|McDonnell XF-85 Goblin|
|Maiden flight||23 August 1948|
|Unit cost||US$3.1 million for the program|
The McDonnell XF-85 Goblin was a fighter aircraft, conceived during World War II and intended to be carried in the bomb bay of the giant Convair B-36 bomber as a defensive "parasite fighter." Because of its small and rotund appearance, it was nicknamed "The Flying Egg."
Design and development
The McDonnell XF-85 Goblin was designed to meet a USAAF requirement for a single-seat "parasite" escort fighter that could be carried by a large bomber. Development of two prototypes was ordered in March 1947. The resulting design was entirely the product of design contraints, which required it to fit into the bomb bay of a B-36 (although it was actually tested under a B-29). The B-36 was the intended mother ship that would carry as many as three Goblins.
A tiny, short fuselage was fitted with low/mid-set foldable swept wings, of 21 ft 1.5 in. (6.44 m.) span. It was powered by a Westinghouse J34-WE-7 turbojet, of 3000 lb. (1361 kg) thrust. There was no landing gear except for emergency skids. The fighter was intended to return to the parent aircraft and dock with a trapeze, by means of a retracting hook.
McDonnell built two Goblin prototypes (USAF Serial no. #46-523 and #46-524). During wind tunnel testing at Moffett Field, California, the first prototype XF-85 was damaged. Consequently, it was the second aircraft that was used for the initial flight trials; its first flight was on the 23 August 1948. As a prototype B-36 was unavailable, all XF-85 flight tests were carried out using a converted Boeing EB-29 Superfortress parent ship. On the first flight, after a little over two hours it became obvious that turbulence around the bomber created difficult control problems. In flight, the tiny fighter was stable, easy to fly and recovered well from spins.  However, many pilots found it difficult to hook the Goblin to its bomber's trapeze.
Termination of the XF-85 program mid-1949 was the result of a number of factors:
- Docking with the bomber "host" proved much more difficult than thought; even experienced test pilots had trouble (though Chuck Yeager stated that the XF-85 test pilot was particularly incapable of formation flying.)
- The XF-85 was no match for the conventional enemy fighters it would have to engage to defend the bombers - it was slower and much more lightly armed.
- The increasing range of jet escort fighters (with flight refuelling) allowed them to accompany bombers on their full missions.
- Tight budgets meant that less important programs such as the XF-85 were canceled.
Later, a B-36 was used as a mother ship for similar tests, carrying a conventional Republic F-84 Thunderstreak fighter. These tests, known as FICON (Fighter Conveyor) experiments, were also found to be of little long term practical use and the whole concept was dropped.
Two prototypes were built, and both still survive: #46-523 in the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio and #46-524 at the Strategic Air and Space Museum in Ashland, Nebraska.
- Crew: 1
- Length: 14 ft 10 in (4.5 m)
- Wingspan: 21 ft 1 in (6.4 m)
- Height: 8 ft 3 in (2.5 m)
- Wing area: 90 ft² (8.3 m²)
- Empty weight: 3,740 lb (1,696 kg)
- Loaded weight: 4,550 lb (2,063 kg)
- Max takeoff weight: lb (kg)
- Powerplant: 1× Westinghouse XJ34-WE-22 turbojet, 3,000 lbf (1,361 kg)
- Maximum speed: 664 mph (1,069 km/h)
- Range: mi (km)
- Service ceiling: 48,000 ft (14,630 m)
- Rate of climb: 12,500 ft/min (3,810 m/min)
- Wing loading: 51 lb/ft² (247 kg/m²)
- Thrust/weight: 0.66
- 4x 0.50 in (12.7 mm) Colt Browning machine guns
- National Museum of the United States Air Force: XF-85 Fact Sheet
- SR-71 Online - XF-85 Goblin on Display
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