From the Planes You’ve (Probably) Never Heard Of Department of Wingspan, we bring you the McDonnell XP-67.


The XP-67 on the tarmac at Lambert Field in St. Louis (US Air Force)

Since its creation in 1939, the McDonnell Aircraft Corporation, and later McDonnell Douglas (which was then absorbed by Boeing in 1997), has produced some of America’s most iconic military and civilian aircraft. Growing rapidly during WWII from its humble beginnings as an aircraft parts supplier, McDonnell’s first foray into aircraft design came with the US Army’s Request for Proposal R-40C, which was intended to encourage American companies to push the boundaries of aircraft design and create technologically advanced aircraft to keep pace with modern European designs. McDonnell initially responded to the request with a truly radical aircraft that placed an Allison V-3420 engine in the fuselage behind the cockpit that turned a pair of pusher propellers on the wings via a 90-degree shaft and gearboxes. The Army wasn’t particularly impressed with the arrangement, and McDonnell was not chosen as a finalist in the competition. Nevertheless, the Army gave McDonnell $3,000 to continue their work.

The unique blended wing and nacelles of the XP-67 “Bat” are shown in this view from above (US Air Force)

McDonnell returned in 1941 with the redesigned XP-67, a twin-engine interceptor with engines housed in the wings rather than in the fuselage. While that arrangement was more traditional, it was the shape of the XP-67 that was unique. In an attempt to make the aircraft as aerodynamic as possible, McDonnell housed the engines in long tapered nacelles that were blended into the wing. The wing was then blended into the fuselage to create a single structure. The resulting shape looked rather like a bat, and the XP-67 received its unofficial nickname “Bat” or “Moon Bat.” With its  laminar flow wing design, McDonnell promised a top speed of 472 mph with a gross weight of 18,600 pounds, although the weight soon ballooned to 20,000 pounds. Still, the Army awarded McDonnell $1.5 million to build two prototypes and test the radical interceptor.

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The XP-67 certainly looked sleek and futuristic, but its performance was unremarkable (US Air Force)

The XP-67 took its maiden flight on January 6, 1944 but, despite the futuristic shape and promises of high performance, the Bat never quite lived up to its billing. The Continental XI-1430 inverted, liquid-cooled V-12 engines failed to deliver adequate power, and engine cooling proved problematic, an issue that was never fully resolved. Flight tests showed that the new fighter flew reasonably well, but its takeoff roll was too long and its climb rate was unacceptable, and it only managed a top speed of 405 mph, far below the 472 mph designers promised. McDonnell proposed replacing the Continental engine with more powerful Rolls-Royce or Allison engines, and even suggested additional turbojets in the nacelles behind the piston engines, but the Army declined McDonnell’s request for additional funding.

The blended lines of the XP-67 are apparent in this head-on view. (US Air Force)

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During a test flight in 1944, the starboard engine caught and test pilot E.E. Elliot was forced to make an emergency landing. Elliot landed safely, but the flames engulfed the fuselage and the single flying prototype was destroyed. Since the XP-67 had shown no real advances in performance over existing designs, the project was canceled. Fortunately, the setback did not deter McDonnell. The company followed the XP-67 with the FH Phantom, the first fully jet-powered aircraft to operate from an aircraft carrier, and went on to become an industry leader in the production of military aircraft and later spacecraft.


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