Flight Control Systems and their Operation CASA 12.2.1
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Questions and Answers

What is the purpose of the cyclic control in a helicopter?

  • To provide directional control about the pitch and roll axis (correct)
  • To control altitude changes
  • To offset torque from the main rotor
  • To increase rotor blade pitch for descent

    • Which control increases or decreases the pitch on the main rotor blades?

  • Yaw Control
  • Collective (correct)
  • Anti-Torque Control
  • Cyclic Control

    • What is the primary function of anti-torque control in a helicopter?

  • To provide yaw control (correct)
  • To assist with altitude adjustments
  • To manage rotor blade pitch
  • To boost cyclic control responsiveness

    • Which mechanism can boost flight controls in helicopters?

    <p>Hydraulic servo jacks</p> Signup and view all the answers

    Why are boosted flight controls important for helicopters?

    <p>They assist with high-speed flight and heavy loads</p> Signup and view all the answers

    What component is directly controlled by the pilot to change rotor pitch in a boosted system?

    <p>Valve in the servo</p> Signup and view all the answers

    What allows helicopters to return to unassisted control in case of a system failure?

    <p>Hydraulic system provision</p> Signup and view all the answers

    Which type of control allows the pilot to manage the attitude and direction of the helicopter?

    <p>Cyclic Control</p> Signup and view all the answers

    What is the primary purpose of the cyclic control system?

    <p>To tilt the rotor disc</p> Signup and view all the answers

    What happens when the cyclic control is moved forward?

    <p>The rotor disc tilts forward</p> Signup and view all the answers

    How does the cyclic control affect rotor blade pitch during its movement?

    <p>It changes pitch angles 180° then back</p> Signup and view all the answers

    What is the role of the horizontal stabiliser in relation to the cyclic control?

    <p>To assist in maintaining level flight</p> Signup and view all the answers

    What occurs due to gyroscopic precession in relation to the cyclic control?

    <p>The cyclic needs to be moved before changing pitch</p> Signup and view all the answers

    What effect does increasing the pitch of the rotor blades have?

    <p>It increases drag and decreases rotor RPM</p> Signup and view all the answers

    Where is the collective pitch control typically located?

    <p>Between the pilot's legs</p> Signup and view all the answers

    What does the collective pitch control change?

    <p>The pitch angle of all main rotor blades simultaneously</p> Signup and view all the answers

    What is one function of the droop compensation device in a helicopter?

    <p>To anticipate power changes during pitch adjustments</p> Signup and view all the answers

    What happens when the collective pitch is lowered?

    <p>The drag on the blades decreases</p> Signup and view all the answers

    What is the relationship between the cyclic control and the direction of helicopter movement?

    <p>Cyclic control changes thrust direction affecting helicopter movement</p> Signup and view all the answers

    Which mechanism is used to allow for adjustments in engine power related to changes in collective pitch?

    <p>The throttle control and governor</p> Signup and view all the answers

    What does a higher drag result from when increasing rotor blade pitch?

    <p>Increased power requirement to maintain rotor RPM</p> Signup and view all the answers

    What is NOT a function of the cyclic control?

    <p>To change the speed of the rotor</p> Signup and view all the answers

    What is the primary requirement during rigging procedures for helicopters?

    <p>To follow the manufacturer's instructions</p> Signup and view all the answers

    Which tool is NOT typically required for helicopter rigging procedures?

    <p>Adjustment wrench</p> Signup and view all the answers

    What should be observed when making minor adjustments after initial rigging?

    <p>Adjustments should be in small increments</p> Signup and view all the answers

    What position should the cyclic control be in during rigging?

    <p>Straight up or perpendicular to the floor</p> Signup and view all the answers

    Which of the following is typically checked during the rigging procedure?

    <p>Mast alignment</p> Signup and view all the answers

    What is the purpose of using rigging jigs and pins?

    <p>To hold components in predetermined locations</p> Signup and view all the answers

    What should be used to determine predetermined degrees in components during rigging?

    <p>Protractor</p> Signup and view all the answers

    What is typically the last step when rigging a cyclic system?

    <p>Establishing the rotor's neutral position</p> Signup and view all the answers

    What mathematical tool is used to measure degrees during rigging?

    <p>Protractor</p> Signup and view all the answers

    Which statement about helicopter rigging adjustments is false?

    <p>Adjustments do not require reference to the maintenance manual</p> Signup and view all the answers

    What is the primary function of the tail rotor in a helicopter?

    <p>To counteract the torque produced by the main rotor</p> Signup and view all the answers

    What is translating tendency in helicopters?

    <p>The movement caused by uneven forces during lift-off</p> Signup and view all the answers

    How is directional control achieved in single main rotor helicopters?

    <p>Through the use of tail rotor pedals</p> Signup and view all the answers

    What does the anti-torque rotor help the helicopter maintain during flight?

    <p>Hover turn capability</p> Signup and view all the answers

    What type of control mechanism do many designs use to correct tail rotor drift?

    <p>Cyclic control biases</p> Signup and view all the answers

    Which of the following is a disadvantage of single rotor designs?

    <p>Complex anti-torque requirements</p> Signup and view all the answers

    What unique feature does the NOTAR system provide?

    <p>No tail rotor at all</p> Signup and view all the answers

    Which component helps change the pitch of the tail rotor blades?

    <p>Pitch change assembly</p> Signup and view all the answers

    What effect does increasing the distance of the tail rotor from the mast have?

    <p>Increases the anti-torque moment produced</p> Signup and view all the answers

    What is a common feature of the Fenestron tail rotor?

    <p>It consists of a fairing that encloses the blades</p> Signup and view all the answers

    What is the significance of the tail rotor thrust direction in relation to the main rotor torque?

    <p>It opposes the torque direction</p> Signup and view all the answers

    Which component of the helicopter provides a high volume of low-pressure air in the NOTAR system?

    <p>Fan inside the tailboom</p> Signup and view all the answers

    What is the purpose of the horizontal component of total rotor thrust after correcting translating tendency?

