On Mon, 19 Apr 2010 14:24:21 +0200, cernauta wrote:

On Sun, 18 Apr 2010 09:34:34 +0200, Willy VINKEN
wrote:

I've seen (lucky) pilots rely on the 'natural' stop position after
switching off.

Some brakes on the flywheel seem really efficient, some are slippery.
Anyone has bright ideas?

I have a DG600M, so a different system, built around the same engine.
The propeller must be installed in such a way that one of the blades
finds the max. piston compression a few degrees (10-20°) before the
ideal vertical position. It's impossible to have both blades set for
the same condition. You will have to paint or "mark" the reference
blade.

The propeller brake works quite well, provided the lining material and
the metal disc surface (flywheel) are both oil-free.
If necessary, renew or resurface the lining after accurate degreasing
of the flywheel's braking surface.

Aldo


Fine, Aldo.
I tried to work it out with the angles, but I don't have the precise
reductor ratio.
Say we have a 3:1 reduction: the full compression (TDC) will be
encountered only once every 3 revolutions, right?
I guess the TDC+~15° reference is chosen because it's easier to feel
than near BDC.
Which means the propeller would stop after another 180°, when the
piston is at BDC+~15°, and compression starts to build up.
It's difficult for me to rely on the assumption that the propeller
will always stop turning near (enough) this precise position.
Does yours?
Also, it should be hazardous to check it on the ground, because
there's no relative wind...
And if my above assumption is correct, I guess the brake's only task
is to prevent the low compression to turn back the propeller when it
is lowered out of wind pressure?

Willy