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Helicopters
Helicopters
Helicopters
Helicopters
Helicopters
Helicopters
Helicopters
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Helicopters

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  • 1. VI. Helicopters
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 2. Helicopters History
    • 1483, DaVinci
      • Developed “Helix”
      • Kind of aerial screw
      • Shows basic understanding that the atmosphere can support weight but no provisions for torque on fuselage
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 3. Helicopters History
    • 1800s, Forlanini (Italy)
      • Used steam engine
      • Counter-rotating “butterfly” wings
      • Could ascend (without pilot) to 40 feet for about 20 minutes
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 4. Helicopters History
    • 1907, Cornu (France)
      • First piloted helicopter
      • Flew for few seconds
      • Used internal combustion engine
      • No controls but well balanced
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 5. Helicopters History
    • 1909, Igor Sikorsky (Russia)
      • Small counter-rotating coaxial rotors
      • First use of airfoil shaped rotors
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 6. Helicopters History
    • 1920s, Petroczy & Von Karmon (Austria)
      • Counter-rotating, coaxial, airfoil rotors
      • 3 40HP engines
      • No controls, just made to lift straight up
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 7. Helicopters History
    • 1923, de Bothezat (U.S.)
      • 4 rotors
      • Complicated power transmission system
      • Low power
      • Several flights of 1 minute @ 6 feet
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 8. Helicopters History
    • 1923, de la Cierva (Spain)
      • Developed Autogyro
      • Solved some control problems by allowing rotors to Flap
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 9. Helicopters History
    • 1936, Focke-Wulfe (Germany)
      • FW-61 established endurance & speed records
      • Mostly flown by Hannah Reich
      • Flown inside stadium for most of records
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 10. Helicopters History
    • 1939, Sikorsky (U.S.)
      • Developed VS-300
      • Broke all FW-61 records
      • Used 3-bladed main rotor, vertical 2-bladed tail rotor & 2 horizontal 2-bladed outrigger rotors for stability and control
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 11. Helicopters Configurations
    • Autogyros
      • Developed by de la Cierva
      • Uses free-spinning main rotor with airplane-like engine/prop for forward motion
      • No power to main rotor, spins from air action = can’t hover or ascend vertically
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 12. Helicopters Configurations
    • Dual Rotor
      • 2 counter rotating main rotors
        • No tail rotor needed
        • May be separate or coaxial
      • Used extensively through history, today few (Boeing, Kaman)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 13. Helicopters Configurations
    • Single Rotor
      • Most used design
      • 1 main rotor for lift and control
      • Tail rotor for anti-torque
        • FAA calls it “Auxiliary Rotor”
        • More precisely known as “Anti-torque Rotor”
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 14. Helicopters Configurations
    • Single Rotor
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Hughes Helicopter H-17 Skycrane 1952 Function: transport Crew: 2 Engines: 1 * G.E. J35 Rotor Span: 130ft Length: Height: 30ft Disc Area: Empty Weight: Max.Weight: 46000lb Speed: Ceiling: Range: 65km Load: 25000lbs Hot Cycle Blades
  • 15. Helicopters Configurations
    • Tilt Rotor
      • Bell V-22
      • Engines and main rotors (“PropRotors”) mounted on wingtips
        • Rotate so rotor is horizontal (on top) to takeoff and land like helicopter
        • Rotate so rotor is vertical to act like prop for high speed forward flight
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 16. Helicopters Types of Rotors
    • General
      • All must change blade angle or Pitch for control actions
      • Called “Feathering”
      • Is rotation around the span axis of the blade
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 17. Helicopters Types of Rotors
    • General
      • Some also:
        • Flap or Teeter
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 18. Helicopters Types of Rotors
    • General
      • Some also:
        • Lead/Lag (Hunt or Drag)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 19. Helicopters Types of Rotors
    • Semi-Rigid Rotor
      • 2-bladed
      • Blades Feather and entire rotor Teeters
      • No Hunting action allowed
      • Very popular in early Bell designs (and others)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 20.