    <p>It rolls the helicopter to the left</p> Signup and view all the answers

    What allows the tail rotor hub to function effectively in changing the pitch of the blades?

    <p>A combination of flapping and feathering hinges</p> Signup and view all the answers

    What can the throttle be used for during a tail rotor failure?

    <p>To produce the amount of torque required for landing.</p> Signup and view all the answers

    What happens when the throttle is rolled from 'off' to 'idle'?

    <p>The idle release button prevents the throttle from returning to 'off'.</p> Signup and view all the answers

    How does a correlating unit function in a piston engine helicopter?

    <p>It matches fuel flow to rotor RPM by adjusting power automatically.</p> Signup and view all the answers

    What is the purpose of the RPM adjustment button?

    <p>To set the RPM that the governor will attempt to maintain.</p> Signup and view all the answers

    What is the significance of the push-pull tubes in a collective system?

    <p>They convert rotary motion to linear movement in the collective control.</p> Signup and view all the answers

    Why should torque tubes be inspected periodically?

    <p>To assess security, bearing wear, and cracks.</p> Signup and view all the answers

    What is the main function of bellcranks in a helicopter collective system?

    <p>To change direction of movement and provide mechanical advantage.</p> Signup and view all the answers

    What is the primary purpose of a mixer box in a helicopter?

    <p>To prevent cyclic inputs from being affected by collective inputs</p> Signup and view all the answers

    What occurs when a collective lever is pulled up in a gas turbine helicopter?

    <p>The rotor RPM is maintained by increasing fuel flow.</p> Signup and view all the answers

    What material are bellcranks usually constructed from?

    <p>Forged aluminum.</p> Signup and view all the answers

    How does a gradient unit function in helicopter control systems?

    <p>It provides artificial feedback to the pilot during control inputs</p> Signup and view all the answers

    Which component helps maintain rotor RPM when the collective control is adjusted?

    <p>Throttle butterfly.</p> Signup and view all the answers

    What happens when a pilot raises the collective lever in a helicopter?

    <p>The swashplate can move up or down depending on the pitch link attachment</p> Signup and view all the answers

    What role do anti-torque pedals play in helicopter operation?

    <p>They counteract the torque generated by the main rotor</p> Signup and view all the answers

    What advantage does the linear actuator provide in Bell helicopters?

    <p>It gives the pilot manual adjustment capability for rotor RPM.</p> Signup and view all the answers

    What can happen due to wear factors in push-pull tubes?

    <p>Wear can dramatically increase in connected units over time.</p> Signup and view all the answers

    Which component is responsible for transferring pilot inputs to the rotor blades?

    <p>Swashplate</p> Signup and view all the answers

    What is the purpose of the mixer box in a helicopter's flight control system?

    <p>To manage torque transfer to the rotor and engines.</p> Signup and view all the answers

    What mechanism assists in trimming a helicopter's flight attitude?

    <p>Gradient unit in conjunction with a magnetic brake</p> Signup and view all the answers

    What is the effect of moving the cyclic control in a helicopter?

    <p>It changes the heading and thrust orientation</p> Signup and view all the answers

    What role does the starter button play in helicopter operations?

    <p>It acts as a starter motor to turn the engine.</p> Signup and view all the answers

    Which position activates both the forward and downward angled landing lights?

    <p>Both</p> Signup and view all the answers

    What determines the required positive pitch for the tail rotor during takeoff?

    <p>The rotor's counterclockwise or clockwise direction</p> Signup and view all the answers

    How does the attachment of a pitch horn affect blade angle movement?

    <p>Influences the angle of attack of the blades</p> Signup and view all the answers

    During cruising, where should the anti-torque pedals be positioned?

    <p>Held in a neutral position</p> Signup and view all the answers

    What occurs if there is no mixer device installed in a helicopter?

    <p>Collective inputs will alter cyclic settings leading to control issues</p> Signup and view all the answers

    Why is trimming necessary for helicopters during flight?

    <p>To compensate for load distribution and maintain proper attitude</p> Signup and view all the answers

    What should the collective lever movement result in for blade angles?

    <p>Simultaneous increase in blade angles on all blades</p> Signup and view all the answers

    What is a potential consequence of using a hydraulic boost in helicopter controls?

    <p>Decreased overall control feel</p> Signup and view all the answers

    What is the primary advantage of a shrouded tail rotor design, known as a Fenestron?

    <p>It provides protection to the rotor and personnel.</p> Signup and view all the answers

    How does a canted tail rotor contribute to the helicopter's performance?

    <p>It provides lifting force during hover.</p> Signup and view all the answers

    What is the purpose of using dual rotors in helicopters?

    <p>To counteract the rotating force affecting the fuselage.</p> Signup and view all the answers

    What configuration do tandem rotor helicopters use?

    <p>Two counter-rotating rotors at the front and rear.</p> Signup and view all the answers

    What distinguishes intermeshing rotor designs?

    <p>They use two counter-rotating rotors mounted close together.</p> Signup and view all the answers

    What is a characteristic of boosted flight control systems in helicopters?

    <p>They utilize electronic signals instead of mechanical linkages.</p> Signup and view all the answers

    Which component in boosted flight controls helps maintain system pressure?

    <p>The relief valve.</p> Signup and view all the answers

    Why are hydraulic pumps crucial in boosted flight controls?

    <p>They ensure hydraulic power is available during autorotation.</p> Signup and view all the answers

    What is the role of servo actuators in flight control systems?

    <p>To assist the pilot in control movement and prevent rotor feedback.</p> Signup and view all the answers

    In a fly-by-wire system, what replaces the conventional mechanical linkages?

    <p>Wires carrying electrical signals.</p> Signup and view all the answers

    What can be said about the performance of a Fenestron compared to conventional tail rotors?

    <p>It is generally more effective when of similar diameter.</p> Signup and view all the answers

    What characterizes contra-rotating rotor systems?

    <p>They achieve directional control by adjusting pitch on each rotor disc.</p> Signup and view all the answers

    What is a disadvantage of using shrouded tail rotors like the Fenestron?

    <p>There is a structural challenge in fitting the shroud.</p> Signup and view all the answers

    Which of the following would NOT be a component typically found in a hydraulic flight control system?

