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F-85 Goblin closeup

The XF-85


The McDonnell XF-85 "Goblin"

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McDonnell XF-85
XF-85 "Goblin"

The XF-85 parasite aircraft was developed to protect B-36 bombers flying beyond the range of conventional escort fighters. In theory, a B-36 penetrating enemy territory would carry its protecting fighter in the bomb bay. If attacked by enemy aircraft, the bomber would lower the Goblin on a trapeze and release it to combat the attackers. After the enemy had been driven away, the parasite fighter would return to the bomber, hook onto the trapeze, fold its wings, and be lifted back into the bomb bay. Although the XF-85 was successfully launched and flown from an EB-29B on several test flights, it was never successfully recovered in flight or flown from a B-36. The test program was canceled in late 1949 when mid-air refueling of fighter aircraft for range extension began to show greater promise.

Two Goblins were built. Flight of the No. 1 aircraft was delayed by ground test damage, so on August 23, 1948, the No. 2 aircraft (S/N 46-524) made the first flight. The XF-85 on display (S/N 46-523), the first Goblin built, made its first and only flight on April 8, 1949. It was transferred to the USAF Museum on August 23, 1950 after cancellation of the XF-85 program.

21 ft. 1 in.
Length: 14 ft. 1 in.
Height: 8 ft. 3 in.
Weight: 4,550 lbs.
Armament: Four .50-cal. machine guns
Engine: One Westinghouse XJ-34 of 3,000 lbs. thrust
Crew: One

Maximum speed:
650 mph.
Combat speed: 581 mph.
Maximum endurance: 1 hr. 20 min.
Combat Ceiling: 46,750 ft.


Westinghouse J34 Turbojet Engine



The Significance

Significance of Type : "A good idea that never quite worked". In 1947, the parasite fighter's prospect looked so good that the Air Force directed Convair Aircraft to modify all B-36 Peacemaker bombers after the 23rd production model to include a trapeze device in the forward bomb bay. It was planned that only one F-85 Goblin would be carried, although the bomber could carry three planes. There was speculation of modifying some B-36s to serve as carriers for several escort fighters.

In August 1947, the USAF had second thoughts about the parasite fighter's possibilities and restricted procurement to two prototypes. McDonnell unveiled the first XF-85 and the modified a B-29 into the EB-29B "MONSTRO" to take the trapeze which would engage the fighter's retractable hook.

Testing of the first XF-85 began at Muroc Air test Center, now Edwards AFB, California, in June 1948. The plane made five captive flights with the EB-29B during which it was lowered and raised on the trapeze, the engine started, and the control tested. On August 1948, the XF-85 S/N 46-0524 was launched and flown for the first time from a test altitude of 20,000 feet. The trapeze was fully extended and the fighter gently lifted away from the trapeze yoke. After clearing the parent bomber, the test pilot performed various maneuvers for fifteen minutes at speeds between 180 and 250 m.p.h. before attempting to hook up to the bomber.

It was discovered that the closer the XF-85 came to the mother plane, the stronger the resistance encountered from the air compressed by the two planes. More power was required to overcome this air cushion. However, the air also became more turbulent as the fighter approached the bomber. On the final attempt to hook up, the pilot came in below and behind the trapeze at a high rate of closure speed. The fighter's hook missed the trapeze by inches and the canopy struck the trapeze and shattered. The pilot mad e a successful emergency landing on the dry lake bed runway. Over the next ten months several similar incidents occurred, and McDonnell recommended suspending further recovery tests. The opinion was that if an experienced test pilot was unable to perform a successful recovery, combat pilots stood very little chance of completing recovery operations. The XF-85 project cost $3,210,664 and flew a total of two hours and nineteen minutes.



F-85 McDonnell Parasite Jet Fighter


FICON (Fighter-Conveyor) was a project intended to provide the B-36 with its own fighter type aircraft to be carried into the combat zone. The first such project involved the McDonnell XF-85, ordered October 9, 1945, a midget fighter designed to be carried within the B-36 bomb bay. Although two XF-85 prototypes were built and flight tested from a B-29B in August 1948, the concept did not prove practical.

In spite of that failure, Convair received a contract for a prototype FICON system to carry and retrieve a Republic F-84E single-seat fighter from a B-36. On January 19, 1951 RB-36F-1, 49-2707, was assigned for modification as the GRB-36F prototype and was able to make its first contact flight on January 9, 1952.

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F-85 Goblin posing F-85 Goblin caught F-85 Goblin flying

The XF-85 was first tested in August 1948 over the Mojave Desert. A B-29 carried it aloft and then extended the parasite on an elaborate 'trapeze.' The Goblin was then released to scamper home on its own. The XF-85 was designed to equip the giant B-36 bombers but was never carried by any aircraft other than a single B-29 which was the only aircraft ever equipped with an operational XF-85 trapeze.



