amt 123

rotating device with a central hub and angled blades that create thrust to move a vehicle through a fluid.

propeller

1. trailing edge

2. hub

3. blade tip

4. leading edge

5. propeller information

6. back of blade

is its outermost point, farthest from the hub, and is critical for efficiency, as

blade tip

the curved or cambered surface designed to create an area of lower pressure as the propeller rotates.

back blade

where the airflow from the upper and lower surfaces meets and exits the blade.

trailing edge

It’s primary functions and capabilities revolve around ensuring efficient thrust generation, minimizing drag, and reducing noise and vibration.

trailing edge

the initial point of contact with the oncoming airflow, initiating the flow separation that generates aerodynamic lift (thrust) and managing the boundary layer to minimize drag.

leading edge

to connect the propeller blades to the engine shaft, transferring rotational power, but it also serves to absorb shock and protect the engine from damage.

hub

on the propeller itself serves crucial purposes for identification, maintenance, and performance optimization, allowing mechanics and pilots to verify correct propeller matching to an engine, check for damage or imbalance (tracking), ensure proper operation, and meet certification requirements, all vital for safety and efficiency.

propeller information

THE FORCE TENDING TO PULL THE BLADES OUT OF THE HUB

centrifugal force

THE AMOUNT OF STRESS CREATED BY CENTRIFUGAL FORCE CAN BE MORE THAN _____ TIMES THE WEIGHT OF THE PROPELLER BLADE.

7,500

TENDS TO BEND THE PROPELLER BLADES FORWARD AT THE TIPS.

THRUST BENDING FORCE

OCCUR AS AIR RESISTANCE OPPOSES THE ROTATIONAL MOTION OF THE PROPELLER BLADES

TORQUE BENDING FORCE

THIS FORCE TENDS TO BEND THE BLADES OPPOSITE THE DIRECTION OF ROTATION.

TORQUE BENDING FORCE

TENDS TO INCREASE A PROPELLR’S BLADE ANGLE. WHEN A PROPELLER BLADE PRODUCES THRUST, THE MAJORITY OF THE THRUST IS EXERTED AHEAD OF BLADE’S AXIS OF ROTATION.

AERODYNAMIC TWISTING FORCE

IS USED TO HELP CHANGE THE BLADE ANGLE OF PROPELLER.

AERODYNAMIC TWISTING FORCE

WHEN A PROPELLER ROTATES, CENTRIFUGAL FORCE TENDS TO ALIGN THE PROPELLER'S CENTER OF MASS WITH ITS CENTER OF ROTATION.

CENTRIFUGAL TWISTING FORCE

OCCURS DUE TO THE AERODYNAMIC AND MECHANICAL FORCES.

BLADE VIBRATION

forces acting on propeller (6);

1. centrifugal force

2. thrust bending force

3. torque bending force

4. aerodynamic twisting force

5. centrifugal twisting force

6. blade vibration

blade angle permanently set by the manufacturer and cannot be adjusted in flight.

fixed pitch propeller

allows its blade angle to be changed only while the aircraft is on the ground.

ground-adjustable propeller

lets the pilot manually change blade angle in flight.

controllable-pitch propeller

uses a governor to automatically adjust blade pitch and maintain a selected engine RPM.

constant-speed propeller

can rotate its blades to a position nearly parallel to the airflow to reduce drag during an engine failure.

feathering propeller

can move its blades into a negative angle to produce reverse thrust.

reverse-pitch propeller

is a special multi-bladed wooden propeller used for ground engine testing and break-in procedures.

test club propeller

types of propeller (7);

1. fixed pitch propeller

2. ground adjustable propeller

3. controllable pitch propeller

4. constant speed propeller

5. feathering propeller

6. reverse pitch propeller

7. test club propeller