On Fri, 01 Aug 2003 20:23:49 GMT, Ryan Ferguson
wrote:

snip

The conversation meandered from that point but I've always wondered since if
diving to increase airspeed would in any way assist in getting the engine
started, assuming of course the prop was fully feathered.

snip

Hmmm. If the prop ain't turning, but is aerodynamically (?) on the
verge of turning, a little more airspeed probably wouldn't hurt.

Never really figured how close the angles work out to zero rotational
force, I figured if the force generated wasn't enuff to overide the
cylinder compression, the prop wouldn't turn.

Never shutdown a PT6A in flight, but feathered 'em for fun, in every
case the propeller windmilled, but at a slow rate.

Do know, from experience with un-feathering accumulators (Baron &
Colemill Navajo's) and un-feathering pumps (Beech 18's) that the
visible angle on the propeller blade doesn't change very much before
the engine starts turning over at a fairly rapid rate.

Have air-started a Twin Co and an Aztec (for the heckofit) and it
seemed really, really similiar to the engines I've started with
feathered props on the ground. A lot of shuddering and shaking at low
rpm until the oil pressure in the gov builds enuff to start driving
the prop back to "flat".

Actually, they shudder a lot more on the ground (no "airspeed" to help
accel the engine) but my rectal condition was nowhere near as critical
with the tires sitting on the tarmac.

TC