuing work on the more successful MB.5 project going on at the same time.

Near the later days of April 1943, the Air Staff brought the program the Tankbuster was designed for to an end. They concluded that, at the time, developing and producing an entirely new ground attack aircraft would impede the current war programs and that the submissions were too specialized in design compared to modifying aircraft already being produced for ground attack duties. One such aircraft they pointed to was the Hawker Hurricane Mk IV, a ground attacker version of the famous fighter which was performing successfully in the role and had started production in March of 1943. Later additions to the ground attack role would be the Hawker Typhoon, which became a scourge to German ground troops. Even if the program had continued towards production, it was significantly unlikely the Tankbuster would have been chosen for the role. The aircraft was way too specialized and disliked by the Air Staff, and Martin Baker was working on an aircraft that would yield much better results. Although the Tankbuster may have been the runt of a doomed program, it still proves to be an interesting, albeit flawed solution in the name of destroying enemy armor.

Design

The Martin-Baker Tankbuster was a twin-boom single-engine design. The aircraft would have been constructed entirely of metal. The airframe itself would be covered in an additional 1/2-inch (12.7mm) armor. This armor would weigh 4,900Ibs (2,223kg) on its own. The armor covered the entire body and also the engine cowling. What’s interesting to note is that the aircraft had two engine intakes, one facing forward and one facing the rear. The radiator and oil tank were mounted in the frontal fuselage. The radiator itself was armored by offset plates that would prevent bullets from ricocheting inside. The cockpit area had clear forward visibility, and would seat a single pilot. The canopy would most likely have had bulletproof glass to complement the rest of the armored body. For it’s engine, the Tankbuster would have mounted a Griffon II engine in pusher configuration. This is relevant to Martin-Baker’s other project, the MB.5, as this aircraft also used the Griffon. The reason the aircraft utilized a pusher configuration was it gave the pilot clear visibility in the front and the gun could be placed directly forward. The pusher configuration isn’t common because of the fact that it leaves the engine open to enemies that are chasing the aircraft. This would have been especially deadly for the Tankbuster, given it has no defensive armament. The tail section and wings would also be constructed of metal. The wings were wide to improve low level flight. There was an attempt to diversify the targets by adding additional weapons to the wings, but this would only overload them. The Tankbuster had a fixed tricycle landing gear. This decision was made to conserve interior space but would have slowed the aircraft considerably. The only armament the aircraft would have been armed with would be a 6-pounder cannon (57mm) that would be frontally mounted, supplied with 30 rounds of ammunition. The aircraft would only be allowed to target heavily armored targets. To assist in aiming, the gun was placed towards on horizontal axis. This would prevent the aircraft from pitching when the gun was fired.

Role

The Tankbuster’s design might seem odd by conventional aircraft standards, but every single feature the aircraft had was to assist in it’s role of attacking enemy armor. Long, flat wings would give the aircraft an edge in low-level flight. The pusher engine would give the aircraft a clear view and nothing to obstruct the cannon. The entire airframe being heavily armored would protect against AA fire and enemy aircraft. Going into battle, the Tankbuster would need escort fighters to protect against opposing interceptors. Once in the combat zone, the Tankbuster would begin its assault on enemy tanks. The De Havilland Mosquito also mounted the 6-pounder Molins gun and was also used in the ground-attack role, but only for a short time before switching to an anti-shipping role. It is likely the Tankbuster would have also undergone this change had it entered production.

Variants

  • Martin-Baker “Tankbuster” – The only version of the Tankbuster drawn was the original design with a single cannon.

Operators

  • United Kingdom – This aircraft would have been operated by the Royal Air Force had it been produced.

Martin-Baker Tankbuster Specifications

Wingspan 47 ft 10.8 in / 14.6 m
Length 41 ft / 12.5 m
Wing Area 471.5 ft² / 43.8 m²
Engine 1x 1,730 hp ( 1,290 kW ) Griffon II Inline-Engine
Weights 12,000 Ibs / 5,440 kg
Climb Rate 2,250 feet/min / 686 meters/min
Maximum Speed 270 mph / 434 km/h
Minimum Speed 75 mph / 122 km/h
Crew 1 pilot
Armament
  • 1x 6-pounder (57mm) Molins M-Class cannon

Gallery

Illustration by Haryo Panji https://www.deviantart.com/haryopanji

Scale model of the Tankbuster [modelingmadness.com]

Sources

Curtiss P-40 Warhawk in Finnish Service

Finnish flag old Republic of Finland (1943)
Fighter– 1 Operated

The Curtiss P-40 Kittyhawk/Warhawk is one of the most iconic symbols of American aviation. Having served with over a dozen nations throughout its career, the aircraft proved itself capable of handling its own in combat. Although the Republic of Finland was never a recipient or official operator of the P-40, they were still able to obtain a single example from a Soviet pilot who landed in Finnish territory with his pristine P-40M. Serving mostly as a training aid, the Finnish P-40 Warhawk would never see combat against any of Finland’s enemies.

History

The Curtiss P-40 (affectionately known as the Kittyhawk for early variants and Warhawk for later variants) is perhaps one of the most recognizable American fighters of the 1930s. Most well known for having served with the “Flying Tigers” American Volunteer Group in the Pacific Theatre, the P-40 also had a fruitful service life on the Western Front and Eastern Front. One of the lesser known parts of the P-40’s history however, is the story of the Finnish P-40M Warhawk. The Finnish Air Force (FAF) had quite an interesting history during the 1940s. Equipped with a wide variety of German, Soviet, British and American aircraft, the word “diverse” would certainly apply to them. Despite Finland never officially receiving Curtiss P-40 Kittyhawk / Warhawks, they were still able to obtain and service a single P-40M Warhawk from the Soviet Air Force during the Continuation War through a forced landing.

P-40 KH-51 after repainting for Finnish service (Kalevi Keskinen)

On December 27th of 1943, a Curtiss P-40M-10-CU known as “White 23” (ex-USAAF s/n 43-5925) belonging to the 191st IAP (Istrebitel’nyy Aviatsionnyy Polk / Fighter Regiment) piloted by 2nd Lieutenant Vitalyi Andreyevitsh Revin made a wheels-down landing on the frozen Valkjärvi lake in the Karelian Isthmus region. Finnish forces were able to quickly retrieve the plane in pristine condition.

