Originally Posted by
212man
DECUs, and any governing system, only govern N1/Ng when the engine(s) are at idle. With the Nr in the normal operating range they govern N2/Nf.
Not quite. After the engine is started, the DECU only controls N1 once the N2 exceeds 9%. Which is why, if you start the engine with the rotor brake on and then move the ECL from IDLE to FLY, the engine stays at idle.
And the other point. The DECU has no idea what the NR is...it doesn't even have an input for NR signal. The trigger for the DECU to govern N2 is when it senses the ECL in FLY position.