Pulling and Pushing a Plane by the Prop?

[Frank Giger]

Somewhere in my past - heck, it might have been before I was a pilot - I remember being admonished to never push or pull and aircraft around by its propeller.

It stuck with me for some reason and I've never done it, grabbing the vertical stab, wing strut, flat handing the cowl to push, or in the case of my Nieuport, just grabbing the horizontal stab supports, lifting the entire tail, and walking it around.

Yet I see guys pulling their planes out of hangars or pushing them in by the prop all the time.

Was that just some folksy wisdom, or was it correct?

[skyfixer8]

I was taught by an old mechanic to pull or push at the root of the blade, and don t turn the blade while doing this. Never trust a magneto. If you think about it, what moves the weight of the plane when the engine is running ?

[Low Pass]

The propeller pulls the plane around the sky, by design. On the other hand, the empennage DOES NOT pull the plane around by design. Just sayin.

[Frank Giger]

Pushing a conventional gear aircraft backwards is a bit like pushing a wet noodle. Just sayin.

[Bill Greenwood]

As a safety matter, I would generally keep my hands and body away from the prop and out of its arc, despite the often shown photos of someone absently minded posing leaning on a prop, even veteran pilots who should know better.
I would not push on one blade, and if needed to push a two blade prop would do it at the hub only. Iwouldnt push on one blade or even two of a 3 blade or 4 blade prop.
Prop makers say not to push/pull on the blades, but it is often done without apparent harm. A person is not going to use as much force as the engine does when pulling the plane. Pushing on the tip of just one blade might cause damage.

[Aaron Novak]

As a safety matter, I would generally keep my hands and body away from the prop and out of its arc, despite the often shown photos of someone absently minded posing leaning on a prop, even veteran pilots who should know better.
I would not push on one blade, and if needed to push a two blade prop would do it at the hub only. Iwouldnt push on one blade or even two of a 3 blade or 4 blade prop.
Prop makers say not to push/pull on the blades, but it is often done without apparent harm. Pushing on the tip of just one blade might cause damage.


Considering that most large males cant exert a force much over 50lbs while standing......pushing on a prop hub should be harmless.

[Mike Switzer]

Unless there is a handle for the purpose (as on some taildraggers) moving a plane by the tail can cause damage. I have seen 2 planes that needed ribs in the tail replaced because of people repeatedly leaning on the tail to lighten the nose & spinning the plane around. Pushing / pulling on the prop at the hub won't cause any damage.

[Frank Giger]

Thanks, all, for your insight.

It's one of those things that I heard and wasn't sure if it was a truism or a real thing.

Sort of like keeping a prop horizontal when the engine's off. I knew they are supposed to be that way but had to dig around to find out why.

For a wooden prop it's a best practice, as moisture in the wood will go to one blade if it's vertical - but I don't think it applies to composite ones.

[Low Pass]

Thanks, all, for your insight.

It's one of those things that I heard and wasn't sure if it was a truism or a real thing.

Sort of like keeping a prop horizontal when the engine's off. I knew they are supposed to be that way but had to dig around to find out why.

For a wooden prop it's a best practice, as moisture in the wood will go to one blade if it's vertical - but I don't think it applies to composite ones.IMO, the only legitimate reason to turn any 2 blade prop horizontal is to hopefully prevent the wing from another plane from whacking it. The bit about moisture collecting in the lower of the two blades is not fact based. My composite Whirlwind is sealed. If I have moisture in the blades, I have big, big problems. At one time a few years back I had a Cub with a Sensenich wood prop. The prop was sealed end to end with epoxy fiberglass and spar varnish. If it had moisture getting inside, it would not be long for the world. And if it did get moisture in the wood, the water would wick along the grain in both directions. A la capillary action.

If someone knows differently, and can explain how orientation matters, please pass it along.