The circumstances of Revin’s landing are quite odd, stirring up a couple of theories on why Revin decided to land his undamaged aircraft in Finnish territory. According to the 2001 January edition of the Finnish magazine “Sähkö & Tele”, Revin intentionally landed his plane in Finnish territory, suggesting he may have been working as a German spy. This magazine sourced a report by a Finnish liaison officer working in Luftflotte 1. Other contemporary sources suggest that Revin had to land due to a snowstorm which disoriented him and resulted in him getting lost, or that he simply ran out of fuel and had to make a landing. The fate of Revin is unknown. Nonetheless, White 23 was dismantled and taken to the Mechanics’ School located in Utti where it was reassembled and refurbished. Now given the identification code of “KH-51”, the aircraft was delivered to Hävittäjälentolaivue 24 (HLe.Lv.24 / No.24 Fighter Squadron) based in Mensuvaara on July 2nd of 1944.

Warhawk “White 23” in Soviet service before its capture by Finnish forces. (Kalevi Keskinen)

Although KH-51 was never deployed in combat, it served as a squadron training aid where numerous HLe.Lv.24 pilots flew the P-40 for practice without incident. On December 4th of 1944, KH-51 was handed over to Hävittäjälentolaivue 13 (HLe.Lv.13 / No.13 Fighter Squadron). No flights are believed to have happened while the aircraft was serving with this unit. On February 12th of 1945, the P-40 was taken to Tampere where a week later it would be retired and stored in the Air Depot. The total flight time recorded with KH-51 in Finnish service was 64 hours and 35 minutes. On January 2nd of 1950, KH-51 met its end once and for all when it was scrapped and sold.

Variant(s) Operated

  • P-40M-10-CU – A single example of the P-40M-10-CU known as “White 23” belonging to the Soviet 191st IAP was captured by Finnish forces after the plane’s pilot (2nd Lt. Vitalyi Andreyevitsh Revin) made a landing on Lake Valkjärvi in the Karelian Isthmus area on December 27th of 1943. The aircraft was dismantled, sent to a mechanics school, given the identification code of “KH-51”, reassembled and given to HLe.Lv.24 where it served as a training aid. KH-51 would later be reassigned to HLe.Lv.13 for a short while.

Gallery

Finnish P-40M-10-CU Warhawk “KH-51”

Sources

  • Keskinen, Kalevi, et al. Curtiss Hawk 75A, P-40M. Vol. 5, 1976.
  • Curtiss P-40 M-10 White 23 (Later Finnish KH-51) .” Soviet Warplane Pages
  • Illustrations by Haryo Panji https://www.deviantart.com/haryopanji

Focke Wulf Fw 187

Nazi flag Nazi Germany (1937)
Twin Engined Fighter – 9 Built

The Fw 187 Falke was a twin engine fighter that was built by Focke-Wulf in 1936, at a time when the newly-formed Luftwaffe did not consider such an airplane type necessary. Despite receiving significant negative feedback, several prototypes were built and three pre-production versions were also constructed. The three pre-production types saw limited service defending the Focke-Wulf factory in Bremen against Allied bombing in 1940. Aside from that, they saw no other combat.

History

The first Fw 187 V1 shortly after being completed.

The twin-engined fighter was a concept few countries pursued in the early days of flight. The type only started serious development in the years directly preceding the outbreak of the Second World War, with planes such as the American Lockheed P-38 Lightning entering service. Most officials across the globe agreed that two-engine fighter aircraft would be rendered unnecessary by cheaper and lighter single-engine designs. In the early 1930s, Germany had no plans to develop such an aircraft either.

However, an aeronautical engineer by the name of Kurt Tank showed an interest. Kurt Tank was the main aircraft designer of the Focke-Wulf company, who developed most of the company’s most famous aircraft. During WWII, he would go on to create the iconic Fw 190 and would later have an aircraft designation named after him, with the Ta 152 and Ta 154. He began work on the new twin-engine project, despite there being no current requirement for such an aircraft. Tank had his first chance to reveal his design at a weapons exhibition held at a Henschel plant in 1936. Tank showed off his innovative design, claiming the twin-engine layout would offer a great speed of 348 mph (560 km/h) if the aircraft mounted the newly developed Daimler Benz DB 600 engines. One of the attendants of the event was Adolf Hitler himself, who found the design particularly interesting.

The Fw 187 on jackstands. This photo was taken during testing of the double-wheeled landing gear.

But to the Technischen Amt (Technical Research Office), the design was unnecessary, as it was believed single-engine designs could perform just as well as the twin-engined concept. Another pre-war doctrine was that the current bombers would be fast enough to outrun the fighters of the enemy, and escort fighters wouldn’t be needed. Tank, not happy with this response, took his design to Oberst (Colonel) Wolfram von Richthofen, the head of the Development section of the Technischen Amt. Tank persuaded him that technological advances would eventually allow the construction of more powerful fighters that would be able to catch up with the bombers which would thus require an escort fighter. Convinced by his claim, Richthofen agreed that it would be better to have a countermeasure now rather than later. Richthofen’s term as chief was short, but in this time he authorized three prototypes of Tank’s twin-engine design. The design was officially given the name of Fw 187.

Work began on the Fw 187 soon after, but, to Tank’s dismay, the requests for the DB 600 engine were turned down. Instead, he had to work with Junkers Jumo 210 engines, as DB 600s were only allocated to projects which were viewed as being highly important. The design work was handed over to Oberingenieur (Chief Engineer) Rudi Blaser, who was the one of the most experienced members onboard Focke-Wulf. Blaser had previously headed the design of the failed Fw 159 monoplane fighter, but he was ready to continue work and move on from his failure. Blaser wanted to achieve only one thing with this design: maximum speed.

The Fw 187 V2 on a test flight.

The first prototype Fw 187 was completed in early 1937. The Fw 187 V1 (designated D-AANA) was first flown by test pilot Hans Sander. In the initial flights, the aircraft reached speeds of up to 326 mph (524 km/h). The Luftwaffe was surprised to learn that despite weighing twice as much as the Bf 109, the Fw 187 was still able to go 50 mph (80 km/h) faster. They accused the team of having faulty instruments. Blaser was determined to prove them wrong and had a Pitot tube (a device that measures air speed using the total air pressure) installed on the nose of the V1, which would accurately tell the performance. Sander once again flew and confirmed the aircraft indeed had attained such a speed. Further flight trials showed the aircraft had superb maneuverability, climbing and diving. These great characteristics led Kurt Tank to name the aircraft his “Falke” or Falcon. This name became official as well, and wasn’t just a nickname the creator gave to his creation.

