Pilot’s Operating Handbook Section 7
EXTRA 500 Description of Airplane and Systems
7.15 Propeller
The aircraft is equipped with a 5-blade, constant speed,
reversible, full feathering and governor-controlled propeller
with a diameter of 2.10 m. The blades are of laminated wood
composite construction with epoxy-fiber glass cover and metal
tipping.
Regulation
For propeller pitch regulation various mechanisms are
responsible depending on operation condition.
Normal
Flight Operation (Power lever between FLT IDLE and
MAX POWER):
In normal flight operation propeller pitch is controlled by the
propeller governor. The propeller governor regulates the
propeller speed to the speed the pilot has selected with the
condition lever. The governor adjusts blade pitch angle so that
the propeller absorbs the mechanic power provided by the
engine at the selected rotational speed. A heavy spring in the
propeller hub and the counterweights at the blade roots tend to
rotate the blades towards coarse pitch up to the mechanic stop,
which defines the feather blade angle. This force towards coarse
pitch (and therefore lower rpm) is opposed by pressurized
propeller servo oil provided by the propeller governor, which
tends to adjust a lower blade pitch angle (and therefore higher
rpm). The governor adjusts servo oil pressure to achieve the
suitable pitch angle and therefore to maintain selected rotational
speed. The lowest possible pitch setting is determined by the
low pitch stop, which is held in the “lowest pitch for flight
position” by the beta valve as long as the power lever is not in
GRD IDLE position or below.
Normal Ground Operation (Power lever between MAX
REVERSE and GRD IDLE):
In ground operation the propeller pitch is controlled manually
(power lever) and the beta valve provides augmentation to
achieve the necessary control forces. In this operation mode the
propeller is held by servo oil pressure against its low pitch stop.
The low pitch stop is adjusted by the beta valve according to the
input the pilot gives with the position of the power lever. As a
result the propeller pitch is adjusted according to the pilots
command input with the power lever position.
26. January 2011 7-39
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