The PT6 engine can be feathered or the blade angle can go to
a reverse setting and the plane can be backed up, as can the
King Air. The prop angle for feathering is about 90 degrees
while normal flight is in the range of 15-45 degrees. Blade
angles less than 15 degrees are called beta and when they
get to 0- [15] degrees they are reverse.

Those numbers are generally correct, but from my memory.
The blade angle is changed when the prop control is pulled
into the reverse range, which is before actually reaching 0
because of forward speed. Pulling the prop control further
spools the engine back into a power range. Reverse is
usually, but not always, locked out in flight. The Pilatus
can be put in reverse in flight as can certain other planes.
But some airplanes that can be reversed in flight are not
safe to do so. A Beech test pilot told me that he had put a
BE E90 in reverse in flight and the airplane did a very fast
flip. On the other hand he also said that the T-tailed King
Airs [f90-200-300] did not do this since the tail was not
blocked by the slipstream. This may or may not be true, it
is just something I was told.
On the ground, dirt ingestion and prop damage are the
limiting factors.



"Doug" wrote in message
oups.com...
| Some seaplane props are featherable and reversable so the
seaplane can
| stop or backup and so the prop can be used as a brake. I
believe the
| Cessna Caravan in Seaplane config can do this, not sure.
|