In the summer of 1937, the airframe had an impressive wing loading of 30.72 Ibs/sq ft (147.7 kg/m2), something no other fighter could equal at that point. Further tests by Sander put the airframe to the extremes to try the limitations of the aircraft in diving. The rudder, during dives, was predicted to begin fluttering after 620 mph (1000 km/h), but Blaser was more cautious, and thought it would start at a lower speed. To counteract this, a balance weight was attached to the rudder. Blaser assured Sander that the aircraft would perform better in dives as long as he didn’t exceed 460 mph (740 km/h). With the new weight attached, Sander took off to begin trials. Hitting 455 mph (730 km/h), Sander noticed the tail had begun violently shaking. With the tail not responding, Sander had started to bail when he reported a loud noise came from the rear. Sander’s control over the aircraft had returned and all vibrations had ceased. Upon landing, it was found that the weight itself had been the culprit of the vibrations and the sound Sander heard was the weight breaking off the rudder.

An aft view of the V6. The surface cooling system is visible in this shot.

Several modifications were made to the V1 during testing. The frontal landing gear was switched out for a dual wheeled design at some point, but was found it offered no benefit over the single wheel and thus was reverted. The propellers were also changed from Junkers-Hamilton to VDM built ones. Weapons were eventually added as well, but these were just two 7.92mm MG 17s. The 2nd prototype arrived in the summer of 1937. Visually, the V2 was identical to the V1, but had a smaller tailwheel, modified control surfaces, and Jumo 210G engines with enhanced fixed radiators.

However, in 1936, there was a change of leadership in the Technischen Amt. The supportive Richthofen was replaced by Ernst Udet. Udet was a fighter pilot, and his experience reflected upon his decisions. He made sure no more biplane designs were being built and all designs were now of monoplane construction. He had a major focus on fighters, and believed them to be the future. The modern fighter had to be efficient, with speed and maneuverability being the utmost importance. And, from this viewpoint, he saw twin engine fighters as not being as capable as single engine fighters. With this mindset, the Luftwaffe now saw no real reason to continue developing the Fw 187 as a single seat interceptor, but it could be developed as a Zerstörer (“Destroyer” heavy fighter), the same role the Bf 110 occupied. This required a crew of more than one and much heavier armament. Tank was reluctant, and felt his design was still as capable as single engine designs were, but he knew continuing to go against the Technischen Amt would result in his aircraft being terminated, so he regretfully obliged.

The V3 was in the middle of construction and changes had to be made as a result of this. The V1 and V2 had already been produced, and any drastic changes would further affect development, so no attempt to convert the two initial planes into two-seaters ever occured. To accommodate a radioman, the cockpit had to be lengthened. This worried Blaser, who was concerned these changes would affect the size and overall performance of the aircraft. Thus, he tried making the changes that affected the aircraft’s performance as little as possible. The fuselage was increased lengthwise, the tailfin was shortened, and increased cockpit volume demanded the fuel tank be moved farther back. Engine nacelles were also shortened to allow installation of landing flaps for when the aircraft carried larger ordnance. The 7.92mms were now complemented with two 20mm MG FF cannons, although V3 never mounted any actual weapons, only mock-ups.

The Fw 187 had good luck up until this point, but this good fortune ran out shortly after the V3 was produced. A few weeks after it was finished in early 1938, the V3 was doing a test flight when one of its engines caught on fire. The aircraft was able to safely land and the fire was extinguished, but the airframe had taken some damage and needed repairs. Tragedy struck once again not too long after, on May 14th. The V1 was lost and its pilot, Bauer, was killed during a landing accident. These two events happening so close together made the already negatively viewed Falke seem not only an unnecessary weapon, but now an unreliable one as well. Two more prototypes were built late in 1938, the V4 (D-OSNP) and V5 (D-OTGN). These two were mostly identical to the V3, but had several slight modifications, such as a modified windshield. Judging by photos, one obvious trait V4 and V5 had over V3 is the lack of the radio mast mounted on the cockpit of the V3. V4 and V5 were sent to the Echlin Erprobungsstelle, a major aircraft development and testing airfield for the RLM (Reichsluftfahrtministerium, German Ministry of Aviation). The trials at this site yielded favorable evaluations of the aircraft and three pre-production examples were ordered.

One of the A-0s flying overhead.

While all of this was going on, Tank was finally able to acquire two DB 600A engines for his Falke. The plane that mounted these engines would be the V6. Before the V6 was built, Tank had shown interest in surface evaporation cooling, a drag reducing novelty which had been researched and developed by Heinkel and was soon to be worked on by Messerschmitt. With the V6 now under construction, Tank drew plans to apply the feature into the prototype to give it peak performance. V6 (CI+NY) first flew in early 1939 and showed how well the new engines and surface cooling made the aircraft perform. On takeoff, the V6 had 1,000 HP from each engine, a 43% boost over the previously used Jumo 210s. During one test flight, the V6 was flying 395 mph (635 km/h) in level flight.

The three pre-production examples previously mentioned were designated Fw 197A-0. These were were fully armed. The A-0s added armored glass to the windshield and carried two more MG 17s. The A-0 planes also returned to using the Jumo 210 engines. Due to the additional weight, the performance of the A-0s was a bit lower than the prototypes. However, the RLM continued to argue against the Falke, claiming that, because it had no defensive armament, the Fw wouldn’t be as effective as the Bf 110 in the same role (despite it being able to outperform the 110 performance-wise). The final decision related to the Falke was an idea to turn it into a night-fighter in 1943. Nothing ever came out of this proposal.

The Factory Defender

Although the Bf 110 seemingly took the Falke’s place, its story continued. As the Royal Air Force (RAF) began its attacks over mainland Germany in 1940, aircraft firms scrambled to defend their valuable factories. Several firms formed a “Industrie Schutzstaffel”, which was an aerial defence program which would have aircraft company’s factories and testing sites be defended by aircraft piloted by test pilots and to be managed by on-site personnel. Focke-Wulf was one such firm and, luckily for them, three fully operational Fw187A-0s were ready and waiting to be used in combat. These examples were sent to the Focke-Wulf factory at Bremen and were sent on numerous missions to defend the plant from Allied bombing. Allegedly, Dipl.-Ing (Engineer’s degree) Melhorn claimed several kills while flying one of these aircraft. After the stint in Bremen, the three were put back into armament and equipment testing. In the winter of 1940 to early 1941, the three were sent to a Jagdstaffel unit in Norway, where they were evaluated by pilots. One of the three was sent to Værløse, Denmark in the summer of 1942 and temporarily assigned to Luftschiess-Schule. It is likely the remaining 3 and prototypes were either scrapped or destroyed by Allied bombing, as no examples are known to have survived the war. Some sources claim the aircraft Melhorn flew was the V6 converted into a single seater and armed for combat, but no proof supports this.

