Propeller & Variable Pitch Propeller Flashcards
Creating forward movement from a propeller is the method of turning ____ motion into ____
Method of turning reciprocal motion into thrust
What are the 2 types of propeller
- Fixed pitch
- Variable pitch
The amount of lift produced by a propeller blade is dependant on what 2 factors
- Speed
- AoA
Why is an propeller designed to have less AoA at the tip than at the hub
Tips travel faster
More lift would be produced
More AoA at hub than at tips
If a propeller blade had the same AoA across its entire length, which section of the propeller would produce more lift?
THE TIP
The tip has greater distance to travel
It travels faster so would produce more lift with the same AoA as the centre of the blade
At the hub of a propeller blade, AoA is HIGHER or LOWER than the AoA at the tip
Hub = HIGHER
Tip = LOWER
The AoA of a propeller blade is dependent on which 2 factors
- Propeller Pitch (Blade angle)
- Forward Velocity
You can determine how far a propeller moves forward in one revolution based on what?
GEOMETRIC PITCH
The efficiency of fixed pitch propeller varies with what
AIRSPEED
Fixed pitched propeller in a climb, assuming power (throttle) constant
Airspeed INCREASES or DECREASES
DECREASES
Fixed pitched propeller in a climb, assuming power (throttle) constant
Relative airflow angle INCREASES or DECREASES
INCREASES
Fixed pitched propeller in a climb, assuming power (throttle) constant
Propeller AoA INCREASES or DECREASES
This has what effect on efficiency
- AoA INCREASES
- Efficiency DECREASES
Fixed pitched propeller in a climb, assuming power (throttle) constant
Propeller is EASIER or HARDER to push through the air
This has what effect on engine workload
- HARDER
- Workload INCREASES
Fixed pitched propeller in a climb, assuming power (throttle) constant
Engine RPM INCREASES or DECREASES
DECREASES
AoA has increased, prop takes bigger bites of the air
This takes more effort. Engine works harder and turns more slowly
Fixed pitched propeller in a descent, assuming power (throttle) constant
Airspeed INCREASES or DECREASES
INCREASES
Fixed pitched propeller in a descent, assuming power (throttle) constant
Relative airflow angle INCREASES or DECREASES
DECREASES
Fixed pitched propeller in a descent, assuming power (throttle) constant
Propeller AoA INCREASES or DECREASES
This has what effect on efficiency
- AoA DECREASES
- Efficiency INCREASES
Fixed pitched propeller in a descent, assuming power (throttle) constant
Propeller is HARDER or EASIER to push through the air
This has what effect on engine workload
- EASIER
- Workload DECREASES
Fixed pitched propeller in a descent, assuming power (throttle) constant
Engine RPM INCREASES or REDUCES
INCREASES
On an RPM gauge what is meant by the following
- Green Arc
- Red Line
- Normal Operating Range
- Never Exceed
What are 2 examples of propeller aerofoil damage
What effect does this have on efficiency
- Stone Chips
- Tip Damage
- Propeller less efficient
A propeller under high stress loads could suffer from what
STRUCTURAL FATIGUE
If a small part of a propeller tip were to detach, what could this result in
SEVERE VIBRATION
What is a key reasons for an engineering filing out nicks on a propeller blade
Prevent fatigue cracks forming and spreading