PT6 Power lever stop, prior to engine limits
Last week I was able to hit the physical stop on the power lever without reaching any of the engines limits. Maintenance verified that the FCU stop is being reached. (so not a rigging issue) Gauges have been calibrated.
I'm look for people's previous experiences here, and perhaps an explanation that would deepen my understanding of the pt6.
Our company only operates one a/c of this type, so I have little to compare it to. But we operate many other a/c using a different version of the pt6. (the other model of the pt6 I fly would massively over temp the engine if you moved the power lever fully forward)
Situation where physical stop is first reaches:
- 700 ITT (limit is 750)
- 2100 ft lbs (limit is 2230)
- 99.7 N1 (limit is 101.5)
- 9500', -3 OAT
While looking into this I've noticed that the physical stop can also be reached on the other engine under the same flight conditions. But the stop seems to correspond with the N1 limit. (the other engine reaches 101.5 right when the Power Lever reaches the stop)
My thoughts are that the N1 gauge on the problem engine is under reading by 2%.
Questions I have:
- Does the travel limit at the FCU correspond with the maximum continuous N1 setting?
- Is the FCU stop adjustable or fixed?
- Could a gauge error, even after calibration, account for the 2% N1 that we seem to be missing?
The engine runs well, and is very close to the other engine and the AFM numbers. But it seems strange to me to hit the travel limit of a power lever without reaching any engine limitations in flight.
Thanks for the replies.