[rwanttaja]

IMO, the only legitimate reason to turn any 2 blade prop horizontal is to hopefully prevent the wing from another plane from whacking it. The bit about moisture collecting in the lower of the two blades is not fact based.
Don't worry, Marvel Mystery Oil will fix that right up. :-)

Ron Wanttaja

[Frank Giger]

IMO, the only legitimate reason to turn any 2 blade prop horizontal...

But...but....that's what I read on the Internet!

;)

Frank "Copper Wrist Band" Giger

[jam0552@msn.com]

IMO, the only legitimate reason to turn any 2 blade prop horizontal is to hopefully prevent the wing from another plane from whacking it. The bit about moisture collecting in the lower of the two blades is not fact based. My composite Whirlwind is sealed. If I have moisture in the blades, I have big, big problems. At one time a few years back I had a Cub with a Sensenich wood prop. The prop was sealed end to end with epoxy fiberglass and spar varnish. If it had moisture getting inside, it would not be long for the world. And if it did get moisture in the wood, the water would wick along the grain in both directions. A la capillary action.

If someone knows differently, and can explain how orientation matters, please pass it along.

Sensenich W72GK48 Continued Airworthiness Requirements:

2. When the propeller is not in use, place the propeller in a horizontal position and if it is exposed to the weather, cover it with a waterproof cover.

3. Do not use the propeller as a tow at to move your aircraft.

-Joel Marketello

[FlyingRon]

Hartzell also warns to not push or pull the airplane by the prop. Of course, anything Hartzell tells me I take with a very large grain of salt.

[Mayhemxpc]

Macauley says to position the two bladed constant speed prop in the 1 o'clock position

[Gunslinger37]

My experience (2 cents worth) is a constant speed, variable pitch, prop should never be pushed on to move the airplane. When stopped, there is a slight play in the hub and you can feel the blades "clunk" when you push or pull. That small movement will cause a grease seal leak in the hub.

[FlyingRon]

My experience (2 cents worth) is a constant speed, variable pitch, prop should never be pushed on to move the airplane. When stopped, there is a slight play in the hub and you can feel the blades "clunk" when you push or pull. That small movement will cause a grease seal leak in the hub.

You've got something wrong with your prop. Nothing goes goes "klunk" in my prop when you pull. There's a tiny amount of play in twist. None of this would be a "grease seal" issue anyhow. Your blades are pulling hard on that hub normally and pushing on it when you're powered back in a descent.

[Low Pass]

Second Ron's comment. If your blades are actually moving a perceptible amount within the hub, you have a significant issue. (Excluding normal twisting action.) But are you sure it's not the entire crank/prop assembly moving fore and aft? A direct drive recip engine should have thrust clearance. This will be evident by the prop clunking back and forth some 20-50 thousandths (verify exact spec for your engine). As a matter of habit and my OCD, I pull and push a prop/crank during preflight to see that it has about the right amount of float.

[martymayes]

some prop blades are (relatively) loose in the hub. They are designed that way. Some are not. Fore/aft pushing/pulling on a propeller tip to move a plane can possibly cause damage to the prop where pushing or pulling on the blade next to the hub is relatively harmless (I say relatively because some people can efforetlessly tear up an anvil). It's just common sense. If I were a prop manufacturer, I'd say NO to pushing or pulling on the prop for any reason because common sense isn't always that common. Any document that says pushing/pulling the plane by the prop is okay would be in a lawyers hands during a trial for sure: "It says right here pushing and pulling on the prop is approved!" Yup.

[iterk]

IMO, the only legitimate reason to turn any 2 blade prop horizontal is to hopefully prevent the wing from another plane from whacking it. The bit about moisture collecting in the lower of the two blades is not fact based. My composite Whirlwind is sealed. If I have moisture in the blades, I have big, big problems. At one time a few years back I had a Cub with a Sensenich wood prop. The prop was sealed end to end with epoxy fiberglass and spar varnish. If it had moisture getting inside, it would not be long for the world. And if it did get moisture in the wood, the water would wick along the grain in both directions. A la capillary action.

If someone knows differently, and can explain how orientation matters, please pass it along.

