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HEINKEL He 177
Undercarraige
During its initial development, the anticipated weight of the He 177 had increased so alarmingly that the provision of a main undercarriage design of sufficient strength to handle a 32-tonne (70,550 lb) loaded weight airframe began to pose a major problem. Neither the engine nacelles nor the wings provided much stowage space for the main undercarriage members, which needed to be of a longer-than-usual design to allow ground clearance for the large diameter four blade propellers of the aircraft's powerplants, and after several extremely complex arrangements had been considered during the aircraft's initial design stages, a rather novel, but still quite complex, system was adopted.
He 177 undergoing maintenance.
[Source: Bundesarchiv, Bild 101I-676-7971A-23/Blaschka/CC-BY-SA]
Instead of the originally projected single wheel leg under each engine nacelle, two massive single wheel legs were attached to the main spar at each engine nacelle, the outboard legs retracting upward and outward into shallow wing wells, the inboard legs swinging upward and inward into similar wells in the wing roots, all units being completely enclosed by flush fitting wheel and strut doors, and almost "meeting" under each engine nacelle when fully extended. The lever-action lower gear strut sections, on which the wheels were mounted onto their axles, also had to pivot to a 90� angle (from their 120� angle while fully extended) to the main gear leg during the retraction cycle, just to fit into their wheel wells.
A more conventional single-leg twin wheel arrangement for each main gear was actually used on the two prototype examples built (one during the war, one post-war) of the He 274 in France, and a few developments that only existed as drawings actually had tricycle gear setups being fitted to the Amerika Bomber entry version of the paper-only He 277, which were also depicted as using single main gear struts with twin wheels. The two hour time that it could take to change just one damaged main gear tire, using special Heinkel-provided 12-tonne capacity main gear jackstand blocks, which were in short supply, was just one of the myriad of problems that the He 177 A's complex main gear format brought about.
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