    • Semi-Rigid
      • Bell 206
    Helicopters Types of Rotors
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 21. Helicopters Types of Rotors
    • Fully Articulated Rotor
      • 3 or more blades
      • Blades can Feather, individually Flap, and Hunt
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
      • Hunting limited by mechanical Dampers
  • 22. Helicopters Types of Rotors
    • Fully Articulated
      • Is most complicated but smoothest in flight
      • Problem: Ground Resonance potential
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 23. Helicopters Types of Rotors
    • Fully Articulated
      • Hughes 500 (McDonnell-Douglas, Boeing)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 24. Helicopters Types of Rotors
    • Fully Articulated
      • Sikorsky S58
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 25. Helicopters Types of Rotors
    • Fully Articulated
      • AStar 350
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 26. Helicopters Types of Rotors
    • Rigid
      • 2 or more blades
      • Blades Feather but all other forces absorbed by bending of the blades
      • Strongest and most maneuverable but needs composites to withstand fatigue
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 27. Helicopters Forces on the Rotors
    • Static Forces
      • Gravity pulls down and blades can bend relatively low
        • Called Droop
      • All need some kind of Droop (Static) Stop to prevent too low and possible Tail Boom strike
        • Especially for Fully Articulated at low RPM
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 28. Helicopters Forces on the Rotors
    • Turning Forces
      • Centrifugal Force tries to hold the blades straight out but lift tries to bend up
      • Result is Coning
        • Upward bending into Cone shape
        • More lift = more Coning
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 29. Helicopters Forces on the Rotors
    • Torque
      • From Newton’s 3 rd Law
      • Main rotor turns in one direction = fuselage tries to turn opposite (Torque)
      • Is directly proportional to power applied to M/R
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 30. Helicopters Forces on the Rotors
    • Torque
      • Compensated for by Tail Rotor thrust
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    What happens if Tail Rotor fails during flight?
  • 31. Helicopters Forces on the Rotors
    • Torque
      • Compensated for by Tail Rotor thrust or counter-rotating M/Rs
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 32. Helicopters Forces on the Rotors
    • Torque
      • Problem: Tail Rotor causes “Translating Tendency” or “Drift”
        • Is movement of entire helicopter in direction of T/R thrust (to right in U.S.)
        • Compensated by slight tilt of M/R mast to left
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 33. Helicopters Forces on the Rotors
    • Gyroscopic Precession
      • Any rotating body (M/R) acts like a Gyroscope and exhibits 2 characteristics:
        • Rigidity
        • Precession
      • Rigidity resists the change from it’s position in relation to space, not the Earth
      • Precession is the fact that the effect of any upsetting force applied to the body is felt 90 o later in direction of rotation
        • Affects the design and rigging of the M/R
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 34. Helicopters Forces on the Rotors
    • Gyroscopic Precession
      • For flight = need to tilt “Rotor Disk” in direction of desired flight
        • Changes lift & thrust vectors toward that direction = movement of helicopter
      • To accomplish = need to make pitch change 90 o earlier
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    De sired direction of flight
  • 35. Helicopters Forces on the Rotors
    • Gyroscopic Precession
      • For flight = need to tilt “Rotor Disk” in direction of desired flight
        • Changes lift & thrust vectors toward that direction = movement of helicopter
      • To accomplish = need to make pitch change 90 o earlier
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 36. Helicopters Forces on the Rotors
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 37. Helicopters Forces on the Rotors
    • Ground Effect
      • Increased lift within ½ rotor diameter of ground
      • “Cushion of Air”
      • Comes from change in angle of attack near ground because relative wind changes
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 38. Helicopters Forces on the Rotors
    • Ground Effect
      • Out of Ground Effect (OGE)
        • Rotor wash is free to accelerate straight down = given angle of attack and lift and large tip vortex
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Rotation Angle of Attack Downwash Relative Wind
  • 39. Helicopters Forces on the Rotors
    • Ground Effect
      • In Ground Effect (IGE)
        • Rotor wash is forced to move outward as well as down = reduced down vector = increased angle of attack + smaller tip vortex
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Downwash Rotation Angle of Attack Relative Wind
  • 40. Helicopters Forces on the Rotors
    • Flight Forces
