RickH wrote:
The very fact that a jet engine works with the reliability that they do is amazing. The suck,squeeze,bang, and blow is very finely balanced in a jet engine.
Don't mean to hijack the original thread but since you asked , Gary,
I've sent an email to a former GE J-79 specialist ( tech rep) and asked him to weigh in.
Hello everyone. I'm new to this board but I'll give my two cents worth. It's actually pretty hard to stall a J79 in normal circumstances. As Rick said, many things could cause one to stall. First thing I would do is a good inlet and exhaust inspection. Then the VSV rigging would be suspect. If that didn't show a problem I would check to see if the PS3 signal is getting to the control. i.e. check for cracks in PS3 tubes. Now days a borescope inspection of the compressor blades would be in order but the J79 didn't have many easy ways to do that. No borescope ports. You could go through the bleed ports, fuel nozzle port etc. Could be a bad MEC.
These engines went through a lot of development. Stall mapping was one kind of testing that was done. A false PS3 (CDP) signal would be applied to fool the control. By doing this you could map a stall line which would show what sort of conditions to stay out of. By rigging feedback and individual stages of the VSVs you could move the stall line to a point that normal operation would never see. But as Rick said, it's a complicated piece of equipment and anything could happen. From the photo, I'd be inclined to think "bird strike". He looks pretty low.
Buck
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