quiz 1 Flashcards
It is normally consists of two or more blades attached to the central hub which is mounted to an engine crankshaft.
propeller
are usually a rotating wings, that have a leading edge, trailing edge, tip, shank, face, and back.
Blades
An angle between the plane of rotation and the chord line.
Propeller Blade Angle
A reference position on a blade that is a specified distance from the center of the hub.
Blade Station
It is the distance that a propeller section Will move forward in one revolution.
Pitch
Is the gradual twist In the propeller blade from shank to tip.
Pitch Distribution
Types of Propellers
Fixed-Pitch Propellers
Ground Adjustable Propellers
Two-Position Propeller
Controllable Pitch Propellers
Constant – Speed Propeller
Automatic Pitch Control
Simplest of propeller designs and is associated with many light, piston engine aircraft.
Fixed-Pitch Propellers
Propellers are similar to fixed pitch propellers In that their blade angles cannot be changed In flight
Ground Adjustable Propellers
Is a design that allows the pilot to select one of two blade angles while to flight, allowing (the use of a low blade angle for takeoff and a high blade angle for cruise).
Two-Position Propeller
were designed to give the pilot the ability to set the blades at any angle on the propeller’s range while in flight, giving the pilot more control over the propeller- than the two-position design.
Controllable Pitch Propellers
This propeller is not controllable by the pilot. Instead. it will theoretically set the propeller blades at the most efficient angle by reacting lo forces generated by engine thrust torque, and airspeed.
Automatic Pitch Control
This propeller system uses a controllable propeller which the pilot Indirectly controls by adjusting a constant-speed control unit commonly called the governor.
Constant – Speed Propeller
The amount of lift produced depends on the:
Airfoil Shape
RPM
Angle of Attack
, Changes in airfoil shape and Blade angle
Propeller Pitch Distribution
The blade angle near the center of the propeller will be_____________ toward the tip. ()
highest with a decrease in blade angle
1.______airfoils near the hub and 2._______ airfoils toward the tip.
1.Low speed
2.high-speed
The pitch distribution and the change in airfoil shape along the length of the blade are necessary because:
each section is moving at a different velocity With the. slowest speeds near the hub and the highest speeds near the Up.
Is the angle between the airfoil chord line and the relative wind.
AOA (Angle of Attack)
Five Operational Forces
centrifugal force
torque bending force
thrust bending force
aerodynamic twisting force
centrifugal twisting force
The force which causes the greatest stress on a propeller.
Centrifugal Force
Tends to bend the propeller blades forward at the tips because the lift toward the tip of the blade flexes the thin blade sections forward.
Thrust Bending Force
Is a force which tends to bend the propeller blade back in the direction opposite of rotation.
Air resistance opposes the rotation of the blade
Torque Bending Force
Tries to twist the a blade to a higher angle by aerodynamic action.
Aerodynamic Twisting Moment
Tends to decrease the blade angle and opposes aerodynamic twisting moment.
Centrifugal Twisting Moment
Propeller produces thrust which the aerodynamic and mechanical forces are present that cause the blades to vibrate.
Vibrational Force and Critical Range
