This example shows that a compressor runs aerodynamically faster on a 'cold' day and would be slower on a 'hot' day. Since the 'day' conditions are those at entry to the compressor an extremely 'hot' day is produced artificially by the ram temperature rise at high Mach numbers. The aerodynamic speed is low enough, despite the engine running at its 100% rated mechanical speed, to get into the rotating stall region on the map so an engine operating at these Mach numbers needs the appropriate features. The General Electric J93 had variable inlet guide vanes and stators. The Pratt & Whitney J58 had inter-stage bleed from the compressor and 2-position inlet guide vanes. The Tumansky R-15 had pre-compressor cooling to reduce the air temperature and avoid low corrected speeds.