09 May 2005, 22:42
When I was in grad-school at Riddle while working at Douglas Aircraft in Long Beach (the class was held at the base near Perris, it's closed now), I wrote a paper on the YF-22 in Aircraft and Spacecraft Development. I distributed the paper to all the officers in my class. In that paper I discussed the Pratt Engine and when I called them to get some data on the engines, they were very hush/hush about it.
This was after the competition. I tried to get N1 and N2 values, idle RPM, MIL PWR setting, and they wouldn't tell me anything. After additional research, I found out that the turbines may be made of ceramic material (single cell casting) with cooling air holes at the tips and slots at the leading edge. The compressors and turbine combinations of N1 and N2 were thought to have been capable of revolving at past sonic velocity. This may be reasonable, hence the supercruise. How is this possible? Perhaps variable position blades to keep from compressor stalls occuring. They are unique engines thats for sure. The GE engines on the YF-23 I don't know anything about except the fact they may have been superior. I have analyzed wind tunnel pictures and data of super-sonic airflow around the inlet and the data does indeed show compressible flow going into the intakes, (not much, but probably enough to allow the variable inlet guide vanes from the first stage vane and between compressor stages to allow diffusion to take place and not destroy the engine). After building several 1/32 scale models of the YF-22 aircraft (Testors), I have concluded that the inlet and intake do not diverge/converge very much further postulating that super-sonic flow may indeed enter the inlet and hence to the engine.
Wright Patterson supplied me with much data on the YF-22 and may still be available by contacting Public Relations. I still think the YF-23 should have won the competition for the reason I stated in an earlier post in this forum. Occamsrasr, thanks.
F-16B, CC 80-0623 ERAU ROTC
MD-11, 90, 80, Cognizant Aerospace Technical Writer - Powerplant RR, GE, and P&W