The concept of a “penetration fighter” evolved towards the end of WW II, when the USAAF anticipated the need for new class of jet fighter aircraft for the long-range escort of its strategic bombers. In 1946, it ordered the McDonnell XF-88 and Lockheed XF-90 to meet this requirement; the following year it would also order the North American YF-93A to fulfill the same role. While these were under development, the Air Force continued to study future penetration fighter configurations, one of which is presented here: Air Materiel Command Design (AMCD) 938A.
AMCD 938A was produced by the Aircraft Laboratory in the Engineering Division of the Air Materiel Command. The memorandum describing it dates from August 18, 1948. The fighter had the same basic configuration as AMCD 938 (details of which are presently lacking) with the exception of fuel distribution. AMCD 938 was designed to incorporate external fuel tanks which furnished a fuel supply up to the time of combat at which time the tanks were jettisoned. AMCD 938A was designed to carry the total fuel load internally.
AMCD 938A was large for a fighter, with a length of 66 ft, a span of 68 ft, and a gross weight of 55,853 lbs. Besides its scale, the aircraft’s most notable feature was a prominent ventral inlet, which would not be seen on a production Air Force fighter till the F-16 of the 1970’s. Wing and tail surfaces were swept at 35º. The AMCD 938A was armed with four 20mm cannon with 250 rounds per gun. High speed at sea level was 719 mph; at 35,000 ft, it was 656 mph. The service ceiling was 50,400 ft and the combat radius was 1,700 miles.
The aircraft was powered by two Pratt & Whitney TDM-428 engines, which were selected because of the higher thrust rating than the Westinghouse J-40. The higher thrust helped to compensate for the increase in size and weight of the design resulting from provision for internal stowage of all the fuel.
As a result of the study, it was concluded that internal stowage of all the fuel in high speed fighter airplanes had many advantages which deserved careful consideration in future design, development and procurement of new aircraft. The advantages included:
- An aerodynamically cleaner airplane for take-off, climb and cruise out to combat.
- Elimination of time and work necessary for the installation of external tanks for every mission.
- Elimination of the logistical problem of equipping and supplying droppable tanks to operational units.
- Elimination of possible buffeting or structural problems caused by installation of external tanks on high speed aircraft.
While this study was not intended to be conclusive in itself, the Aircraft Laboratory recommended that further consideration be given to this problem, possibly by actual flight and wind tunnel investigation. The author has found no evidence that this particular study ever reached that stage, however.
To read the memorandum in depth, please click through the image gallery above.
All images from NARA Archives II, College Park, MD, RG 341
Serial No. MCREXA4-4308-10-1 Add. 1, Memorandum Report on Preliminary Design Study, Penetration Fighter, AMC Design 938A, Headquarters, Air Materiel Command, Wright Field, Dayton, Ohio, Engineering Division, Aircraft Laboratory, August 18, 1948, in the files of the National Archives II at College Park, MD, RG 341