Anyone ever have a drop in prop RPM on a PT6 but no increase in torque or decrease in fuel flow?

it was on a kingair 200, the rpm droped but all engine peramiters remained the same. it caused a violent yaw and loss of direction controll and now we cant replicate the problem

Answers:
PT6 engines are very reliable, but I did have one go to idle RPM, this was accompanied by a drop in fuel flow however and it was due to a glitch in the Fuel Control Unit.

This was on an EMB-110 powered by a pair of PT6A-34 turboprops.

A drop in RPM will usually be a result of either a change in propeller pitch with an increase in torque or a susbtancial decrease in power with a drop in fuel flow.

I sugest you check your FCU, and prop hub assy.




Update:
The PT6 is a free turbine and the prop can stop with the engine turning, the Pratt 120 series engines can be fitted with a prop-brake (as fitted on ATR aircraft). However, this will result in increased ITT readings.

Check your oil for traces of metal, something could be very wrong with the planetary reduction gear-box. If the prop did not turn by hand I would suggest you not fly with this engine until a cause has been determined and the problem solved.
could you have had an air bubble change prop pitch?

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