PAC 750XL
20
PROPELLER
The PAC 750XL is equipped with a three blade, Hartzell, constant speed, feathering and
reversible pitch propeller, model HC-B3TN-3D/T4. The propeller uses a single oil
supply from a governing device to hydraulically actuate a change in blade angle. The propeller
blade angles are : -
Fine
:
18.3
0
Feather
:
86.5
0
Reverse Pitch
:
-8.1
0
While the propeller is operating, the following forces are constantly present: spring force,
counterweight force, centrifugal twisting moment of each blade, and blade aerodynamic
twisting forces. The spring and counterweight forces attempt to rotate the blades to higher
blade angle, while the centrifugal twisting moment of each blade is generally acting toward
lower blade angle. Blade aerodynamic twisting force is usually very small in relation to the other
forces and will attempt to increase or decrease blade angle.
The propeller indicating system comprises an indicator, a circuit breaker, a tachometer
generator and associated wiring. The propeller speed indicator is graduated as a percentage
of the power turbine speed and it is located in the centre of the instrument panel.
