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In the summer of 1943, the US began building up its heavy bomber forces in Europe at a more rapid rate, and greater numbers of B-17s and B-24s were dispatched against targets inside Germany. However, whenever they flew beyond the range of their P-47 escort, however, they risked being mauled by Luftwaffe fighters.
In fact, until the long-ranged P-51D came along to escort B-17s and B-24s over Europe, many bombing missions ended in catastrophic losses of crews and airframes due to a lack of protection. As bombers grew to truly intercontinental range, fighter escorts would have been simply impossible in the early days of jet technology; the bombers themselves were little more than flying fuel tanks. So, the idea of adding ‘parasite’ fighters to the bombers, that would ride along until needed deep in enemy territory, gained popularity.
Docking two wingtip to wingtip
As explained by Scott Lowther in his book Boeing B-47 Stratojet & B-52 Stratofortress Origins and Evolution, Wright Field went forward with practical flight tests in the late 1940s, modifying a C-47 cargo plane wingtip to dock with a single Q-14 Culver Cadet. Unsurprisingly, some difficulties were found in learning just how to go about docking two wingtip to wingtip when flight tests began in August 1949, but the wrinkles were ironed out and the two aircraft accumulated more than 28 hours of conjoined flying time during hundreds of flights in late 1950.
Combination aircraft experiments
The experiments were built upon for project MX-1018, which involved attaching one Republic EF-84D jet fighter to each wingtip of an ETB-29A. Flight tests began in July of 1950 and continued until April 1953 when one of the EF-84Ds, docked to the left wing e of the ETB-29A, pitched up and rolled over onto the bomber’s wing. The nose of the fighter and the outer wing of the bomber were sheared off and both planes crashed with a loss of all crew, ending the project. However, during the testing programme it was found that the jet fighters could reduce engine power to idle or even shut down entirely and the combination of aircraft would still fly perfectly well. The system was intentionally never flown in rough air though.
Stuck in small cockpits for two days
Beyond MX-1018 was `Tom-Tom’. This was similar in concept but with two swept-wing Republic RF-84F fighters docked to the wingtips of a modified Convair RB-36F. This began flight testing in 1955 and continued into 1956, ending when one of the RF-84F’s began ‘flapping’ violently, soon breaking the aircraft coupling mechanisms. In this case all aircraft were able to safely land, but the programme was terminated. Once again, testing showed aerodynamic benefits for the B-36 but challenges for coupling in flight. The hope for `Tom-Tom’ was that it might prove sufficiently useful so as to enter service, providing two fighters to cover the B-36 on its long journey over enemy territory. Exactly how thrilled the fighter pilots would be, stuck in their small cockpits for the better part of two days (the B-36 could stay in the air for around 40 hours), is not a detail that is well documented.
B-36/B-47 Wing Tip-Tow
As these programmes were getting under way, the NACA was tasked with studying the concept of a B-36 with a B-47 attached to each wingtip. Whoever thought that attaching two B-47s to a B-36 was a good idea is a detail that seems to have been lost to time… perhaps the notion came from Boeing, perhaps Convair, perhaps the Air Force, perhaps someone at the NACA. In any event, available design information is lean. The lone NACA document presents only the planform of the wings with no additional details. The reconstruction presented here is thus provisional. It is shown with wingtip docking mechanisms taken from the Tom-Tom programme.
Takeoff problems for B-36/B-47 Wing Tip-Tow
For several reasons it is unlikely that this combination aircraft would have lifted off all hooked together. For starters, it can be seen that when level, the B-47s are raised high enough that their landing gear would not have reached the ground when the B-36 was still rolling down the runway. At low enough speeds the B-47s would have tilted far over, perhaps far enough to scrape their outboard wingtips on the ground. And there’s the issue of the 462ft wingspan: there are few runways in the world wide enough to handle an aircraft with landing gear that widely spaced.
B-36/B-47 Wing Tip-Tow: Range extension for the B-47s
The probable purpose of this aircraft would be range extension for the B-47s. The B-36 would fly with the attached B-47s idling their engines from the US to near Soviet airspace. The B-47s would then detach and fly to their targets, their tanks full or nearly so, to penetrate deep into enemy territory. The B-36 would presumably then fly home. In this situation the B-36 would presumably swap out its own internal bomb load for more fuel tanks.
The crews of the B-47s would at least be able to get up and move about, unlike the crews of the Tom-Tom F-84s. But even with that fantastic benefit, the idea seems to have existed for only a very brief time.
Boeing B-47 Stratojet & B-52 Stratofortress Origins and Evolution is published by Mortons Books and is available to order here.
Photo credit: U.S. Air Force