On installations with rear mount alternators like Cont io/o 470s
in Skylanes, and such, the alternator turns backwards. There
is a special pulley with the fan fins in the opposite direction.

If you use automotive stuff, you will find that the fins are
backwards and the centerline of the belt is about 1/8" farther
from the alternator case than it is on the aircraft one.

Needless to say, the alternator could care less which
direction it is turning.

Bill Hale A&P

abripl wrote:
One known problem is that aircraft engines turn CCW looking at the prop
but auto alternators have cooling fins optimized for CW. But thats not
apparently as much a problem as the pulley nut potentially comming
loose. For CW rotation the engine torque will tend to tighten the
pulley nut but for CCW it will tend to loosen it. It happened to me
today )on the ground) after 60 hours of use and the alternator was not
charging just spinning the pulley. Make sure you check your pulley nut
tightness ocassionally if you are using an auto alternator.