    <p>Microprocessor.</p> Signup and view all the answers

    What is the function of electrical transducers in a fly-by-wire system?

    <p>To amplify and relay control signals</p> Signup and view all the answers

    What does bias control do in helicopter trimming?

    <p>Increases or decreases tension in pilot control linkages</p> Signup and view all the answers

    What is the primary purpose of horizontal stabilisers on a helicopter?

    <p>To stabilize the fuselage against pitch movements</p> Signup and view all the answers

    Why can stabilisers be detrimental during rearward flight?

    <p>They accentuate longitudinal oscillations</p> Signup and view all the answers

    What defines synch elevators in helicopter design?

    <p>They move with cyclic inputs to enhance stabiliser response</p> Signup and view all the answers

    What is the main function of stabilators on a helicopter?

    <p>To provide longitudinal stability using electronic systems</p> Signup and view all the answers

    How are tail rotor blades usually balanced during manufacturing?

    <p>Through dynamic and static balancing procedures</p> Signup and view all the answers

    What does static balancing of blades require?

    <p>Precision weight addition as per manufacturer specifications</p> Signup and view all the answers

    What is the significance of control rigging after replacing helicopter components?

    <p>It ensures correct control system adjustments and tolerances</p> Signup and view all the answers

    What is commonly a risk when adding weight to rotor blades?

    <p>Unauthorized adjustments may compromise safety</p> Signup and view all the answers

    What is an effect of increased angle of attack on the stabiliser?

    <p>Increased stabilization of fuselage</p> Signup and view all the answers

    What does dynamic balance of tail rotor blades achieve?

    <p>It mitigates vibrations during operation</p> Signup and view all the answers

    What role do electronic servo systems play in helicopters?

    <p>To maintain configurations without pilot intervention</p> Signup and view all the answers

    What happens to the control movements as a result of maintenance procedures in helicopters?

    <p>They demand accurate rigging for flight safety</p> Signup and view all the answers

    What is one significant advantage of the NOTAR system compared to conventional tail rotor systems?

    <p>Reduced vibration</p> Signup and view all the answers

    What does the strake attached to the tail boom primarily achieve?

    <p>Improves lift on the left side</p> Signup and view all the answers

    How does the Coanda Effect relate to the performance of the strake?

    <p>It increases lift force on one side of the tail boom</p> Signup and view all the answers

    What role does the tail thruster cone play in the MD NOTAR system?

    <p>Allows high speed fan-driven air to exit</p> Signup and view all the answers

    Which component is crucial for ensuring airflow above the tail boom in the NOTAR system?

    <p>Direct jet thruster</p> Signup and view all the answers

    In what condition does the Coanda Effect reach its maximum efficiency for the NOTAR system?

    <p>While hovering in nil wind conditions</p> Signup and view all the answers

    What is a disadvantage of using a strake on the tail boom?

    <p>It exposes the tail boom to pressure from downwash</p> Signup and view all the answers

    What is the main purpose of the NOTAR's anti-torque system?

    <p>To reduce the need for a traditional tail rotor</p> Signup and view all the answers

    What factor significantly affects the thrust required by the NOTAR system at higher altitudes?

    <p>Increased helicopter weight</p> Signup and view all the answers

    How does the circulation-control tail boom contribute to the anti-torque force?

    <p>By distorting the rotor wake to create suction</p> Signup and view all the answers

    What is a key advantage of the Fenestron tail rotor design?

    <p>It effectively minimizes damage from external factors</p> Signup and view all the answers

    What happens to lift forces on either side of the tail boom under normal downwash conditions?

    <p>Lift forces cancel each other out</p> Signup and view all the answers

    What is one benefit of the NOTAR system in terms of control during sideways flight?

    <p>It reduces required pedal input significantly</p> Signup and view all the answers

    What design factor contributes to the airflow management of the NOTAR system?

    <p>A pressurized air jet is emitted from the tail boom</p> Signup and view all the answers

    Why is the tail rotor in conventional rotorcraft subjected to confused airflows?

    <p>Due to the rotor downwash and fuselage interference</p> Signup and view all the answers

    What is the main purpose of the collective control in a helicopter?

    <p>To change the pitch of the main rotor blades for altitude adjustment</p> Signup and view all the answers

    Which flight control system primarily directs the helicopter's yaw?

    <p>Anti-torque/Directional control</p> Signup and view all the answers

    What mechanism do boosted flight controls typically use to enhance pilot control?

    <p>Hydraulically powered servo jacks</p> Signup and view all the answers

    How does the cyclic control affect the rotor blade angle during flight?

    <p>It alters the angle as each blade completes its revolution</p> Signup and view all the answers

    What occurs if a helicopter's hydraulic system fails?

    <p>Unassisted control may still be possible</p> Signup and view all the answers

    What allows a pilot to control the altitude of the helicopter?

    <p>Collective control</p> Signup and view all the answers

    What is a significant advantage of using boosted flight controls in helicopters?

    <p>They help manage heavy flight loads more efficiently</p> Signup and view all the answers

    What component adjusts the direction of the swashplate in the cyclic control system?

    <p>Control column</p> Signup and view all the answers

    How does moving the cyclic control forward affect the helicopter?

    <p>It tilts the rotor disc forward, moving the helicopter forward.</p> Signup and view all the answers

    What is the function of changing the pitch of individual rotor blades prior to cyclic control displacement?

    <p>To account for gyroscopic precession.</p> Signup and view all the answers

    What effect does decreasing the pitch angle of rotor blades have?

    <p>It decreases drag and increases rotor RPM.</p> Signup and view all the answers

    What occurs when the collective pitch control is raised?

    <p>There is a simultaneous increase in pitch angle of all rotor blades.</p> Signup and view all the answers

    What is the role of the horizontal stabiliser in a helicopter?

    <p>To keep the tail down for level flight.</p> Signup and view all the answers

    How does the cyclic control affect the helicopter’s lift?

    <p>It tilts the rotor disc, altering the lift direction.</p> Signup and view all the answers

    What happens to rotor RPM when pitch increases?