      • Same as airplane:
        • Lift up
        • Weight (Gravity) down
        • Thrust forward and up
        • Drag back and down
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 41. Helicopters Forces on the Rotors
    • Flight Forces
      • In hover:
        • Lift and Thrust both act up
        • Weight and Drag act down
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 42. Helicopters Forces on the Rotors
    • Flight Forces
      • Forward Flight:
        • Thrust vector tilted in desired direction = overall loss of upward lift = need more power applied
        • Similar to airplane in turn
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 43. Helicopters Flight Conditions
    • Dissymmetry of Lift
      • At a hover with no wind the rotor blades are all traveling at the same speed in relation to the air around them
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 44. Helicopters Flight Conditions
    • Dissymmetry of Lift
      • Any relative air motion (wind or flight) = blade going into wind ( Advancing Blade ) travels faster than Retreating Blade
        • Think in terms of Airspeed
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    100 mph
  • 45. Helicopters Flight Conditions
    • Dissymmetry of Lift
      • Faster airfoil = more lift on Advancing side (and less lift on Retreating side)
      • Lift not equal = Dissymmetry of Lift
      • Without compensation = roll to left (and gets more severe with speed increase)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 46. Helicopters Flight Conditions
    • Dissymmetry of Lift
      • Compensated for by allowing the blades to Flap or the rotor to Teeter
        • Advancing blade Flaps (Teeters) up = decrease in angle of attack due to upward vector of Relative Wind
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 47. Helicopters Flight Conditions
    • Dissymmetry of Lift
      • Compensated for by allowing the blades to Flap or the rotor to Teeter
        • Retreating blade Flaps (Teeters) down = increase in angle of attack due to Relative Wind change
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 48. Helicopters Flight Conditions
    • Coriolis Effect
      • Caused by Flapping or Teetering up
      • Blade flaps up = Center of Mass moves closer to axis of rotation = RPM increases
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 49. Helicopters Flight Conditions
    • Coriolis Effect
      • The inertia of the rotor stays constant so as the Axis of Rotation is reduced the Speed of Rotation must increase
      • Is same as skater in spin with arms out then speeds up when arms are moved in to sides
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 50. Helicopters Flight Conditions
    • Coriolis Effect
      • Creates force to accelerate the blade (Hunting action)
      • Fully Articulated head allows limited Hunting action
        • Uses hydraulic or composite dampers to minimize movement
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 51. Helicopters Flight Conditions
    • Coriolis Effect
      • Semi-Rigid usually uses “UnderSlung Rotor Head”
        • Teetering Axis is above Feathering Axis (“Delta Hinge” arrangement) = as teeters it also swings to high side
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 52. Helicopters Flight Conditions
    • Coriolis Effect
      • Semi-Rigid usually uses “UnderSlung Rotor Head”
        • Center of Mass of the Rotor then stays basically in line with driveshaft/mast
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 53. Helicopters Flight Conditions
    • Translational Lift
      • Increased lift during the translation to forward flight from a hover
      • Occurs between 16 and 24 knots airspeed
        • Feel vibration and definite increase in lift (that point is called “Effective Translational Lift”)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 54. Helicopters Flight Conditions
    • Translational Lift
      • At hover and below 15 knots , the ground is forcing the rotor downwash outward and creating some turbulence around rotor blades
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 55. Helicopters Flight Conditions
    • Translational Lift
      • At hover and below 15 knots , the ground is forcing the rotor downwash outward and creating some turbulence around rotor blades
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
      • Above 15 kts , the blades “bite” into undisturbed air = more efficient = less power needed
  • 56. Helicopters Flight Conditions
    • Translational Lift
      • Above about 50 knots , drag starts to increase greatly and we need more power to further accelerate
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 57. Helicopters Flight Conditions
    • Transverse Flow Effect
      • At slow airspeeds (less than 20 kts.) = air through rear of rotor is accelerated downward longer than air at front = decrease in angle of attack in rear
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 58. Helicopters Flight Conditions
    • Transverse Flow Effect
      • Effect felt 90 o later = drift to right
      • Pilot must compensate with some left Cyclic to keep going in a straight line
