an ejection seat arm flail injury prevention apparatus comprises a pair of rigid support arms on each side of the ejection seat that deploy outwardly to support a semi - rigid backstop substantially behind the ejection seat occupant . when the ejection seat is propelled out of the aircraft and is subjected to the windblast , the occupant &# 39 ; s arms are allowed to flail in a rearward direction in the windblast until the occupant &# 39 ; s arms impact the semi - rigid backstop . the backstop is semi - rigid in that it deforms sufficiently to enable the rearward motion of the occupant &# 39 ; s arms to be arrested without impact injury , yet is sufficiently rigid to prevent the occupant &# 39 ; s arms from rebounding off the backstop or striking the rigid support arms .