Wouldn't it cause at least a spike in the vibration though? I imagine that the blades are quite finely balanced, and putting a solid mass in there should upset things, shouldn't it?

I'm an engine mechanic and have worked the F-108 on the KC135R (CFM-56 to the civilian folks) for 10 years. The amount of internal damage those engines are allowed to have is amazing. Just to give you an example of what those engines can take and keep going, I scoped an engine that had injested 15 or more sparrows. I found feathers coming out of the 12:00 bleed valves. I talked to the crew chief and he told me they took birds down both No. 2 and No.3 on take off and the engines didn't even skip a beat. When I scoped No. 2 I found minor damage that was no cause for the engine to be removed from the wing. Also, I was doing an engine run and we comp stalled No. 1 engine at TRT. Most of 9th stage compressor was damaged in some way but again was within tech data limits.

So to answer your question, yes they are balanced but the engines are built to take alot of abuse and keep going.

KC135guy

KC135,

Just what I was looking for. Thanks for that. It really is amazing that they can handle that sort of stress. Hats off to the powerplant design engineers.

BTW, what does TRT mean?

I believe it's takeoff rated thrust.

nice pic man...