Proping Question

Barry wrote:

We turn the prop vertical in the winter to prevent water from pooling inside
the spinner and then freezing into a block of ice. This happened to me once,
and the vibration it caused was impressive. We shut down, pulled the plane
into a heated hangar, turned the prop vertical, and waited for the ice to melt
and drain out.



As do we.

Same name, same reason. G

"Barry" wrote in message
...
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.

We turn the prop vertical in the winter to prevent water from pooling
inside
the spinner and then freezing into a block of ice. This happened to me
once,
and the vibration it caused was impressive. We shut down, pulled the
plane
into a heated hangar, turned the prop vertical, and waited for the ice to
melt
and drain out.


Interesting, and worth remembering.

There is also a much older version of the advise--recommending that wooden
props be left horizontal when parked for long periods so that moisture in
the wood will not migrate to one blade, causing an imbalance.

Peter

The engine is not designed to turn in a specific direction. Some
accessories are, such as mags, vacuum pumps, starter, alternator. The
engine itself will happily run in the other direction, several twins do
just that.



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.


-m

"Newps" wrote in message
. ..

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.


That's only true with 2 cyclce engines, even then, ignition timing is a
factor. The rotational derection of a 4 cycle engine is determined by the
cam, valve and ignition timing. Twin engine aircraft with counter rotating
props/engines have beend designed specifically to do so. The engines as a
whole, are not interchangable.

On May 15, 10:02 am, Newps wrote:
The engine is not designed to turn in a specific direction. Some
accessories are, such as mags, vacuum pumps, starter, alternator. The
engine itself will happily run in the other direction, several twins do
just that.

That backward-running engine has a different camshaft, mags and
oil pump to allow it to run that way. Engines won't run backwards just
because we try to start them backwards. The intake/compression/power/
exhaust strokes MUST happen in that order, and a backward-turned
engine has them all messed up.

Dan

On May 15, 4:11 pm, wrote:
On May 15, 10:02 am, Newps wrote:

The engine is not designed to turn in a specific direction. Some
accessories are, such as mags, vacuum pumps, starter, alternator. The
engine itself will happily run in the other direction, several twins do
just that.

That backward-running engine has a different camshaft, mags and
oil pump to allow it to run that way. Engines won't run backwards just
because we try to start them backwards. The intake/compression/power/
exhaust strokes MUST happen in that order, and a backward-turned
engine has them all messed up.

Dan

Forgot to mention: an alternator generates just fine when run
backwards. I did it on an inboard boat I built, because there was no
room in that tight compartment for the alternator to sit alonside the
engine in its usual spot and had to be mounted backwards in front. An
alternator generates alternating curent that is internally rectified,
and the direction of rotor rotation is irrelevant. The only
consideration is the cooling fan blade angle; installing an older fan
with straight radial blades solves the problem.
The DC generator must be turned in one direction only.

Dan

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