I case anyone else is asking themselves what a unstart is.
In the early years of operation, the analog computers would not always keep up with rapidly changing flight environmental inputs. If internal pressures became too great and the spike was incorrectly positioned, the shock wave would suddenly blow out the front of the inlet, called an "Inlet Unstart". During unstarts afterburner extinctions were common. The remaining engine's asymmetrical thrust would cause the aircraft to yaw violently to one side. SAS, autopilot, and manual control inputs would fight the yawing, but often the extreme off-angle would reduce airflow in the opposite engine and stimulate "sympathetic stalls". This generated a rapid counter-yawing, often coupled with loud "banging" noises, and a rough ride during which crews' helmets would sometimes strike their cockpit canopies.[40] One response to a single unstart was unstarting both inlets to prevent yawing, then restarting them both.[41] Lockheed later installed an electronic control to detect unstart conditions and perform this reset action without pilot intervention.[42] Beginning in 1980, the analog inlet control system was replaced by a digital system, which reduced unstart instances.
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I case anyone else is asking themselves what a unstart is.
In the early years of operation, the analog computers would not always keep up with rapidly changing flight environmental inputs. If internal pressures became too great and the spike was incorrectly positioned, the shock wave would suddenly blow out the front of the inlet, called an "Inlet Unstart". During unstarts afterburner extinctions were common. The remaining engine's asymmetrical thrust would cause the aircraft to yaw violently to one side. SAS, autopilot, and manual control inputs would fight the yawing, but often the extreme off-angle would reduce airflow in the opposite engine and stimulate "sympathetic stalls". This generated a rapid counter-yawing, often coupled with loud "banging" noises, and a rough ride during which crews' helmets would sometimes strike their cockpit canopies.[40] One response to a single unstart was unstarting both inlets to prevent yawing, then restarting them both.[41] Lockheed later installed an electronic control to detect unstart conditions and perform this reset action without pilot intervention.[42] Beginning in 1980, the analog inlet control system was replaced by a digital system, which reduced unstart instances.
http://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird
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