The Fw 187 was no secret weapon. After the fighting in France died down, the Propaganda Ministry began producing film and photos of the Fw 187 in 1940-1941 to persuade the Allies into thinking the Falke was fully operational and replacing the Bf 110 as the Luftwaffe’s all new Zerstörer. In reality, the latter was taking over the role of the former. The campaign sort of worked, as the Fw 187 was now a part of the rogue’s gallery that the Allies expected to fight. Identification cards, models and even movies were made to train pilots in the event they should encounter the two engine terror in combat. One such film denotes that the Fw 187 is “a rare bird” and that they should comically “make it extinct”. This shows that the Allies didn’t completely fall for the propaganda that claimed it was being produced in mass quantity.

Design

The Fw 187 had a twin engine design. The airframe was of all light metal construction. To reduce drag, the airframe was actually narrower at its widest point than other fighters of the time. The wings were of metal construction and divided into three sections. The connected segments carried the fuel and the outer segments had the flaps installed. The first and second prototypes had a single seat cockpit. The cockpit was covered by a canopy that slid aft. The cockpit itself wasn’t built for comfort, as it was built for an average sized pilot. The cramped cockpit lacked the necessary space to mount certain instruments and had these mounted outside on the engine cowlings. V1 had tail sitting landing gear, with all three wheels being able to retract into the hull. V2 was similar to V1, but had modified control surfaces. Beginning after the first two, all examples of the Fw 187 had an extended greenhouse cockpit to accommodate the radioman. The cockpit now opened up in two sections, one to the front and one to the rear. The fuselage was lengthened to some degree as well. The extended cockpit required the fuel tank to be moved down the fuselage. The engine nacelles were shortened to allow landing flaps to be added. V3 also had a radio mast mounted on the rear part of the cockpit. V4 and V5 had this removed.

For engines, the majority of the Falke’s used the Jumo 210 engine. V1 mounted the 210Da, V2-V5 using the 210G, V6 using the powerful DB 600A engines and the A-0 reverting back to 210Gs. The aircraft performance stayed the same overall, with the V6 having peak performance speedwise.

For armament, V1 mounted two MG 17 machine guns. V3 had accommodations for two more MG FF cannons but only mockups were added. When the A-0s were rolled out, an additional two MG 17s were added to fill the Zerstorer role. The extra two had their ammunition mounted in front of the radioman’s seat.

Variants

  • Fw 187 V1 – First prototype. Mounted two Junkers Jumo 210Da engines. Originally mounted Junkers-Hamilton propellers but was changed to VDM airscrews. Originally had two wheeled forward landing gear which was switched to single during development. Fitted with two MG 17 machine guns.
  • Fw 187 V2 – Second prototype, had different rudders and a semi-retractable tail-wheel. Had fuel-injection Jumo 210G engines.
  • Fw 187 V3 – Third prototype. Two seat version, the cockpit was lengthened to accommodate the radioman. The engine nacelles were shortened some degree to allow new landing flaps.V-3 also mounted two MG 17 machine guns and two MG FF cannons.
  • Fw 187 V4/Fw 187 V5 – Fourth and fifth prototypes. Nearly identical to V-3, aside from several small modifications, such as having different windscreens.
  • Fw 187 V-6 – Sixth prototype. High speed version that mounted Daimler Benz DB 600A engines.
  • Fw 187A-0 – Pre-production version. Three were constructed. Armed with two MG FF cannons and four MG 17 machine guns. Frontal armored windshields were added. These three were tested and sent to various locations for trial and defensive purposes.

Operators

  • Nazi Germany – The sole operator was Nazi Germany, which reportedly used the Falke during the air defense of Bremen in 1940.

Focke Wulf Fw 187A-0 Specifications

Wingspan 50 ft 2 in / 15.3 m
Length 36 ft 6 in / 11.1 m
Height 12 ft 7 in / 3.8 m
Wing Area 327.2 ft² / 99.7 m²
Engine 2x 700 hp (522 kW) Junkers Jumo 210Ga 12-cylinder liquid cooled inline engines
Propeller 2x 3-blade VDM airscrews
Powerplant Ratings
Horsepower output Altitude
Take Off 700 hp Sea Level
Normal 730 hp 3,280 ft
Weights
Empty 8,150 lbs / 3,700 kg
Loaded 11,000 lbs / 5,000 kg
Climb Rate
Rate of Climb at Sea Level 3,450 ft / 1050 m per minute
Time to 6,560 ft / 1999.4 m 1.9 minutes
Time to 19,700 ft / 6000 m 5.8 minutes
Speed 329 mph / 530 km/h at 13,780 ft / 4,200 m

322 mph / 518 km/h at Sea Level

Range 560 mi / 900 km
Maximum Service Ceiling 32,810 ft / 10940 m
Crew 1 Pilot

1 Radio Operator

Armament
  • 2x 20mm MG FF cannons
  • 4x 7.92mm MG 17 machine guns

Gallery

llustrations by Haryo Panji https://www.deviantart.com/haryopanji

Focke-Wulf Fw 187 V1- Prototype
Focke-Wulf Fw 187 Night Fighter
Focke-Wulf Fw 187 A-0
The V5 on standby. A visual difference between the V3 and the V4/V5 is the absence of a radio mast mounted on the cockpit.
Side view of the V6.
A period 3-way illustration of the Fw 187 A-0
The Fw 187 V3 after it’s engine fire. Notice it’s greenhouse cockpit and the way it opens.
A cockpit view of one of the A-0s. Note the glass floor.
The V4 taking off. The V4 and V5 were slightly modified versions of the V3.
Three pre-production Fw 187 A-0s on standby.
An aft view of the V6. The surface cooling system is visible in this shot.

