About AS350B2 Arriel1D1 engine free wheel friction

[CafucZhou]

There is something wrong with our engine.

When the pilot did the autorotation training, the NF and the NR remains the same.

As you know, the free wheel should disengage the power turbine and the rotor when autorotation.

Then we did the inspection as the maintenance manual.



"D. Inspection and check of the free wheel

(1) Make sure there is no leak.

(2) Make sure the free wheel operates correctly.

NOTE: As seen from front of engine: lock the shaft; clockwise, the free wheel box

must rotate freely; it must lock up in the other direction."



The free wheel is all right as the manual.

But actually the free wheel is friction in autorotation flight.

So, could you tell me is this free wheel nothing wrong?

Is there a standard torque when the free wheel must be disengaged?

[fadecdegraded]

Did you retard the throttle when conducting the Autorotation

[DonQuixote23]

Did you retard the throttle when conducting the Autorotation

It certainly sounds like this was not done. How did it behave on shutdown? Did the Nr and Nf split then?

[helicopterray]

Do NOT retard the throttle when carrying out autorotations in an AS350 aircraft.

The procedure is to get into stabilized cruise at 60kts and lower the collective against the low stop. Record Nr.

As you know, the free wheel should disengage the power turbine and the rotor when autorotation.
This will happen when the engine actually quits. Not on an autorevs check.

To check function of freewheel, rotate the M/R blades backwards when static on the ground. The turbine wheels should rotate. Rotate the blades forward, the turbine blades do not rotate.

[helicopterray]

I spoke before thinking this through.
The autorevs check I mentioned is for maintenance where we set up the autorevs RPM by adjusting the collective low stop.

The autorevs for pilot training does in fact pull the throttle back to simulate engine failure. The Nr and Nf are supposed to separate.

[Rigidhead]

Helicopterray,

You are correct that you should not have to reduce the throttle in an Autorev check, however there should be an Nr Nf split if the low stop is adjusted correctly and you are at an appropriate weight for the test.

A good habit is to plot the Autorev chart before the test in order to be at a gross weight that puts you in a range of a good target Nr.(perhaps just over 400 Nr) If the target is not high enough, you will not get a split, and not a real autorotation Nr.
If you are too heavy and the Nr goes high when you are on the lower stop, you will have to check the collective and once again not have a real autorotation Nr.

If you pre plot your weight and altitude you will be at a good weight and have a clear result to make any required adjustments. (FLM section 8.3)

I have seen aircraft that needed to be adjusted over 30 RPM just to get a good split with a total change of closer to 35 to meet the chart. If that machine ever had an engine failure the pilot would have been riding the low rotor horn all the way to a nasty landing.

Regards,

Rigidhead