handpropping question

[FunkyMonkey]

When you guys have to turn it over backwards because shes flooded do you use a hand on each blade and "flip" it, or do you use the same procedure as forward only on the other side?

[jmvolpp]

Re: handpropping question

It won't need to be "flipped". Just pull it through slowly in such a manner that, if it does something you didn't expect, no part of your anatomy is in the way.

Mike V.

[Taylor Maid]

Re: handpropping question

I don't know what they guys do, but this girl does it the same as if it was hot. I don't want any parts of me coming up missing and being sold on Ebay!

[Len Petterson]

Re: handpropping question

Propping in reverse to clear the engine: Make shure you turn off the mags! She could start!

A hint: by chance my trotlle set up ended up with: a all the way back is idle.
It as worked so well for me I left it there, I don't have to fiddle and hopping to have the right setting for idle! It goes plonk aginst the stop and whats it, it gives 500 rpm.

And anytime you turn a propp, have the Tail tied down, shocks in pace, brakes on. good footing, stay clear, keep hands clear, check trottle, shut of the fuel, dont matter if it is forward or backwards
good
Len

[Robert Lees]

Re: handpropping question

All posts that were NOT related to handpropping have been moved to a more appropriate thread.

[FunkyMonkey]

Re: handpropping question

Propping in reverse to clear the engine: Make shure you turn off the mags! She could start!

A hint: by chance my trotlle set up ended up with all the way back is idle.
It as worked so well for me I left it there, I don't have to fiddle and hopping to have the right setting for idle! It goes plonk aginst the stop and whats it, it gives 500 rpm.
Len

It can start backwards? I thought the mags wouldnt send a spark when turned in reverse?

[1938BF50]

Re: handpropping question

SAFETY RULE #1...ALWAYS TREAT THE PROP AS LIVE.

Even when propping backwards, you can get a slight "kickback" on compression. With an impulse mag IT CAN FIRE and start at that point. Been around tractors all my life and have had a couple "incidents" with impulse mags tripping at bad times. Once, I literally rested my arm on the flywheel of my John Deere H at a show and had it start (in gear). That was a lively dance for a few seconds. Damn glad there were no kids climbing on it at the time!

Impulse mags are GOOD just respect that they come to life real fast!

[FunkyMonkey]

Re: handpropping question

I should admit that the reason I asked this question to begin with is because after flying my taylorcraft for some time (without impulses) I was chastised by a fellow aviator while handpropping a cub (with impulses). He said that turning the prop backwards with a hand on each blade is unsafe because the engine can still start backwards. He may be right so im merely nit picking but I believe that knowing the reason behind a procedure is just as important as knowing the procedure. I just cant see how the engine can start backwards with the mags turning in reverse. In fact i believe impulse mags advance the spark even more? This would mean the engine would have to turn even farther forward to get a spark. However thats irrevelent if its being turned backwards in the first place. I suppose there could be a compression kickback but I've just never seen that happen and I think my hands would be long out of the way anyway. Please correct me if im wrong.

I guess I'm just mad because somebody corrected my technique when I thought it was safe without giving a techinical explanation except that he's "seen engines start backwards".

By the way he was just a bystander not the owner of the cub.

[fearofpavement]

Re: handpropping question

[QUOTE=FunkyMonkey;35111]He said that turning the prop backwards with a hand on each blade is unsafe because the engine can still start backwards. He may be right so im merely nit picking but I believe that knowing the reason behind a procedure is just as important as knowing the procedure. I just cant see how the engine can start backwards with the mags turning in reverse. In fact i believe impulse mags advance the spark even more? This would mean the engine would have to turn even farther forward to get a spark. However thats irrevelent if its being turned backwards in the first place. I suppose there could be a compression kickback but I've just never seen that happen and I think my hands would be long out of the way anyway. Please correct me if im wrong.

I guess I'm just mad because somebody corrected my technique when I thought it was safe without giving a techinical explanation except that he's "seen engines start backwards".
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Well, I have seen an engine rotate backwards during a start attempt but have never seen an engine start while being rotated backwards but would certainly heed other poster's advice to always turn off the mags when clearing the engine. (also, to make this effective the throttle should be full open as the point is to pump large volumes of air through the engine to pump out the excess fuel vapors, similar to starting a flooded car that has a carburator)

To respond to the impulse coupling issue, the impulse coupler serves two purposes. One is to retard the timing and the other is to give a powerful spark. On an engine equipped with an impulse coupler, if it is close to its release position, moving the prop tip as little as 1/8" could cause the mag to fire. That is a reason one shouldn't let their guard down near a propellor. When the engine is turned in the direction it runs, there is a catch in the impulse coupler (a device mounted inside the mag) that starts winding a spring and keeps part of the mag from rotating. When the spring gets wound to a certain point, the catch releases and rapidly spins the mag. As the engine is closer to top dead center when this happens it is more likely to fire the cylinder and there is less likelihood of the engine rotating backwards. Some engines have no impulse couplings, some have it only on one mag and some have it on both mags. It is not easy to tell from just looking at the mag whether or not it has a impulse coupler installed. If there is an impulse installed on just one mag, then the engine should be started on that mag only. Hope that helps.

[flyguy]

Re: handpropping question

Good info FOP. Exactly that happened to me not too long ago. When I position my prop after a flight I always am careful to turn it backwards. All I did was reach up and touch the prop, couldn't have moved it more than a few thousandths of an inch at most. The coupler clicked. Nothing happened, but it woke me up for sure. I mean, what are the odds?

Not because of that, but I have to come down on the side of using the safest technique and assuming that it MIGHT somehow fire. Just a case of keeping as many aces up your sleeve as possible. Like extra gas, altitude, or runway. I also don't "flip" the prop to do this, I just carefully pull it through compression, always works for me without a lot of effort and jerking around.

Anytime I move the prop I turn it backwards and check first to see if the keys are in my pocket. Then I still stay out of the way.

By the way, I often start my 85 with just the tips of my fingers, on one hand, without flipping it at all. I know where the coupler clicks and I just pull it positively thru that point while walking away to the side. Obviously, if it is cold I do have to pull it thru the regular way several times first, with the ignition off.
DC

[whake]

Re: handpropping question

How about hand propping a hot engine, say a half hour after a coffee stop. I pull it through a couple times and it usally starts. Sometimes I have to give it a shot of prime . My primer goes in just over the carb.

[Ragwing nut]

Re: handpropping question

They can fire on compression kick back when rotating one backwards if you have good hot mags. I have had it happen to me. Doesn't have to have an impulse either. As stated above always treat a prop hot whenever propping even when the mags are turned off. A7 switches are not the most reliable device in the cockpit. Funny how there is no AD's on them unlike Bendix switches.

mike