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 59. Helicopters Flight Conditions
    • Transverse Flow Effect
      • As airspeed increases = entire rotor has basically undisturbed airflow = no Transverse Flow Effect is felt
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 60. Helicopters Flight Conditions
    • Autorotations
      • Flight with no engine power applied to the main rotors
      • Air is normally drawn down through rotors but if have engine failure = aircraft drops and wind goes up through rotors = keeps them rotating at near normal RPM
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 61. Helicopters Flight Conditions
    • Autorotations
      • When engine fails, pilot lowers Collective stick to bottom = sets in minimal angle on all blades and adjusts Cyclic to certain forward airspeed
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 62. Helicopters Flight Conditions
    • Autorotations
      • With Relative Wind from underneath and forward:
        • Lift and Drag vectors are changed so Resultant is forward of Axis of Rotation = tries to accelerate rotor and is called Autorotative Force
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 63. Helicopters Flight Conditions
    • Autorotations
      • With Relative Wind from underneath and forward:
        • Occurs in middle 25 – 75% of rotor
        • Is called the Autorotative (Autorotation) Region
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 64. Helicopters Flight Conditions
    • Autorotations
      • With Relative Wind from underneath and forward:
        • In outer 30% of rotor = blade twist makes the angle of attack low and the speed makes the drag high
        • Resultant is behind the Axis of Rotation
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 65. Helicopters Flight Conditions
    • Autorotations
      • With Relative Wind from underneath and forward:
        • Is a Decelerating force (Anti-Autorotative Force) and is called the Driven (or Propeller) Region
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 66. Helicopters Flight Conditions
    • Autorotations
      • With Relative Wind from underneath and forward:
        • Inner 25% has an angle of attack higher than the Critical Angle of the airfoil = Stall Region and also creates an Anti-Autorotative Force
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 67. Helicopters Flight Conditions
    • Autorotations
      • At some forward airspeed these forces combine to stabilize the RPM (achieve equilibrium)
      • RPM means Inertia = energy available to use when near the ground
        • This Autorotation RPM is critical rigging adjustment
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 68. Helicopters Flight Conditions
    • Autorotations
      • At about 50 feet above the ground, the pilot pulls back on the Cyclic to flare the aircraft (pulls the nose up some = reduced airspeed)
        • = momentary increase in airflow and higher RPM (= more inertia)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 69. Helicopters Flight Conditions
    • Autorotations
      • At about 10 feet above the ground, the pilot pulls up on the Collective and starts to use that energy in the rotor to cushion the landing
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 70. Helicopters Flight Conditions
    • Autorotations
      • Also leads manufacturers to publish “Height-Velocity Diagram” in Flight Manual
      • Also known as the “Dead Man’s Curve”
      • If fly in shaded area combinations of Height (Altitude) and Velocity = can’t successfully Autorotate
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 71. Helicopters Flight Conditions
    • Retreating Blade Stall
      • As we move forward = Retreating Blade flaps down to compensate for Dissymmetry of Lift by increasing the angle of attack
      • At some high forward airspeed (especially if the rotor RPM is allowed to get low) a portion of the airfoil (rotor disk) will exceed the Critical Angle of Attack and Stall
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 72. Helicopters Flight Conditions
    • Retreating Blade Stall
      • Generally occurs at the 7 – 9 o’clock position (looking down on the rotor = left rear of rotor) = vibrations + nose pitches up
        • gyroscopic precession = loss of lift in rear of rotor
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 73. Helicopters Flight Conditions
    • Retreating Blade Stall
      • Nose pitch up = excessive angle of attack in front (stall) = loss of lift on left and roll to left
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 74. Helicopters Flight Conditions
    • Vortex Ring State (Settling With Power)
      • If descending at 300 fpm or more + less than 10 mph forward airspeed + 20 to 100% power applied = can descend inside rotor downwash
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 75. Helicopters Flight Conditions
    • Vortex Ring State (Settling With Power)
      • Blades produce tip vortices (like any airfoil) + upward flow of air in middle of rotor (from descent) = Vortex across entire rotor = loss of lift and increased descent rate
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 76. Helicopters Flight Conditions
