Engine went "whomph" II

[Lance F]

The GE CJ610-6 turbojet engine that twice let us down is out and apart. I saw it today and here's a pictures for those interested. The damage is limited to the 2nd stage compressor section with bent rotor blades and dented nozzle section. Apparently when the T/R deployed at full thrust it caused a compressor stall stong enough to push the rotor section forward into this nozzle. As previously reported, we tried flying with the engine in this condition, and very soon after TO gave us a big compressor stall and flameout.
The damage is considered relatively minor. The shop was very surprised not to see any damage in any of the other stages (there are 8 total) of the compressor.
Repair cost quote is $40K.
We still don't know why the T/R deployed.

 

[TangoWhiskey]

Wow. What kind of material are the actual vanes made of? Some of those in that stage are very ... bent ... and curled.

 

[bbchien]

Wow. this is why I own a piston(2) engine(s). I can afford to write the checks. That could have been $250K.

 

[AWACSEng]

I bet if this (uncommanded TR deployment) ever happens again with your maitenance department, they won't hesitate to boriscope the engine before returning it to service.

 

[Everskyward]

I bet if this (uncommanded TR deployment) ever happens again with your maitenance department, they won't hesitate to boriscope the engine before returning it to service.

I guess I was surprised they didn't do it to begin with. Or did they? We had a (very small) bird strike on the outside of the nacelle inlet and the mechanic found one feather and a drop of blood on one of the vanes and they had it borescoped just in case.

 

[AWACSEng]

Of course we will never know if the damage was all from the TR deployment, the second comp stall, or a combination of both. If we report compressor stalls in flight, MX will scope the motor just to have a look-see. Maybe not a bad practice.

 

[Lance F]

The boroscope wasn't in the shop at the time. The only copilot in the operation had borrowed it to check out an engine problem on his Porsche 968

 

[C. Kelley]

I work with GE as an engineer for large gas and steam turbines, mostly dealing with power plants and process mills. Usually a compressor stall on a large gas turbine is bad news bears. Sometimes they get away scratch free but most of the time it requires going into the compressor. Most of the time on large units it happens during startup, due to compressor bleed valves malfunctioning, or because the variable inlet guide vanes are miscalibrated. The lucky thing is that pieces didn't come off of one of those compressor blades and grenade the rest of the compressor or even the turbine buckets. It takes very little to completely destroy one but sometimes they can eat large, solid objects and be just fine. I would assume they would have pretty decent containment in the event of one corn-cobbing and eating itself, though.

What kind of material are the actual vanes made of?

GE aviation is a different entity within GE but if they are anything alike then probably only a select few know. With my section I have access to drawings associated with the turbines but none of these include the material specifications for casings, buckets, or blades (vanes). I guess the more they keep secret the more in demand they remain for parts. However, I have been known to be wrong from time to time though . It will be interesting to me if anyone knows.