On May 15, 5:59 am, "Doug Palmer" wrote:
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?

Of course turning it backward may damage the vac pump but I've never
flown a hand prop'ped airplane that had a vac system.
The problem with turning it backwards is that it can still on forward.
If you turn it and stop near the compression, it will then turn back
the other way. So, either way assume its hot.
Once you've been flying a hand propped airplane for awhile you will
realize that it is not safe or reasonable to use a full body kick
every time you turn the prop. So I would pull the prop through with an
open palm hand such that if the prop did start I would be ok (some of
the old guys actually start the plane this way). Then, when its time
to start, I hit the mags and do a full kick. If you primed the engine
correctly it should only take about an 1/8 of a turn for it to fire.
BTW: I would never hand prop a nosewheel plane.

-Robert