"Doug Palmer" wrote in message
ink.net...

Several pilots found themselves in a debate at our field yesterday. The
issue is weather it is safer to move the propeller on a (parked) aircraft
in the direction of usual engine rotation, or opposite usual rotation.
This is assuming that the propeller needs to move for some reason.

The reasonings ranged from "you should not turn an engine backwards" to
"turning the engine backwards disarms the impulse coupling", to several
issues in between.

Any thoughts from the groups collective wisdom?

There is potential for damage to a vacuum pump if turned backward.