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- 3. REVISION
- 11. Propellers (Terminology) Airflow due to Rotational Velocity
- 12. Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity
- 13. Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow
- 14. Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow Chord Line
- 15. Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow = AofA Chord Line
- 16. Propellers (Terminology) Induced Flow Airflow due to Rotational Velocity Relative Airflow = AofA = Blade Angle Chord Line
- 17. Total Inflow Propellers Blade Twist Rotational Velocity Approx 4 o Angle of Attack
- 18. Effect of Airspeed Induced Flow Airflow due to Rotational Velocity At Zero Airspeed
- 19. Effect of Airspeed Induced Flow Airflow due to Rotational Velocity (Same) At a Forward Airspeed = Total Inflow TAS + -
- 20. Effect of Airspeed Induced Flow Airflow due to Rotational Velocity (Same) = Total Inflow TAS + - At a Forward Airspeed Need larger for same
- 21. Effect of Airspeed _ _ _ _ 100% 75% 50% 25% True Airspeed Propeller Efficiency at Max Power Fine Coarse
- 22. Pitch of Propeller Blade _ _ _ _ 100% 75% 50% 25% True Airspeed Fine Coarse Propeller Efficiency at Max Power Variable Pitch
- 23. Why a different Number of Blades?
- 24. Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF
- 25. Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Total Reaction
- 26. Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Lift Drag Total Reaction
- 27. Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Total Reaction Thrust
- 28. Aerodynamic Forces Total Inflow Airflow due to Rotational Velocity RAF Total Reaction Thrust Prop Rotational Drag
- 29. Aerodynamic Forces (Effect of High Speed) TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction Thrust Slow Speed Fixed Pitch
- 30. TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)
- 31. TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)
- 32. TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction Thrust High Speed Fixed Pitch Aerodynamic Forces (Effect of High Speed)
- 33. 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)
- 34. 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)
- 35. TAS+Induced Flow Airflow due to Rotational Velocity RAF Total Reaction Thrust Slow Speed Variable Pitch Aerodynamic Forces (Effect of High Speed)
- 36. 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)
- 37. Windmilling Propeller Negative TAS Airflow due to Rotational Velocity
- 38. Windmilling Propeller Negative TAS Airflow due to Rotational Velocity TR
- 39. Windmilling Propeller Negative TAS Airflow due to Rotational Velocity TR Negative Thrust (Drag)
- 40. Windmilling Propeller Negative TAS Airflow due to Rotational Velocity TR Negative Thrust (Drag) Negative Rotational Drag (Driving The Propeller)
- 41. 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.
- 42. Feathered Propeller Note that in Firefly/Tutor prop goes to “Fine Pitch” if engine rotating, “Coarse Pitch” if engine seized Although twisted, in aggregate, blade at “Zero Lift α ”. Therefore drag at minimum.
- 43. 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
- 44. Take-Off Swings
- 45. Take-Off Swings Tail wheel aircraft only: Asymmetric blade effect Gyroscopic effect
- 46. Take-Off Swings
- 47. Take-Off Swings Affect all aircraft on rotate?
- 48. Take-Off Swings All Aircraft: Don’t forget crosswind effect!
- 49. Centrifugal Twisting Moment Tries to fine blade off
- 50. Aerodynamic Twisting Moment Tries to coarsen blade up Relative Airflow Total Reaction
- 51. Aerodynamic Twisting Moment Windmilling Tries to fine blade off Relative Airflow Total Reaction
- 52. ANY QUESTIONS?
Notas del editor
- PICTURE
- PROPELLERS (TERMINOLOGY) Airflow due to rotational velocity Induced flow This is the air drawn through the disc. Relative airflow Where is AOA? (Chord line/relative airflow) Always looking for optimum AOA, which is? (4) What is other angle? (Chord line/Airflow due to rotational velocity) Quick look at AOA of blade from hub to tip to maintain 4o AOA (If prop stationary then the airflow through would be TAS)
- PROPELLER BLADE TWIST What is the problem with a prop blade? What is the tip doing relative to the hub?
- EFFECT OF AIRSPEED Induced flow + TAS does what to AOA? Less efficient How do we counter this?
- EFFECT OF AIRSPEED Induced flow + TAS does what to AOA? Less efficient How do we counter this?
- EXAMPLES OF PROPS WHY DIFFERENT? Depends on Power output of the engine
- WINDMILLING PROPELLER Negative AOA Normally the prop will fine-off to maintain rpm (rotational drag) This will even try to drive the engine (oil failure) Could cause engine failure so: we want the blade to produce zero torque and reduce drag to a minimum How is this done?
- SLIDE 40 FEATHERED PROPELLER The idea is to reduce the drag
- TAKE-OFF SWINGS Prop rotating clockwise from cockpit All Aircraft: Torque Reaction means greater rolling resistance on one wheel. (Newton’s 3rd Law) More weight supported by wheel more drag. USE MODEL Helical slipstream acts more on one side of the fin than the other Rotating clockwise from behind - Tail wheel aircraft only: Asymmetric blade effect Top picture both propeller sections are equal also distance travelled are equal. Picture exaggerated but downgoing blade has greater AOA more thrust. Distance travelled by downgoing blade greater. Gyroscopic effect When tailwheel raised all effects are zero (until rotate?) But, force applied to top of disc (gyro) then clockwise rotation will cause yaw to the left Obviously anticlockwise all reversed. Affect all aircraft on rotate? All Aircraft: Don’t forget crosswind effect. (if yaw to left because of slipstream then get a crosswind from the right)
- CENTRIFUGAL TWISTING MOMENT This makes it more difficult for the pitch changing mechanism when increasing pitch. Better to increase the number of blades rather than make larger
- AERODYNAMIC TWISTING MOMENT Tries to increase AOA, this partially offsets CTM When windmilling in a steep dive the ATM is reversed and enhances CTM. This could prevent pitch mechanism from working
- PICTURE