Treat every prop as live!

[C-FAH Q]

BEVIN,
I preach this to every pilot that comes to our shop. I doesn't gaurantee anything, but it helps reduce the chance.

[Piper J3]

Originally Posted by scottmillhouse

This is a good reminder for all of us. From my Lycoming experience, I always worry with the Rotax in the RV-12 when you have to turn the prop over 20 or more times to pump the oil back into the oil tank to check level. I know that power AND both ignition switches must be on for ignition but it still makes me nervous.

Actually with Rotax 912 the Capacitive Discharge Ignition gets its power from separate coil windings. It is not powered by the 12V battery. It is necessary for the engine to spin at least several hundred RPM for sufficient voltage to self-power the CD ignitions. Perfectly safe to turn prop on Rotax 912.

[Tag]

I was taught and have always performed this check at the end of every flight, but I do notice that the practice doesn't seem to be prevalent...

[rjtjrt]

1.
The Aussie gent involved in video is to be applauded for his courage in writing the article and posting the video. He opened himself up to a lot of less than complimentary comment in other forums (thankfully not in this one).
The reason he got caught is detailed in the written article.

2.

Originally Posted by Piper J3

Actually with Rotax 912 the Capacitive Discharge Ignition gets its power from separate coil windings. It is not powered by the 12V battery. It is necessary for the engine to spin at least several hundred RPM for sufficient voltage to self-power the CD ignitions. Perfectly safe to turn prop on Rotax 912.

I'm sure this has been posted before, but there is a video of hand propping a Rotax. Not easy to start but it can be.

https://youtu.be/-JUBrHYsh4E

[Jesse]

For those who turn the prop backwards, definitely DO NOT do his on a Rotax. A 1/4 turn backwards and you're supposed to an oil pressure purge to prevent deflating the lifters. NEVER turn a Rotax backwards.

[bret]

My engine prop combo came from a Mooney that got its tail eaten by a runaway hand propped Cessna last year......scary!

[Boyd Birchler]

I had this happen to me!
I had a Decathlon that would occasionally have a valve stick on the first take off of the day. So I thought I would check the engine by turning it over,while cold in the hangar, to see If I could locate the abhorrent valve. My back was up against the door I had verified the mag switches were off.

I got ready to turn the prop and thought: if I have a bad P lead/hot mag this would be a very bad place to be,with the prop arch only a few inches from my legs with my back touching the hangar door behind me, should the engine start I'd be in real trouble.

I went to the other hanger and found a set of good chocks and chocked the plane. I then got in front of the plane and pulled the blade through.. it started on the the first slow pull!!! Just like the one in the video, it only ran a few seconds. I had already shimmied out side ways before it quit.

If I had not chocked it? How long would it have been before I got help?

Nearly 30 years later I still have great respect for props.

[DanH]

Good time for a reminder. Live props happen for several reasons, not the least of which is p-leads left to flop about while hanging from their crimped terminal ends. Eventually they disconnect themselves.

Secure those p-leads. If you're flying Slicks, all it takes is an adel clamp on the ground screw:



While on the subject of bad mag wiring...I once saw a live prop nearly bite a few friends standing in a group around a prop. The cause was the loss of the p-lead ground path. Some knothead had grounded the p-lead at the switch end, which meant the poor little electrons had to find their way home through the airframe rather than through the p-lead shield. There are many more joints (thus places to corrode and/or break) when grounding through the airframe, as compared to two connections total (switch and mag) for a shield ground.

[sblack]

I was sitting in a champ (no electrics) getting ready for a hand start for some ski flying. We were at the priming stage where the flipper yells "switches off" and pulls it through - even more important in winter. The mag switch (old lever type) is behind the front seat and the sun was low and in my eyes. I did not have the switch all the way off - I thought it was, but I only fly that plane once or twice a year and I got it wrong - one mag was live. The flipper was demonstrating hand propping to another guy, who was quite nervous. He said, as he turned it through, "always assume it is live, even if the switches are o...." the words weren't out of his mouth when it fired and started. He looked at me like "you @#$%@#$%". And then, in a panic I did the dumbest thing ever - I shut it off! I have no idea why. I should have kept it running because that was the whole objective of the exercise and also I would not have been able to hear him cussing me out. I tried to pass it off as just giving the new guy a demonstration of why to treat the prop as live, but that did not get me very far. I paid for that for many weeks and rightly so. I screwed the pooch on that one and it could have been deadly.

At least when hand propping, people are aware of what is going on and are usually trained and the airplane is chocked, or there is a guy in the cockpit. Even then it has sometimes gone wrong. But when doing maintenance or pre-flight, people are totally not expecting ignition and the airplane is not secure, there could be stuff or people in front of it and what follows is usually really really bad. So be careful out there. Mag check at shutdown certainly can't hurt.

[fabricflyer]

Several years ago, a couple friends of mine went to look at a Chief one of them was wanting to buy. The plane was in a hanger full of planes with it's doors locked. While waiting for the owner to arrive, they looked in the plane windows, saw that the mag switch was off, and decided to turn over the prop to check to relative compression of the motor. They got the surprise of their life when the motor cranked. They had to hold the plane for quite a while till the owner arrived. They were very lucky that no one got hurt or plane got damaged. The owner was not a happy camper when he arrived. Stuff happens so don't play around with a prop.
Allen Blackwell
Very slow build RV7A