engine surge problem
 

Got a problem with a B727 200RE centre engine -17 JT8D. After workshop visit to comply with High pressure compressor disk AD check, the engine surged at high altitude reaching FL350. were able to operate by putting bleed onto this engine.
The workshop then changed the Nozzle guide vanes but we still got the surge at high altitudes and then later on approach at 500 ft.
Another workshop visit and the C1 fan blades were changed, but the air test failed again due to another surge at FL 380 when throttling back to cruise power.
All sense lines, bleed lines and intake duct already checked.

ANYBODY OUT THERE WITH ANY IDEAS ?

Don't know about the -17 but the -15a had a little pot full of Versilube? I think, that had something to do with high altitude throttle control. Anyway it needed bleeding and topping up occasionally.

There was also a water trap that used to get it's bleed hole clogged causing freezing.

It was a long time ago so I'm probaly completely off the mark.:sad:

Try checking your anti-ice valves, one of them may have failed open. Also, don't know much about the JT8 but the JT3 had a surge bleed valve that would sometimes fail to open when the power was pulled back. Fuel scheduling... Could be any number of things...

If its the center engine, I'd check the inlet lip skin for a dent or deformation from perhaps a bird strike or de-icer bucket, the duct vortex generators are all installed and not bent, and also the inlet access door is correctly installed and sealed. We used to take engines that stalled in the center spot and install them on a pod and they'd happily run for hours before the stall margin decreased enough to warrant removal. Doesn't the -17 have additional smaller surge bleed pots which if stuck will make it touchy. We also used to pour a bit of lube down the lines from the PRBC to the bleed valves to ensure they weren't sticking. Hope this helps.

Mant thanks for your ideas guys, much appreciated we will be them up.

Has the engine gas path been boroscoped?

Was it ran in the test bed after it's WS visits?

Somebody Called?.....:O;)

Yes the engine went back on the test bed again and passed the surge margin test.

mirabeau....

Just curious if you got this sorted and what the fix was

"Borescope" actually...:ok:

bus429, you're not trying to be internet spelling police and failing are you?

Borescope and boroscope are both acceptabe spelling for the tool we speak of.

I can't think of another reason for your random post.

Have a look

Boroscope.co.uk - Borescopes, inspection borescopes, provision borescopes, flexible borescopes, rigid borescopes, bore inspection equipment, fibre optic borescope