Flew to Peterborough Conington a few months ago. Parking was very tight and after trying to turn the aircraft in a very small space I decided that I would shut down and push it backwards.

The aircraft was PA28 Archer, which I had only recently been checked out on, and I was embarrassed when I realised that I didn't have a clue where, if any, the safe points would be to push her back.

The very nice man in the tower said it was fine to leave her where she was as we were only staying for 1 hr, but does anybody know of any safe points on the A/C where you can push or pull to manoeuvre her on the ground?

Total,

Well, that depends on the aircraft and how it's built. Typically you're OK to push on the prop hub (checking that mags are off and key is out).

Presuming all-metal airplanes, other locations for low-wings are usually the leading edge of the wing along a line of chord-wise rivets (implies a structural member which the rivets are attached to), but do it reasonably close to the root (say, no more than halfway, as oppposed to out on the wingtip). On high-wing airplanes you are almost always safe to push on the struts.

Rag and tube is a bit different and really requires showing someone.

Hope that helps,

Pitts2112

Push and pull on the prop (adjacent to the spinner, obviously). Push on the Leading edge of the wing (again - close into the fuselage) or push with one hand on the grab hook above the step, top of the fuselage, and the other on the walkway.

Just about covers the options. Also pays to look in the luggage compartment - sometimes the tow bar is attached to the rear bulkhead.

I flew into Conington a few months ago in the Koliber (:{ ). I landed, taxied into the parking area and turned the aircraft so that she was tail-on to a parking space. Then I jumped out, (yes, I did stop the engine first ) towbar in hand, ready to push her back.

This is something we did after every flight and I was quite used to doing by myself, but a chap came hurrying over to help me. Without asking, he put his hands on the retractable leading edge slats and and was about to start pushing when I shouted at him to "kindly desist, please! "

He had actually put his hands each side of the black stenciled marking on the slats which clearly read DO NOT PUSH.

(The reason for not pushing on one of the slats is that they move together, pushing on just one of them may distort the linkage leading to asymetic slat deployment and an incommanded roll etc, when you are slowing down nicely on finals or just about to touch down. If they must be retracted, they must be moved together.)

I understand that if you want to push on the struts of high wingers (C150/152, Cub etc.) you should only do so at their ENDS - preferably at the fus. end, where there is a strong fixing point. Pushing in the middle can bend such struts.

Chris N.

Push and pull on the prop (adjacent to the spinner, obviously). Push on the Leading edge of the wing (again - close into the fuselage) or push with one hand on the grab hook above the step, top of the fuselage, and the other on the walkway.
Just about covers the options. Also pays to look in the luggage compartment - sometimes the tow bar is attached to the rear bulkhead.
In the Instructor's forum recently an instructor said that he would severely chastise anyone he saw pushing or pulling an aeroplane by the prop. "Never, never", he said.
Couldn't understand it myself as the prop is the bit that puills the aircraft along anyway innit?

In the Instructor's forum recently an instructor said that he would severely chastise anyone he saw pushing or pulling an aeroplane by the prop. "Never, never", he said.
Couldn't understand it myself as the prop is the bit that puills the aircraft along anyway innit?

Interesting - at my club this is the usual way to move our aircraft, largely due to the fact that most of our towbars have snapped!

Logically, the loads generated by pulling the aircraft forward with the prop can't be any higher than those generated when you start your take-off run, can they?

Cheers,

David

I think it is unadvisable to pull constant speed props though.

I am sure that the thing about not pulling on the prop comes from the aircraft manufacturers not for any technical reason but because of the product liability laws in the USA and the danger of someone getting hurt if they turn the prop with a live mag.

Interesting point about pulling form the prop.

There is an article in this months Pilot telling us that you should NEVER pull the aircraft by its prop (I think the reference may have been to props with csus but I cant remember).

This is totally contrary to my experience and all the engineers I have known quite happily "man handle" the aircraft by its prop - albiet I am always keen to ask people to hold the prop as near the hub as possible to avoid placing any undue stress on the prop (which perhaps is also ill founded).


:confused:

I think the stuff about not pulling the prop is rubbish. The UK flying mags will print any old trash; just look at all the stuff about GPS not being authorised etc.

The in-flight stress on a prop blade, or the hub, or the end of the crankshaft (the flange), is far more than any human could exert on it. I've been looking for a reference for the relationship between thrust and horsepower but can't find it right now...

What one should not do is push/pull on the spinner; typically that is only 2mm thick aluminium and not hard to bend. Or, obviously, hold the prop blades anywhere except at their base. One also needs to be careful to not press against any prop heating or de-ice material as it is normally only stuck-on.

Re not touching propellors.

I never touch a propellor if I can avoid it, all that stuff about dodgy earths on mags etc. I think the main reason I don't do it is to tune me into mentally avoiding propellors. If you never walk through the arc and never touch the prop then you have less chance of walking into it when it is spinning. Didn't an instructor run through the arc of a 152 prop a few years ago

I guess stressing the prop is not an issue if you pull it by the root (if you dare). I generally push on the wing root or use the tow bar.

Sorry for the thread drift, I know theoretically it is possible for an engine to start up if there is a live mag but does anyone know how likely this is? All the engines I try to start seem reluctant to start with the benifit of both mags and a starter motor! Perhaps some types of engines start easier than others.

If the engine has stopped at Top Dead Centre (TDC), in theory it could take only a tiny force to flip it over TDC and the compression released could (nearly) be enough to start the engine. Although I think the momentum of the propeller would fail to complete a full compression of the next cylinder without some other force acting - perhaps from you grabbing onto the propeller having slipped on some ice or wet grass...

With the fuel and mags off, mixture at ICO and the throttle fully closed, I'm happy to man-handle light aircraft by the propeller. I am used to hand-propping though.

All in all it is pretty unlikely that the engine would start, but you really don't want it to happen, ever.

tp

With the fuel and mags off, mixture at ICO and the throttle fully closedSomething which I think we are forgetting here is the normal way of stopping an aircraft engine - by starving it of fuel, with the mags on. In other words, even with the mags on, we remove from the fuel lines the fuel which is needed to sustain the engine (let alone start it) when we shut the engine down.

Therefore, as far as I can tell, the chances of an engine starting when you pull the prop through are pretty much nil, and I have no problem with doing this regularly. Of course, it is always a good idea to take sensible precautions, especially when those precautions are free. Check the mags are off and the mixture lean before touching the prop. When moving a prop, always stand to one side of it, and keep your fingers behind the blades rather than in front of them (the same kind of precautions which you would use if swinging a prop). Turn the prop slowly, so there's less chance of its momentum carrying it through a full cycle. These precautions are common sense and cost nothing, so do them - although the logical part of my brain tells me that the risk they are reducing is negligable anyway.

FFF
---------------