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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.

PropellersObjectives:

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.

MOD

Propellers

Propellers(Terminology)


Airflow dueto RotationalVelocity


Induced Flow



Induced Flow


Relative Airflow


Induced Flow


Relative Airflow

ChordLine


Induced Flow


Relative Airflow

= AofA

ChordLine


Induced Flow


Relative Airflow

= AofA

= Blade Angle

ChordLine

Total Inflow

Propellers Blade Twist

Approx 4o

Angle of Attack

Rotational

Velocity

Effect of Airspeed

Induced Flow


At Zero Airspeed

Induced Flow

Airflow dueto RotationalVelocity (Same)

At a Forward Airspeed

= Total InflowTAS +

-

Effect of Airspeed

Effect of Airspeed

Induced Flow

Airflow dueto RotationalVelocity (Same)

= Total InflowTAS +

-

At a Forward AirspeedNeed larger for same

Effect of Airspeed

_

_

_

_

100%

75%

50%

25%

True Airspeed

Fine

CoarsePropellerEfficiencyat Max Power

Pitch ofPropeller Blade

_

_

_

_

100%

75%

50%

25%

True Airspeed

Fine

Coarse

Variable Pitch

PropellerEfficiencyat Max Power

Why a different Number of Blades?

Aerodynamic Forces

Total Inflow


RAF

Aerodynamic Forces

Total Inflow


RAF

TotalReaction

Aerodynamic Forces

Total Inflow


RAF

Lift

Drag

TotalReaction

Aerodynamic Forces

Total Inflow


RAF

TotalReaction

Thrust

Aerodynamic Forces

Total Inflow


RAF

TotalReaction

Thrust

PropRotationalDrag

Aerodynamic Forces(Effect of High Speed)

TAS+Induced Flow


RAF

TotalReaction

Thrust

Slow SpeedFixedPitch

TAS+Induced Flow


RAF

TotalReaction

Thrust

High SpeedFixedPitch


TAS+Induced Flow


RAF

NB: Rotational Dragreduced, RPM ?

Thrust



TAS+Induced Flow


RAF

NB: Rotational Dragreduced, RPM increases.Don’t exceed limits.

Thrust



TAS+Induced Flow


RAF

TotalReaction

Thrust

Slow SpeedVariablePitch


Faster TAS+Induced Flow


RAF

TotalReaction

Thrust (eventuallyreduces) High

SpeedVariablePitch(same or possibly greater)


WindmillingPropeller

Negative

TAS

Airflowdue to RotationalVelocity


Negative

TAS


TR

Negative

TAS


TR

Negative Thrust (Drag)


Negative

TAS


TR


Negative RotationalDrag (DrivingThe Propeller)


Negative

TAS


TR


Negative RotationalDrag (DrivingThe Propeller)

This may causefurther damage,

even Fire.


Note that in Firefly/Tutor prop goes to “Fine Pitch”if engine rotating, “Coarse Pitch” if engine seized

Feathered Propeller

Although twisted, in aggregate, blade at “Zero Lift α”. Therefore drag at minimum.

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

Relative Airflow

Total Reaction

Tries to fine blade off

ANY QUESTIONS?

PropellersObjectives:

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.

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