Turning Prop backwards

[Alan Maurer]

Mooney People

Had not had a chance to fly for a few weeks and I believe Mike Busch said that this does nothing but not sure. Can pulling the prop through in reverse deposit any oil on the cylinder walls or is it a waste of time???

Thanks

Alan

N913ND

[LANCECASPER]

Yours is a G1000 so it doesn't have a vacuum pump - so nothing to hurt there. I've never heard of any gain in doing that, but maybe.

For those that have a vacuum pump, they shouldn't for sure.

[PeteMc]

No expert, but going from memory of some engine seminar years ago...  I think the old theory of turning the prop backwards has to do with single velocity oil.  If, like most of us, you're using multi velocity oil (at least in the winter) then there is no need. 

Other issue unrelated to the oil was to pull the prop through just to hear the starter click and to make sure there wasn't a big block of ice rattling around in the spinner.  (Though I never got the rattling part, if it's ice I figure its frozen to something.) 

 

[N201MKTurbo]

1 hour ago, PeteMc said:

No expert, but going from memory of some engine seminar years ago...  I think the old theory of turning the prop backwards has to do with single velocity oil.  If, like most of us, you're using multi velocity oil (at least in the winter) then there is no need. 

Other issue unrelated to the oil was to pull the prop through just to hear the starter click and to make sure there wasn't a big block of ice rattling around in the spinner.  (Though I never got the rattling part, if it's ice I figure its frozen to something.) 

 

I’ve had ice in the spinner. It was frozen in place. You will know right away when your engine tries to leave the airplane.

[GeeBee]

I don't like it but not for any mechanical reasons. When I move a prop, I'm wary of the engine kicking, either backwards or forward (Lycomings seem to want to kick backwards sometimes). I've seen them go both ways. So when I move a prop, I move it as I would if I were hand propping the airplane both in hand and body placement. That way, no matter which way the engine might kick when getting a mind of its own, my pinkies will easily become disconnected from the prop and there will be no tendency to pull me into the blade swing.

[cliffy]

If you hear the click its the impulse coupling driving the magneto If you don't you have Shower of Sparks ignition (going in normal rotation direction_

I've seen 2 people hit by props One just moved it a few degrees. Ain't pretty if it connects with human tissue

Be VERY cautious when ever your hand is even just on the prop and not moving it  It can happen with 1 degree of prop movement. 

[AdamJD]

I just listened to "Ask the A&Ps" podcast episode 4 with Mike Busch, Colleen Sterling and Paul New.  They address this exact question.  The answer was, there is NO benefit to pulling the prop through in either direction.  In the opposite-than-normal direction (backwards), the pump moves backwards, so you are adding no oil.  And you are likely scraping oil OFF of the cylinder walls.  In the normal direction, you are at risk for starting the prop and causing personal harm if you have impulse coupler and you are still scraping oil OFF of the cylinder walls.  So both directions are a negative.  

If you have a radial engine, then there is another reason for pulling the prop through.  I assume your Mooney M20R is not a radial engine.

[PT20J]

Cylinders get lubricated by splash from the whirling crankcase components. The oil control ring scrapes the excess off and returns it to the crankcase through holes in the piston skirt. If you rotate the prop, you are not moving it fast enough to splash new oil on the cylinders but are scraping it off with the oil ring.

If your mags have impulse couplings, and you need to rotate the prop, it's safest to do it backwards because this will avoid triggering the impulse coupling which might cause a spark if a p-lead is broken and the mag is hot.

Never rotate a radial engine backwards because this will force any oil that has collected in a lower cylinders back into the intake tubes where it can then come back during a subsequent start and create a hydraulic lock which can bend a connecting rod. 

Skip

[Fly Boomer]

16 hours ago, Alan Maurer said:

Mooney People

Had not had a chance to fly for a few weeks and I believe Mike Busch said that this does nothing but not sure. Can pulling the prop through in reverse deposit any oil on the cylinder walls or is it a waste of time???

Thanks

Alan

N913ND

Regarding ice in your spinner -- "park" the prop with one blade (and consequently, the opening in the spinner) pointing down.  If it gets warm enough to melt, the water will drip out the opening.

[AndreiC]

On 12/4/2023 at 11:03 AM, Fly Boomer said:

Regarding ice in your spinner -- "park" the prop with one blade (and consequently, the opening in the spinner) pointing down.  If it gets warm enough to melt, the water will drip out the opening.

I learned this the hard way after getting ice in my spinner at least 3 times over a couple of winters parked outside (Piper Cherokee at the time). The vibration of the engine on start up will surely let you know something is amiss. The solution: get the airport to bring an engine pre-heater and point it at the spinner for 5-10 minutes. Works like a charm.