gearbox Prop brake inoperate in Ground

[Check Team FR]

After installation of prop assy on the prop shaft, the propeller turn in opposite direction.

1) Magnetics plugs checks on Gearbox but they are perfect, no traces of metal particles.

2) To be sure, we had fushed the gearbox : after this operation, the prop brake works by manual action.

3) On the other hand during the runnup, the prop brake no longer works.

4) The magnetic plugs are still correct.

Why did the prop brake work after flushing ?

But no longer work after ?

What is the cause or problem with the brake ?

Thank u in advance for your answer...

[Lkuest]

I don't understand what you mean by "during runnup, the prop brake no longer works." The starter disengages the propeller brake at initial RPM, then is held apart by oil pressure as the engine accelerates.

If you mean "after engine operates and is shut down," then you may have a defective propeller brake. Of note, it is normal for the propeller brake to not work below certain cold ambient air temperatures due to excess oil viscosity (engine has not been run).

As for why it works after brake flush and not after engine run, I don't know. It may have something to do with the manual separation of the prop brake that makes it seat better. You can confirm this by inserting the tool to unseat the prop brake, apply air, then immediately removing it without flushing the gearbox to see if the problem duplicates. Also, if the propeller brake pads are worn, flushing will only help a little. You'll still have worn brake pads.

[Check Team FR]

Yes, during runnup is normal, the brake release. When the engine shutdown, the brake was inoperated.