XF-85 Goblin

During the strategic air offensive against Germany during World War 11, the US Army Air Forces had faced serious and deadly opposition from Luftwaffe interceptors. To counter this threat, the development of long-range fighters to escort the bombers had become one of the USAAF's highest priority projects.

The wartime problem was solved by the development of longrange escort fighters, but as the war was ending, the USAAF was beginning to develop bombers such as the Boeing B-50 and Convair B-36, whose range was three to five times greater than that of the bombers that had been used against Germany. This necessitated the development of escort fighters capable of matching the longer range, a problematic situation which led to the consideration of other, more radical, solutions.

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F-85 Goblin sketch

The XF-85

As early as the summer of 1944, when the USAAF was pondering its dilemma, the idea of developing an escort fighter that could be carried by a bomber was proposed. Even then, it really wasn't a new idea'. In the early 1930s Curtiss F9C-2 Sparrowhawk fighters had successfully conducted similar operations on a routine basis, flying from a 'trapeze' apparatus slung beneath the US Navy dirigibles Akron and Macon. The idea of conducting such operations from bombers flying at much higher speeds presented a great many additional problems. Not the least of these was the fact that the weight of the fighter would cut the bomb load proportionally. Future bombers, however, would be bigger, so if a fighter could be made smaller, a workable equation was theoretically possible.

Early in 1945, the USAAF's Air Technical Services Command (ATSC) began sounding out various airplane builders on the idea of building an ultra lightweight 'parasite' fighter that could be carried by the new, larger bombers that would be coming on-line in the late 1940s. McDonnell Aircraft of St Louis, a new, and certainly eager, company was willing to give it a try. McDonnell's original proposal was submitted in March 1945, and in October the USAAF ordered two prototypes under the designation XP-85, and with the stipulation that the resulting fighters had to fit entirely vi,ithin a B-36 bomb bay.

In September 1947, the USAAF became the US Air Force, and in July 1948, the latter took delivery of the first XP-85 at Muroc (now Edwards) AFB, which was redesignated XF-85 under the Air Force policy of designating fighters as fighters rather than as pursuit planes.

Two Goblins were built. Flight of the No. 1 aircraft was delayed by ground test damage, so on August 23, 1948, the No. 2 aircraft (S/N 46-524) made the first flight. The XF-85 on display (S/N46-523), the first Goblin built, made its first and only flight on April 8, 1949. It was transferred to the USAF Museum on August 23, 1950 after cancellation of the XF-85 program

Span: 21 ft. 1 in.
Length: 14 ft. 1 in.
Height: 8 ft. 3 in.
Weight: 4,550 lbs.
Armament: Four .50-cal. machine guns                    Engine: One Westinghouse XJ-34 of 3,000 lbs. thrust
Crew: One

Maximum speed: 650 mph.
Combat speed: 581 mph.
Maximum endurance: 1 hr. 20 min.
Combat Ceiling: 46,750 ft.



The XF-85, which was named Goblin because of James Smith McDonnell's belief in the spirit world, was the smallest jet fighter that would ever be built. It was a tiny, rotund creature that looked more like an amusement park airplane than a serious Air Force program. The Goblin was only 15 feet long, with a wingspan of 21 feet. Its gross weight was 5600 pounds. It was powered by a Westinghouse J34 turbojet, and could be launched at altitudes up to 48,200 feet. Its performance could thus be maximized, because - unlike most fighters - it wouldn't have to expend time and fuel getting to altitude.

F-85 Goblin &B-36

The F-85 and B-36

In the proposed scenario, B-36s deep inside enemy territory would, upon encountering enemy interceptors, release a swarm of Goblins to chase them away. The F-85s would have a duration of an hour or more, which was considered adequate for the job. The Goblin would fit into a B-36, and it looked good on paper, but somehow the idea of F-85s chasing MiG-17s is somewhat surreal.

The first 'parasite -ready' B-36 wasn't yet available, so the XF-85 test flights, that began on 28 August 1948, were conducted from a B-29 fitted with the 'trapeze' that was designed for the B-36. There were only seven flights conducted, but the XF-85 pilot was able to reattach the Goblin to the trapeze in only three of these. In the cases of these aborts, he had to bring the tiny airplane in for belly landings because it was designed without landing gear.

By 1949, it had -become clear to the Air Force that parasite fighters would not be a practical solution to the escort fighter program, and on 24 October, the XF-85 program was terminated. Both prototypes were, however, preserv6d rather than being scrapped.

