CHAPTER 61
PAGE 5
SERVICE MANUAL EXTRA 300LT
PAGE DATE: 12. June 2015
61-20-00 CONTROLLING
The propeller blade pitch change is conducted by a governor
(refer to Figure 1). Once an engine rotational speed is
selected it will be held constant independent of airspeed or
power variations.
The governor itself is actuated via a vernier control cable
ending on the left side of the rear cockpit (blue control knob;
1, figure 1 & 8, figure 2). This cable is routed on the left side
of the fuselage, penetrates the firewall, the rear engine
baffles and is then routed to the governor. The cable is
attached at its front end to the engine by a clamp block and in
the cockpit area to the steel tube structure by self-clinching
plastic tiedown straps. The RPM vernier control unit is
mounted to a fuselage bracket. The firewall and engine baffle
penetrations are covered with clamp sheets. The firewall
penetration (2, figure 1) is additionally sealed with PRC-
812 (Products Research & Chemical Corp., USA) firewall
sealant.
Mechanical stops for low pitch and high pitch limit the pitch
change level. In case the oil pressure is lost, the installed
counterweights automatically force the blades into high
pitch.
RPM Vernier control cable
Side View
Governor
2
Figure 1 Controlling
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