Forum: F-16 Procedures

I was told that I would have a better chance seeing GOD then seeing a GE - 129 compressor stall?

Thoughts

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During normal operation, or is this a challenge? Whistle

Crack the PB or PAB line loose on the MEC and do a throttle snap to MAX. Twisted Evil

Wait, let me cover my ears first...

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It happened at my last shop to my supervisor back in '01. She was at the trim pad before i came into and I can't remember if it happened in transition into burner, out of burner, or just in burner. But I know guys at the shop heard a loud bang. And our is on the other end of the ramp. I know she was very shooking up when we came in. And of course it suck cause we had to scope it. That's just my two cents. But you'll have a better chance finding gold if you grab a shofel and start digging where you stand now. Beer

We had a GE-100 in the 18th Fighter Squadron that would stall on take-off roll. Everything was changed on the engine except the gearbox. IGV's were rigged, and rigged again, and it still would stall when transitioning to AB. The engine would only stall when installed in the jet. They could not get it to stall in test cell. Engine was sent back to GE. Never saw it again.

GE's are a very good engine, and stalls are very far and few between. GE makes such a reliable and easy engine to work on, Prat & Whitney decided to borrow a lot of their technology on their new engines.

Mind you this was a -100, and not a 129.

We had a -100 stall doing an idle run in the chocks on the flightline......it knocked pictures off the wall in the flightline shack! To the best of my knowledge we could never reproduce the malfunction.

I'm just a lowly pointyhead so I don't know much about engines but the question I have is what is the loud bang that everyone is talking about ie.....

[/quote]Crack the PB or PAB line loose on the MEC and do a throttle snap to MAX.

Wait, let me cover my ears first...

Quote:

Raptor_DCTR wrote:

I'm just a lowly pointyhead so I don't know much about engines but the question I have is what is the loud bang that everyone is talking about ie.....

The "BANG" Shocked

is a compressor stall. Airflow inside the the compressor "stalls" on the blades. The air's angle of attack affects the blades of a compressor the same as a wing. When they "stall" the flow separates or stops and you get a stall or surge. The pressures involved create quite the BANG. You hear it and feel it for quite some distance.

All that air/pressure in the compressor forgets where it is suppose to be going and "burps" out the intake and/or the exhaust. Either with or without fireball.... Twisted Evil

It can over-temp the hot sections of the engine as the airflow inside the engine drops to almost nothing. It's hard on the rotating assemblies as well as the RPM can change drastically.

Doesn't matter if you're an engine guy or not, whether your expecting it or not, a stall WILL scare the living daylights out of you when it happens. (and just about everyone else within about a half-mile)

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NOTE: In two videos below you notice the giddy laughter afterwards.... after you gain your witts it always seems to be funny... guess it doesn't matter where you're from either... LMAO

My first time (a couple decades ago) was on the line and the stall was induced by the operator. (Yes the old turbojet engines you could induce a stall with an "improper" throttle movement) I stood at the end of the communications cord yelling "0h $h|+, what was that!!!???" Shocked

I did pass his "test" though, as I did not leave him sitting in the aircraft alone with "bad-motor". (This was brought to light several years later when it was planned for another new airman Wink

)

Watch these...
http://www.youtube.com/watch?v=i5loBBmPnzY
http://www.youtube.com/watch?v=8D5AqAxE330
http://www.youtube.com/watch?v=jFiaT1yIKOM

Most stalls recover automatically and the engine will return to normal operation after it passes through. In a "non-recoverable stall" the bad airflow chokes off the engine and the remaining fuel burns out of the combustion chamber overtemping everything downstream.

That Engine Guy wrote:

Crack the PB or PAB line loose on the MEC and do a throttle snap to MAX.

Wait, let me cover my ears first...

As for disconnecting the lines.... (not that someone would do that intentionally)

If an engine comes to be tested after maintenance and someone doesn't tighten all the pressure-lines it can cause a stall. (PB is Burner Pressure, PAB is Augmentor Burner Pressure, Pt6 is turbine exhaust pressure, etc...) These lines feed pressure inputs to the engine's control system. Electronic and/or hydro-mechanical systems regulate flow (air and fuel) inside the engines. If the wrong readings are being given to the control system (IE loose/leaking pressure lines) the engine is very likely to stall when the throttle is moved quickly or the augmentor is used. Do both and you're almost guaranteed a stall with loose pressure sensing lines.

This wouldn't be considered "normal operation" mind you, but more stalls will occur on the test-cell (Hush-House) than on installed engines. Issues like this are one of the reasons Viper motors must go across "the Cell" prior to being flown after maintenance.

Hope this explains your stall question...

Keep 'em runnin' (Stall free...) Thumb

I saw a stall once on a pickled motor. The run man was sure it would stall, so we all were prepared, but it scared the living daylights out of everyone anyway. Everyone but the runcrew cleared out of the arch the jet was in and when it happened it was accompanied by so much smoke, we thought the engine had actually caught fire and blown apart! Those of us outside ran inside to make sure everyone was alright and those (the two ground crew anyway), ran out side they were so freaked out! Fire trucks magically appeared by themselves even though it was past midnight on a moonless night. I was told I would never see that happen again!

After everyone calmed down, we ran the jet again and it was fine. Oh, the ground man was sufficiently chewed out byt the run man for bolting, and someone else was on the ground for the second run. I was brand new so all I was aloud to do was watch, but I was commended for running INTO the arch to help instead of away from it.

This also was a -100, not a -129.

For any of the pointy heads or guys who never seen a stall, there are quite a few P&W -100 videos of the stalling in trans. to AB on youtube.com. Just to throw that out there.

Forum: F-16 Procedures

Harry Potter and GE's don't stall?