Uncontrolled copy not subject to amendment
Principles of Flight
Principles of Flight
Learning Outcome 5:
Be able to apply the principles of flight and control
to rotary wing aircraft
Part 1
Questions
Name the Forces Acting on a Glider in Normal Flight.
a. Force, Weight and Lift.
b. Drag, Weight and Thrust.
c. Drag, Weight and Lift.
d. Drag, Thrust and Lift.
Questions
How does a Glider Pilot Increase the Airspeed?
a. Operate the Airbrakes.
b. Lower the Nose by pushing the Stick Forward.
c. Raise the Nose by pulling the Stick Back.
d. Lower the Nose by pulling the Stick Back.
Questions
A Viking Glider descends from 1640 ft (0.5 km).
How far over the ground does it Travel (in still air)?
a. 17.5 kms.
b. 35 kms.
c. 70 kms.
d. 8.75 kms.
Questions
When flying into a Headwind, the distance covered
over the ground will:
a. Be the same.
b. Decrease.
c.
Increase.
d. No change.
Propellers
Objectives:
1. Define Blade Angle and Blade Angle of Attack.
2. Show with the aid of a diagram the Aerodynamic
Forces acting on a Propeller Blade in flight.
3. Explain Aerodynamic and Centrifugal Twisting
Moments acting on a propeller.
4. Explain the effect of changing forward speed on:
a. A Fixed Pitch propeller.
b. A Variable Pitch propeller.
(and thus the advantages of a variable pitch propeller).
5. Explain the factors causing swings on take-off for:
a.
A Nose-Wheel aircraft.
b.
A Tail- Wheel aircraft.
Propellers
MOD
Propellers
(Terminology)
Propellers
(Terminology)
Airflow due
to Rotational
Velocity
Propellers
(Terminology)
Induced Flow
Airflow due
to Rotational
Velocity
Propellers
(Terminology)
Induced Flow
Relative
Airflow
Airflow due
to Rotational
Velocity
Propellers
(Terminology)
Induced Flow
Chord
Line
Relative
Airflow
Airflow due
to Rotational
Velocity
Propellers
(Terminology)
Induced Flow
Chord

Line
= AofA
Relative
Airflow
Airflow due
to Rotational
Velocity
Propellers
(Terminology)
Induced Flow
Chord
Line

Airflow due
to Rotational
Velocity
Relative
Airflow
= AofA
= Blade Angle

Propellers Blade Twist
Rotational
Velocity
Total Inflow
Approx 4o
Angle of Attack
Effect of Airspeed
Induced Flow
Airflow due
to Rotational
Velocity


At Zero
Airspeed
Effect of Airspeed
TAS
+
-
Induced Flow
= Total Inflow
Airflow due
to Rotational
Velocity
(Same)


At a Forward
Airspeed
Effect of Airspeed
TAS
+
Induced Flow
Airflow due
to Rotational
Velocity
(Same)
-


At a Forward
Airspeed
Need larger  for same 
= Total Inflow
Effect of Airspeed
_
100%
Fine
_
Propeller 75%
Efficiency
_
at Max Power
Coarse
50%
25%
_
True Airspeed
Pitch of
Propeller Blade
_
100%
Fine
_
Variable Pitch
Propeller 75%
Efficiency
_
at Max Power
Coarse
50%
25%
_
True Airspeed
Why a different Number of Blades?
Aerodynamic
Forces
Total Inflow

RAF
Airflow due
to Rotational
Velocity
Aerodynamic
Forces
Total Inflow

Total
Reaction
RAF
Airflow due
to Rotational
Velocity
Aerodynamic
Forces
Total Inflow

RAF
Drag
Lift
Total
Reaction
Airflow due
to Rotational
Velocity
Aerodynamic
Forces
Total Inflow

Thrust
Total
Reaction
RAF
Airflow due
to Rotational
Velocity
Aerodynamic
Forces
Total Inflow

RAF
Thrust
Total
Reaction
Prop
Rotational
Drag
Airflow due
to Rotational
Velocity
Aerodynamic Forces
(Effect of High Speed)
TAS+Induced Flow

RAF
Airflow due
to Rotational
Velocity
Thrust
Total
Reaction
Slow
Speed
Fixed
Pitch
Aerodynamic Forces
(Effect of High Speed)
TAS+Induced Flow

RAF
Airflow due
to Rotational
Velocity
Thrust
Total
Reaction
High
Speed
Fixed
Pitch
Aerodynamic Forces
(Effect of High Speed)
TAS+Induced Flow