Sources

Vultee XA-41

USA flag United States of America (1944)
Prototype Ground Attack Aircraft – 1 Built

XA-41 in flight

The Vultee XA-41 was a single-engine aircraft that began life as a dive bomber. Months later, its role was changed to a low-level attack aircraft. The XA-41 performed admirably in flight tests, but the United States Army Air Corps (USAAC) eventually decided that the fighter aircraft then in service were already performing well enough in the attack role. Despite its job being erased, the XA-41 continued development as a testbed, showing off the powerful XR-4360 engine it mounted and how much it could carry. The aircraft itself would have been deadly had it been produced in large numbers, as it boasted four 37mm cannons. As the war went on, the XA-41 was still being tested. Throughout the trials, the aircraft had extremely good performance, even being able to outturn a P-51, but its speed wasn’t quite enough for its role. At one point, it was given to the Navy for testing and eventually it would wind up at Pratt & Whitney (PR). At PR, it served as a testbed through the war and was eventually scrapped in 1950.

History

Cutaway Concept for the XA-41

The XA-41 began as part of a United States Army Air Corps (USAAC) requirement in October 1941 for a new single-seat attack aircraft. The Douglas A-20 Havoc (and soon to be produced North American A-36 Apache) was performing well at the time, but the USAAC wanted something new. The aircraft requested had to be able to reach at least 300mph (482.8kph) at sea level, have a service ceiling of at least 30,000ft (9,144m), and a range of 1,200 miles (1,932km). For the attack role, the aircraft was to have either 37mm, 20mm, or 50. cal guns mounted in the wings. Given this imposing armament, it is likely the aircraft would have attacked soft targets or even been used for tank-busting.

The USAAC commissioned Vultee Aircraft Corporation, Kaiser Fleetwings, and Curtiss to design a new aircraft for the role. Kaiser Fleetwings developed the XA-39, which would have mounted the R-2800-27 engine. Their aircraft didn’t progress beyond the mockup stage. Curtiss reused their naval XTBC-1 prototype for their part, renaming it the XA-40. This also didn’t go beyond the mockup stage. Vultee’s answer was the V-90, a ground attack aircraft mounting the fairly new and powerful R-4360 engine. Interestingly, the XA-41 started off as a dive bomber, despite it being commissioned as an attack aircraft. It isn’t often stated, but the Army had been interested in dive bombers since 1940, going as far as purchasing several Navy designs. The Army bought several SB2D-1 Helldivers in December of 1940 and renamed them the A-25 Shrike. They also had a troubled history with one of Vultee’s own aircraft, the A-35 Vengeance, which they tried numerous times, but to no avail. The XA-41 was most likely a chance for the Army to have a successful dive bomber or attack aircraft. The Army was satisfied with Vultee’s V-90 design and awarded a contract for two prototypes on November 10, 1942. Shortly after a mockup inspection, the Army interestingly switched the role from a dive bomber to a dedicated attack aircraft. The switch was rather abrupt and caused a delay in the development.

XA-41 Prototype

On April 30th, a new contract was signed which included a static mockup. Vultee continued construction on the project until the prototype was halfway completed, at which point the Army decided that the most current aircraft, the Republic P-47 Thunderbolt and North American P-51 Mustang, were already quite capable in the attack role. But this wouldn’t be the end of the XA-41. Maj.Gen Oliver P. Echols, Chief of the Material Division, opted not to cancel the program and instead complete it in order to show the true potential of a new attack aircraft with the new R-4360 engine. This decision went through on November 20th, with the prototype ¾ the way through completion. The 2nd prototype was cut at this point and only one would be built (Serial No. 43-35124/5).

On February 11th, 1944, the XA-41 flew for the first time from Vultee Field, California, with test pilot Frank Davis at the controls, and landed at March Field, California. Several flights after this were conducted at the nearby army base. The aircraft was flown by both Vultee and Army pilots, and both agreed it handled well. There were some problems here and there, which Vultee quickly fixed with some additions to the airframe. On June 25, the Army accepted the XA-41. On July 16th, on its 60th flight, the aircraft was ferried to Eglin Field, Florida. Testing proved the XA-41 was an exceptional aircraft, with many great features. The craft had an excellent turn rate, being able to outturn the P-51. For its size, it carried an impressive arsenal of weapons. But the Army wanted an attack aircraft that could also defend itself if the need would arise, and the 350mph (563.2 km/h) of the XA-41 wasn’t that impressive compared to other aircraft in service. The United States Navy became interested in the XA-41 at some point and the prototype was given to them for testing at Patuxent River, Maryland. The Navy wanted to see if the aircraft could be flown from aircraft carriers. After the Navy briefly tested it, the XA-41 was given to Pratt & Whitney (PR) on August 22, 1944. It was obvious at this point that the XA-41 would never see combat, but would remain in the US as a testbed aircraft. Serving with PR, it was used as a flying testbed for their R-4360 engine, as well as having a supercharger mounted. As testing continued, the aircraft was purchased by PR on October 9 and re-registered as NX6037N. There are few documents that reference the XA-41 post-war. The only thing mentioned is that the sole XA-41 was finally scrapped in 1950, having served for many years at PR.

Design

The XA-41 was a conventional single-engine aircraft. It had a slight gull wing and a tail sitter configuration. The landing gear in the wings would retract inboard and was placed widely to allow better landing performance. During development, the tail wheel had doors installed to completely cover it in-flight. The cockpit was placed far forward and raised to allow the pilot to see over the engine, giving him better visibility when attacking ground targets. The ventral tail had an extension that spanned most of the length of the aircraft. This was added during development. A spinner was also added at some point. The XA-41 mounted the PR XR-4360 Wasp Major engine, which was the main reason the Army and PR were so interested in the project.

For armament, the XA-41 had four M2 Browning .50 cal machine-guns mounted in the wings. For the attack role, it was meant to mount four more 37mm cannons (sources don’t mention what particular kind of gun) in the wings. All armament in the wings was placed outside of the propeller’s range. For bombing, the XA-41 had a bomb bay that could carry four 500Ibs bombs, a torpedo, additional fuel, or two 1,600Ibs weapons. In total, it had up to 6,500Ibs of ordnance. Documents mention that up to 1,100Ibs of additional bombs could be mounted to the wings. The aforementioned competing XA-39 only sported the four Brownings, two 37mms, as well as a predicted carrying capacity of six 500Ibs bombs.

Variants

  • XA-41 – [The sole prototype built, used as a testbed for the XR-4360 engine.]

Operators

  • United States of America – The United States Army Air Corps would have operated it had it entered production. After serving as a testbed for the Army, the Navy and Pratt & Whitney also did tests with the aircraft.

