Uncontrolled copy not subject to amendment 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 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.

MOD Propellers

Propellers (Terminology)

Airflow due to Rotational Velocity

Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity

Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow

Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow Chord Line

Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow   = AofA Chord Line

Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow    = AofA  = Blade Angle Chord Line

Total Inflow Propellers Blade Twist Approx 4 o Angle of Attack Rotational Velocity

Effect of Airspeed Induced Flow Airflow due to Rotational Velocity   At Zero Airspeed

Induced Flow Airflow due to Rotational Velocity (Same)  At a Forward Airspeed  = Total InflowTAS + -- Effect of Airspeed

Induced Flow Airflow due to Rotational Velocity (Same)   = Total InflowTAS + -- At a Forward Airspeed Need larger  for same 

Effect of Airspeed _ _ _ _ 100% 75% 50% 25% True Airspeed Fine Coarse Propeller Efficiency at Max Power

Pitch of Propeller Blade _ _ _ _ 100% 75% 50% 25% True Airspeed Fine Coarse Variable Pitch Propeller Efficiency at Max Power

Why a different Number of Blades?

Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF 

Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Total Reaction 

Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Lift Drag Total Reaction 

Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Total Reaction  Thrust

Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Total Reaction  Thrust Prop Rotational Drag

Aerodynamic Forces (Effect of High Speed) TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction  Thrust Slow Speed Fixed Pitch

TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction  Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)

TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction  Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)

TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction  Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)

TAS+Induced Flow Airflow due to Rotational Velocity RAF NB: Rotational Drag reduced, RPM ?  Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)

TAS+Induced Flow Airflow due to Rotational Velocity RAF NB: Rotational Drag reduced, RPM increases. Don’t exceed limits.  Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)

TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction  Thrust Slow Speed Variable Pitch Aerodynamic Forces (Effect of High Speed)

Faster TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction  Thrust (eventually reduces) High Speed Variable Pitch (same or possibly greater) Aerodynamic Forces (Effect of High Speed)

Windmilling Propeller Negative   TAS Airflow due to Rotational Velocity

Windmilling Propeller Negative   TAS Airflow due to Rotational Velocity TR

Negative   TAS Airflow due to Rotational Velocity TR Negative Thrust (Drag) Windmilling Propeller

Negative   TAS Airflow due to Rotational Velocity TR Negative Thrust (Drag) Negative Rotational Drag (Driving The Propeller) Windmilling Propeller

Negative   TAS Airflow due to Rotational Velocity TR Negative Thrust (Drag) Negative Rotational Drag (Driving The Propeller) This may cause further damage, even Fire. Windmilling Propeller

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

Tail wheel aircraft only: Asymmetric blade effect Gyroscopic effect

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?

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.