Re: Propellor "reverse thrust"

Date:         29 Aug 97 00:53:40 
From:         twdalbello@ucdavis.edu (Teryn Dal Bello)
Organization: University of California, Davis
References:   1
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showie@uo.guelph.ca wrote:
>On the subject of reverse thrust, I took a flight on a Manx Airlines
>Shorts 330 a few years back. When the plane landed, a big roar went up
>and the plane slowed dramatically. Do prop planes such as this deploy
>reverse thrust by somehow altering the pitch of the propellor blades to
>the extent they "blow" air forward? Or is something else taking place?

Most turboprop airplanes, such as the Beechcraft King Air, have the
ability to reverse the pitch of the blades in order to generate negative
thrust.  For exmaple, a Hercules C-130 has the capability of backing up
down a runway, or taxi way, by reversing the pitch of the blades and
applying engine power.  However, when an airplane is landing and thrust
reversing is employed, it may produce more "drag" around the propeller
than actual negative thrust due to the complex aerodynamics of reversing
thrust in a landing configuration.  Some smaller business jets, use
'thrust deflection' as opposed to 'thrust reversing'.  Thrust deflection
does not direct the thrust forward but actually produces an aerodynamic
disturbance by directing the thrust outward at a steep angle.  In
contrast, thrust reversing actually provides a little component of forward
thrust.

Teryn DalBello teryn@fml-100.arc.nasa.gov
UCD Engineering/NASA ARC