All true wood props (NOT composite OVER wood..) will have 3 drain holes ( I think I remember from teaching this years ago, that they are typically .040" or a #60 drill) These MUST be kept open and free of paint or wax/resin etc. The moisture DOES get into the prop. Some through the hub area. It MUST have a way out. This is why a true wood prop should be stored horizontally. If your Sensenich Cub prop was "glassed over" it was contrary to the maintenance instructions from the manufacturer and AC43.13. We have to refer back to the older version...AC43.13.1a ( Sensenich has told me that when the FAA dropped the wood prop section of AC43.13 in revising 1a to 1b the FAA advised them to continue to reference 1a). I believe that Sensenich will make a copy of that info available but even the current web site doesn't reference the holes any more... OK..as a follow up, I went to my old AC43.13.1a para 569... It's all there

[Greg Wilson]

All true wood props (NOT composite OVER wood..) will have 3 drain holes ( I think I remember from teaching this years ago, that they are typically .040" or a #60 drill) These MUST be kept open and free of paint or wax/resin etc. The moisture DOES get into the prop. Some through the hub area. It MUST have a way out. This is why a true wood prop should be stored horizontally. If your Sensenich Cub prop was "glassed over" it was contrary to the maintenance instructions from the manufacturer and AC43.13. We have to refer back to the older version...AC43.13.1a ( Sensenich has told me that when the FAA dropped the wood prop section of AC43.13 in revising 1a to 1b the FAA advised them to continue to reference 1a). I believe that Sensenich will make a copy of that info available but even the current web site doesn't reference the holes any more... OK..as a follow up, I went to my old AC43.13.1a para 569... It's all there

Absolutely, a problem with "new" techniques or procedures is making certain that they are applicable to older products they often times are not. Just as a wood core prop vs. varnished wood they are different and must be treated differently. I have referred back to my CAM 18 with full approval of my local FSDO as it is more in line with the structures that I was working with than the 43.13.

[Bob H]

A prop absorbs around 5 lbs/hp as thrust so a 100 hp engine generates ~500 lbs force. Props are designed to accept that force as bending and torsional loading. So pulling on a prop by hand to move a plane would never exceed the service loads.
Bob H

[Mayhemxpc]

Is that per blade or for the whole prop? In either case a C-150 weighs more than 500 lbs.

[wyoranch]

Is that per blade or for the whole prop? In either case a C-150 weighs more than 500 lbs.
It does not take 500lbs of force to roll a 150. I am a fat slob and I can push one around with 1 hand. lol
Rick

[iterk]

It does not take 500lbs of force to roll a 150. I am a fat slob and I can push one around with 1 hand. lol
Rick

I know we've decided that we are smarter than the engineers at the various prop factories and that you won't hurt (especially a fixed pitch) prop by pushing or pulling but keep the force as near the hub as you can even in a fixed pitch prop. If you are rocketing around with a variable pitch or ground adjustable I strongly suggest you follow the manufacturer's instructions and invest in a tow bar and get in the habit of using it.....AND TAKING IT OFF EVERY TIME YOU PUT IT DOWN! I have a couple of horror stories about props and tow bars...(Think not only tow bar but New MT prop AND ENGINE TEAR DOWN!! at $40k+). My beloved customer's broke the habit. I had to fix it...and the McCaulley on the Mooney wasn't much cheaper... It's NOT the way I wanted to earn my living..

The leverage of pushing and pulling really does have a detrimental effect on the blades (to some extent even of a fixed pitch prop) and their setting especially when they don't have the benefit of centripetal force to lock all the pieces in place as they do when in their "working" mode.

[martymayes]

So pulling on a prop by hand to move a plane would never exceed the service loads.
Lso you won't mind if I push/pull on your prop? Not responsible if something is damaged of course!

[1600vw]

I would say it depends on the size of airplane, what it is setting on, and how far you plan to move it. My little airplane at 400 lbs takes very little effort to move it on the hangar floor a foot or two. But put it on an incline in the grass and its a bitc$ to move. Now take something like a twin engine sitting on concrete.