Proping Question

On May 15, 10:59 am, "Mark T. Dame" wrote:
Ron Natalie wrote:

The argument against it is that people claim it hurts the vacuum pump.

That was what I was taught many moons ago. I have never confirmed it,
but my brain tells me that the engine is designed to turn in one
direction, so don't turn it in the other. No real proof (I'm not an A&P
and have never played one on TV), but just my own logic.

Except when absolutely necessary (like to get the tow bar connected)
you shouldn't be turning the prop at all. There's no good reason to
justify the dangers.

If the engine is properly shutdown (boost pump off, throttle slightly
above idle, and mixture to cut off) the chances are greatly reduced than
if you just kill the engine by turn off the mags. Additionally, some
people recommend checking your mags before shutdown to make sure you
don't have a broken P lead which would also help. A flying club I used
to belong to had a "policy" (not a rule, just a suggestion that it would
be nice if you did it) of turning the prop vertical after parking it to
keep the birds from sitting on it and pooing on the plane.

Obviously the safest way to prevent an accidental fire while hand
turning the prop is to not do it. When I do turn a prob by hand, I try
to do it in the direction it turns while running, turn slowly to
minimize any compression (don't know if that is true either, just what I
was taught), and only use the palms of my hand on the face of the prop
to minimize the possibility of the prop smacking the back of my hand
should it fire. YMMV.


Although I agree with the dangers of accidental engine starts, what I
would like to know if there really have been any cases of inadvertant
engines starts when the prop is turned half a rotation with the
mixture in cut-off even if the magnetos were on. All the cases I am
aware of are related to hand-propping, which is not the same as
turning the prop to reposition the blades.

On May 15, 10:18 am, Andrew Sarangan wrote:


Although I agree with the dangers of accidental engine starts, what I
would like to know if there really have been any cases of inadvertant
engines starts when the prop is turned half a rotation with the
mixture in cut-off even if the magnetos were on. All the cases I am
aware of are related to hand-propping, which is not the same as
turning the prop to reposition the blades.- Hide quoted text -

- Show quoted text -

Yes, engines have hurt people. You can kill it with the idle
mixture cutoff, but if someone has fooled with the primer (or boost
pump on an injected system), fuel will be present and any spark could
set it off. An example is a failed start attempt, due either to a
flooded engine or cold weather. That prop will be dangerous with the
mags on. Turning it forward is insane.

Dan

Andrew Sarangan wrote:


Although I agree with the dangers of accidental engine starts, what I
would like to know if there really have been any cases of inadvertant
engines starts when the prop is turned half a rotation with the
mixture in cut-off even if the magnetos were on. All the cases I am
aware of are related to hand-propping, which is not the same as
turning the prop to reposition the blades.

Start no, kick over a turn or two, yes. Even with the engine cut
off with the mixture, there can end up with just enough fuel in the
system to fire the thing over a turn. I've had it happen on a 172N
we had in the club.

Andrew Sarangan wrote:
Although I agree with the dangers of accidental engine starts, what I
would like to know if there really have been any cases of inadvertant
engines starts when the prop is turned half a rotation with the
mixture in cut-off even if the magnetos were on.

Early in my piloting career, while my instructor deftly distracted me
with questions about the cruising speed of an unladen swallow, I managed
to turn the mags off before pulling the engine to cutoff, so that it
stopped because the ignition died. Spotting my mistake, my instructor
asked me to run the starter over, and the engine gleefully spat to life
on the very first blade, and ran for another 5-10 seconds.

Then he asked me if I wouldn't mind terribly putting the plane away myself.

Take any aircraft X and put renter A before you who does something
similar but doesn't catch the mistake, and you too can become another
statistic by trusting that the prop is dead, that the p-lead works, and
that the cylinders are dry.

TheSmokingGnu

"Andrew Sarangan" wrote in message
oups.com...
snip

Although I agree with the dangers of accidental engine starts, what I
would like to know if there really have been any cases of inadvertant
engines starts when the prop is turned half a rotation with the
mixture in cut-off even if the magnetos were on. All the cases I am
aware of are related to hand-propping, which is not the same as
turning the prop to reposition the blades.

I had a friend who claimed that he had a warm engine start in his hangar
when he repositioned the prop. The hanger door was closed and he had
nowhere to go. Claimed his back was against the door and he held his hand
on the center of the spinner to stop the aircraft from moving forward.
Luckily the fuel was shutoff and it only ran for a very short time. I
forget where the gas came from. He may have been spinning a tale but he
really wasn't that kind of guy.

Happy landings.

"Private" wrote in message
news:0Ft2i.188319$aG1.182030@pd7urf3no...

I had a friend who claimed that he had a warm engine start in his hangar
when he repositioned the prop. The hanger door was closed and he had
nowhere to go. Claimed his back was against the door and he held his hand
on the center of the spinner to stop the aircraft from moving forward.
Luckily the fuel was shutoff and it only ran for a very short time. I
forget where the gas came from. He may have been spinning a tale but he
really wasn't that kind of guy.


Interesting. I used to know an old timer that told the same tale.

"Private" wrote in message
news:0Ft2i.188319$aG1.182030@pd7urf3no...

"Andrew Sarangan" wrote in message
oups.com...
snip

Although I agree with the dangers of accidental engine starts, what I
would like to know if there really have been any cases of inadvertant
engines starts when the prop is turned half a rotation with the
mixture in cut-off even if the magnetos were on. All the cases I am
aware of are related to hand-propping, which is not the same as
turning the prop to reposition the blades.

I had a friend who claimed that he had a warm engine start in his hangar
when he repositioned the prop. The hanger door was closed and he had
nowhere to go. Claimed his back was against the door and he held his hand
on the center of the spinner to stop the aircraft from moving forward.
Luckily the fuel was shutoff and it only ran for a very short time. I
forget where the gas came from. He may have been spinning a tale but he
really wasn't that kind of guy.

Happy landings.


I hope he was wearing gloves!

Actually I have either heard or read the same story a couple of times over
the years, and I really do have my doubts.