23yo model walks into propeller

[mikehallam]

Have a heed it's not so blindingly obvious.

Naturally just like mag switches in a/c being the opposite to most laymen's & therefore 'intuitative' understanding, Thumbs up usually means "O.K."

mike hallam.

[Crash one]

"Also, I note, a number of posters saying that they always make sure that the master switch is off before venturing near their propellers."
I've asked for confirmation the master was off before helping someone by handpropping. It avoids the possibility of mags on with a key going to start.

I beg to differ (my bold) it most certainly does not. If you fly an a/c with magneto ignition you should know that the mags are a seperate spark generating device, completely independent of master switches, batteries, key starters, push button starters, generators, fuses, you name it.
The mags off switch or key connects the mags to earth making them "safe" if that earth connection is faulty in any way the mags are live.
This is easily proved, Start your engine in the usual manner then switch of the master switch. Did the engine stop? Try popping all the contact breakers, pull fuses.
I always check for "dead cut" by switching of both mags, one at a time, to kill it. No doubt the wrong technique in some cases but the old Stromberg didn't have a mixture control.
I don't like the idea of running the thing at 1000rpm & pulling "Idle cut off" that does not prove that the mags earth works.

[Rod1]

“At our club we pull the planes around by grabbing it by the the prop!
All our planes are Rotax 912S and 914 powered.

Hand cranking is necessary to get the oil-gurgle.
This is not dangerous with the Master switch off, magnetos off and a cold engine, right? Is it dangerous with a warm engine?

Is it dangerous to move a plane by pulling the prop blades?
Surely not!??”

The Rotax 912/914 does not have mags. The Electronics require the crank to be turning at 250 rpm to generate a spark (ref Rotax 912 manual) even if the swiches are on. The Master has no impact on ignition working.

Rod1

[Deeday]

Originally Posted by Rod1

The Electronics require the crank to be turning at 250 rpm to generate a spark

A friend of mine, Rotax-owner and self-maintainer, when I asked him about this story, pointed out that with a typical reduction ratio of 2.43:1, the prop only needs a fraction of that rpm, and not even for a full revolution. So my guess is that it's not impossible at all to hand-swing a Rotax.

[VOD80]

I used to have an Auster and didn't mind hand swinging that - nice, long prop high up off the ground and slow revving engine. I hand swung a Pitts S1 at Felthorpe with its tiny, sharp toothpick of a prop down by my knees. Not so much fun.

A little video of it all going wrong:

[mikehallam]

Silvaire, as Deeday notes, the Rotax 912 series flat four has a gearbox reduction & the prop position is thus random. Two strokes ditto.

mike hallam.