Proping Question

"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.

"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?

This is one issue where you don't want to get bogged down in the
technicalities involving vacuum pumps and impulse couplings.
The bottom line on this issue is that you should NEVER.....EVER...... trust
a propeller not to kill you if you turn it by hand IN EITHER DIRECTION while
it's attached to the airplane.
Dudley Henriques

In article ,
"Dudley Henriques" wrote:

"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?

This is one issue where you don't want to get bogged down in the
technicalities involving vacuum pumps and impulse couplings.
The bottom line on this issue is that you should NEVER.....EVER...... trust
a propeller not to kill you if you turn it by hand IN EITHER DIRECTION while
it's attached to the airplane.
Dudley Henriques

Some engines (I'm thinking Rotax in particular) are highly allergic to
turning the prop backwards. On a Rotax, it introduces air into the oil
galleys, which can result in premature engine failure.

I subscribe to the following precautions:

1. Check mag grounding prior to shutdown.

2. shut down with idle cutoff and throttle at idle.

3. If you turn the prop, do so in a way that it will not strike either
you or anything (or anyone else) if it kicks off.

I actually had a prop hit me from residual compression (no ignition) one
time.

On 2007-05-15 07:46:15 -0700, "Dudley Henriques" said:


"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?

This is one issue where you don't want to get bogged down in the
technicalities involving vacuum pumps and impulse couplings.
The bottom line on this issue is that you should NEVER.....EVER...... trust
a propeller not to kill you if you turn it by hand IN EITHER DIRECTION while
it's attached to the airplane.
Dudley Henriques

People will say it is technically impossible, but I think it is wishful
thinking. An engine may not run backwards very well, but I have seen
too many malfunctioning magnetos to believe that it could never happen.
It might be improbable, but I would not bet my life on the idea that it
is impossible.
--
Waddling Eagle
World Famous Flight Instructor

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?

This is one issue where you don't want to get bogged down in the
technicalities involving vacuum pumps and impulse couplings.
The bottom line on this issue is that you should NEVER.....EVER......
trust
a propeller not to kill you if you turn it by hand IN EITHER DIRECTION
while
it's attached to the airplane.
Dudley Henriques

People will say it is technically impossible, but I think it is wishful
thinking. An engine may not run backwards very well, but I have seen
too many malfunctioning magnetos to believe that it could never happen.
It might be improbable, but I would not bet my life on the idea that it
is impossible.
--
Waddling Eagle
World Famous Flight Instructor

It doesn't really have to "run" to hit you, it only has to "kick" once. And
that is cold comfort indeed, since immediate death is far from the worst
thing that can happen to a person.

(rant omitted)
Peter

"C J Campbell" wrote in message
news:2007051622001427544-christophercampbell@hotmailcom...

People will say it is technically impossible, but I think it is wishful
thinking. An engine may not run backwards very well, but I have seen too
many malfunctioning magnetos to believe that it could never happen. It
might be improbable, but I would not bet my life on the idea that it is
impossible.
--

On a 2 cycle engine, ignition time is all it takes. Some golf carts actually
work that way. The starter and ignition time is selectable by the direction
indicatior on the dash.

But on a 4 cycle engine, the valve timing would have you intaking through
the exhaust, and exhausting through the intake.

"C J Campbell" wrote in message
news:2007051622001427544-christophercampbell@hotmailcom...
On 2007-05-15 07:46:15 -0700, "Dudley Henriques"
said:


"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?

This is one issue where you don't want to get bogged down in the
technicalities involving vacuum pumps and impulse couplings.
The bottom line on this issue is that you should NEVER.....EVER......
trust
a propeller not to kill you if you turn it by hand IN EITHER DIRECTION
while
it's attached to the airplane.
Dudley Henriques

People will say it is technically impossible, but I think it is wishful
thinking. An engine may not run backwards very well, but I have seen too
many malfunctioning magnetos to believe that it could never happen. It
might be improbable, but I would not bet my life on the idea that it is
impossible.
--
Waddling Eagle
World Famous Flight Instructor


Rule number one for me has always been "never give the machinery an
advantage".
If it CAN kill me, it just MIGHT kill me, so I treat it that way.
:-)))
Dudley Henriques

On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
wrote:

People will say it is technically impossible, but I think it is wishful
thinking. An engine may not run backwards very well,

During World War II (really!) I worked on a farm in Concord, Mass.
There was a great steel-wheeled tractor that was started with a hand
crank. One time the tractor backfired while the lad was spinning the
crank, and the engine started running backwards. He jumped aboard and
had a great time wheeling it around the yard, one speed forward and
three in reverse. Blue skies! -- Dan Ford