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Moving GA Aircraft by pulling on the prop

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Moving GA Aircraft by pulling on the prop

Old 06-20-2015, 03:25 AM
  #31  
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Originally Posted by Grumble View Post
The horror!!!!

Note sure that's an apples to apples comparison. Floats vs pavement. It takes a lot less mechanical work/stress to move a float.
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Old 06-20-2015, 03:32 AM
  #32  
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Originally Posted by JohnBurke
It would be helpful if you will go ahead and contact the manufacturers so that they can have their errant direction removed from their publications, to avoid further future confusion.
I cannot recall any of the piston aircraft I've flown having an AFM Section 2 or Section 8 prohibition on moving the aircraft using the propeller.

EDIT:

Because I can admit when I'm wrong, I went back and looked at the AFM of the last piston I flew and in Section 8 there is a caution to not pull or push on control services or propeller while moving the airplane. I'm curious exactly how the manufacturer would have someone moving the aircraft by hand towbar impart enough force to get the aircraft rolling without placing their hand on the base of the prop (or the cowl)...but Burke is right, its there in the book.

Last edited by BoilerUP; 06-20-2015 at 03:43 AM.
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Old 06-22-2015, 04:05 PM
  #33  
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Invest in a nose gear hand-tow bar.....more maneuverability and no chance of prop damage
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Old 06-22-2015, 10:41 PM
  #34  
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I've seen several towbars left on the nose gear, hit with the propeller. A chunk of one just missed my head. I've seen them jam the gear doors on a few aircraft, too. Someone brought me a Bonanza a few years ago, and when I pointed to damage to the nose gear doors, they said "bet you can't guess how that happened." I told them it looked like they left the tow bar on and went flying. They did.

It's a lot harder to leave a power tow on there, and taxi, but not impossible.
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Old 07-03-2015, 06:59 AM
  #35  
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Originally Posted by AutoPirateOn View Post
There is absolutely no chance of pulling on the prop will hurt anything, with one exception: don't pull at the tip of the prop. If you do, the prop will act like a lever and give you a mechanical advantage that will put a huge force near the hub that might damage it.

Stop and think about it for a second, what pulls the airplane through the air? The propeller obviously. It's designed to take a lot of pulling force, but not a whole lot of sideways force, so try and minimize that by pulling close to the hub with both hands.

Also, thinking that using your hands will damage the prop itself is not correct. Have you ever smashed your head on one? Ask a line guy who has been on the job for anytime longer than a month how hard those props are. Even the wooden ones. The only way you will hurt it is if you beat it with a hammer.

They do jack airplanes by the wings, but you'd had better know the proper area to do it. Otherwise you will punch the jack through the sheet metal. The point is almost always right under the wing spar.
This is excellent advice.

My father was an ANG pilot and aeronautical engineer for the Department of the Army. He also had a Howard DGA for many years.

One time, while moving the airplane out of the hangar, another individual decided to help by pulling on the propeller and my father went ballistic. My brother and I were pushing on the wing struts as instructed and my mother was providing wingtip clearance.

After Dad cooled down, and that took a while, he told me the torque exerted by pulling on a propeller blade could affect the propeller's balance. This was more important because the Howard is a tail-dragger. The propeller's hub sits up higher than a tricycle gear airplane.

The lesson I took away from that is NEVER pull an airplane by its propeller regardless of whether on not it's a fixed-pitch prop or constant speed prop.
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Old 07-03-2015, 07:26 AM
  #36  
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Actually, it's not excellent advice. The quote you reference suggests that because the "propeller pulls the airplane through the air," then pushing or pulling the propeller by hand can't hurt it. It's a ridiculous non-sequitur comparison. An air load on the propeller acting against the chord line, vs pulling perpendicular to the chord line at a single point on the propeller have nothing in common.

Unbalancing a propeller doesn't change because it's a conventional gear airplane; in fact, conventional gear has nothing to do with propeller balance. Moving the airplane with the propeller generally won't impact balance, though it can impose stresses on the propeller, hub, and engine mounts that were not intended.