XA-41 Specifications

Wingspan 54 ft / 16.4 m
Length 48 ft 7 in / 14.8 m
Height 14 ft 5 in / 4.4 m
Wing Area 540 ft² / 164.5 m²
Engine 1x 3,000 hp ( 2240 kW ) XR-4360-9
Propeller 1x 4-bladed Hamilton Standard propeller
Weights
Empty 13,400 lb / 6078.1 kg
Gross 18,800 lb / 8527.5 kg
Maximum 23,359 lb / 10595.4 kg
Climb Rate
Rate of Climb at Sea Level 2,326 ft / 708.9m per minute
Maximum Speed 353 mph / 568 kmh at 15,000 ft / 4572 m
Cruising Speed 270 mph / 434.5 kmh
Range 800 mi / 1287.4 km
Maximum Service Ceiling 27,000 ft / 8229.6 m
Crew 1 pilot
Armament
  • 4 Browning M2 machine guns (400rpg)
  • 4 37mm cannons (30rpg)
  • Up to 6,500 Ibs of weapons

Gallery

llustrations by Haryo Panji https://www.deviantart.com/haryopanji

Vultee-XA-41 Original Prototype Colors
Vultee XA-41 with possible service markings (artist interpretation)
XA-41 at Patuxent River
XA-41 on the runway
XA-41 in a slight climb
XA-41 parked on the ramp

Sources

 

Douglas XTB2D-1 Skypirate

usa flag USA (1945)
Prototype Torpedo Bomber – 2 Built

XTB2D-1 on the Runway
First prototype of the Skypirate on the runway.

The Douglas XTB2D-1 “Skypirate” was a large, single-engine torpedo bomber built for use on the Midway class carriers during World War 2. At the time, it was the largest aircraft to be used aboard a carrier, dwarfing even two-engine designs. Unfortunately for the Skypirate, engine troubles, little support from the US Navy (USN), and numerous setbacks with the construction of Midway-class carriers nearly doomed it from the start. By the time it was airworthy, it was trying to fill an obsolete role which other aircraft, such as the TBF/TBM Avenger, already filled adequately. Work continued after the war, with several attempts to revive the program but it proved to be too costly and the Skypirate program was finally cancelled in 1947, with the two prototypes being scrapped in 1948.

History

With engagements such as the Battle of the Coral Sea and the hunt for the Bismarck, the effectiveness of torpedo bombers, such as the TBF/TBM Avenger and Fairey Swordfish, was clear. With the announcement of the large Midway-class carriers, the possibility of a new torpedo-bomber/scout bomber came about. In February 1942, a competition was put forward by the Navy for this role. The Douglas Aircraft Company, based in Southern California, proposed the Skypirate. The single-engine Skypirate was picked from eight different designs, most of which were two-engined. The Bureau of Aeronautics (BuAer) wasn’t expecting a single engine design to be submitted, assuming the specified massive carrying capacity would require a two-engine design. The program was being headed by Ed Heinemann as lead designer and Bob Donovan as the chief engineer, who would be on the project until the end.

XTB2D-1 Frontal View
An impressive look at the massive Skypirate from the front.

In November of 1942, Douglas was given permission to begin production of two prototypes and a mockup of the XTB2D-1 (then called the Devastator II, before being changed to Skypirate). Delays in the development of the Midway class would continue to hamper the Skypirate throughout its life. The finished product was a formidable aircraft, capable of carrying four torpedoes from land or two torpedoes from a carrier, the former being four times the carrying capacity of the TBM Avenger. In March and May of 1943, the mockup was inspected and an order for 23 production aircraft was put in. This was enough for a single squadron to operate from a Midway carrier. Problems began about this time, with the delivery of engines and propellers being delayed. By 1944, the Skypirate was still not airborne and it was obvious it wouldn’t be operational anytime soon. With earlier torpedo bombers performing adequately, a lack of support from the Navy, most of the Japanese fleet in shambles and continued delays with the Midway class (which would eventually sail after the war), the 23 production planes were cancelled. On February 18th, 1945, the first Skypirate was rolled out of the production facility, being completed on March 13th and finally going airborne on May 8th. Neither of the prototypes had any defensive armaments, but they were tested with torpedoes and drop tanks. Although no production was to ever start, the Skypirates would continue flying until the end of the war. During one such flight in June of 1945, a Skypirate was damaged mid-flight, but the craft was brought down safely. Engine problems were a frequent issue with the Skypirate and propeller problems would ground it in August of 1945, not flying again until after the war.

Skypirate Landing
Perhaps the most well known photo of the aircraft, the Skypirate prepares to land.

Postwar, the aircraft industry changed with the introduction of jet aircraft, thus eliminating the need for many prototypes being developed during the war. The Skypirate was no exception. With the torpedo bomber role now fading, the Douglas firm looked at other options to revive their Skypirate. Some ideas included using the Skypirate for an electronic warfare role or even as an anti-submarine aircraft (a role overtaken by another piston engine aircraft, the Grumman AF Guardian), but none of these propositions ever managed to become reality. As the Cold War was just beginning, the Skypirate program ended in 1947 and the 2 prototypes were scrapped in 1948.

Design

The Skypirate is most likely the largest single-engine aircraft to ever be designed for carrier operations. In comparison, the twin-engined B-25 Mitchell medium bomber measured around the same in length and width.

In flight
The 2nd prototype in flight, notice how the tail is shorter in comparison to the first prototype.

The initial Skypirate design had an internal bomb bay, which the prototypes dropped in favor of four external Mark 51 Mod 7 bomb hardpoints. These hardpoints could carry a range of weapons including 500Ib-2000Ib bombs, torpedoes, depth charges, mines or even incendiary bombs. The use of up to 4 Mk.13 Torpedoes (from land) were planned had it entered production. The Skypirate could alternatively carry up to 8,400Ibs of bombs. For offensive armament, the Skypirate had 4 M2 Browning machine guns in the wings. For defense, it had a Firestone model 250CH-3 remote turret behind the cockpit which carried 2 M2 Brownings and a turret in the back of the lower fuselage which carried a single M2 Browning. The lower turret was remotely fired through electronic control and powered hydraulically. Drawings indicate that Mark 2 Gun Containers could be added for extra forward firepower but none were ever attached during testing. 300 gallon drop tanks were also fitted during testing and could have been used had the craft been operational.

The Mockup
The sole mockup made alongside the 2 prototypes.

