I am reading Brian Trubshaw's Concorde: The Inside Story (Sutton Publishing, 2000, 0-7509-2393-8). On page 123, Trubshaw writes:
After entry into service the availability of an uprated engine showed that the intake was operating super-critically during cruise at ISA +5° with matched ramp angles of 7½ to 8°. In terms of efficiency, this was not good since the intake was operating at maximum capture.
Could someone kindly explain that passage in layman's terms, especially the meaning of the ISA acronym?
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R. J. Emery