    • Vortex Ring State (Settling With Power)
      • Increasing power to control descent rate = increases problem by increasing the amount of vortex created
      • Must accelerate out of it or descend below it (if there’s enough altitude)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 77. Helicopters Flight Conditions
    • Vortex Ring State (Settling With Power)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 78. Helicopters Flight Conditions
    • Ground Resonance
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    http://www.chinook-helicopter.com/Fundamentals_of_Flight/Ground_Resonance/Ground_Resonance.html
  • 79. Helicopters Controls
    • Axes of Flight
      • Same as airplane: Longitudinal Axis = Roll, Lateral Axis = Pitch, Vertical Axis = Yaw
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 80. Helicopters Controls
    • Flight Controls
      • 3 basic controls: Cyclic, Collective, Pedals
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 81. Helicopters Controls
    • Flight Controls
      • 3 basic controls: Cyclic, Collective, Pedals
      • Cyclic:
        • Controls Pitch and Roll
        • Tilts rotor disk in desired direction of movement
        • Is primary airspeed and flight path control (pitch & roll)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 82. Helicopters Controls
    • Axes of Flight
      • Cyclic:
        • Uses Swashplate to do job
          • Is device with rotating component and stationary component
          • Connected by double-row ball bearing
          • Lower (stationary) part connected to Cyclic stick via push-pull tubes and/or hydraulics
          • Upper (rotating) part connected to main blades and rotates with them
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 83. Helicopters Controls
    • Axes of Flight
      • Cyclic:
        • Uses Swashplate to do job
          • Pilot pushes Cyclic stick in direction of desired movement
          • Swashplate is tilted to change M/R blade pitch a different amount depending on where it is in rotation
            • The pitch changes cyclically as it rotates
            • Direction of tilt is designed to take Gyroscopic Precession into account
            • May or may not tilt same as rotor disk action
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 84. Helicopters Controls
    • Axes of Flight
      • Cyclic:
        • Example system: Huey (Bell UH-1)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Fore & Aft tubes Lateral tubes
  • 85. Helicopters Controls
    • Axes of Flight
      • Collective:
        • Changes the pitch of all blades the same amount at the same time (collectively)
        • Controls the overall lift generated by the rotors
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 86. Helicopters Controls
    • Axes of Flight
      • Collective:
        • Uses the Swashplate to do the job by raising or lowering it to change the pitch on all blades
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 87. Helicopters Controls
    • Axes of Flight
      • Collective:
        • Collective stick also has engine throttle(s)
          • Motorcycle style rotating throttle except must rotate away from you to increase
          • Turbines usually governed so open throttle wide open and let governor keep RPM steady
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 88. Helicopters Controls
    • Axes of Flight
      • Collective:
        • Example system: Hughes (Schweizer) 269
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 89. Helicopters Controls
    • Axes of Flight
      • Pedals:
        • Control Yaw by controlling the thrust of the Tail Rotor (on single-rotor helicopters) and driven by main transmission so will still work if engine quits
          • Dual rotors = differential cyclic control by pedals
          • Coaxial rotors = rudder in rotor downwash
        • Push left pedal to yaw to the left, right pedal to yaw to the right
          • Left pedal increases T/R thrust
        • Needed especially during slow and high power conditions (I.e. takeoff and landing)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 90. Helicopters Controls
    • Axes of Flight
      • Tail Rotor Types:
        • Semi-rigid
          • Most common until recently
          • Usually 2-bladed
          • Has same Dissymmetry of Lift problems as M/R so will teeter usually (some let blades flap)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 91. Helicopters Controls
    • Axes of Flight
      • Tail Rotor Types:
        • Semi-rigid
          • Most common until recently
          • Usually 2-bladed
          • Has same Dissymmetry of Lift problems as M/R so will teeter usually (some let blades flap)
          • Most use Offset Hinges so pitch is physically changed as rotor teeters = minimal actual teetering action
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 92. Helicopters Controls
    • Axes of Flight
      • Tail Rotor Types:
        • Fenestron
          • French design
          • Enclosed multi-bladed variable-pitch fan
          • Safer and quieter
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 93. Helicopters Controls