Along with such an impressive weapons payload, the Skypirate was full of advancements which would have improved its performance. To get such a large aircraft off the ground, the Skypirate was powered by a single Pratt & Whitney XR-4360-8, the largest radial engine ever built up to that time. The engine had a unique exhaust style that combined the exhausts in alternating rows to lower the effects of backpressure. Being a carrier-based aircraft, the Skypirate had folding wings as well as a catapult hook. The inclusion of a tricycle landing gear was also interesting, as it helped with bomb loading and carrier space. Most single engine aircraft of the time preferred using a tailwheel. The Skypirate had large flaps that extended the length of wingspan. The outer flaps served as ailerons while the midsection flaps were used as dive flaps. The dive flaps could also be lowered to help the aircraft cruise or assist in turning to help ease the stress off the aircraft when fully loaded. To assist with bombing or flight in general, a Type 3 Sperry vacuum-controlled, hydraulic autopilot was also to be added. A de-icing system was also added that pumped hot air over the wings and tail section.

The planned modifications of the prototypes are interesting to note. The 2nd prototype (Bu.36934) differed from the first, having a shorter tail of 8.6 ft, compared to the regular 10.5 ft tail of the original design. This was done most likely to conserve valuable space when inside a carrier. Along with these differences, plans to fit a jet engine in the fuselage of the 2nd prototype were made, but nothing ever came to fruition. The first prototype (Bu.36933) had a larger tail and was planned to be converted for the scout bomber role. These plans included adding cameras onboard. As with the jet engine designs, these also never came to be.

Variants

  • XTB2D-1 Bu.36933 – Prototype version, lacked any armament
  • XTB2D-1 Bu.36934 – The 2nd prototype. The tail was shortened to 8.6 ft. Also lacked any armament.
  • TB2D-1 – Proposed production version, 23 were ordered and planned production was to be 100 built every month. These versions were to be fitted with four .50 caliber machine guns in the wings, two in a Firestone power turret and one remotely controlled in the ventral hull. Eventually, the production versions were cancelled in favor of higher priority projects.

Operators

  • United States of America – Slated to be used aboard the Navy’s Midway-class carriers, with the end of the war and other setbacks, the XTB2D-1 was never used operationally.
XTB2D-1 Rollout
The design team poses with the first Skypirate on rollout day.

TB2D-1 Specifications

Wingspan 70 ft / 21.3 m
Length 46 ft / 14 m
Height 22 ft 6 in / 6.9 m
Wing Area 605 ft² / 184.4 m²
Engine 1x 3,000 hp ( 2240 kW ) XR-4360-8
Propeller 1x 8 bladed Hamilton Standard contra-rotating propeller
Fuel Capacity 501 US gal / 1896 L
Oil Capacity 28 US gal / 106 L
Empty Weight 18,405 lbs / 8350 kg
Gross Weight 28,545 lbs / 12950 kg
Maximum Weight 34,760 lbs / 15765 kg
Rate of Climb at Sea Level 1,390 ft / 425 m per minute
Time to 10,000 ft / 3048 m 8.2 minutes (Normal) 10.2 minutes (Military)
Time to 20,000 ft / 6096 m 22.3 minutes (Normal) 26.5 minutes (Military)
Maximum Speed 340 mph / 550 km/h at 15,600 ft / 4755 m
Cruising Speed 168 mph / 270 km/h

312 mph / 500 km/h (with torpedoes)

Range 1,250 mi / 2010 km (Torpedoes)

2,880 mi / 4635 km (Maximum)

Maximum Service Ceiling 24,500 ft / 7470 m
Crew 1 pilot

2 gunners

Armament 4 Browning M2 machine guns mounted in the wings (1600rds)

2 Browning M2 machine guns mounted in turret (1200 rds, incl remote 50.)

1 remote Browning M2 machine guns mounted in ventral hull

4 x Mk 13 Torpedoes (from land)

2 x Mk 13 Torpedoes (from carrier)

2 x 2,100 lbs Bombs

Total of 8,400 lbs payload capacity

2 x Mark 2 Gun Containers

Gallery

llustrations by Haryo Panji https://www.deviantart.com/haryopanji

Douglas XTB2D Skypirate Side View
Douglas TB2D Skypirate Side View – With the Defensive Gun Pod

 

XTB2D End
The last known photos of the Skypirates before being scrapped.
XTB2D Loaded
One of the prototypes with mounted Mk-13 torpedoes.
XTB2D Backside
A back view of one of the prototypes
XTB2D-1 on the Runway
First prototype of the Skypirate on the runway.
XTB2D-1 Frontal View
An impressive look at the massive Skypirate from the front.
Skypirate Landing
Perhaps the most well known photo of the aircraft, the Skypirate prepares to land.
In flight
The 2nd prototype in flight, notice how the tail is shorter in comparison to the first prototype.
The Mockup
The sole mockup made alongside the 2 prototypes.
XTB2D-1 Rollout
The design team poses with the first Skypirate on rollout day.

Sources

 

VL Pyörremyrsky

Finnish flag Finland (1945)
Prototype Fighter – 1 Built

The VL Pyörremyrsky prototype parked on a ramp [Colorized by Michael J.]
The VL Pyörremyrsky (translates as Hurricane) was a prototype Finnish fighter plane designed to keep up with its contemporaries. It was to be domestically produced, using wood, but using the same engine as the Bf 109 G. Due to limitations brought about due to the war, only one prototype was produced and it wasn’t ready until the end of 1945.

Development and History

As Finland found itself still at war with the Soviet Union in 1942, with no end in sight, it turned to ways to bolster its military force. In order to become as self sufficient as possible, it was engaged in various projects for domestically designed and produced weapons systems. The VL Myrsky project was severely behind schedule and the air force realised that it would be outclassed by the newer Soviet aircraft by the time it reached production. With this in mind, it placed order number 2012/42 on 26th November 1942 for a new aircraft design, under the name Pyörremyrsky.

The State Aircraft Factory (Valtion Lentokonetehdas) was tasked with producing the new fighter and Captain of Engineering Torsti Verkkola was assigned chief designer of the team. The main premise was that the aircraft was to be made out of wood, as much as was possible, and that it was to be comparable with the German Messerschmitt Bf 109G. Verkkola used the Bf 109 as the base for his design, making modifications to allow it to be produced with local skills and materials. However, as the war dragged on, and the Finnish Air Force required more proven aircraft, as well as repairs to the planes already in service, the Pyörremyrsky found itself given a lower priority.