    <p>Rotor RPM decreases as drag increases.</p> Signup and view all the answers

    What is a potential effect of the tail rotor being too high?

    <p>It causes an undesirable drag ratio.</p> Signup and view all the answers

    How does the collective lever interact with the throttle control on piston engine helicopters?

    <p>It requires an additional linkage for power adjustments.</p> Signup and view all the answers

    What design feature can some newer helicopters utilize for the horizontal stabiliser?

    <p>Electronic movement based on flight conditions.</p> Signup and view all the answers

    What is a significant result of increased pitch angle in rotor blades?

    <p>It requires more power to maintain rotor RPM.</p> Signup and view all the answers

    What effect does lateral movement of the cyclic control have on the helicopter?

    <p>It tilts the main rotor sideways, enabling lateral movement.</p> Signup and view all the answers

    Why is it important for the pitch of rotor blades to change simultaneously in the collective system?

    <p>To maintain coordinated flight without losing control.</p> Signup and view all the answers

    What is the primary function of the throttle during a high side governor failure?

    <p>To limit fuel flow to maintain RPM in the green arc</p> Signup and view all the answers

    Why can't the throttle be used to correct for a low side governor failure?

    <p>It can only operate within governed limits</p> Signup and view all the answers

    What mechanism prevents a pilot from flaming out the engine when throttling from 'flight' to 'idle'?

    <p>Idle release button</p> Signup and view all the answers

    What is the role of the correlating unit in a piston engine helicopter?

    <p>Increases power automatically with collective pull</p> Signup and view all the answers

    What ensures moisture protection in adjustable push-pull tubes?

    <p>Sealed rod ends with PROSEAL or METAL SET</p> Signup and view all the answers

    Which component is important for confirming the security and integrity of torque tubes?

    <p>Bearing wear and cracks inspection</p> Signup and view all the answers

    What is the primary function of bellcranks in a helicopter's flight control system?

    <p>To change the direction of movement within the system</p> Signup and view all the answers

    What operation does the RPM adjustment button facilitate?

    <p>Setting the RPM the governor will attempt to maintain</p> Signup and view all the answers

    What happens when collective is pulled up in a gas turbine helicopter?

    <p>Fuel flow is increased</p> Signup and view all the answers

    What is the purpose of the mixer box in relation to flight control systems?

    <p>Facilitates coordination of movements between systems</p> Signup and view all the answers

    How is engine cooling achieved using the starter in a helicopter?

    <p>By forcing cool air through the engine</p> Signup and view all the answers

    What characterizes the construction of the push-pull tubes used in cyclic and collective systems?

    <p>Composed of adjustable and non-adjustable fittings</p> Signup and view all the answers

    What is the effect of increasing all blade angles generally referred to as up collective?

    <p>May decrease rotor RPM due to increased drag</p> Signup and view all the answers

    What is the main purpose of using spherical bearings in the construction of bellcranks?

    <p>To allow smooth operation within the collective system</p> Signup and view all the answers

    What is the main function of the mixer box in helicopters?

    <p>To prevent collective input from affecting cyclic input</p> Signup and view all the answers

    What does the gradient unit provide to the pilot during flight?

    <p>Artificial feel of control movement</p> Signup and view all the answers

    How does the swashplate control the rotor thrust?

    <p>By transferring pilot cyclic and collective inputs to the blades</p> Signup and view all the answers

    Which factor does NOT affect the adjustment of the swashplate?

    <p>The number of rotor blades present</p> Signup and view all the answers

    During takeoff in U.S. made helicopters, which pedal must the pilot depress to add pitch to the tail rotor?

    <p>Left pedal</p> Signup and view all the answers

    What is the primary purpose of anti-torque control pedals?

    <p>To counteract main rotor torque</p> Signup and view all the answers

    What does trimming a helicopter typically require from the pilot?

    <p>Maintaining constant pressure on the cyclic</p> Signup and view all the answers

    What does the pitch horn's position on the rotor blade control?

    <p>The angle of the rotor blade</p> Signup and view all the answers

    What enhances the feel of movement for the pilot in helicopters with hydraulic controls?

    <p>A gradient system</p> Signup and view all the answers

    What must the pilot do to change the attitude of the helicopter when it is flying nose-heavy?

    <p>Apply constant back pressure on the cyclic</p> Signup and view all the answers

    What effect does lowering the collective lever have on the swashplate?

    <p>It moves the swashplate upward while maintaining its angle</p> Signup and view all the answers

    What is one primary function of the trim motor in a helicopter?

    <p>To adjust the cyclic control movement against spring pressure</p> Signup and view all the answers

    Which element allows for the upward or downward movement of the swashplate?

    <p>A combination of cyclic and collective inputs</p> Signup and view all the answers

    Which statement best describes the function of the anti-torque control during cruising flight?

    <p>The pedals are maintained in neutral position for stability</p> Signup and view all the answers

    What must rigging procedures for helicopters adhere to?

    <p>Manufacturer's instructions</p> Signup and view all the answers

    What is typically used to ensure the cyclic control is centered during rigging?

    <p>Cyclic centering device</p> Signup and view all the answers

    Which tool is commonly used to determine the angles in the rigging process?

    <p>Rigging protractor</p> Signup and view all the answers

    What is a critical requirement when making minor adjustments during the rigging process?

    <p>Maintenance manual guidelines</p> Signup and view all the answers

    What is the primary purpose of rigging jigs and pins in the rigging process?

    <p>To hold components in place</p> Signup and view all the answers

    Which item is essential for leveling the helicopter during rigging?

    <p>Jack</p> Signup and view all the answers

    When setting up the rotor during rigging, what is the first step?

    <p>Determining the neutral position</p> Signup and view all the answers

    What common equipment might be utilized to verify the required dimensions during rigging?

    <p>Measuring scale</p> Signup and view all the answers

    Which statement is true regarding the rigging process of the cyclic system?

    <p>It includes multiple check points.</p> Signup and view all the answers

    What should be observed when adjusting the flight controls after rigging?