The Goblin lived and died in an era when the Air Force was keen to try anything. In any other time, it is doubtful that any funding -much less the $3 million that was actually spent on the XF-85 -could be found for such a project. In the end it was a marginally viable idea that was complicated by an airplane whose silly appearance no one could take seriously.

The XF-85 Goblin resurrected the concept of a parasite fighter - an aircraft carried by and launched from a bomber for which it was intended to provide defence. Designed as the Model 27 under the leadership of Herman D Barkley, the XF-85 was intended to be carried by the Convair B-36 bomber and was the subject of a Letter of Intent for two prototypes on 9 October 1945. A small, egg-shaped aircraft with vertically-folding wings and triple vertical tail surfaces, the fighter was intended to be launched from and recovered by a retractable trapeze. This was to be extended beneath the parent bomber, no undercarriage being fitted to the fighter.


The McDonnell XF-85 Goblin

The problem of providing long-range fighters to escort bombers to their targets was not easily solved during World War II. With the development of the mighty six-engine B-36 Peacemaker bomber, designed to fly at true intercontinental ranges, the problem was acute. None of the first generation of jet fighters, with their voracious appetites for bulky fuel, could be expected to accompany the B-36 for any significant distance. Nor could relays of such fighters be effective over a 5,000+ mile range. However, the B-36's four capacious bomb bays, suggested a solution to the McDonnell Aircraft Company: a diminutive jet fighter, fitted into one end of the bomb bay, would allow the mighty bomber to carry along its own fighter protection and still have room for a useful payload.

In the middle 1940s, this idea had great appeal. When danger appeared, a fresh fighter pilot could drop into his cockpit and be released to deal with the enemy; afterwards, he could hook up to the mother ship again for the return flight home. With no heavy landing gear, a small fuel capacity and light armament, such a fighter might be highly maneuverable and effective.


The F-85

 McDonnell’s XF-85, constructed in response to the Air Force’s MX-472 Parasite Fighter proposal, proved to be the smallest jet fighter ever built. The Goblin, as it came to be known, was a marvel of ingenuity. Seated in his cramped cockpit, the pilot virtually straddled a J34-WE-22 engine rated at 3,000 lbs. thrust, with no afterburner, which would provide a theoretical top speed of 650 mph. Four .50 cal machine guns (never actually installed) would provide an adequate sting, and enough fuel for a one-hour flight would be carried. That, plus a reasonable degree of airworthiness and combat maneuvering ability, was asking a lot of a pod-shaped airframe less than 15 ft long.

Two XF-85s were built for evaluation at the Flight Test Center. From the first free flight, which took place on 23 August, 1948, it was apparent that the design concept was pushing the very limits of practicality. Folding 21-ft wings gave reasonable performance but the short-coupled fuselage soon revealed stability problems. Six stubby tail fins, canted at odd angles in order to fit into the bomb bay hangar, failed to provide enough keel area and winglets were eventually fitted to the wing tips. Even so, the problems involved with mid-air launch and recovery eventually proved insuperable.

The prototype Goblins never flew with a B-36. Instead, a modified B-29 (designated an EB-29B), suitably nicknamed Monstro after Pinocchio’s whale, was fitted with a complex trapeze for the flight tests. The test aircraft was wheeled into a deep, specially-designed loading pit and the mother ship towed over it; its trapeze would be extended, and the XF-85 lifted into the bomb bay. Preliminary testing went well, and the tiny fighter was successfully launched on several different occasions. Once separated from the launch aircraft, it performed well enough in the air. Severe buffeting problems, however, were encountered whenever a reattachment was attempted. The first free flight culminated in a shattered cockpit canopy, quickly followed by an emergency landing on the dry lake bed far below. Subsequent flights revealed an air cushioning effect when the two aircraft neared the point of connection, made worse by air turbulence caused by the complex structure of the trapeze. A number of the subsequent flights resulted in the diminutive jet landing on its steel skid. The obvious difficulty which experienced test pilots had in making the system work, coupled with steady progress in aerial refueling techniques, eventually caused the Air Force to lose interest in the entire parasite fighter concept, and the XF-85 project was abandoned late in 1949. The aircraft went off to display purposes. The parasite fighter concept carried on for a few more years with the promising F-84 FICON project, but official interest soon flickered out and the idea faded into memory.

Recently, the remains of the filled-in XF-85 loading pit were rediscovered in an out-of-the-way spot near the present B-2 testing facility at Edwards AFB. From an innovative project which began with such promise, all that remains two XF-85s resting in Air Force museums, and a sunken pattern in the concrete ramp at South Base.


 XF-85 Goblin Photo Gallery


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