Message posted by Peter Merlin on August 13, 2009 at 11:59:13 PST:
Mach 3.2 is the design cruise speed for the Blackbirds, but maximum allowable Mach number was dependent on outside air temperature and its effect on compressor inlet temperature (CIT). The pilot was authorized to accelerate to Mach 3.3 as long as CIT remained at or below 427 degrees Centigrade. Speeds exceeding Mach 3.3 were occasionally recorded, but generally the pilot tried to avoid this area of the performance envelope because it placed excessive thermal stress on the airframe. In 1975, Lockheed studied the possibility of expanding the flight envelope of the SR-71 with some modifications. The results of several studies concluded the maximum speed limit could be extended to Mach 3.5 for short periods of time. The only structural limit to speeds above Mach 3.5 was a KEAS (knots equivalent airspeed) limit of 420, set by a need to keep inlet duct pressures and temperatures from exceeding acceptable values. Limited inlet capture-area and excessive engine CIT also limited operation at higher Mach numbers, even with proposed modifications.
In Reply to: Re: Differences between A-12 and SR-71? posted by werD on August 13, 2009 at 9:37:14 PST:
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