Propellers Flashcards
Propellers change _____ energy into _______ energy
-Chemical
-Kinetic
Thrust produced by a propeller depends on what 5 things?
-Shape of the blade
-Area of the blade
-Angle of attack
-Density of the air
-Speed of the airfoil through the air
The speed of the blade through the air changes along the _______ of the blade
Length
The angle of attack changes along the _______ of the blade for maximum efficiency
Length
Pitch angle is the angle between?
The chord line of the blade and the plane of rotation.
Angle of attack is the angle between?
The chord line and relative wind
Geometric pitch
Path the propeller would take if acting as a screw through a solid
Effective pitch
Is the actual path through the air
Slip
Is the difference between geometric and effective pitch
The efficiency of a propeller is a ratio between?
Thrust horsepower and Torque Horsepower
Thrust horsepower
How much of the engine is actually pushing air aftward
Torque horsepower
How much engine power is needed to run the propeller
Engine power translated into thrust depends on?
-Engine speed
-Aircraft air speed
-Blade pitch
5 forces acting on a propellers?
-Centrifugal
-Thrust bending
-Torque bending
-Aerodynamic twisting
-Centrifugal twisting
Thrust bending force?
Pull the blades forward near the tip
P-factor has 2 parts
-Asymmetrical thrust
-Slipstream yaw effect
What are the different ways to mount a propeller on a crankshaft?
-Flanged crankshaft
-Splinned shaft
-Tapered shaft
What are the two factors that make the AOA of a prop blade vary?
-Forward speed of the aircraft
-RPM of the engine
Which force acting on a propeller puts the greatest stress on the propeller?
Centrifugal Force
Explain the procedure of ground adjustable propellers being adjusted.
When the aircraft is on the ground an AMT adjusts the desired blade angle of each prop blade using a blade paddle and propeller protractor.
What is the purpose of a constant-speed propeller?
Blade pitch of the propeller blades change the load of the engine by making the propeller easier or harder to turn, this keeps the engine speed constant.
What is a counterweight propeller?
Has weight attached to blade roots to help move blades into high pitch and oil pressure moves blades against the force to counterweights into low pitch.
What are non-counterweight propellers?
Uses oil pressure and aerodynamic twisting force to increase pitch, and centrifugal twisting force and internal spring force to decrease pitch.
Some constant speed propellers are reversible, explain how this works?
Low pitch stops can be released so the blades can be moved from low pitch to a negative blade angle allowing propeller to produce thrust in the reverse direction.
On turboprop engines what are the two standard operating modes and when are they used?
-Alpha:flight mode
-Beta: ground mode
What are the 3 common fixed pitch propeller designs and there characteristics?
-Climb prop: Lower pitch angle transferring ore engine power at takeoff but slower cruise speed
-Cruise prop: Max efficiency at altitude, but longer takeoff.
-Standard: Split difference
What does the pilot use the propeller control lever and throttle for?
-Prop control lever to set desired engine RPM
-Throttle to set engine power(MAP)
Name two controls and two instruments pilots use to monitor engine performance.
Controls: Throttle, condition lever, prop control
Instruments: Tach, torquemeter, fuel flow, EGT
Name 2 types of material used for composite blades.
-Carbon fiber
-Graphite
-Fiberglass
-Kevlar
What type of work can AMT’s perform on propellers?
-Remove and install
-Inspection
-Service/maintain
-Minor repair
-Tracking and balancing
What can happen if unequal amounts of grease are added to different prop blades?
Unequal amounts of grease can cause prop imbalance
What information about the prop can be found in the TCDS?
-Blade length limits
-Approved prop/engine combinations
-Approved governors
-Model number explanation
-TBO reference
Name the tools for adjusting blade pitch?
-Blade paddle
-Propeller protractor
Why is it important to remove damage to propellers?
Forces acting on propellers can cause minor damage to worsen. Propeller damage can cause severe vibrations, engine shutdown, engine/aircraft damage, accidents
Name some considerations when applying grease to a propeller?
-Use of the correct grease
-Proper application of the grease
-The proper amount of grease applied
Name the types of constant-speed prop?
-Counterweight
-Non-counterweight
-Hydromatic
Explain constant speed?
Governor controlled, the prop changes blade pitch automatically keeping engine RPM constant
What is a critical engine?
1 of 2 engines on a multi-engine aircraft, the engine on the side of the aircraft that is producing less thrust is labeled as the critical engine
What are the 2 instruments used on recip engines to monitor engine/prop performance?
-Tach
-Manifold pressure gauge
What is asymmetrical thrust?
At take off/climb, down going blade has a lager AOA than up going blade creating more thrust on that side of the prop