    • Axes of Flight
      • Tail Rotor Types:
        • NOTAR
          • Developed by Hughes Helicopters (then McDonnell-Douglas now Boeing)
          • Uses fan inside tail boom with exhaust out side of boom through variable vent connected to pedals
          • Also uses Coanda Effect from rotor downwash
            • Air flowing over the curved surface “sticks” to that surface and creates lift sideways
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 94. Helicopters Controls
    • Miscellaneous
      • Stabilizer surfaces
        • Fixed Horizontal
          • Creates download on tail to keep fuselage more level during high speed flight
        • Synchronized Elevator
          • Connected to Cyclic
          • Changes pitch to change tail down load for various flight speeds
        • Fixed Vertical
          • For directional stability
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 95. Helicopters Controls
    • Miscellaneous
      • Hydraulics
        • For larger or heavier M/R systems
        • Mostly use Irreversible type systems to overcome flight loads and dampen vibrations in sticks
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 96. Helicopters Controls
    • Miscellaneous
      • Example system:
        • Bell 206
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 97. Helicopters Controls
    • Stabilizer Controls
      • Are inherently unstable
      • As rotor lift/thrust vector tilts away from vertical = creates vector to pull away from center
      • = negative stability
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 98. Helicopters Controls
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
      • Compensations
        • Bell Stabilizer Bar
          • Bar below M/R @ 90 o to blade span
          • Acts like gyroscope and uses Rigidity in Space characteristic to try and keep rotor and aircraft in one attitude
          • Worked too well so needs hydraulic damper to limit it’s effectiveness and allow reasonable maneuverability
  • 99. Helicopters Controls
    • Compensations
      • Offset Flapping Hinge
        • On fully-articulated rotor heads and on some tail rotors
        • Hinge moved a distance from rotor’s rotation axis = acts like lever to provide restoring force
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 100. Helicopters Controls
    • Compensations
        • Stabilization Augmentation System (SAS)
          • Like simple autopilot
          • One- or two-axis
          • Only to aid stability, not true autopilot
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 101. Helicopters Controls
    • Vibrations
      • Large number of moving and rotating parts = susceptible to vibrations
      • Vibrations = abnormal wear, premature part failure, and uncomfortable ride for people
      • Must minimize vibes
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 102. Helicopters Controls
    • Vibrations
      • Types
        • Low Frequency
          • Feel as “beat” in structure and may be able to almost count the beats
          • Comes from Main Rotor
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 103. Helicopters Controls
    • Vibrations
      • Types
        • Low Frequency
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
      • Vertical vibe
        • Up & down motion
        • Caused by blades being Out-of-Track
  • 104. Helicopters Controls
    • Vibrations
      • Types
        • Low Frequency
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
      • Lateral vibe
        • Side-to-side motion
        • Comes from blades being out of balance or spaced unequally
  • 105. Helicopters Controls
    • Vibrations
      • Types
        • High Frequency
          • Felt as “buzz” in structure
          • Comes from cooling fan, engine and/or accessories, gearboxes, or (most commonly) Tail Rotor
          • May only notice if some part of body goes to sleep
            • Feet = Tail Rotor (through pedals)
            • Butt = others
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 106. Helicopters Controls
    • Vibrations
      • Measurement of vibes
        • Feel
          • Adjust until feels OK (at minimum level)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 107. Helicopters Controls
    • Vibrations
      • Measurement of vibes
        • Electronic
          • Use accelerometers to measure rate and strength accurately
          • Use Strobe light or “Clock” to locate
          • Use above as coordinates on chart to determine exactly where and how much weight to add or remove
          • Can use to troubleshoot (narrow down vibe rate and look at those components operating at that rate)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 108. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of balance condition
          • May require Static or Dynamic procedures (or both depending on helicopter)
          • Some require Static balancing after assembly
            • Put on balance stand and adjust until no movement when released
            • T/R done like propeller (knife-edge stand)
            • M/R done on special stand with Bullseye level
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 109.
