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Helicopters
 

Helicopters

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    Helicopters Helicopters Presentation Transcript

    • VI. Helicopters
      • History
      • Configurations
      • Types of Rotor Systems
      • Forces Acting on the Rotor
      • Flight Conditions
      • Controls
      • Stabilizer Controls
      • Vibrations
      • Power Systems
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
      • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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?
    • 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
    • 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
    • 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
    • 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
    • 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
    • Helicopters Forces on the Rotors
      • History
      • Configurations
      • Types of Rotor Systems
      • Forces Acting on the Rotor
      • Flight Conditions
      • Controls
      • Stabilizer Controls
      • Vibrations
      • Power Systems
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
      • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • Bell 47 Transmission: Planetary system
    • 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
    • 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
    • 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
    • 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
    • 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
    •