Abstract: A fail-safe flexible coupling is provided for coupling shafts, typically in an aircraft, wherein the coupling includes a plug coupled to the first shaft and a socket coupled to the first shaft and a socket coupled to the second shaft. The plug is arranged and configured to loosely mate with the socket when the shafts are being rotated together by virtue of their primary coupling. When the primary coupling fails, the socket and plug engage each other notwithstanding the failure of the primary coupling between them. The plug is particularly characterized by a screw portion and head portion. The screw portion is threaded into the first shaft. The coupling is secured to the first shaft by the head portion of the plug.

Abstract: A fail-safe flexible coupling is provided for coupling shafts, typically in an aircraft, wherein the coupling includes a plug coupled to the first shaft and a socket coupled to the first shaft and a socket coupled to the second shaft. The plug is arranged and configured to loosely mate with the socket when the shafts are being rotated together by virtue of their primary coupling. When the primary coupling fails, the socket and plug engage each other securely though the shafts continue to be driven notwithstanding the failure of the primary coupling between them. The plug is particularly characterized by a screw portion and head portion. The screw portion is threaded into the first shaft. The coupling is secured to the first shaft by the head portion of the plug.