    <p>Stable flight characteristics</p> Signup and view all the answers

    What is the primary function of the anti-torque rotor?

    <p>To counteract the torque produced by the main rotor</p> Signup and view all the answers

    What does translating tendency refer to in helicopter flight?

    <p>The tendency for the helicopter to drift to one side</p> Signup and view all the answers

    Which of the following systems eliminates the need for a tail rotor?

    <p>NOTAR</p> Signup and view all the answers

    How is directional control achieved in single main rotor helicopters?

    <p>By adjusting the tail rotor pitch using pedals</p> Signup and view all the answers

    What mechanical configuration does a conventional tail rotor depend upon?

    <p>A drive linked to the main transmission of the helicopter</p> Signup and view all the answers

    What effect does increasing the distance of the tail rotor from the mast have?

    <p>It increases the anti-torque moment produced by the tail rotor</p> Signup and view all the answers

    What is a characteristic of the Fenestron tail rotor?

    <p>It utilizes a shrouded design for improved efficiency</p> Signup and view all the answers

    What is the primary role of the pitch change assembly in the tail rotor?

    <p>To alter the pitch of the tail rotor blades</p> Signup and view all the answers

    What stabilizing effect does the tail rotor aim to provide when a helicopter is in hover?

    <p>It counters the yaw induced by the main rotor</p> Signup and view all the answers

    What are the two primary forces acting on a helicopter when it first lifts off the ground?

    <p>Torque couple and tail rotor thrust</p> Signup and view all the answers

    What technological feature is utilized in the NOTAR system to create directional control?

    <p>A fan and boundary layer effect</p> Signup and view all the answers

    What is a major challenge in designing helicopter rotor systems?

    <p>Managing the anti-torque problems effectively</p> Signup and view all the answers

    How does shifting the cyclic control to the left correct translating tendency?

    <p>It tilts the rotor disc to the left</p> Signup and view all the answers

    What mechanism is used in helicopter pedals to adjust tail rotor thrust?

    <p>A mechanical linkage</p> Signup and view all the answers

    What is the primary function of bias control in helicopters?

    <p>To adjust the tension in linkages</p> Signup and view all the answers

    Which system provides inputs to the hydraulic actuating arms to maintain the helicopter in a desired configuration?

    <p>Electronic servo systems</p> Signup and view all the answers

    What is the purpose of horizontal stabilisers in helicopters?

    <p>To stabilize the fuselage and dampen oscillations</p> Signup and view all the answers

    What is the function of synch elevators in helicopter design?

    <p>To pitch up and down with cyclic movements</p> Signup and view all the answers

    How is static balance typically achieved for helicopter blades?

    <p>By adding weight at specific locations</p> Signup and view all the answers

    What is one method for balancing tail rotor blades?

    <p>Employing universal balancing equipment</p> Signup and view all the answers

    What is the significance of rigging in helicopter control systems?

    <p>To adjust controls for correct movement tolerances</p> Signup and view all the answers

    Which of the following statements about the balancing procedure is false?

    <p>Static balance can be performed in an open room.</p> Signup and view all the answers

    What impact does rearward flight have on stabilisers?

    <p>They accentuate longitudinal oscillations.</p> Signup and view all the answers

    What is the method of dynamic balance commonly used for?

    <p>To eliminate vibration in drive shafts</p> Signup and view all the answers

    What role do computer-controlled inputs play in modern helicopters?

    <p>They provide automatic trim control.</p> Signup and view all the answers

    Which aspect is a primary consideration when designing vertical stabilisers for helicopters?

    <p>Airflow influence due to forward flight</p> Signup and view all the answers

    During the balancing procedure for tail rotors, why is adding unauthorized weight dangerous?

    <p>It disrupts the balance and safety of the rotor.</p> Signup and view all the answers

    What is a primary function of modern electronic stabilisation in helicopters?

    <p>Providing inputs for improved flight control</p> Signup and view all the answers

    What benefit does the Fenestron tail rotor provide compared to conventional tail rotors?

    <p>Improved safety for personnel and rotor protection</p> Signup and view all the answers

    What is the purpose of the canted tail rotor in helicopters like the UH-60 ‘Blackhawk’?

    <p>To generate additional lifting force in a hover</p> Signup and view all the answers

    In a tandem rotor helicopter, what dictates directional stability?

    <p>The thrust produced by each rotor</p> Signup and view all the answers

    What is a primary advantage of the intermeshing rotor design?

    <p>Enhanced stability and counter-torque effects</p> Signup and view all the answers

    How does the contra-rotating rotor system achieve directional control?

    <p>Through changes in rotor pitch on each disc</p> Signup and view all the answers

    What component is essential for the operation of boosted flight controls?

    <p>Hydraulic pump</p> Signup and view all the answers

    What does the accumulator in a boosted flight control system help to maintain?

    <p>Hydraulic pressure levels</p> Signup and view all the answers

    What is a primary benefit of the fly-by-wire control system in helicopters?

    <p>Reduces weight and maintenance complexity</p> Signup and view all the answers

    What type of rotor system does the Kaman K-Max utilize?

    <p>Intermeshing counter-rotating rotors</p> Signup and view all the answers

    What factor primarily influences the pressure settings of hydraulic systems in helicopters?

    <p>The specific design and operational requirements</p> Signup and view all the answers

    What function do the filters in the boosted flight control system serve?

    <p>Ensure hydraulic fluid cleanliness</p> Signup and view all the answers

    What is the primary purpose of the relief valve in a hydraulic system?

    <p>To set and maintain system pressure</p> Signup and view all the answers

    What kind of configuration is typical in a helicopter with dual rotors?

    <p>Rotors vertically separated with one at the front and rear</p> Signup and view all the answers

    What is the disadvantage of the conventional tail rotor design?

    <p>Higher risk of damage from foreign objects</p> Signup and view all the answers

    What is one key advantage of the NOTAR system over conventional tail rotors?

    <p>Elimination of tail rotor blade stall</p> Signup and view all the answers

    Which component of the MD NOTAR system helps to reduce vibration?

    <p>Direct jet thruster</p> Signup and view all the answers

    What is the primary purpose of the strake attached to the NOTAR system?

