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Ralph; To my knowledge there are no constant speed propellers approved
under
the type certificates for any of the Coupes, Alons, or M10. There are
several
controllable or pitch adjustable (either manual or automatic) propellers
that
are authorized for the Coupe, but only one for the Alon/M10.
The controllable Beech Roby R002 0r R003, the Ground adjustable
Hartzell HA12UF or HA12UO, or the Koppers Aeromatic F200 are eligible on
all
Coupes. Only the ground adjustable Hartzell is eligible on the Alon/M10.
Anything else would have to be licensed in the experimental category.
The advantage to having a prop that changes pitch while running is
that you can set them for maximum performance in the climb and then change
them for cruise. A fixed pitch is often a compromise of one or the other.
Most constant speed propellers are controlled with oil pressure and
a
governor. Since our small continental engines are not equipped with
crankshafts that have oil pressure internal to the crankshaft, any
constant
speed prop that is controlled with oil pressure would require a special
drive/pump and control mechanism. The early Bonanzas, which came with an
electric controllable propeller were often modified to accept the Hartzell
constant speed prop using a special "T" drive on the vacuum pump to
provide
the required oil under pressure to control the prop. This type of prop and
control is also about 3 times as expensive to purchase as our simple fixed
pitch props.
Airplanes with retractable landing gear (read as less drag at
higher
speeds) benefit more from a controllable propeller than our old fixed gear
airplanes.
Lynn Nelsen
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