Notes on the Initiation of Limb Flailing.

An analysis is made of the aerodynamic forces tending to pull the limbs and head of an ejection seat occupant away from their rest position. Two distinct mechanisms are identified forward acting pressure forces which are shown to act on the front of any body, and a forward acting force caused by an obstruction behind the body. Quantitative estimates of these forces show that they may far exceed the ability of the occupant to hold his limbs in position. Various possible remedies are discussed, including, for example, the use of flaps or spoilers to change the angle at which the flow separates from the limb or helmet should eliminate these forward acting forces, and hence prevent limb flailing for those ejections where the seat is pointing stably into the airstream. Such corrective action would not necessarily solve the limb flailing problem if the seat can acquire large angular spin rates, or a substantial angle of yaw to the flow. Author