Pulling and Pushing a Plane by the Prop?

[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.