 The intake has changed in a split second from its most efficient configuration with most of its supersonic compression taking place inside the duct to the least efficient as shown by the large loss in pressure recovery, from about 80% to about 20% at M3 flight speeds.There is a large drop in intake pressure and loss in thrust together with temporary loss of control of the aircraft.Not to be confused with an unstart, with its large loss in duct pressure, is the duct over-pressure resulting from a hammershock.