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R22 Engine RPM above rotor RPM?

r22 robinson tachs overspeed engine rotor

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#1 ChopperStudent

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Posted 26 February 2014 - 17:29

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


#2 iChris

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Posted 03 March 2014 - 17:26

 

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

 

 

Sounds like a bad excuse from a new pilot or CFI and student trying to mitigate their involvement in a common overspeed incident. If there were no prior or post discrepancies with belt tensioning or the tachometers, you can’t rely on any dubious explanation like that from the pilot or crew. Moreover, if they were that observant, there wouldn’t have been an overspeed in the first place.

 

Likely another training incident, nothing wrong we the helicopter. May have been the old autorotation with a power recovery or the quick-stop maneuver they got behind on.

 

That type of split is unlikely unless for one of the following:

 

1. Engine RPM (ERPM) overspeed on start up, before belts tension, if the throttle is not in the fully closed position, ERPM could rise rapidly.

 

2. Clutch system failure (electrical or mechanical)

 

3. Problems with the breaker points in the right magneto and/or associated wiring. The sensor for the engine tachometer is the breaker points in that right magneto.

 

4. Not following the maintenance manual caution: The installation of electrical devices can affect the accuracy and reliability of the electronic tachometers. Therefore, no electrical equipment must be installed in the R22 helicopter unless the factory specifically approves the installation.

 

If it was an obvious overspeed, that’s probably all it was.  


Edited by iChris, 03 March 2014 - 17:31.

  • WolftalonID and troll.detector like this
Regards,

Chris

#3 WolftalonID

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Posted 03 March 2014 - 18:56

Thats probably why Harley never made a helicopter.....

The boys would be yelling, "get to da choppa" and then revving it up all the time just to hear it rumble!!!

iChris I like that comment "dubious". The only time I can recall potentially overspeeding an engine when everything else was normal was in governor off training scenarios. I never did, but you have to be very observant of the moment or it would happen fast.

Makes me wonder the details of the situation this one post OP knows but didnt disclose. That migt be the key to an answer.... Maybe.
Sometimes we think we know it all....only later to discover we only knew all we had learned. Never stop learning.





Also tagged with one or more of these keywords: r22, robinson, tachs, overspeed, engine, rotor

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