Torque increase for a prop decrease - why?
That's exactly right, however only if power remains constant.
Actually,
Power = torque x RPM (x some constant, depending on units used)
This is really just a rotational version of the simple formula from Yr 11 Physics, ie
Work = Force x Distance which leads to
Power (Work/Time) = Force x Speed (Distance/Time)
which in the rotational sense is
Rotational power = Rotational Force (Torque) x Rotational Speed (RPM)
So with a prop RPM increase in a King Air, I would expect the torque to drop (if power remains a constant) like Captahab said. If there is a fuel flow decrease, it may be an indication that there has been a power decrease (even though the throttle hasn't been moved). Dunno how how the FCU functions on a PT6 when a manual prop governor is attached.
Hope this makes sense.
VI