Austro-Hungarian Empire (1916)
Triplane Bomber Prototype – 1 built
The Lloyd 40.08 was a prototype triplane bomber built for Austria-Hungary under an order for a new bomber by the Luftfahrtruppen (LFT, Aviation Troops) in 1915. The 40.08 “Luftkreuzer” (Air Cruiser) was a twin boom design that would have carried 200 kg of bombs into battle. The aircraft had frequent problems with its design, such as being front-heavy and the center of gravity being too high. Attempts to fix the issues were minimal and it would never fly. The aircraft was sent to a scrapyard in the end, but it was an interesting venture of a now-defunct empire.
World War I showcased the first widespread use of combat airplanes and the subsequent specialization of aircraft to fit certain roles. Bombers proved their effectiveness and most countries involved developed some sort of bomber for their early air forces. One shining example is the Gotha series of bombers, which were able to bomb London and eventually replace Zeppelin raids entirely. The Austro-Hungarian Empire was no exception to building their own bombers. At the time, in 1915, Austria-Hungary was fighting on several fronts, with the ongoing Russian front dragging on and by May, Italy had joined and had begun fighting its neighbor. A new bomber would be a helpful addition to Austria-Hungary’s military.
In 1915, the Luftfahrtruppen sent out an order for a 3-engine bomber design. The exact date the order was given in 1915 is unknown, but it is very likely the order was a reaction to Italy joining the war, as similarly, Austria-Hungary attempted to buy Hansa-Brandenburg G.1 bombers to bolster their aircraft complement. The requirement specified that two engines would be mounted inside fuselages and the main engine in a central hull. The bomb payload would be 440 Ibs (200 kg) and defenses would be six machine guns mounted around the aircraft. Expected flying time was up to 6 hours. Given the long flying time, strategic bombing might have been in mind but the bomb load is much smaller compared to other bombers in the role. Tactical bombing would be more practical in the long run for the aircraft. Three companies would submit their designs and would be awarded funding: Oeffag, Phönix, and Lloyd.
Lloyd was one of several aircraft manufacturers in Austria-Hungary. Most of their aircraft that entered production were reconnaissance planes, but they had designed and built several experimental designs as well, some of which had unique and unorthodox designs, such as their FJ 40.05 Reconnaissance/Fighter hybrid. Their bomber design would also verge on to the strange. This would be the only bomber the company would produce. Lloyd came forward with two designs in January of 1916, the Luftkreuzer I and the Luftkreuzer II. The first would eventually be redesignated the 40.08 and the second would be redesignated the 40.10. A complete 40.08 was constructed by June 20th, 1916 and was ready for testing. Given there is no further evidence of work on production examples of the 40.10, it can be assumed the 40.08 was chosen over this design.
Engine testing would shortly begin with the 40.08 at the Aszod Airport. Early testing showed the design was severely flawed. The center of gravity was too high and the aircraft was too front heavy. During ground testing, this problem became clear with the aircraft tipping forward, resulting in damage to the front. A frontal wheel was added to fix this problem, as well as other minor changes. With the modifications completed in Aspern (a section of Vienna), the aircraft was slated to finally take off, with a pilot being assigned to the aircraft. The aircraft would attemp a take off in October of 1916, with Oberleutnant Antal Lányi-Lanczendorfer at the controls. Attempts at flight proved the aircraft was too heavy as well and it would never get truly airborne. A solution came with reducing the bomb load to decrease the takeoff-weight, but at the cost of ordnance.
Little work was done on the aircraft between October and November. In December, large rails were fixed to the bottom of the aircraft, replacing the tailings on the aircraft in February of 1917. With the number of problems the Luftkreuzer faced, it was obvious it would not be possible to improve the plane fast enough for it to have any value on the battlefields of Europe. In March of 1917, all work had stopped on the Luftkreuzer after an attempt to revise the aircraft was denied. The sole Luftkreuzer was sent to storage where it would remain for almost a year. In January of 1918, what was left of the aircraft was taken to an aircraft boneyard and destroyed in Cheb (located in soon to be Czechoslovakia). Thus concludes the story of Austria-Hungary’s attempted triplane bomber.
Austria-Hungary itself wouldn’t survive by the end of the year and would dissolve into Austria and Hungary and new national states such as Czechoslovakia. This wouldn’t be the only bomber built nor used in Austria-Hungary. Several other companies had designed large bombers, but none of these would enter production either. The only bombers that would be operated by the Luftfahrtruppen and see combat would be German and license-built Hansa-Brandenburg G.1s. These were bought in 1916 and would go on a single sortie before being sent to training duty, as they were found to be heavily outdated by the time they arrived on the battlefield. In the end, Austria-Hungary wouldn’t see itself using a mass-produced bomber.