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of balance condition
            • M/R also may require Blade Sweep to be adjusted (for chordwise balance)
            • = stretch string between blades and adjust until blades are exactly 180 o apart (adjust by “sweeping” blades forward or aft as necessary)
    Helicopters Controls
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 110. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of balance condition
          • Dynamic balancing done during operations on ground and in air
          • Uses Electronic gear to measure rate and strength and charts to show adjustments
        • Some M/Rs don’t need dynamic after static but all T/Rs do
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 111. Helicopters Controls
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Example: Chadwick-Helmuth Vibrex ® system
  • 112. Helicopters Controls
    • Vibrations
      • Measurement of vibes
        • Example chart:
          • T/R balance
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 113. Helicopters Controls
    • Vibrations
      • Measurement of vibes
        • Example chart:
          • T/R balance
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 114. Helicopters Controls
    • Vibrations
      • Measurement of vibes
        • Example chart:
          • M/R balance
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 115. Helicopters Controls
    • Vibrations
      • Measurement of vibes
        • Example chart:
          • M/R balance
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 116. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of Track condition
          • Track = path Blade tips follow during rotation
          • In-Track = all tips follow same path (or Cone the same amount) and = minimal vertical vibes
          • All M/Rs need to be checked and adjusted and some T/Rs
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 117. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of Track condition
          • Ground check
            • Use marking stick or Flag
            • Marking Stick uses crayon or grease pencil on end of long stick and carefully raise to bottom of blades to make mark on lowest one (adjust until marks all blades)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 118. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of Track condition
          • Ground check
            • Flag is strip of canvas suspended between F shaped pole + put crayon mark on blade tips (different color on each blade) then move Flag so just touches each blade to get a colored mark
            • Use colors to determine which blade needs adjustment
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 119. Helicopters Controls
    • Vibrations
      • Flag Tracking
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Flag Tracking
  • 120. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of Track condition
          • Ground check
            • All are adjusted by changing the length of the Pitch Links (controls Angle of Incidence of blades)
            • Link between Swashplate and M/R blade
            • Increase angle = more lift = blade flies higher
            • Each manufacturer usually has standard adjustments (I.e. 1/6 turn = ½” blade movement)
            • Limitation: can’t check in flight
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 121. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of Track condition
          • Ground & Flight
            • Use spotlight or strobe
            • Spotlight uses colored reflectors attached to blade
            • Light shows colored streaks and can see “altitude” difference between them
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 122. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of Track condition
          • Ground & Flight
            • Strobe is keyed by pickup on swashplate
            • Flashes once for each blade
            • Has reflectors on each blade with different angled “Target” line
            • Flashes ‘stop’ targets at one location and can easily see difference and which blade to adjust
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 123. Helicopters Controls
    • Vibrations
      • Correction of vibes (M/R & T/R)
        • If out of Track condition
          • Ground & Flight
            • For ground and hover adjustment = use Pitch Links
            • For in-flight adjustment = most blades have trailing edge fixed trim tabs to allow limited bending
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 124. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating
          • See all types: Horizontal and Vertically mounted Opposed engines & some Radials
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 125. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating
          • Verticals and Radials usually are Dry-sump with M/R Transmission (GearBox) mounted on top and using same oil supply
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 126. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating
          • Verticals and Radials usually are Dry-sump with M/R Transmission (GearBox) mounted on top and using same oil supply
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Bell 47
  • 127. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating
          • Horizontals usually use some form of Belt Drive
            • Multiple V-belts or one wide “timing” belt
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 128. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating
          • None have propeller for cooling air blast and “fly wheel” for starting
          • All use some form of Cooling Fan driven by engine to blow air across cylinders
          • All are generally hard to start (no fly wheel to help process keep going)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 129. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating Instruments
          • Since M/R is essentially a Variable-pitch Propeller = all use both Tachometer (RPM) and Manifold Pressure gauges for power measurement
          • Engines must be operated at relatively constant RPM (to allow enough Lift & Thrust) and usually very near the manufacturer’s Overspeed limit
