Helicopter airframe with tail boom and rotor shapes boom asymmetric to main boom and rotor stream impact aided by extensible sheets or boom skin-spiralling coils.

摘要

In relation to the stream from the rotor (7) the tail boom (8) is shaped so as to separate the stream from at least one side of the boom without forming an eddy flow and this continuously along most of the boom length. Thus the boom (8) is assymmetric in the critical regions in a plane spanned by the main direction and also the direction of rotor stream impact. The rotor drive shaft (6) is run along the boom (8). Interference sheets (19) projecting from the boom (8) in the specified critical regions can be extended and/or twisted and/or swiveled relative the boom line. In a variant, the outer skin of the boom is fitted out with coils in spirals round the boom to extend from the subframe and at variable coil pitch. The coils can possibly be obtained by deforming the outer skin of the boom and the skin itself can be locally extended by pressure pads.