[...] Pulling power can also cause a yaw in the opposite direction!

No, it won't.

I said "can cause". Yes, it can, and does... but I should've been
clearer.

First, in many trainers the major left-turning tendency is from the
corksrewing propeller slipstream... about twenty times the precession
force, ten times the P-factor, and three times the torque force (which
is a banking force really). So, as you alluded to, planes are designed
to compensate at cruise for this by slightly canting the engine to the
right, and the vertical stabilizer to the left.

In a high-power, low-speed situation like the takeoff roll, the
slipstream wind hits the tailfin from its left, thus increasing the
angle of attack and causing the tailfin to move right (left yaw).

Conversely, in a low-power, high-speed situation like a descent, the
slipstream force is much less than the oncoming air, and the slight
left cant of the vertical stablizer causes a slight _right_ yaw, which
often has to be compensated for with a little _left_ rudder. This is
what I was thinking of when I said "pulling power".

Latet, for what it's worth, I'll suggest that a simulators newsgroup
isn't
a very good place to get actual airplane *facts*.

I'd agree that most replies on the net are by necessity in some way
incomplete. For example grin, when you mentioned friction and
precession as causes of gyro drift, you left out the fact that gyros
operate in what's known as "inertial space". The motion of the earth
itself through the universe will always mean that gyros cannot forever
stay correct from an earthling's point of view. This is most visible
at the higher latitudes (above and beyond the variation differences you
pointed out).

For a neat example: consider that you're parked at the North pole, and
you set your DG to "N". It's pointing towards a certain direction in
space. But wait twelve hours and the DF will read "S", because the
earth rotated the entire plane halfway around. However, this is just
nit-picking and all in fun

Cheers,
Kevin