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 130. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating
          • Usually uses Correlated Throttle and Collective
            • Pull up on collective = more blade pitch = more lift/thrust generated = more drag
            • Need more engine power to keep RPM constant
            • Correlation increases throttle automatically as Collective is pulled up (may not do entire job, though)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 131. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Reciprocating
          • Usually uses Correlated Throttle and Collective
            • Pull up on collective = more blade pitch = more lift/thrust generated = more drag
            • Need more engine power to keep RPM constant
            • Correlation increases throttle automatically as Collective is pulled up (may not do entire job, though)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Bell 47
  • 132. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Turbines
          • Are ideal powerplants as operate most efficiently at constant RPM and have very high power to weight ratio
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 133. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Turbines
          • Are TurboShaft engines
            • All output power is converted to rotating shaft power (Torque)
            • Torque sent to Transmission to drive Main & Tail Rotors and other necessary components
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 134. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Turbines
          • Are TurboShaft engines
            • Two basic types: Direct Shaft & Free Turbine
            • Direct Shaft has PTO shaft connected to all Compressor and Turbine section stages
            • Are very hard to start as must turn all engine + Main and Tail rotors
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 135. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Turbines
          • Are TurboShaft engines
            • Two basic types: Direct Shaft & Free Turbine
            • Free Turbine has some Turbine stages which only supply PTO power
            • Easier to start as rotors not mechanically connected to main part of engine
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 136. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Turbines
          • Are TurboShaft engines
            • Measure power output with Tachometers, Torquemeters, and Turbine Temperature gauges
            • Tachs measure RPM in % (due to high actual RPM)
            • Free Turbine versions need to measure both main engine (N 1 ) and Power Turbine (N 2 ) and usually have separate gauges
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 137. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Turbines
          • Are TurboShaft engines
            • Torquemeters measure power being absorbed by M/Rs
            • Similar to MAP gauge on recips
            • Measures in % or in Pounds of Torque
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 138. Helicopters Controls
    • Power Systems & Other Components
      • Powerplants
        • Turbines
          • Are TurboShaft engines
            • Turbine Temps very important as are directly proportional to how hard the engine’s working and critical during the start cycle
            • May be TIT, ITT, TOT, or EGT system (manufacturer’s choice)
            • CAN NOT exceed max. limit or will damage Turbine section components
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 139. Helicopters Controls
    • Power Systems & Other Components
      • Transmissions
        • For speed and/or directional change of rotating shaft(s)
        • May be Rack & Pinion or Planetary Gear systems
        • Uses engine oil or has own supply
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 140. Helicopters Controls
    • Power Systems & Other Components
      • Transmissions
        • For speed and/or directional change of rotating shaft(s)
        • May be Rack & Pinion or Planetary Gear systems
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
    Schweizer (Hughes) 269 Transmission: Rack (Ring Gear) and Pinion
  • 141. Bell 47 Transmission: Planetary system
  • 142. Helicopters Controls
    • Power Systems & Other Components
      • Transmissions
        • Engine drives M/R Transmission which in turn drives the T/R, Hydraulic pumps, Electrical Generator, Cooling Fans (if appropriate for the aircraft), and Rotor Tach sending unit connected to (usually) Dual Tach (Rotor and Engine RPM on same gauge)
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 143. Helicopters Controls
    • Power Systems & Other Components
      • Clutch
        • USED TO RELIEVE THE ENGINE LOAD DURING STARTING
        • May be Manual, Electrical, or Centrifugal
        • Manual and Electrical pull Idler Pulley against Belt(s) to tighten them and connect engine with Transmission
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 144. Helicopters Controls
    • Power Systems & Other Components
      • Clutch
        • Centrifugal uses hinged Shoes pushed against a Drum by Centrifugal Force
          • Shoes on arms attached to engine crankshaft
          • Drum attached to Transmission
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 145. Helicopters Controls
    • Power Systems & Other Components
      • Freewheeling Unit
        • FOR AUTOROTATION PURPOSES
        • Disconnects M/R from engine if engine turns slower than M/R
        • Usually either Roller or Sprag style
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 146. Helicopters Controls
    • Power Systems & Other Components
      • Freewheeling Unit
        • FOR AUTOROTATION PURPOSES
        • Disconnects M/R from engine if engine turns slower than M/R
        • Usually either Roller or Sprag style
    • History
    • Configurations
    • Types of Rotor Systems
    • Forces Acting on the Rotor
    • Flight Conditions
    • Controls
    • Stabilizer Controls
    • Vibrations
    • Power Systems
  • 147.  

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