Profile of the Pyörremyrsky. Source: Warthunder forums

Upon the cessation of hostilities between Finland and the Soviet Union in September 1944, the Pyörremyrsky project had only a partially completed prototype and the Ministry of Defence (puolustusministeriö) cancelled the advance order of 40 aircraft, as well as the second prototype on the 29th September, but they did allow the first prototype to be completed. In Autumn 1945 the prototype, now christened PM-1 (which led to the nickname Puu-Mersu or Wooden Messerschmitt), was ready for pilot tests. On the 21st of November 1945, Luutnantti (Lieutenant) Esko Halme took off in PM-1 from Tampere-Härmälän airfield. The flight only lasted 25 minutes as part of the engines’ exhaust system came loose, forcing an emergency landing as Lt. Halme was unable to see through the exhaust blowing into his cockpit. Despite the incident, Halme reported good flying controls and characteristics. PM-1 would do 2 more test flights at Härmälän airfield before moving to Kuorevesi for Air Force testing. In total 31 test flights were performed, amounting to 27 hours of flight time. All 8 pilots reported the same, smooth and controlled flying characteristics, good speed and turning ability, however it was not quite up to the same performance of the Bf 109 G but close enough. The last flight of PM-1 was on the 22nd of July 1947, when Kapteeni (Captain) Osmo Kauppinen took off for a 20 minute general test flight. After this it was put into storage until it was officially removed from the Air Force’s rolls on the 1st April 1953. This was mainly due to the lack of ability to source new engine parts as part of the armistice Finland signed with the Allies forbade them from receiving military goods from Germany, as well as the decline of the piston aircraft as a fighter.

The Air Force didn’t want such a unique piece of Finnish aviation history to be scrapped however and ordered it to be preserved. It was sent to the State Aircraft Factory’s depot and was refurbished in the early 1970’s and sent to the Finnish Air Force Museum, where it is still on display.

The experiences learnt with the Pyörremyrsky were not totally in vain or wasted as the basic design was used in the development of the VL Vihuri fighter trainer.

Design

Access panels open revealing the engine. Source: Suomen Hävittäjät

Captain Verkkola used the Bf 109’s low-wing cantilever monoplane configuration as his base for the Pyörremyrsky. The Germans were also willing to supply the Daimler-Benz DB 605A-1 liquid cooled V12 engines and VDM 9-12087 three-bladed light-alloy propellers that were used on the Bf 109 series. It was also installed with a German produced Telefunken FuG 7a model of compact airborne receiver/transmitter.

The main body of the aircraft was built using the vast amounts of wood available to the Finns, with metal being used where absolutely necessary, like the cockpit and engine housing. While many believe the design is similar, if not copied from the Bf 109, there are many differences outside of just the materials used. The rear portion of the fuselage is of wooden monocoque design, with the horizontal stabilizers mounted at the near end, as opposed to the Bf 109’s which are mounted on the vertical stabilizer. The wings were of negative transverse V shape and covered in plywood panelling.

PM-1 at the Tampere trial airfield in the Summer of 1945. Source: Suomen Hävittäjät

Unlike the wing fuel tanks found in the Bf 109, the Pyörremyrsky had a single tank behind the cockpit, protected by a 10mm thick armoured plate. The landing gear was copied from the Bf 109 but the Finns made some changes to eliminate the narrow and problematic system that plagued the Germans. The tailwheel was also retractable, thus helping it with aerodynamics.

Due to wartime shortages, Finland was forced to rely on substandard replacement products. The use of Lukko glue was one of the main reasons for the failings in the VL Myrsky and so it has been suspected that the Pyörremyrsky would have suffered similar issues to its sister aircraft had it been pushed into service or flown for longer periods of time.

Armament was not fitted to the PM-1 but it was designed to be installed with a Motorkanone mounted 20 mm (.78 in) MG 151/20 cannon and two nose mounted synchronized 12.7 mm LKK-42 machine guns. It was also proposed that the wings would have provisions for two 100kg bombs each for fighter bomber duties, but it is not clear if the proposal was ever considered seriously.

Operators

  • Finland – The VL Pyörremyrsky was intended to be used by the Finnish Air Force.

VL Pyörremyrsky Statistics

Wingspan 34 ft 1 in / 10.38 m
Length 29 ft 11 in / 9.13 m
Height 12 ft 9 in / 3.89 m
Wing Area 204.5 ft² / 19 m²
Engine 1 × Daimler-Benz DB 605A-1 liquid cooled V12 engine (1,475 hp)
Empty Weight 5,774 lb / 2,619 kg
Wing Loading 35.7 lb sq ft/ 174kg/m2
Maximum Takeoff Weight 7,300 lb / 3,310 kg
Fuel Capacity 435 L
Climb Rate 16,404 ft / 5000 m in 4.30 minutes
Maximum Speed 324mph / 522 kmh at sea level

400 mph / 645 kmh at 6000 meters/19,685 feet

Cruising Speed 236mph / 380 kmh
Flight time 2.5 hours
Maximum Service Ceiling 36,900 ft / 11,250 m
Crew 1x Pilot
Armament 1x 20 mm (.78 in) MG 151/20 cannon (150 rpg)

2x 12.7 mm LKK-42 machine guns (300 rpg)

4x 220.5 lb /100 kg Bombs or

2x 39.62 Gal / 150 L Drop Tank

Gallery

VL Pyörremyrsky Sideart by Escodrion
PM-1 in the Finnish Air Force Museum, next to a BF-109G. Source: Wikimedia
Close up of the undercarriage. Notice how they are copies of the BF-109 but close inwards. Source: Wikimedia
The PM-1 cockpit. Taken at the Tampere trial airfield in the Summer of 1945. Source: Suomen Hävittäjät
Profile of the Pyörremyrsky. Source: Warthunder forums

Sources

Suomen Ilmavoimien Historia 14 Suomen Hävittäjät, Kalevi Keskinen, Vammalan Kirjapino Oy 1990, Suomen Ilmavoimien Historia 17 LeR2, Kalevi Keskinen, Edita OYJ 2001, www.ilmailumuseot.fi, Valtion Lentokonetehtaan historia – Osa 2: Tampereella ja sodissa 1933–1944. Jukka Raunio, 2007, Images: Side Profile Views by Escodrion – https://escodrion.deviantart.com, Colorized Images by Michael J.