R22 Engine RPM above rotor RPM?
 

Has anyone ever heard of an R22 engine overspeed that was between 110 & 116%, but left the rotor below 110% (split needles)? Can belts normally slip like that with a sudden increase in throttle/torque or

A> There is an issue with the belt tension settings
B> The flight crew's perception/interpretation of the tachs was incorrect
C> Something else?

If it was A> is there anything you could detect on a preflight or on engine run-up (blades taking more than 5 seconds to turn etc?)

Regards

I am inclined to go with B based on what you are saying.
But A sounds like it could be possible I guess but I have never seen it.
What stage of flight did this occur?
What was the belt tension like after shut down?
Was the clutch light behaving normally during the flight?

I've seen on a few 44's & 22's where there is a miss-match between the two needles during normal flight. You start the flight and both needles are "top of the green" then after a while the ERPM begins to either increase or decrease by as much as 5 - 6%. No change in the RRPM and the engine was running normally. Never really found out what caused these issues, instrument or pickups?

May-be this?

Some Freq. on the radio will cause a spike in rpm:{, Hard to get electrons to work togeather some times,:eek: The MM has a list of Freqs that do the dirty deed.:rolleyes:

What stage of flight did this occur?
I believe in hover power recovery after autorotation

What was the belt tension like after shut down?
Mechanics said no problem found

Was the clutch light behaving normally during the flight?
Nothing out of the ordinary mentioned

sounds like an indication issue rather than a real change in ERPM

Could be various electrical reasons for this such as hilberg's theory. Could be tricky to isolate.

Definite engine overspeed
 

To be clear, my understanding is the high volume/pitch of the engine sound and student's incorrect throttle manipulation were consistent with an engine overspeed - there was no doubt there. The real question is what was going on with the rotor RPM indication not following the engine RPM?

Ok understood, if no fault found with belt tension, my vote goes back to B.
If you ever work it out can you tell us so we all can learn.

Does it really matter? Either way you are looking at some engineering work to check if anything had been damaged and then fixing it.