Forces acting across the prop disc while the propeller is in motion, while it's being acted upon by centripetal forces, are very different than forces applied to one or two points along the prop when it's static.

Balance is a function of weight distribution, and is adjusted by adding or removing weight from the propeller itself, or from the hub or spinner. Balancing can be done statically or dynamically. I don't believe I've ever seen a propeller unbalanced by pressing or pulling on the prop by hand, but something as simple as a missing washer on a prop spinner or dressing a nick on a prop blade will lead to a degree of prop imbalance.

Height above the ground (gear height or position based on gear configuration) doesn't impact balance; balance is a function of weight distribution throughout the spinning propeller disc. If the propeller is unbalanced, it's unbalanced whether on conventional gear ("taildragger") or tricycle gear, whether close to the ground, or high above the ground. Balance issues are typically manifest at higher RPMS, though are more pronounced in certain RPM ranges, regardless of landing gear configuration or relation to the ground.

Propellers bend. They bend in normal operation. If you've ever seen the effects by looking at the prop disc from the side during a load, you'll see it coning forward with a considerable amount of bend in some cases, and in certain RPM ranges, harmonics lead to a degree of wave in the prop blade. The impact this has on the propeller blade and the load it imposes is very, very different when the propeller is spinning, than it is when the propeller is not moving, in a static state.

A propeller can be made to be imbalanced aerodymically, or more specifically, a vibration caused, by bending one blade and not the other. This isn't actually a prop imbalance, but rather a difference in the local angle of attack of the blades, and can lead to vibration that's different in nature, and imposes different stresses, than a weight imbalance. In this case, bending of a blade or changing of it's angle of incidence at a given point will cause the propeller to experience different forces at different points in the arc, as well as on a continuing basis as it rotates, and can cause unusual and unpredictable harmonics.

I'm not aware of any towbars that attach to propellers to move aircraft. Those who would suggest that one can't hurt a propeller by pushing or pulling on it on the ground (because props move airplane in flight) miss the point entirely, and might be hard pressed to explain why we don't have devices designed to move airplanes on the ground using the propeller to push or pull. Think about it.
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Old 07-12-2015, 08:01 AM
  #37  
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Originally Posted by tomgoodman View Post
"Don't use prop blades as handles...it can do really jumbo-sized harm to a propeller if you use the prop blades as convenient handles for maneuvering the plane on the ground."
--McCauley Textron Co.

"Avoid pulling the airplane around by the prop. Yes, this seems the perfect solution to a vexing problem of how to change the airplane’s position without having to walk around and get the tow bar, but it’s worthwhile to make the extra effort. Neither the engine nor the prop particularly benefit from the loads imposed by horsing the whole airplane around."
--AOPA safety training, sponsored by Hartzell Propeller inc.

"... never push or pull on the prop blades. Forget what anyone has told you about pulling near the hub or the strength of the propeller. Aluminum blades can bend, and it doesn’t take much to put the blades out of track with one another."
--"Propeller Care" by Jeff Simon, A&P, author "The Educated Owner"
Your post seems to have been ignored. Even after posting quotes from manufacturers, there was still 3 and half pages of mostly speculation. After all, I fly in the real world. What does the manufacturer know?

Typical "I know a little bit about everything" pilots.
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Old 07-16-2015, 06:56 AM
  #38  
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The biggest threat to pulling an aircraft by the prop is losing body parts! I had one crank over with a millimeter of movement and spun a half a dozen times. Could have easily killed me, just lucky!
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Old 07-23-2015, 05:25 PM
  #39  
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Originally Posted by LeftWing View Post
Your post seems to have been ignored. Even after posting quotes from manufacturers, there was still 3 and half pages of mostly speculation. After all, I fly in the real world. What does the manufacturer know?

Typical "I know a little bit about everything" pilots.
Ah jeez, you mean just cause i didnt hurt it this time, i wont break it next time.... What a buzz kill
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