Originally Posted by
FGD135
yr right, Torque limit is not, and cannot, be based on engine speed. There is no direct relationship between engine speed and torque. On a cold day, for example, an engine in good condition could achieve max torque at a speed much lower than some other engine, in lesser condition, on a hot day. There is no direct relationship.
The same engine, even, under two different sets of ambient conditions could reach the torque limit at different speeds. For example, a takeoff at low elevation in cold temperatures and a takeoff at higher elevation in hot conditions on the same day. The Ng is guaranteed to be different between these two scenarios. How can a torque limiter possibly be based on engine speed, given such typical circumstances?
The poster gave almost no supporting information, so SPUDO was quite justified in giving the *most likely* reason as torque limiter, given that this is the only time, on a properly operating PT6 engine, that power lever advance should have no effect.
The next most likely reasons are mis-rigged power lever, crook Ng governor or instrument error.
GTang, some more information please. What aircraft type? Does it achieve rated takeoff torque? Have you flown other aircraft of the same type? If so, how do they compare?
Clearly you don't understand how and why the Tq limiting works and how it senses it. I would suggest that you find out how it works before you make any more comments. This is because you are incorrect with your statements.