RAF
Airflow due
to Rotational
Velocity
Thrust
Total
Reaction
High
Speed
Fixed
Pitch
Aerodynamic Forces
(Effect of High Speed)
TAS+Induced Flow

RAF
Airflow due
to Rotational
Velocity
Thrust
Total
Reaction
High
Speed
Fixed
Pitch
Aerodynamic Forces
(Effect of High Speed)
TAS+Induced Flow

RAF
Airflow due
to Rotational
Velocity
Thrust
NB: Rotational Drag
reduced, RPM ?
High
Speed
Fixed
Pitch
Aerodynamic Forces
(Effect of High Speed)
TAS+Induced Flow

RAF
Airflow due
to Rotational
Velocity
Thrust
NB: Rotational Drag
reduced, RPM increases.
Don’t exceed limits.
High
Speed
Fixed
Pitch
Aerodynamic Forces
(Effect of High Speed)
TAS+Induced Flow

RAF
Airflow due
to Rotational
Velocity
Thrust
Total
Reaction
Slow
Speed
Variable
Pitch
Aerodynamic Forces
(Effect of High Speed)
Faster TAS+Induced Flow
RAF

Thrust
(eventually
reduces)
Total
Reaction
(same or possibly greater)
Airflow due
to Rotational
Velocity
High
Speed
Variable
Pitch
Windmilling
Propeller
Negative

TAS
Airflow
due to
Rotational
Velocity
Windmilling
Propeller
Negative

TAS
TR
Airflow
due to
Rotational
Velocity
Windmilling
Propeller
Negative

TAS
TR
Negative Thrust
(Drag)
Airflow
due to
Rotational
Velocity
Windmilling
Propeller
Negative

TAS
TR
Negative Thrust
(Drag)
Negative
Rotational
Drag (Driving
The Propeller)
Airflow
due to
Rotational
Velocity
Windmilling
Propeller
Negative

TAS
TR
Negative Thrust
(Drag)
Negative
Rotational
Drag (Driving
The Propeller)
This may cause
further damage,
even Fire.
Airflow
due to
Rotational
Velocity
Feathered
Propeller
Although twisted, in aggregate, blade at “Zero Lift α”.
Therefore drag at minimum.
Note that in Firefly/Tutor prop goes to “Fine Pitch”
if engine rotating, “Coarse Pitch” if engine seized
Take-Off Swings
All Aircraft:
Torque Reaction means greater rolling
resistance on one wheel
Helical slipstream acts more on one
side of the fin than the other
Take-Off Swings
Take-Off Swings
Tail wheel aircraft only:
Asymmetric blade effect
Gyroscopic effect
Take-Off Swings
Take-Off Swings
Affect all aircraft on rotate?
Take-Off Swings
All Aircraft:
Don’t forget crosswind effect!
Centrifugal Twisting Moment
Tries to fine blade off
Aerodynamic Twisting Moment
Relative Airflow
Total Reaction
Tries to coarsen blade up
Aerodynamic Twisting Moment
Windmilling
Total Reaction
Relative Airflow
Tries to fine blade off
ANY QUESTIONS?
Propellers
Objectives:
1. Define Blade Angle and Blade Angle of Attack.
2. Show with the aid of a diagram the Aerodynamic
Forces acting on a Propeller Blade in flight.
3. Explain Aerodynamic and Centrifugal Twisting
Moments acting on a propeller.
4. Explain the effect of changing forward speed on:
a. A Fixed Pitch propeller.
b. A Variable Pitch propeller.
(and thus the advantages of a variable pitch propeller).
5. Explain the factors causing swings on take-off for:
a.
A Nose-Wheel aircraft.
b.
A Tail- Wheel aircraft.
Questions
Blade Angle of Attack is between?
a. The Chord and Relative Airflow.
b. The Rotational Velocity and the Relative Airflow.
c. The Total Reaction and the Chord.
d. Lift and Drag.
Questions
Increasing speed with a fixed pitch propeller will?
a. Be more efficient.
b. Reduce efficiency.
c.
Make no difference.
d. Increase the Engine speed.
Questions
The Forces trying to alter the Propeller Blade
Angle of Attack are?
a. ATM and CTM.
b. CDM and ATM.
c. CTM and REV.
d. AOA and ATM.
Questions
The Resultant Forces that a Propeller produce are?
a. Lift and Thrust.
b. Thrust and Propeller Rotational Drag.
c.
Drag and Total Reaction.
d. Drag and Thrust.