Pushing/ pulling on the prop

skyking3286 said:
With a taildragger, its hard to find a towbar on the field.
Click to expand...
6 feet or so of line with an eye splice on each end. Don't have a picture handy.

Forward, loop through the low handle, pull with both eyes in hand. Reverse, once around the tailwheel spring, through one of the eyes and pull with the other.
 
Somedays I squeak when I walk ... so I found an easy way to move my tail wheel plane around in the hangar and on the ramp:
iu

I place the tail wheel in the center and secure it with a bungee. Really works well and makes it very easy to maneuver the plane around quickly.
 
Jim K said:
I've owned this airplane for 9 months and missed this sticker until today:
View attachment 98286

Also never heard that before. I was taught that the prop is the strongest part of the aircraft and and the best place to pull from. I mean it travels at the speed of sound and pulls the aircraft around....
Click to expand...
Confession: I do push at the base of my prop (aluminum, fixed-pitch).

But whenever anyone tries to reassure you by going on and on about how many hundred pounds of thrust the prop produces, or how many hundred pounds of downward force the horizontal tail produces, remind them that that's distributed over the whole surface area, not concentrated in a single spot like when you're pushing on it.
 
Dan Thomas said:
When that propeller is spinning there are HUGE centrifugal forces on those blades, pulling them straight out, just the same way a helicopter's rotor gets its rigidity.
Click to expand...

Dan Thomas is correct. A spinning prop is subjected to large centrifugal forces while operating and the thrust force generated by the blades is designed to be supported while the prop is spinning. On many helicopters if the blades were to slow down or stop rotating in flight, the blades would cone upwards beyond yield from the weight of the helicopter.
 
skyking3286 said:
I've heard its not so much the prop but the crankshaft being pulled and pushed...
Click to expand...
If the crank can't take that, then it can't handle the big thrust the flying prop puts on it. It pulls the whole airplane along, after all. Hundreds of pounds of thrust, plus all the bending forces caused by gyroscopic precession in any yaw or pitch changes.
 
kaiser said:
My club wants us to push aircraft from the cowling.
Click to expand...
I bet they'll soon be replacing broken cowl shockmounts and for repairs to cracked cowlings.

I've often wondered why such places never ask mechanics about stuff like that. Instructors come up with it on their own, apparently. Such foolishness is job security for the maintenance guys.
 
Paul V said:
On many helicopters if the blades were to slow down or stop rotating in flight, the blades would cone upwards beyond yield from the weight of the helicopter.
Click to expand...
On ALL helicopters.

Edit:

proxy-image


Look at that short little green band on the inner scale. That's the safe rotor RPM range. Too high and the centrifugal forces can damage something. Too low and the decreasing centrifugal forces let the blades start coning upward as the lift decreases and the pitch increases to counter that loss of lift.
 
Last edited:
Coincidentally, just this week our club plane had a $15k repair bill because the spinner cone had broken off from its bulkhead and was rattling on the prop roots. The shop felt that the damage to the prop warranted replacing the whole assembly. Most likely cause - pilots pushing the airplane with the spinner. While pushing from the prop roots should be ok, I think the general advice of not pushing any part of the prop is a reasonable one, especially in clubs and FBOs. There are motorized towbars (Robotow, for example). It is a fraction of the cost of a prop repair bill.
 
Last edited:
Disclaimer - do whatever your prop manufacturer/club/partnership/significant other tells you do do regarding pushing/pulling on your prop, but...

In any four-seat single I have flown, I have always been told/shown to make sure the mags are off, attach the tow bar and push using the prop where the base of the blade goes into the hub. Not the most experienced pilot, but back in the day I flew a bunch of flight school and rental aircraft and that was always the way I was shown. That goes for wrong-winged 172 trainers with fixed-pitched propellers as well as constant-speed.

That spans about 5 CFI/CFIIs with mucho experience. Again, see disclaimer above.
 
How many Cessna 177B have had damaged props due to this pushing or pulling? The lack of the strut and the higher wing really make you start with the prop roots every time.
 
sarangan said:
Coincidentally, just this week our club plane had a $15k repair bill because the spinner cone had broken off from its bulkhead and was rattling on the prop roots. The shop felt that the damage to the prop warranted replacing the whole assembly. Most likely cause - pilots pushing the airplane with the spinner. While pushing from the prop roots should be ok, I think the general advice of not pushing any part of the prop is a reasonable one, especially in clubs and FBOs. There are motorized towbars (Robotow, for example). It is a fraction of the cost of a prop repair bill.
Click to expand...
I've never encountered a rental operation that provided motorized towbars.
 
Paul V said:
A spinning prop is subjected to large centrifugal forces while operating and the thrust force generated by the blades is designed to be supported while the prop is spinning.
Click to expand...
Which makes the stress near the hub MUCH higher than the bending stress from thrust alone.
I don't have an exact example handy, but this is reasonably close to explain how loads add up to a load and bending moment at one point...
If you bend your prop by pushing near the hub, get down on your knees and thank the Lord that you discovered that your prop was on the edge of failure and that it didn't happen in the air.
 
Thinking about how much force is imparted to my prop hub by gyroscopic precession when I fly a hammerhead.
 
Jim K said:
I've owned this airplane for 9 months and missed this sticker until today:
View attachment 98286

Also never heard that before. I was taught that the prop is the strongest part of the aircraft and and the best place to pull from. I mean it travels at the speed of sound and pulls the aircraft around....
Click to expand...
Huh. And strangely, nothing on the sticker about the enormously greater risk of rubber banding a payment envelope to the prop.

I don’t understand…
 
Llewtrah381 said:
Huh. And strangely, nothing on the sticker about the enormously greater risk of rubber banding a payment envelope to the prop.

I don’t understand…
Click to expand...
The imbalance would be catastrophic, it would undoubtedly cause the engine to be ripped right out of the mounts and go careening prop and all down the ramp. Oh the humanity!
 
Question, so how do you get a prop off if it is stuck on the crankshaft? Fixed pitch, Franklin 150hp engine.
 
How do you push or pull a high wing single engine plane with no struts....the main gear legs. I do this on my 195 every time I fly.
 
Must admit, reading/thinking through this thread, that while one must “honor” the manufacturer’s sticker, it’s hard to imagine a guy like me, who makes a bunch of old-man noises picking up a 50lb bag of Quikrete, can damage a plane by pulling on the prop, especially near the hub and on both sides. MAYBE pulling on one tip but…

Then again, a CS prop could conceivably have seals that pushing in particular could damage, since that’s not an ordinary load for the prop. Dunno.
 
Llewtrah381 said:
...Then again, a CS prop could conceivably have seals that pushing in particular could damage, since that’s not an ordinary load for the prop. Dunno.
Click to expand...
During an engine-failure exercise, pulling the prop control all the way out causes a noticeable improvement in descent angle, so it's conceivable that the force of drag on a windmilling prop could exceed what the average human could apply.
 
I will push on the blade right next to the hub. I always hang the keys on the sun visor so I can see them before I touch the prop. With my plane I have to don white gloves before I push on the prop....Right hand steering the tow bar and left hand pushing the prop, I would estimate about 30 lbs of push.
 
You must log in or register to reply here.
Back
Top