Convair XF-92 - Design and Development

Design and Development

Prior to August 1945, the Vultee Division of Consolidated-Vultee looked at the possibility of an swept-wing aircraft powered by a ducted rocket. Years earlier, the company had performed designs which involved liquid-cooled radiator engines. If properly designed, fuel would be added to the heat produced by small rocket engines, creating a "pseudo-ramjet".

In August 1945, the United States Army Air Forces (USAAF, since renamed "United States Air Force") issued a proposal for a supersonic interceptor capable of 700 mph (1,100 km/h) speeds and reaching an altitude of 50,000 feet (15,000 m) in four minutes. Several companies responded, among which was Consolidated-Vultee, which submitted its design on 13 October 1945. This design featured swept wings and V-tails, as well as a powerful propulsion system. Besides the ducted rocket, four 1,200 pounds-force (5.3 kN) rockets were positioned at the exhaust nozzle, along with the 1,560 pounds-force (6.9 kN) 19XB turbojet produced by Westinghouse.

In May 1946 Convair (then still Consolidated Vultee) won with their proposal for a ramjet-powered aircraft with a 45° swept wing under USAAF Air Materiel Command Secret Project MX-813. However, wind tunnel testing demonstrated a number of problems with this design.

In constrast to popular myth, this aircraft and subsequent Convair delta wings owed nothing to the research of Alexander Lippisch. Convair engineers designed the delta wing before becoming aware of Lippisch's work, using the 1944 work of Robert T. Jones on very thin delta wings. Lippisch's thick delta wing design was tested by the NACA at Langley Research Center, where it proved completely unsuitable for transonic and supersonic flight.

Using the 1,560 lbf (6,900 N) Westinghouse J30 assisted by a battery of six 2,000 lbf (8.9 kN) liquid-fueled rockets, the layout placed the engine in a seemingly oversized cylindrical fuselage, with the pilot in a cockpit centered in the middle of the fuselage, serving double duty as a shock cone for the engine intake. The basic layout of the fuselage was very similar to the Miles M.52 design, although the M.52 did not use a delta wing. The design was presented to the U.S. Air Force in 1946, and was accepted for development as the XP-92.

In order to gain in-flight experience with the delta wing layout, Convair suggested building a smaller prototype, the Model 7002, which the USAAF accepted in November 1946. The design was similar in general layout as the original, but by placing the pilot in a conventional cockpit at the front, instead of centered in the fuselage, the resulting aircraft looked considerably less odd. In order to save development time and money, many components were taken from other aircraft; the main gear was taken from a North American FJ-1 Fury, the nosewheel from a Bell P-63 Kingcobra, the engine and hydraulics were taken from a Lockheed P-80 Shooting Star, the ejector seat and cockpit canopy were taken from the cancelled Convair XP-81, and the rudder pedals were taken from a BT-13 trainer.

Construction was well underway at Vultee Field in Downey, California when North American Aviation took over the Vultee plants in summer 1947. The airframe was moved to Convair's plant in San Diego, and completed in the autumn. In December it was shipped without an engine to NACA's Ames Aeronautical Laboratory for wind tunnel testing. After testing was completed, the airframe was returned to San Diego, where it was fitted with a 4,250 lbf (18,900 N) Allison J33-A-21 engine.

By the time the aircraft was ready for testing, the concept of the point-defense interceptor seemed outdated and the (now redesignated) F-92 project was cancelled. They also decided to rename the test aircraft as the XF-92A.