The Luftkreuzer was a large triplane, twin-boom design. On the end of each boom, an Austro-Daimler 6-cylinder engine was mounted in tractor configuration (engine faced forward) and ended with a wooden propeller. These propellers did not counter rotate. Each boom itself was a reused fuselage taken from the Lloyd C.II aircraft. Each wing on the aircraft was actually a different length; with the top wing having a 76.3 ft (23.26 m) wingspan, the middle wing with a 73.42 ft (22.38 m) wingspan and the lower wing being 55.2 ft (16.84 m) wingspan. The central wing would be connected to the main fuselage and booms while the upper and lower wings would be connected via struts.
The main hull was rather tall and was one of the causes for why the aircraft was so front heavy and had such a high center of gravity. The cockpit was located beneath the upper wing and had several windows on both sides. The lower extended area was where the bombardier would sit, and was between the middle and lower wings. The central hull also contained the main engine, an Austro-Daimler 12-cylinder water-cooled engine in a pusher configuration. This engine was linked to a wooden two-bladed propeller. The hull was designed in a way so that the gunners would have a clear field of vision. Despite its prototype status, the aircraft was fully marked with the Luftfahrtruppen’s insignia, including one very large symbol painted directly in the front of this aircraft. The Luftkreuzer originally only had two main landing gear legs, with 4 wheels being mounted to each leg. When it was realized the aircraft was front heavy, a 3rd landing gear leg was directly in front of the central hull. No photos exist that show this third landing gear leg.
The armament would consist of 4 machine guns and 440 Ibs (200 kg) of bombs. The bombs would be mounted in the main central hull. The machine guns would most likely be Schwarzloses. These guns would be placed around the airframe, with two being in the central hull and the other two being located in the side hulls. Certain gunner stations would be equipped with a searchlight to aid in night missions. The aircraft was never fully armed before being scrapped, but it is likely it was loaded with bombs or ballast, given that the aircraft had weight issues before taking off and the solution given was to lower the bomb load.
Lloyd 40.08 – The only version of the aircraft built. Never truly flew.
Austro-Hungarian Empire– The Lloyd 40.08 was built in and for the Austro-Hungarian Empire’s Lufthahrtruppen, but did not see action.
*Given that the aircraft never truly flew, speed and similar flight statistics were never found.
Lloyd 40.08 Specifications
76 ft 3 in / 23.26 m
31 ft 3 in / 9.6 m
16ft 5 in / 5 m
110.0 ft² / 10.2 m²
1 × Pusher Austro-Daimler 12-cylinder water cooled engine 300 hp (224 kW)
2 × Tractor Austro-Daimler 6-cylinder inline water-cooled engines 160 hp (120 kW)
United Kingdom (1915 & 1917)
Anti-Airship Fighter – 1 Each Built
In 1915, Germany began bombing Great Britain by Zeppelin. For the first time, Britain itself was under threat by enemy aircraft. Early attempts to counter the Zeppelins were ineffective. The Royal Air Corps needed an aircraft to be able to endure long, nighttime missions to chase the Zeppelins. The Pemberton-Billing aircraft company designed the PB.29E quadruplane for this task. The aircraft didn’t perform as hoped, but before a final conclusion could be made it was lost in a crash. Years later in 1917, with the company under new management and renamed Supermarine, the program would rise again as the PB.31E. The PB.31E was dubbed the Nighthawk, and like its predecessor, proved to be ineffective in the role. The fighter is significant for its unusually large quadruplane layout and the first aircraft to be built by Supermarine.
The arrival of the Zeppelin in 1915 as a new type of weapon was an unwelcome one. It offered a new way of strategic bombing, as Zeppelins were faster and able to ascend higher than aircraft at the time. Zeppelins also served as a weapon of terror, as the civilians of England had never been faced with anything like it before, especially since the Zeppelins attacked mainly at night. Early attempts to counter Zeppelin raids proved ineffective, as anti-aircraft guns had a hard time spotting and aiming at the Zeppelins. Early forms of countermeasures involved aircraft dropping flares to illuminate the Zeppelins for gunners to see. None of these aircraft were used to actually intercept the airships. The Royal Air Corps needed an aircraft that would be able to reach and pursue Zeppelins on the homefront and on the battlefield. A potential solution came from a man named Noel Pemberton Billing.
