4 Unusual Allied Prototype Planes of WWII

Throughout WWII, the Allied forces tested numerous aircraft designs in the hopes of gaining an edge in aerial combat. While many of these prototypes never made it into mass production, they showcased unique engineering concepts. Below are four unusual Allied prototype planes that stood out for their innovative, yet ultimately impractical designs.

High Altitude (Wellington Mark VI)

The Vickers Wellington was a critical medium bomber in the early years of WWII. However, as enemy fighters improved, the British sought to develop a version capable of flying at higher altitudes, safe from interceptors and flak. The result was the Wellington Mark V, a high-altitude variant designed with a pressurized cabin.

Fitted with Bristol Hercules engines, the Wellington Mark V could reach altitudes of 35,000 feet, but engine performance at such heights proved troublesome. Subsequent versions, like the Wellington Mark VI, were equipped with Rolls-Royce Merlin engines, which performed better in the thin air. However, bombing at high altitudes proved less effective, and the logistical challenges of maintaining the pressurization system limited its use. While around 60 were produced, none saw combat, and the design was scrapped by 1943.

Mid-Engined Fighters (Bell P-39 Airacobra)

The Bell P-39 Airacobra was one of the most distinctive Allied fighters, largely due to its unusual mid-engine configuration. Instead of placing the engine in the nose, the Airacobra’s Allison V-1710 engine was mounted behind the cockpit. This design allowed for a 37mm cannon to be placed in the nose, firing through the propeller hub—an innovative feature that provided considerable firepower.

Though the mid-engine design improved aerodynamics, it also created problems with stability and performance, especially at high altitudes where the P-39 struggled due to the lack of a turbocharger. While it was not popular among British and American pilots, the Soviet Union used the P-39 extensively on the Eastern Front, where its low-altitude performance and heavy armament proved effective.

Handley Page Manx

The Handley Page Manx was a radical prototype designed to test the viability of a tailless aircraft. First flown in 1943, the Manx had a pusher-propeller configuration, with the engines mounted at the rear of the aircraft. It also featured swept wings and a distinctive, almost wing-like fuselage, eliminating the need for a traditional tail section.

The Manx was meant to explore new aerodynamic principles, particularly in relation to stability and control. However, the prototype suffered from various technical issues, including problems with engine cooling and structural weaknesses. Though it made a few test flights, the project was eventually abandoned, with no further development of tailless bombers taking place during the war.

Proposal R-40C

In 1940, the U.S. Army Air Corps launched a competition to design a high-performance, long-range interceptor that could outperform existing fighter planes. One of the most unusual entries was the Vultee XP-54, also known as Proposal R-40C. The XP-54 had a striking appearance, featuring a high-mounted pusher engine and a “cranked” wing design with a forward-swept section near the cockpit.

The XP-54 incorporated a number of ambitious features, including a pressurized cockpit, a unique ejection seat system, and an adjustable tail for better control at different altitudes. However, the engine underperformed, and the aircraft’s complexity led to numerous delays. Only two prototypes were ever built, and the XP-54 never saw combat. By the time it was ready for testing, the U.S. military had already shifted its focus to more practical fighter designs.