The Vertical Take-Off and Landing (VTOL) fighter aircraft had always been on the minds of aeronautical engineers once viable thrust sources became available. This field was evolved some - at least conceptually - during World War 2 (1939-1945) where one of the more notable entries became the proposed German Focke-Wulf "Triebflugel" fighter. This unique aircraft relied on three ramjet engines held at the ends of three individual wings which were, themselves, set to rotate about a tubular fuselage housing the sole pilot. The aircraft stood upright when landed and achieved horizontal flight once having attained the desired altitude. Needless to say, the ambitious project never materialized and remained one of the many "paper airplanes" entertained by German engineers and air ministry leaders, particularly in the latter stages of the war.
The post-World War 2 period continued to allow engineers to develop many aircraft within the confines of a peacetime environment but with the added advantage of a maturing turboprop and turbojet field. This led several prominent nations to delve into viable VTOL aircraft which resulted in such creations as the American Lockheed XFV-1 and the Convair XFY-1 "Pogo" and the French SNECMA C-450 "Coleopter". All of these designs held physical and operational similarities - they sat vertically when landed or taking off (i.e. a "tailsitter" design), seated a single pilot near the nose, and used some form of thrust - be it jet or prop - to achieve a minimum operating altitude before transitioning to horizontal flight.
Along with the Convair entry, the Lockheed XFV-1 was conceived of through a USN requirement issued in 1950 calling for a shipborne VTOL aircraft capable of operating from a small deck space. The idea was to give convoy-type ships an armed protective measure against incoming enemy aerial threats. Sitting vertically when at rest, the aircraft took up little space and required just as much when taking off or landing. Such instruments could also be had "at the ready" and respond to threats in short order. Design of the XFV-1 was attributed to Art Flock.
It was decided to power the new fighter through a contra-rotating propeller arrangement, the two propeller units each spinning three blades apiece in opposite directions to achieve inline propulsion. The propeller units would be fitted at the extreme nose of the aircraft and driven by the Allison XT40-A-6 turboprop outputting 5,850 horsepower and coupled to Curtiss Electric propellers. The XT40-A-6 was to serve as an interim solution prior to the fitting of the more powerful, in-development YT40-A-14 model which promised upwards of 7,000 horsepower - this engine essentially a pairing of Allison T38 units driving the propeller units through a common gearbox.
As a naval fighter, it was proposed to arm the XFV-1 through 4 x 20mm cannons or 48 x 2.75" aerial rockets - these to be held in the wingtip pods to help clear the spinning propeller blades.
It was soon found that the A-6 engine could not meet the required VTOL thrust and thusly the XFV-1 prototype had to be fitted with a cumbersome wheeled undercarriage system comprised of twin-strutted main legs held under the vehicle's mass. The fixture was a temporary solution but non-retractable by design and solely intended to test the XFV-1 during its horizontal flight phase.
In March of 1951 two prototypes were ordered from Lockheed and three from CONVAIR with the Lockheed model becoming the first of the entries to go airborne. A brief test "hop" was recorded on December 23rd, 1953 but a true formal first-flight was not had until June 16th, 1954. The XFV-1 was able to accomplish a total of 32 flights but was never used to transition from vertical-to-horizontal flight (and back) due to the unavailability of the YT40-A-14 engine. It was, however, able to achieve a vertical stance after having taken off horizontally (as a conventional aircraft) with a brief hovering action also had.
The Allison YT40-A-14 engine ran into its own troubles and was not a success which played a large part in the XFV-1's program demise during June of 1955. Additionally, Navy authorities realized that the aircraft required an experienced, steady hand at the controls and also would never showcase the performance of conventional fighter types when going head-to-head in combat. As such there proved little to recommend further funding of its research.
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