Noel Pemberton Billing was a man of many talents. He was an inventor, aviator, and at one point a member of Parliament. At the time, he was invested in many forms of new technology and aircraft was one of them. Having formed his own aircraft company in 1913, he built several aircraft types for the Royal Naval Air Arm (RNAA), such as the PB.25. He had taken a short break from designing planes for the RNAA and wanted to pursue aircraft to help in the war effort. The task of taking on Zeppelins got him interested in designing a plane to fill the role.
His answer was the PB.29E, a quadruplane aircraft. Information regarding the PB.29E is sparse and no specifications can be found for it. To get the aircraft to the altitudes at which Zeppelins usually lurked, Pemberton Billing applied triplane principles in making the aircraft, except taking it a step further and adding an extra wing. Having more wings, in theory, would assist with lift, a necessary factor when trying to chase the high-flying Zeppelins. Work began in late 1915, with the aircraft being finished before winter. The PB.29E was intended to fly for very long missions and needed to operate at night. To assist in spotting the behemoths, a small searchlight was to be mounted in the nose of the aircraft. The sole PB.29E crashed in early 1916. From test flights, the aircraft proved to be cumbersome and would not have been able to pursue Zeppelins. The two Austro-Daimler engines did not prove to be sufficient for the intended role, and performance suffered from it.
On September 20th, 1916, Noel Pemberton Billing sold his company to Hubert Scott Paine so he could become a member of Parliament. His career in Parliament was full of slander and conspiracy, and ultimately negatively affected the war effort. Soon after being acquired, Paine renamed the company as the soon to be famous Supermarine Aviation Works, in honor of the firm’s telegraph address. Work continued on a Zeppelin interceptor, which would eventually become the PB.31E. The PB.31E was technically the first aircraft built by Supermarine and it resembled a larger and more advanced version of the PB.29E. It retained many aspects from its predecessor: the quadruplane layout, the mounted searchlight, and endurance for long nighttime missions. The armament was expanded with a second Lewis gun mounted in the rear cockpit as well as a Davis gun mounted on top of the cockpit above the wings. To make the crew more comfortable, the cockpit was fully enclosed, heated, and had a bunk for crewmembers. The Austro-Daimler engines were replaced by 100hp Anzani radial engines. Expected speed was 75 mph (121 km/h) and it was to operate up to 18 hours.
The aircraft was constructed in February of 1917, with a second in the works. On board the project was R.J Mitchell, the future designer of the Supermarine Spitfire. He began as a drafstman for the company and several designs concerning the fuselage and gun mounts of the PB.31E are labeled with his name. To the engineers, the aircraft was dubbed the Supermarine Nighthawk, however, this name was never official. Early flights were conducted at the Eastchurch airfield by test pilot Clifford B. Prodger. Tests showed that, like its predecessor, the engines weren’t capable of propelling the aircraft to its desired level of performance. To reach altitudes most Zeppelins were found at took an hour. Not to mention, newer Zeppelins could go even higher. Its expected 75 mph (121 km/h) top speed was never reached, with the aircraft only going 60 mph (96 km/h). However, it had a safe 35 mph (56 km/h) landing speed, which would have given the aircraft easy landing capability. With the performance lacking, the RAC deemed the project to be a dead end.
With the introduction of new incendiary rounds which easily ignited Zeppelins, Britain could defend itself with the improved AA guns. Along with the new rounds, the RAC started using the Royal Aircraft Factory B.E.2 to intercept Zeppelins at night. Originally intended for dogfighting, the B.E.2 proved to be ineffective and slow against fighters, but Zeppelins were easier, and much larger targets. With the Nighthawk now not needed, Supermarine ended up scrapping the first and incomplete second prototypes in 1917. Although the Nighthawk would never have been successful had it entered production, it still represents major innovations in aircraft design. It was one of the first true night-fighting aircraft to be designed, a concept later heavily utilized in the Second World War. The honor of being the first aircraft built by Supermarine under their name also goes to the Nighthawk.
The PB.29E was a quadruplane designed to chase and intercept Zeppelins. Its fuselage was mounted between the lower two wings, with a gunner port being mounted in the upper two wings, leaving an opening in the middle between the two. Two crewmembers occupied the central fuselage with a single gunner gunner position in a seperate section above. The cockpit was open to the elements, as well as the gunner port. For armament, a single Lewis gun was mounted for attacking Zeppelins. For engines, the PB.29E had two Austro-Daimler six-cylinder engines in a pusher configuration. The tail itself was doubled.
