page_title: McDonnell XP-67
section_title: Testing
hierarchical_section_title: McDonnell XP-67 / Design and development / Testing
caption_attribution_description: The experimental U.S. Army Air Forces McDonnell XP-67 Bat (s/n 42-11677) in flight. This aircraft was damaged beyond repair by a midair fire in September 1944.
context_page_description: The McDonnell XP-67 "Bat" or "Moonbat" was a prototype for a twin-engine, long-range, single-seat interceptor aircraft for the United States Army Air Forces. Although the design was conceptually advanced, it was beset by numerous problems and never approached its anticipated level of performance. The project was cancelled after the sole completed prototype was destroyed by an engine fire.
context_section_description: An extensive aerodynamic test program of the numerous advanced aspects of the design was begun by McDonnell, NACA, and the University of Detroit. The design demanded skin that was perfectly smooth and precisely shaped to maintain its laminar-flow characteristics, mandating the development of new construction techniques, as the company had never produced an entire aircraft before. Wind tunnel testing uncovered problems with engine cooling airflow through the engine nacelles, which were never fully resolved. Difficulties were also encountered in obtaining engines, as wartime production demands hampered Continental's efforts to deliver running examples of the experimental XIV-1430 engines to competing aircraft test programs. The project was also delayed by intense competition for testing time at the NACA wind tunnel facility in Langley, Virginia.
  The first XP-67, 42-11677, was ready for ground trials on 1 December 1943. The aircraft was fitted with XIV-1430-17/19 engines and General Electric D-23 turbo-superchargers but no pressurization equipment or armament was installed. On 8 December, the aircraft was damaged by fires in both engine nacelles, caused by a malfunction of the exhaust manifold slip rings. By 6 January 1944, the damage was repaired and the XP-67 made its first flight, which ended after six minutes due to engine trouble. After modifications were made to the engine installations, two test flights were carried out. On the fourth flight, the engine bearings burned out when the engines were accidentally overspeeded.
  By this time, it was becoming obvious that the XP-67 was hampered by a serious lack of power. The engines were only delivering 1,060 hp (790 kW), well short of their promised 1,350 hp (1,007 kW) rating. Company founder Jim McDonnell, frustrated by engine procurement delays and the XI-1430's subpar output, began to campaign for funding to re-engine the prototype with a pair of Allison or Rolls Royce piston engines augmented by auxiliary Westinghouse turbojets in the aft nacelles. Although McDonnell promised a very impressive 500 mph (805 km/h) top speed with the new powerplants, the Army rejected the proposal, demanding more testing of the existing design. As a result of wind tunnel tests, the tailplanes were raised 12 in (31 cm) while the XP-67 waited for replacement engines.
caption: XP-67 in flight
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