For an air seal test of an LM2500, we lock the output shaft of the intergral power turbine so it can't move.
First run we did not even get to idle before the unloaded and unlocked PT started to approach its full running speed.
We shut the engine down, and Byron built a locking fixture for the output shaft of the PT. Then we ran the engine to idle, and just above that to check VSV activation threshold.
Everything goes great.
The VSV tuning is bang on, and the air seal flow is in the range of what we want to see.

I didn't get much footage because I was on fuel purge and hookup duty, and I only had one camera.