Re: Propellor "reverse thrust"

Date:         05 Sep 97 17:27:22 
From:         rparp* (Thundercraft)
Organization: Uniserve
References:   1 2
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>The power levers to the PT6 and most other turboprops have a flight
>range where the engines act much like a piston engine using the throttle
>However, on the ground, the levers are lifted and pulled back over a
>stop into a mode known as "beta mode".  Movement of the levers in beta
>mode give the levers manual command of the propeller pitch while the
>engine speed stays more or less at a set speed.

Actually, the PT6's on a Twin Otter can be put into beta range while
in the air.  40 degrees of flap and full beta make for one very steep
approach, which is needed in some remote airstrips.

the PT6's that were used on the Dash7 could not be put into beta until
the main wheels were on the ground.  ...and as a side note, you can only
have 40 degrees of flap on a Dash7 with the throttles at idle.  the moment
you either advance them, or go into Beta (detent lever must be pulled
down) they retract to 25 degrees as the plane is only going in one
direction with that much flap.