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Lockheed XP-90 / XF-90


Prototype Escort / Penetration Fighter Aircraft


Its size and weight held the Lockheed XF-90 from competing favorably against the McDonnell XF-88 Voodoo for the USAF.
Authored By: Staff Writer | Last Edited: 3/15/2019
On August 28th, 1945, the United States Army Air Forces (USAAF) announced a new requirement calling for a twin-engine "penetration fighter" with swept wings suitable for escorting a new generation of jet-powered bombers over enemy territory and back. Armament called for 6 x 0.50 caliber heavy machine guns or 4 x 15.2mm (0.60 cal) large caliber heavy machine guns. By this time in history, World War 2 was over in both Europe and the Pacific - the conflict serving to establish the fighting doctrine for the USAAF in which large formations of bombers, escorted by nimble long range fighters, would wreak havoc on enemy targets below. The primary Cold War enemy would now become the Soviet Union which was attempting to outpace the West with its own collection of jet-powered fighters and bombers.

Various concerns heeded the call including Vultee, Curtiss, Goodyear, Lockheed, McDonnell, and Northrop. The Lockheed proposal - XP-90 - initially revolved around a swept-wing design as expected but there was a brief change to a full delta planform in 1947. A mockup was built but the proposed aircraft was thought to be too heavy and lack the needed capabilities for the role (drawings of this version of the XP-90 went on to showcase an aircraft that appeared not unlike the classic Avro Vulcan of Cold War fame). As such, the program was reverted back to a more conventional swept-wing form, though through an all-new design, and this emerged in late 1947.

The finalized aircraft was a sleek offering with a very pointed nosecone, low-mounted swept-back monoplane wings, and a single vertical tail fin with raised horizontal planes. The cockpit was just aft of the nose cone under a two-piece, lightly-framed (single-seat) canopy offering good views of the action ahead and to the sides (vision to the rear was blocked by the partially raised fuselage spine). The twin engine arrangement was aspirated by two small intakes found along the lower sides of the fuselage. The undercarriage was of a retractable tricycle arrangement with single wheels to each leg. Of particular note in the XP-90 design was its "variable incidence" vertical tail fin which could be adjusted to move forward or back to help adjust the horizontal stabilizers.

The XP-90 designation was eventually revised to become XF-90 in accordance to the shift from "Pursuit" (P) aircraft from the piston-powered days to "Fighter" (F) aircraft of the jet age.

The early changes to the XF-90 product forced a delayed first flight, this occurring on June 3rd, 1949. The initial prototype (46-0687) was outfitted with 2 x Westinghouse XJ34-WE-11 turbojet engines of 3,000 lb thrust each though lacking afterburner capability. Even with its twin engine arrangement, the large and heavy XP-90 lacked the necessary power for take-off and was further outfitted with Rocket Assisted Take-Off (RATO) canisters for support. The second prototype (46-0688), showcasing 2 x Westinghouse XJ34-WE-16 engines with afterburner (the first USAF aircraft with this feature), fared better but performance still proved wanting: as with many early fighter jets, the XF-90 only reached Mach 1 in a dive. The first prototype was eventually retrofitted with XJ34-WE-16 afterburning turbojets.

The second prototype (as "XF-90A") completed its first flight on April 12th, 1950.

The XF-90 competed unsuccessfully against the McDonnell XF-88 and North American YF-93A (an offshoot of the F-86 "Sabre" fighter). The XF-88 was selected as the winner by the USAF and contracted for production until the of a "penetration fighter" soon passed from the minds of USAF authorities - the focus now given to meeting the threat of Soviet nuclear bombers head on through development of dedicated interceptors. This forced the XF-88 to evolve along other lines and become the classic F-101 "Voodoo" supersonic fighter.

After a time in storage, the first prototype was used in structural tests with NACA until destroyer in 1953. The second prototype survived no fewer than three atomic blast during its post-flying test phase. Its hulk was then delivered to the National Museum of the United States Air Force in Dayton, Ohio.

In its finalized form, the production quality F-90A was to field a primary armament of 6 x 20mm cannons and support for 8 x 5" (127mm) HVAR rockets for attacking bombers. The cannons were to be fitted horizontally below the engine intakes - three guns to an intake. It was to also hold a bomb-carrying capability up to 2,000 lb of stores (2 x 1,000 lb bombs on two hardpoints). Performance included a maximum speed of 665 miles per hour with a range out to 2,300 miles, a service ceiling up to 39,000 feet, and a rate-of-climb of 5,555 feet per minute. Empty weight was 18,050 lb with a Maximum Take-Off Weight (MTOW) of 31,060 lb.






Specifications



Year:
1949
Status
Cancelled
Crew
1
[ 2 Units ] :
Lockheed - USA
National flag of United States United States (tested)
- Fighter
- X-Plane / Developmental
Length:
56.17 ft (17.12 m)
Width/Span:
40.03 ft (12.2 m)
Height:
15.75 ft (4.8 m)
(Showcased structural dimension values pertain to the Lockheed XF-90A production model)
Empty Weight:
18,089 lb (8,205 kg)
MTOW:
31,129 lb (14,120 kg)
(Diff: +13,040lb)
(Showcased weight values pertain to the Lockheed XF-90A production model)
2 x Westinghouse XJ34-WE-15 afterburning turbojet engines developing 4,100 lb of thrust each.
(Showcased powerplant information pertains to the Lockheed XF-90A production model)
Maximum Speed:
662 mph (1,065 kph; 575 kts)
Service Ceiling:
39,042 feet (11,900 m; 7.39 miles)
Maximum Range:
2,287 miles (3,680 km; 1,987 nm)
Rate-of-Climb:
5,555 ft/min (1,693 m/min)
(Showcased performance values pertain to the Lockheed XF-90A production model; Compare this aircraft entry against any other in our database)
PROPOSED:
6 x 20mm internal cannons

OPTIONAL:
8 x 2.5" (127mm) High Velocity Aerial Rockets (HVARs)

Up to 2,000 lb of externally-carried drop ordnance (in place of rockets).
(Showcased armament details pertain to the Lockheed XF-90A production model)
XP-90 - Original Product Designation
XF-90 - Revised Product Designation; first prototype, initially with non-afterburning turbojet engines installed.
XF-90A - Second prototype with afterburning turbojet engines installed.
F-90A - Proposed production model designation

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