    <p>To spoil the airflow on one side</p> Signup and view all the answers

    How does the Coanda Effect contribute to the NOTAR system?

    <p>By reducing lift on one side of the tail boom</p> Signup and view all the answers

    What is a disadvantage associated with the strake in the NOTAR system?

    <p>Exposure to downward pressure from rotor downwash</p> Signup and view all the answers

    What role does the fan play in the NOTAR system?

    <p>It drives air into the tail boom</p> Signup and view all the answers

    In the NOTAR system, what causes the tail boom to move to the right?

    <p>Reduced lift from the left side due to the strake</p> Signup and view all the answers

    Which statement is true regarding the effects of wind on the strake?

    <p>It reduces benefits as forward speed or wind increases</p> Signup and view all the answers

    What does the circulation-control tail boom do in the NOTAR system?

    <p>Delays boundary layer separation</p> Signup and view all the answers

    Which feature of the Fenestron tail rotor contributes to its effectiveness?

    <p>Shrouded design that minimizes damage</p> Signup and view all the answers

    What primarily assists the NOTAR system in achieving directional stability?

    <p>Movable vertical stabilisers</p> Signup and view all the answers

    Which aspect limits the performance of a conventional tail rotor?

    <p>Confused airflow due to disturbances</p> Signup and view all the answers

    What factor does the NOTAR system significantly reduce, especially at higher weights and altitudes?

    <p>Rotor thrust requirements</p> Signup and view all the answers

    What happens to the downwash effect on the strake as sideways speed increases?

    <p>It decreases, thereby reducing its benefits</p> Signup and view all the answers

    Study Notes

    Flight Control Systems

    • Helicopters have three primary flight controls: cyclic, collective, and anti-torque/directional.
    • Cyclic controls pitch and roll axes.
    • Collective controls the pitch of main rotor blades, allowing for ascent and descent.
    • Anti-torque/Directional counteracts torque of the main rotor and provides directional control in flight about the yaw axis.

    Automatic Flight Control Systems (AFCS)

    • AFCS allows for control of the helicopter's altitude, attitude, and direction.
    • Altitude is controlled by varying the pitch of the rotor blades to produce more or less thrust.
    • Attitude is controlled by adjusting the pitch of the rotor blades to achieve a specific tilt or angle of the aircraft.
    • Direction is controlled by adjusting the pitch of the tail rotor to counteract the torque of the main rotor.

    Boosted Flight Controls

    • These systems enhance control efficiency by using hydraulic, electro-mechanical, or electro-hydro-mechanical servos and actuators.
    • They are designed to overcome flight loads at high speed and weight, ensuring safe and effective control.
    • Hydraulic servo jacks are commonly used to assist the pilot in controlling the pitch of the rotor blades.
    • Backup hydraulic systems provide redundancy in case of failure.

    Cyclic Control

    • The cyclic control column tilts the stationary plate of the swashplate, which then affects the rotating plate and alters the pitch of each blade throughout its rotation.
    • It's used to tilt the rotor disc, thereby changing thrust and lift, causing the helicopter to move in the direction of the tilted disc.
    • It can be moved forward, backward, left, and right to control the helicopter's movement.

    Collective Control

    • The collective pitch control (collective lever) simultaneously changes the pitch of all main rotor blades collectively, irrespective of their position.
    • It's located on the left side of the pilot's seat and controls helicopter climb or descent by altering the collective pitch of the blades.
    • This change in angle of attack affects the rotor RPM.
    • For helicopters with piston engines, a correlating unit adjusts throttle to maintain consistent rotor RPM.
    • For gas turbine helicopters, a second fuel governor or anticipators help maintain RPM.

    Systems Components: Cyclic & Collective

    • Push-pull Tubes: These tubes transfer motion from the pilot controls to the flight control system.
    • Torque Tubes: These tubes, installed perpendicular to the helicopter's centerline, transmit rotary motion into linear motion – for example, influencing the collective pitch control.
    • Bellcranks: Bellcranks redirect the motion of push-pull rods, altering travel and providing mechanical leverage within the system.
    • Mixer Box: This component ensures the collective input does not affect the cyclic input when the two controls are used together.
    • Gradient Units: These create artificial feel for the controls, which could otherwise feel numb when hydraulic boost is used.
    • Swashplate: This crucial component, consisting of a stationary and rotating plate, transmits the pilot's cyclic and collective inputs to the rotor blades.

    Anti-Torque Control

    • The anti-torque pedals, commonly called tail rotor pedals, control the tail rotor's pitch.
    • This mechanism counteracts the torque of the main rotor, preventing uncontrolled yaw (rotation) of the helicopter.
    • The control allows precise directional control throughout flight, including during takeoff, where maximum tail rotor pitch is needed.

    Anti-Torque Control

    • Helicopters use an anti-torque device (e.g., tail rotor) to counteract the torque produced by the main rotor.
    • The tail rotor produces thrust in the opposite direction of the main rotor rotation to prevent the helicopter from rotating in the opposite direction.
    • Torque can be countered by using two rotors turning in opposite directions, like in Tandem Rotor Helicopters (CH-47 Chinook) or Intermeshing Rotor Helicopters (Kaman K-Max).

    Translating Tendency (Tail Rotor Drift)

    • During takeoff, there's a tendency for the helicopter to drift to the right due to uneven forces from the main rotor torque and tail rotor thrust.
    • This tendency is corrected by moving the cyclic stick to the left, tilting the rotor disc slightly left, and stopping the drift.
    • Some designs automatically correct tail rotor drift by tilting the main rotor mast slightly left or using a bias in the cyclic control mechanism.

    Rolling Tendency

    • After correcting for translating tendency, a rolling tendency emerges due to the horizontal components of the rotor thrust and tail rotor thrust forming a couple.

    Tail Rotor Configuration

    • Various types of anti-torque tail rotor control systems exist:
      • Conventional tail rotor: Most common design, driven by the main transmission, and provides directional control through pedal input.
      • NOTAR (NO TAil Rotor): System eliminates the tail rotor, using a fan inside the tailboom to create airflow for anti-torque and directional control.
      • Fenestron (Fantail) tail rotor: Shrouded tail rotor offers protection, quieter operation, and potential for greater effectiveness.

