17.2.4 Propeller Types Flashcards
What is a fixed pitch propeller?
A fixed pitch propeller is usually one piece and constructed of wood or aluminium, used for up to about 200 kW (250 hp) performance and speeds around 250 km/h (160 mph).
What determines the blade angle of a fixed pitch propeller?
The blade angle (pitch) is fixed and determined according to the purpose it is to be used.
What type of pitch is needed for steep climbing and towing?
A low (fine) pitch is needed for steep climbing and towing.
What type of pitch is preferred for cruising flight?
A higher (coarse) pitch is preferred for a more gradual climb and cruising flight.
What is a disadvantage of fixed pitch propellers?
Maximum propeller efficiency is possible only at one predetermined RPM and airspeed.
How does air density affect power required to maintain constant RPM?
Increased air density requires more power to maintain constant RPM, while decreased air density requires less power.
What is a controllable pitch propeller?
A controllable pitch propeller allows the pilot to change the pitch of the blades in flight, irrespective of aircraft operating conditions.
What controls are available in an aircraft equipped with a controllable pitch propeller?
The aircraft has a throttle control for engine power output and a propeller control for regulating engine RPM.
What is the function of the constant speed unit (governor)?
The constant speed unit allows a constant speed propeller to maintain a constant RPM by automatically changing its blade pitch.
What happens when the propeller exceeds the preselected RPM?
The fly weights are forced outward, which changes the tension on the speeder spring, leading to a change in blade pitch.
What is the relationship between blade angle and engine RPM?
Reducing the blade angle decreases the torque required to spin the propeller, increasing airspeed and engine RPM, while increasing the blade angle increases the torque required.