The PB.31E was a quadruplane like the PB.29E, but it was larger utilized a different fuselage design. Instead of having the fuselage between the lower two wings, the PB.31E positioned its body between the middle two wings. The body itself was of all wooden construction. To reduce splinters if the aircraft was fired upon or in the event of a crash, the fuselage was taped and covered in heavy fabric. To make the long missions more comfortable the cockpit was heated and completely enclosed by glass. A bunk was added for one crew member to rest during the flights as well, as the expected flights could last up to 18 hours. A searchlight mounted protruding from the center of the nose for use in patrols at night. The searchlight was movable to allow pointing it at different targets. It was powered by an onboard dynamo hooked up to a 5hp A.B.C petrol engine. For fuel storage, the PB.31E had 9 individual petrol tanks located around the cockpit area. The tanks were built to be interchanged if they were damaged or empty. In the front of the aircraft were several slits behind the searchlight that would assist in cooling. The wings of the PB.31E had significant cord to them. The tailplane was doubled like on the PB.29E, and the tail itself was lower to allow the rear mounted Lewis gun more range
of fire. For engines, the PB.31E had two Anzani radial engines in tractor configuration. These engines gave the PB.31E its slow speed of 60 mph (96 km/h), and its hour-long ascent to 10,000 ft (3000 m). The fluid lines, controls and other parts connected to the engines were placed outside the fuselage in armored casings. For armament, the PB.31E carried a frontal Lewis gun, a top mounted Davis recoilless gun and a rear Lewis gun. The Davis gun was built on a mount that allowed an easy range of motion in most directions. Lewis gun ammo was stored in six double cartridges and 10 Davis gun rounds were stored onboard as well. Also on board were an unknown amount of incendiary flares to be dropped should a Zeppelin be directly below the craft.
29E– First aircraft built for the Anti-Zeppelin role. Armed with a single Lewis gun. Crashed during testing.
31E– Second aircraft. One prototype and one unfinished plane. Resembled a larger version of the PB.29E. Carried a Davis gun and two Lewis guns. Scrapped once the design was deemed unworthy.
Great Britain – The two prototypes were built and tested in England.
Nazi Germany (1938)
Armored Ground Attack Aircraft – 1 Replica Built
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.
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.
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.
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.
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.
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.
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.
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
21 ft 4 in / 6.5 m
23 ft 7 in / 7.2 m
5 ft 3 in / 1.6 m
1x 1,200 hp (894 kW) DB 601 Inline Engine
8,160 lbs / 3,700 kg
348 mph / 560 km/h
1,240 mi / 2,000 km
Maximum Service Ceiling
31,170 ft / 9,500 m
1x 1010 lbs (500 kg) bomb
At least 2 machine guns of unknown type (Most likely MG 15 or MG 17)
United Kingdom (1942)
Anti-Tank Aircraft Design – None Built
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.
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.
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.
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.
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.
Martin-Baker “Tankbuster” – The only version of the Tankbuster drawn was the original design with a single cannon.
United Kingdom – This aircraft would have been operated by the Royal Air Force had it been produced.
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.
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.
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 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.
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.
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.
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.
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.
Nazi Germany – The sole operator was Nazi Germany, which reportedly used the Falke during the air defense of Bremen in 1940.
United States of America (1944)
Prototype Ground Attack Aircraft – 1 Built
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.
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.
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.
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.
XA-41 – [The sole prototype built, used as a testbed for the XR-4360 engine.]
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
70 ft / 21.3 m
46 ft / 14 m
22 ft 6 in / 6.9 m
605 ft² / 184.4 m²
1x 3,000 hp ( 2240 kW ) XR-4360-8
1x 8 bladed Hamilton Standard contra-rotating propeller
501 US gal / 1896 L
28 US gal / 106 L
18,405 lbs / 8350 kg
28,545 lbs / 12950 kg
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)
340 mph / 550 km/h at 15,600 ft / 4755 m
168 mph / 270 km/h
312 mph / 500 km/h (with torpedoes)
1,250 mi / 2010 km (Torpedoes)
2,880 mi / 4635 km (Maximum)
Maximum Service Ceiling
24,500 ft / 7470 m
4 Browning M2 machine guns mounted in the wings (1600rds)