Originally Posted by Cardinal Puff
...May also not have enough power applied to arm the autofeather system on the approach.
Correct, but that is more an 'effect' rather than a cause. Because the system is designed only for use during take-off, and because the system has to allow a rejected take-off to be carried out without resulting in an autofeather, both power lever position and engine torque pressure are sensed.
The autofeather system will not arm unless torque on BOTH engines is above a specified value (this will vary slightly depending on mod status), and unless the power levers themselves are physically quite far forward. The power lever position is sensed in order to allow deactivation (disarming) of the system during a RTO
prior to torque dropping below the torque sensor threshold.
So, even if enough power was carried in the approach to satisfy the torque sensor threshold, it is very unlikely that the power levers would both be far enough forward to arm the system.
Michael