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-   -   Hand-propping (https://vansairforce.net/community/showthread.php?t=92416)

scsmith 10-24-2012 04:45 PM

Hand-propping
 
Rather than cause thread drift on Paul's thread about the broken starter, I figured I would start a new thread.

So, I've thought about hand-propping my IO-360 angle valve.

The problem I have is that the Whirl Wind 200RV prop is so light that it has no flywheel effect. Add to that, the trailing edge is pretty sharp, so it is hard to get much of a stroke on it anyway. But, I don't know, it would have to fire on the blade that you are pulling through to get it to go to the next blade anyway.

With a very low battery (the reason I would be hand propping) I can not be sure that the Light Speed EI would fire at TDC. If it fired 25 BTDC I think it would cut my fingertips off with the sharp trailing edge. On the rare occasion that I might need to do this, I think I would wish that the other mag had an impulse coupling.

I have hand-propped a O-470 with 2 bladed prop on a C-182. The only thing that made that difficult was that it was 15F outside, and it took a lot of pulls, priming some more every few pulls, to finally get enough fuel vapor in the cylinders to fire. By the time I got it started, I was stripped down to a Tee-shirt.

jrs14855 10-24-2012 05:03 PM

hand propping
 
I have hand propped four and six cyl Lycomings with Hoffman and MT two and three blade props, several were 10-1 compression. Also Navajo Chieftain several times. In the day many of the aerobatic airplanes didn't have starters.

Squeak 10-24-2012 05:08 PM

Steve, I have hand propped lots of aircraft over my years of flying and thought I could prop about any single engine. Was at an airport 200 miles from home and had a dead battery and tried propping my RV7A 0-360 Catto Prop and it got me on a backfire. Took 30 stitches in left hand and broke my right. It's not worth it!!

Ron Lee 10-24-2012 05:18 PM

Steve, if that occurs, charge the battery. How long would that take?

Then to prevent the change of it happening, install some sort of warning system if the master is left on.

Replace battery before it becomes marginal.

Consider this like get-home-itis. You have two options:

1) Do what is needed to avoid hand-propping even if it means a delay in getting somewhere, or

2) Risk serious injury or death.

David Paule 10-24-2012 06:14 PM

I'm pretty sure that hand-propping only gets you one cylinder to fire in any event. And you could wear cheap work gloves when propping it.

Just be careful.

Dave

Ironflight 10-24-2012 06:37 PM

Yeah....I think hand-propping your set-up might be beyond my comfort level Steve. I am happy giving a 360 a go if it has Mags, a two-blade prop, and is a tail-dragger (and the -6 sits low enough as a tail dragger that it was about on the Go/No Go line for me). I'd have hand propped the Val when it had Mags, but with the P-Mags, I'd have to think about it. In our case last weekend, it wasn't a matter of charging the battery or jumping - we had no starter, so we were lucky that it was a simple engine/prop combo.

And just to put it all in perspective, I grew up flying Cubs - hand propping was the first thing I learned, and it is almost second nature. Still scares me if if I don't have the right conditions!

Paul

RV8RIVETER 10-24-2012 06:49 PM

We have the same set-up, only our angle valve is the dual mag kind. I defintiely would not want to hand prop it.

As a safety note. It is very easy to hand prop, even accidently. To set the scene, our RV-8 was in the hangar, top cowl off, throttle idle, mixtured cut-off (as it was shutdown), hangar door closed and spinner 10 inches awayfrom the inside of the door. My partner was working on our mag, one side quit firing and he simply moved the prop. Bang, the engine starts immediately and runs for about 2 seconds. Needless to say, scared the #$%^ out of him. Turns out he had left one of the mag switches on. The only thing that saved him was the plane was chocked (he was between the prop and hangar door) and he always treats a prop like the mag is hot.

Scott Hersha 10-24-2012 07:37 PM

It depends on what electric ignition system you have, but on my Lightspeed, I'm pretty sure it fires at TDC at start-up. Doesn't have any trouble starting my engine. I've propped an O-360, but not with 10:1 compression ratio. That might be a little tough. The O-470 carbed engine is a low compression engine and not as hard to hand prop especially with a long prop.

Mark C. 10-24-2012 08:15 PM

Interesting all the issues with props, just last night I decided to mount my Catto Tri-Prop just to turn the prop on my brand new 1 year old IO 360 Mattituck Engine to push some lubricant around, 4 plugs are out having moisture plugs for storage. On my second pull off the compression stroke the next blade came around and hit me right in the head knocking me to the ground, no blood just a nasty dent on the head. Today I pulled all the plugs, learned my lesson... Still not sure why my wife came out to the garage laughing when she saw me on the ground...

JonJay 10-24-2012 08:54 PM

I don't have hard facts, but my guess is most contemplate hand propping after leaving the master on over night, not mechanical failure. In most of our airplanes, if your battery is dead, you have no alt. current, no charge, no electrical. In most of our airplanes, no electrical means you are not even going to consider going anywhere unless it is a true emergency.
I have propped a few 0320/0360's, usually after enough charge was put on the battery to get the alt. alive. It is not my favorite thing to do, but I wouldn't say it is necessarily "difficult".
I propped my old L3 without any electrical system hundreds of times, for many years, cause that is what you do. Of course, it was only 65hp, which is just enough to kill you.
A lot of thought goes into it before I ever consider a hand prop. It is very dangerous and the engine and prop hold no prejudice or forgiveness.


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