Propellers Flashcards
Why do some aircraft engine have a critical range of operation?
The engine and propeller combination have a resonant frequency problem in which excessive vibration can occur in a certain range of RPM. The tachometer for an aircraft with this limitation is marked with a red arc. When it is necessary to pass through this range it must be done as quickly as practical.
Does centrifugal twisting moment on a propeller blade tend to move the blades toward high pitch or toward low pitch?
Toward low pitch.
Do the counterweights on a propeller tend to move the blades toward high pitch or toward low pitch?
Toward high pitch.
What is the function of the accumulator used with some McCauley feathering propellers?
The accumulator stores oil under pressure when the engine is operating normally. This oil is used to help the propeller blades move toward low pitch when the propeller is being unfeathered.
What is meant by the alpha range of operation of a turboprop propeller?
This is the in-flight mode of operation from takeoff to landing.
Should an adjustable-pitch propeller be in high pitch or low pitch for takeoff?
In low pitch.
What can be done to prevent the front cone from bottoming when installing a propeller on a splined shaft?
Install a spacer behind the rear cone to move the propeller forward on the shaft.
Why is a propeller indexed to the engine crankshaft?
The relationship between the propeller and the engine crankshaft is chosen to produce the minimum vibration.
What is the adjusted inside the governor for a constant-speed propeller to change the speed at which the propeller is operating?
The compression of the speeder spring.
What is done to cause a McCauley propeller to feather?
Oil is allowed to drain out of the propeller.
What keeps a McCauley feathering propeller from feathering when the engine is shut down on the ground?
A spring-loaded latch mechanism prevents the blades moving into the feather position when the engine is shut down on the ground. In the air, aerodynamic forces to keep the propeller rotating fast enough that centrifugal force holds the blades unlatched so then can move to the feather position when oil pressure is taken out of the propeller.
What is done to cause a hydromatic propeller to feather?
High-pressure engine oil is directed into the propeller through the governor.
What does the pilot do to change the RPM of an engine equipped with a constant-speed propeller when it is operating within the constant-speed range?
The pilot moved the propeller pitch control. This changes the compression on the speeder spring inside the governor which moves the pilot valve. The pilot valve directs the oil into or out of the propeller to change the pitch of the blades. The change in pitch changes the air load on the propeller which changes the RPM.
What is the difference between the controllable propeller and constant-speed propeller?
Basically, it is the control system. A controllable-pitch propeller uses a manually operated oil valve to control the pitch, and a constant-speed propeller uses a governor to control the valve.
When making a magneto check on an engine equipped with a constant-speed controller, should the propeller control be in the low-pitch or high-pitch position?
It should be in the low-pitch, high RPM position.