    NOTAR System Components

    • NOTAR systems comprise:
      • Air intake: At the top rear of the fuselage, feeding the fan.
      • Fan: Driven by the main gearbox, generating low-pressure air.
      • Slots: Allow air to escape, energizing the boundary layer of the main rotor downwash.
      • Tail thruster cone: Directs high-speed air through a "direct jet thruster" for control.
      • Fixed baffle plates: Adjust airflow before exiting the thruster cone.
      • Movable vertical stabilizers: Play a role during forward flight.
      • Strake: On the opposite side of the slots, used to "spoil" the downwash for anti-torque.

    Strakes and Anti-Torque

    • Strakes, attached lengthwise to the tail boom, create a lift force by disrupting the airflow, reducing the required tail rotor thrust.
    • This effect, known as the Coanda Effect, is most prominent during hover but lessens with forward flight.
    • Strakes also improve directional stability, particularly during sideways flight.

    Fenestron Tail Rotor

    • Shrouded tail rotor offers protection and improved airflow compared to conventional tail rotors.
    • Minimizes accidental damage and produces comparable thrust with a smaller rotor.
    • The vertical stabiliser provides forward flight torque compensation.

    Canted Tail Rotor

    • Angles the tail rotor from the vertical, providing lifting force in a hover, as seen in the UH-6O "Blackhawk" helicopter.

    Dual Rotors

    • Utilize two rotors turning in opposite directions to counteract torque, offering alternatives to conventional tail rotors.
      • Tandem Rotor Helicopter: Rotors at front and rear of the fuselage provide directional stability based on individual thrust.
      • Intermeshing Rotor Design: Rotors mounted side-by-side on the fuselage.
      • Contra-rotating Rotors: Two main rotors above and below the fuselage, driven by coaxial shafts provide directional control by adjusting pitch on each rotor.

    Boosted Flight Controls

    • Provide enhanced control response through a hydraulic system.
    • System components include:
      • Hydraulic Pump: Driven by the transmission, providing power during autorotation.
      • Reservoir: Contains fluid, a screen for filtration, and a sight gauge for level monitoring.
      • Relief Valve: Sets system pressure, typically between 250 psi and 2000 psi.
      • Filters: Protect the hydraulic system, often with warning mechanisms for blockage.
      • Accumulators: Store pressurized fluid to provide extra power when needed.
      • Actuators: Move control surfaces, equipped with pilot and irreversible valves for precise operation.
      • Servo Actuators: Assist pilot control, prevent rotor feedback, and enhance responsiveness.

    Flight Control Fly-By-Wire

    • Electronically connects cockpit control surfaces to actuators, for greater precision and performance.
    • Eliminates mechanical linkages, reducing weight and maintenance.
    • Uses electrical signals and transducers to measure pilot commands and operate actuators.

    Trim Controls

    • Helicopters don't have trim tabs, but trim control is achieved through:
      • Bias Control: Adjusting tension in linkages to adjust control stick positions, minimizing pilot input.
      • Electronic Servo Systems: Computer-controlled inputs to actuators maintain desired aircraft configurations.

    Horizontal Stabilisers

    • Provide stability by preventing follow-through pitching movements, particularly during gust-induced blow-back.
    • Increase lift at the rear of the aircraft, helping to control pitch and maintain stability.

    Stabilisers

    • Stabilisers dampen dynamic oscillations by stabilising the fuselage and the disc.
    • They are important for longitudinal stability in forward flight.
    • They are detrimental to rearward flight, as they accentuate longitudinal oscillations.
    • Vertical stabilisers are fitted at odd angles to account for airflow from forward flight and rotor downwash.

    Synch Elevators

    • Synch elevators are stabilisers that pitch up and down with fore/aft cyclic movements.
    • They enhance stabiliser response at varying airspeeds.

    Helicopter Stability

    • It is difficult to provide satisfactory longitudinal stability even with the best designed stabilisers.
    • Modern helicopters use electronic stabilisation systems, such as gyro-controlled autopilots and computers, to provide inputs into the main control linkage system.

    Balancing

    • Drive shafts are normally dynamically balanced during manufacturing to reduce vibration.
    • Tail rotor blades require static balance, both span-wise and chordwise, and dynamic balance.

    Static Balance

    • Static balance can be accomplished using specific or universal balancing equipment.
    • The balancing procedure is similar for tail rotors, but the balancing point may vary.

    Blades Balance

    • Older blades have spanwise weight placed on blade tips and chordwise weights added to the blade.
    • Modern blades have weight added to the blade hub.
    • Blades are balanced in either a vertical or horizontal position.

    Balancing Equipment

    • Balancing equipment is often available from the manufacturer or as universal equipment.
    • Universal balancers operate using a disc attached to a cable and dampened in oil.
    • Static balancing must be done in a closed room for accuracy.

    Control Rigging

    • Maintenance for control rigging usually involves removal and replacement of components.
    • Control movements are critical and require adjustments to ensure correct pitch and cyclic travel.
    • Rigging procedures are often required after removal and replacement of components.
    • Early helicopters had complex rigging due to large tolerances in fuselage construction.

    Rigging Procedures

    • Rigging procedures must be in accordance with the manufacturer’s instructions.
    • Minor adjustments may be required after initial flight, but these must be made according to the maintenance manual and in small increments.

    Rigging Equipment

    • Special tools such as jigs, rigging pins, and holding fixtures are often required for rigging.
    • Other items, such as mast alignment, may need to be checked.
    • Equipment for rigging cyclic and collective varies with helicopter type.
    • Common equipment includes a measuring scale and a universal protractor.

    Cyclic Control Rigging

    • The cyclic control is placed in the neutral position, typically straight up.
    • Rods are adjusted to check points, such as bellcranks, servo units, and the swashplate.
    • The rotor may be held in position or checked with a protractor.
    • Extreme positions are set by stops located on bellcranks or the swashplate.

