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 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.
- X-Plane / Developmental
46.10 ft (14.05 m)
44.46 ft (13.55 m)
21.49 ft (6.55 m)
20,944 lb (9,500 kg)
26,555 lb (12,045 kg)
657 mph (1,057 kph; 571 kts)
46,998 feet (14,325 m; 8.9 miles)
1,000 miles (1,610 km; 869 nm)
8,700 ft/min (2,652 m/min)
6 x 0.50 caliber Browning M2 Heavy Machine Guns (HMGs) in nose.
4 OR 6 x 20mm cannons in nose assembly.
Downey Penetration Fighter - Base Series Name; no formal project or military designation was assigned the proposal.