The flashcards below were created by user Luker on FreezingBlue Flashcards.

  1. Define Airfoil
    Coverts the movement of air over its surface into a force useful for lift
  2. Define Lift
    Force produced by airfoil, perpendicular to relative windand opposes graviety
  3. Define Drag
    force acting on a body and opposite to relative wind. resistenace of the atmosphere to the motion of the aircraft
  4. Define Thrust
    Force developed by the rotor bllades, parallel to relative wind, opposes weight and drag
  5. Define Chord
    distance from leading edge to trailing edge
  6. Define Span
    Distance from root of blade to tip
  7. Define angle of attack
    Angle of Chord relative to the relative wind
  8. Define relative wind
    opposes direction of airfoil movement
  9. Define Stall
    When the angle of attack is exceeded, to low of airspeed
  10. Define Centre of Pressure
    the point on the airfoil where lift is produced
  11. Define Pitch angle
    The angle the blade is making to a reference point
  12. What causes Coning
    Lift and centifugal force or weight
  13. What controls Vertical movement
    and how-collective, changes blade pitches equally
  14. What provides directional control, how is this accomplished?
    Cyclic, changes pitches of blades opposite to each other
  15. What provides Yaw control, and hows is this done?
    Tail rotor pedals, collectivly changes pitch on the tail rotor pedals
  16. Define Translating tendency
    when you add or reduce power, it wants to move the nose of the aircraft
  17. how is the a/c designed to compensate for translating tendency
    mast is tilted 2 deg
  18. Which was does the main rotor head rotate on a European a/c
    CW When viewed from above
  19. How is pitch changed on a individual rotor blade, which axis?
    the feathering axis
  20. why are the blades washed out
    to comp for the lift across the lenght of the blade
  21. Define Dissymmertery of lift
    difference between the amount of lift on the advancing and retreating blades of the rotor system due to airspeed
  22. what is it called when the blades flap up and down
    Corilious effect
  23. how do you comp for corrilious effect, (what is adjusted)
    lead-lag hinge, allows the blade to move fore and aft
  24. Name 3 types of rotor heads
    • RigidSemi
    • RigidFully
    • Articulated
  25. what direction can blades move in a rigid rotor system
    only movement is pitch, blades can flex
  26. What design feature is incorperated into some semi rigid rotor systems
    under sliging comp for corrilious effect
  27. what direction can blades move in a FullyArticulated rotor system
    feathers flaps lead-lags
  28. explain the transfer of motion that the swashplate provides
    transfers movement of cyclic and collective from stationary push pull movements to rotating push pull movements in the rotor system
  29. What does charactistic of a spinning rotor does the swashplate comp for
    Gyroscopic precession
  30. Define Translational Lift
    Increase in lift as the rotor enters horzional flighthigher airflow velocity supplies a greater mass of air per unit of time
  31. "A condition of increased drag and loss of lift at the aft portion of the rotor disc" is defined by what term
    • Transvers Flow-Caused by the air having a greater induced velocity and angle
    • -More lift in the front than the back
  32. Self excitied viberations occurs on the ground is defined by what term?
    Ground resonance
  33. What rotor head system is most seceptiable to ground resonance?
    Fully Ariticulated, if out of phase
  34. If the skid gear catches on a root or freezes to the ground before you try to take off,what would this condition be defined as?
    Dynamic Rollover
  35. What are the two primary reasons for blade stall?
    • Insufficient airspeed
    • Too great angle of attack
  36. What would be an indicator of a blade about to stall
    viberation of the main rotor head
  37. What must the pilot do if he/she sences retreating blade stall?
    • Unload rotor system
    • slow down
  38. Name the 2 Viberations that occour to the main rotor head?
    • Lateral-out of balance
    • Vertical-out of track
  39. Name 3 types of viberations found in a helicopter
    • Hight
    • Med
    • Low
  40. When dynamically balancing the main rotor, which should be balanced first? Balance or track?
    Track then balance
  41. 'Lifting rotors are driven by the action of the air moving through the blades as the a/c decends' What term is used to describe this?
  42. Name two different types of Freewheel unit?
    • Ramp and Roller
    • Sprag
  43. What two procedures would require adjusting the lenght of the pitch links ?
    • for autorotation
    • for out of track
  44. Condition of powered flight where the helicopter settles into its own downwash, (settling with power) -What is the proper name for this definition?
    Vortex ring state
  45. Name some conditions that can result in the Loss of Tail Rotor Effectiveness (LTE)?
    • requires high power
    • low airspeeed
    • unanticipated manuevers
    • No translational lift in main rotor-robs power from tail rotor resulting in LTE
  46. Name 3 different types of tail rotor designs?
    • Traditional design of two or more blades
    • fenstrom
    • Notar
  47. What hinge is incorperated into the design of the rotor system to counter the efferct of dissymmerty of lift?
    Teetering Hinge
  48. in a Notar helicopter, a design feature incorperated into the tail boom takes advantage of what aerodynamic princpal?
    Cowanda effect
  49. What is one of the main purposes of strakes on the tail boom?
    help counter main rotor torque
  50. Define engine derating, and why is it done?
    • de-rated by making 100% torque at less power than the engine can produce
    • because the power output decreases at altitude
  51. name two types of clutches?
    • belt tightener
    • centrifugal
  52. What type of helicopter needs clutches?
    Recip or fixed shaft, free turbines don't need a clutch
  53. With regaurds to a tail rotor drive shaft, what are the two most important design considerations?
    • Shaft must be flexiable (torque from tail boom)
    • Must be driven when a/c is in autoration
  54. Why is the vertical fin offset?
    offset to move the tail rotor sideways, takes over for tail rotor at airspeed
  55. Why is the horizontial stabilizer an inverted airfoil?
    Holds the nose up in forward flight to reduce drag
  56. How is the direction changed in a tandem rotor helicopter?
    by changing the direction of thrust from each rotor system
  57. Why is a stabilizer bar used on some two bladed rotor systems?
    to increase dynamic stabability
Card Set:

Theory of flight Rotary Wing
Show Answers: