World War 2 (1939-1945) showcased to American warplanners the need to invest in "penetration fighter" types - their value proven by the excellent North American P-51 "Mustang" fighter serving as escort to larger, slower-moving bomber types. Before the end of the war, the turbojet engine was making headlines as the future of military powered flight and it only seemed natural to concentrate a future penetration fighter initiative around this propulsion scheme. Many attempts at fulfilling the category were made but none managed a future beyond "X-" and "Y-" designated prototypes and flight models. Eventually the doctrine of penetration fighters used to accompany bomber formations was dropped from USAF (United States Air Force) strategy as the concentration now fell to dedicated interceptors, higher-flying strategic bombers and advancing ground- or submarine-based missile technology.
Back in late-August of 1945, with the Japanese surrender in hand to formally end World War 2, the USAAF (United States Army Air Force) was looking to the post-war future when it presented a new penetration fighter requirement. The specification called for a twin-engine, jet-powered platform large dimensions (for a fighter) to couple with a new generation of long-range, high-flying bombers. The selection of two engines showcased the inherent limitation of existing turbojet technology of the time - fuel thirsty as they were the engines limited operational ranges of any aircraft fielding just one powerplant. Beyond this requirement, the new aircraft would utilize the latest in aerodynamic data, either that as developed stateside or information captured from the Germans at the close of the war in Europe. As such, the wing mainplanes were to be swept and all tail surfaces would follow suit. Cabin pressurization would be required for the altitudes in play.
The service called for a design with base maximum speed of 600 miles per hour and an operational range out to 900 miles with an operating ceiling of 50,000 feet. Initial armament would be 6 x 0.50 caliber Heavy Machine Guns (HMGs) with the option to convert this arrangement to 4 OR 6 x 20mm cannons down the road.
Consolidated Vultee - born from the merger of Consolidated Aircraft and Vultee Aircraft (and predecessor to Convair) - moved to sell the USAAF on the idea of its penetration fighter design. The aircraft emerged from the drawing boards at its Downey Division (California) location and presented just one take on the requirement. As requested the mainplanes were swept back, mid-mounted appendages along the fuselage sides. The conventional tail unit incorporated a single vertical fin and held its horizontal planes low along the fin's sides. An intake arrangement was featured ventrally with additional slots cut into the sides of the aft fuselage section. The cockpit was held well-forward of midships with the pilot sitting under a relatively unobstructed "tear-drop" style canopy for maximum vision.
Engineers took the design several steps further. Firstly a "triple engine" arrangement was planned to exercise the most power from the available technology. Beyond increasing performance, this engine arrangement increased reliability should one unit fail the pilot. It was planned to fit 3 x Westinghouse 24C series turbojets into the design, two in a ventral fairing (aspirated by the ventral intakes and exhausted under the empennage) and a third within the empennage section (aspirated by the side-mounted intake slots and exhausted under the tail fin). Placement of the engines in the body and tail of the aircraft meant that the nose section could accept all of the planned armament and centralize firepower on a given target.
Secondly, the group produce two working plans for the aircraft - the first was to feature a "bicycle style" wheeled undercarriage arrangement (retractable) and the second to sport a traditional, conventional tricycle undercarriage. For the former, this allowed the wings to be reduced in thickness, making them lighter, stronger and flexible for high-speed flight. When ground-running, the aircraft relied on outriggers - thin, simple wheeled legs - to hold up the edges of the aircraft's wings and thus keep the aircraft from tipping. In the more conventional tricycle undercarriage approach, a thicker wing was to be used to house the main landing gear legs.
The design team estimated their aircraft to feature a maximum speed of 657 miles per hour, a combat radius of 1,000 miles and a service ceiling of 47,000 feet. Both presented versions were estimated with roughly the same performance values.
At any rate, the Downey Penetration Fighter did not proceed beyond this planning stage for it was not accepted by USAAF authorities. After review, the design was thought to have grown too with its engine trio which also elevated maintenance requirements and complicated repair. There was no denying the estimated performance figures and reviewers appreciated the excellent vision for the pilot but there was some additional concern in regards to agility for such a large aircraft - a key quality of fighter types.
Selection moved on to a few different designs from competing sources - the McDonnell XP-88/XF-88 "Voodoo", the Lockheed XP-90/XF-90, and the North American YF-93 - but none of these were furthered beyond "fly-off" competition forms as the idea of a penetration fighter quickly fell to history and the idea of a dedicated penetration fighter also fell with it. Bombing enemy targets in their own territory took a back seat to intercepting incoming waves of nuclear-armed Soviet bomber formations.
Aircraft like the supersonic Convair F-102 "Delta Dagger" were pushed through as dedicated interceptors while the XP-88 went on to see its own ultimate evolution as the McDonnell F-101 "Voodoo" fighter - these offerings detailed elsewhere on this site.
(OPERATORS list includes past, present, and future operators when applicable)
✓Air-to-Air Combat, Fighter
General ability to actively engage other aircraft of similar form and function, typically through guns, missiles, and/or aerial rockets.
✓X-Plane (Developmental, Prototype, Technology Demonstrator)
Aircraft developed for the role of prototyping, technology demonstration, or research / data collection.
46.1 ft (14.05 m)
44.5 ft (13.55 m)
21.5 ft (6.55 m)
20,944 lb (9,500 kg)
26,555 lb (12,045 kg)
+5,611 lb (+2,545 kg)
(Showcased structural values pertain to the base Consolidated Vultee Downey production variant)
3 x Westinghouse 24C turbojet engines developing 3,000lb of thrust each (estimated).
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