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The parasitic fighter
With immediate post-war emphasis on massed bomber formations, and a hard-won lesson from the Second World War that bombers could only survive when escorted by long-range fighters, the advent of the jet age brought its own collateral problem: how could a fuel-hungry fighter compromised on duration ever provide the necessary cover on intercontinental flights?
As explained by David Baker in his book US Air Power 1945–1990 Volume 1: US Fighters and Fighter-Bombers 1945-1949, by mid-1942 plans for a post-war Air Force prompted concerns when it became apparent that jet engines would supplant the piston-engine for high-speed combat aircraft. Geographically isolated from potential enemies, the fighter role was prioritised around protecting the bombers.
The Army Air Forces (AAF) had put tremendous effort into its demand for long range escort duties supporting the massed armadas of B-17s and B-24s and found a solution with later marks of the P-47 and P-51 which, with aerodynamic refinements and drop tanks, achieved the range to accompany the bombers all the way from England to Berlin and back. In the Pacific theatre, the B-29 had its own concentrated armament and survived against enemy fighter forces protecting Japan while the lessons of the European theatre became entrenched. But escorting bombers across intercontinental distances and through denied airspace would be altogether different.
XF-85 Goblin
The evolution to what would become the XF-85 Goblin began with a requirement dated January 1944 and the Air Technical Service Command call for a diminutive piston-engine fighter with a view to it being applied as a parasitic aircraft. Such concepts had been tried before, the first during the First World War and several during the 1930s but none had been successful. Nevertheless, with very long-range missions anticipated for the prospective B-35 and B-36, attention focused on the B-29 as the carrier. Options included small fighters attached to the wingtips of the bomber, underslung from the lower fuselage for release off a trapeze to a system whereby the fighter was buried within the fuselage of the bomber and likewise deployed on a trapeze.
The AAF restructured the requirement in January 1945 for internal carriage in the host aircraft, so as to reduce drag from a protruding airframe, stipulating the use of a jet engine in the fighter, all encompassed in a research programme designated MX 472. While the B-29 remained the prime carrier of choice the far greater range of the B-35 and the B-36, both candidates for full-scale production, enhanced the potential value of an effective and reliable programme. By 1945 the propeller-driven B-36 was in full-scale development and the jet-powered XB-35 was being assembled, but with no certainty as to its future prior to flight tests.
XF-85 Goblin prototypes
Only McDonnell bid on the request for proposals and on 19 March 1945 a team led by Herman D Barkey submitted their Model 27D. It was a radical design for a bizarre concept, comprising an egg-shaped structure to which were attached 37 degree swept wings, folding vertically until dropped for free flight, three vertical stabilisers and two horizontal stabilisers with dihedral. Propulsion was provided by a single 3,000lb (13.3kN) Westinghouse J34-WE-22 and with sufficient fuel for a flight of 30 minutes. Four .5-in machine guns could be carried in the nose.
Despite the post-conflict embargo on new production orders, the AAF awarded a contract to McDonnell on 9 October for two XF-85 Goblin prototypes (46-523 and 46-524) together with a static test airframe. The mock-up was inspected on 10–12 June 1946 and on passing scrutineering the company was awarded a formal Letter of Intent with a concurrent stipulation to Convair that all B-36s from the 24th production B model must have provision for carrying the parasitic fighter. A batch of 30 production Goblins was planned, confirmation pending satisfactory flight trials. It was an option that some B-36Bs would carry three fighters and no bombs. Within a few weeks, that requirement was rescinded and a production plan abandoned.
Flight tests
The Goblin would be restrained by a nose hook attached to an extended portion of the bomber’s underslung trapeze for the parasite to fly off and back on again without landing, although a retractable steel skid was provided for an emergency recovery on the ground. The Goblin was expected to display a top speed of 648mph (1,043km/hr) and use its limited operating range to fend off enemy fighters, although there was no specific plan to refuel the aircraft so that it could fly a second time. In examining the operating plan, some AAF pilots doubted the viability of the concept and queried the advisability of reducing the bomb load for such a limited capability.
Flight trials were assigned to a specially modified EB-29B (44 84111) but the first aircraft was damaged on arriving at the NACA’s Ames Aeronautical Laboratory for wind tunnel tests so it fell to the second aircraft to conduct three captive flights from 22 July 1948.
The first free flight was flown by Edwin Schoch on 23 August from 20,000 (6,096m) above Muroc Dry Lake. Snatched by violent turbulence on the underside of the EB-29B, the Goblin smashed into the trapeze, shattering the canopy and the pilot’s helmet and goggles before dropping down for an emergency landing. Repaired, it conducted three further tests on 14 and 15 October 1948 but on the next flight turbulence again prompted an emergency lakebed landing. The same fate awaited the first aircraft when it made its one and only flight on 8 April 1949, demonstrating that the concept was far too troublesome and the programme was cancelled on 24 October 1949.
Parasitic fighter role reinvented
Ironically, in flight tests, the XF-85 demonstrated a unique agility and in simulated combat proved very difficult to shoot down. The Goblin programme had endured for five years and demonstrated the persistence of the AAF in trying to find a solution to the problem of the vulnerable bomber, although most of the programme personnel were well aware that it was too fascinating a research opportunity to retire it prematurely. The parasitic role would be reinvented for the FICON (Fighter Conveyor) programme, gifting the B-36 with another parasitic fighter concept, although that one was driven by the photo-reconnaissance role.
US Air Power 1945–1990 Volume 1: US Fighters and Fighter-Bombers 1945-1949 is published by Helion & Company and is available to order here.
Photo credit: U.S. Air Force
