How Things Work: Supersonic Inlets - By Diane Tedeschi - Air &
Space magazine, November 2002 “We were in a turn and climbing
when one of the inlets showed signs of instability. Shortly
thereafter—KER BLAM!—the aircraft slammed my head against the
side of the cockpit and then momentarily became unstable as it
yawed, pitched, and vibrated.” This is an account of a
supersonic engine inlet failure, or “unstart,” recalled by
retired reconnaissance systems officer Roger Jacks in SR-71
Revealed, a book by retired Lockheed SR-71 pilot Richard H.
Graham. It shows what can happen when a supersonic inlet stops
delivering the uniform stream of air upon which efficient jet
engine operation depends. When a jet airplane is flying faster
than Mach 1—beyond the speed of sound—the air entering the
engines is moving supersonically as well. But no turbojet engine
compressor—the rotating disks and blades at the face of the
engine that compress the air before it is mixed with fuel—is
capable of handling supersonic air flow. The jo