    Flight Control Systems

    • Helicopters have three basic flight controls: cyclic, collective, and anti-torque/directional.
    • The cyclic controls pitch and roll by tilting the rotor disc.
    • The collective controls the helicopter’s altitude by increasing or decreasing the pitch of all main rotor blades simultaneously.
    • The anti-torque/directional control counteracts the main rotor’s torque and provides directional control about the yaw axis.
    • Flight control systems allow both pilots and Automatic Flight Control Systems (AFCS) to control altitude, attitude, and direction.
    • Boosted flight controls are designed to overcome the flight loads encountered at high speeds and high all-up weight.
    • They utilize hydro-mechanical, electro-mechanical, and electro-hydro-mechanical servos and actuators to assist the pilot.

    Cyclic Control

    • The cyclic control column alters the plane of the stationary plate of the swashplate, changing the blade angle as the rotor spins.
    • The cyclic control is used to tilt the tip path plane of the main rotor, which influences the helicopter's direction.
    • Movement of the cyclic forward or aft tilts the disc and moves the helicopter in that direction.
    • Moving the cyclic from side to side causes a sideways movement of the helicopter.
    • Gyroscopic precession requires the pitch of each rotor blade to be changed 90 degrees prior to the movement of the cyclic stick.
    • Some helicopters have a horizontal stabilizer on the tail connected to the cyclic linkage.
    • This stabilizer, often called an elevator, helps maintain a level flight attitude and can be adjusted to control the tail's position for different flight phases.

    Collective Control

    • The collective pitch control lever adjusts the pitch angle of all main rotor blades simultaneously.
    • Raising the collective increases blade pitch, increasing lift and potentially reducing rotor RPM.
    • Lowering the collective decreases blade pitch, decreasing lift and potentially increasing rotor RPM.
    • To maintain constant rotor RPM, the throttle control or a governor adjusts engine power to compensate for changes in drag caused by collective pitch adjustments.
    • The collective lever is connected to the rotor system via push-pull tubes.
    • Rotor RPM compensation is achieved through correlating units or governors, which automatically adjust engine power or fuel flow.

    Swashplate

    • The swashplate consists of two “stars” (or orbits) that transfer pilot input to the rotor blades.
    • The stationary plate is connected to the pilot controls, and the rotating plate is connected to the rotor blades via pitch links.
    • Movements of the stationary plate, from both the cyclic and collective, are transferred to the blades through the rotating plate.

    Anti-Torque Control

    • The anti-torque pedals, also known as tail rotor pedals or rudder pedals, control the pitch of the tail rotor.
    • The tail rotor counteracts the main rotor's torque and provides directional control.
    • During takeoff, the tail rotor requires the highest positive pitch due to maximum main rotor power.
    • On U.S. made helicopters (counterclockwise rotating), depressing the left pedal increases tail rotor pitch.

    Anti-Torque

    • Helicopters use a tail rotor or other anti-torque mechanisms to counteract torque from the main rotor.
    • The main rotor generates torque that rotates the aircraft in the opposite direction of the rotor's spin.
    • The tail rotor, positioned to the right, produces thrust to the right, creating a moment (force over distance) to counter the main rotor torque.
    • Translating tendency (tail rotor drift) occurs because of uneven forces applied by the main rotor and tail rotor: two to the right and one to the left.

    Rolling Tendency

    • After the rotor disc tilts slightly left to correct translating tendency, a rolling tendency to the left is created.
    • This occurs because the horizontal component of total rotor thrust points left while tail rotor thrust points right.
    • These forces form a couple tending to roll the helicopter left.

    Tail Rotor Configuration

    • The tail rotor provides directional control for single-rotor helicopters.
    • Pedals change the pitch of the tail rotor, altering the helicopter's heading.

    Conventional Tail Rotor

    • Powered from the main transmission of the helicopter.
    • Must rotate at all times during flight, even if the engine is not operational.

    NOTAR System

    • Eliminates traditional tail rotors.
    • McDonnell Douglas developed the system.
    • Utilizes a fan inside the tailboom to generate high-volume, low-pressure air exiting through slots, creating a boundary layer flow of air.
    • Boundary layer alters airflow around the tailboom, producing thrust opposite the main rotor torque.
    • Direct jet thruster at the end of the tailboom provides directional yaw control.

    NOTAR Advantages

    • Safer operation compared to conventional tail rotors.
    • Eliminates tail rotor strikes and foreign object damage.
    • Improved control in crosswinds, reduced vibration.

    NOTAR Components

    • Air intake at the rear of the fuselage.
    • Fan driven by the main gearbox.
    • Two slots along the right-hand side of the tail boom.
    • Tail thruster cone.
    • Fixed baffle plates.
    • Movable vertical stabilizers.
    • Strake on the left-hand side of the tail boom.

    Strakes and Anti-Torque

    • The strake "spoils" the downward airflow on the left side of the tail boom, reducing lift and generating a force to the right.
    • This offsets the main rotor torque.
    • The strake utilizes the Coanda effect (airflow curving around a surface creates lift) to increase lift on the right side while reducing lift on the left side.
    • Benefits include reduced tail rotor blade pitch angles, less power required, and improved anti-torque at higher weights.

    Fenestron Tail Rotor

    • Shrouded tail rotor, providing protection from foreign object damage and blade injuries.
    • Eliminates lift asymmetry, making flapping unnecessary.
    • More effective compared to conventional tail rotors of a similar diameter.

    Canted Tail Rotor

    • Angled from the vertical, providing anti-torque reaction and some lifting force in a hover.
    • Example: UH-60 Blackhawk helicopter.

    Dual Rotors

    • Counteracts main rotor torque using two rotors turning in opposite directions.
    • Can be coaxial (mounted one above the other) or tandem (one at the front, one at the rear).

    Tandem Rotor Helicopter (CH-47 Chinook)

    • Uses two counter-rotating rotors located at the front and rear of the fuselage.
    • Directional stability depends on which rotor produces more thrust.

    Intermeshing Rotor Design (Kaman K-Max)

    • Two intermeshing counter-rotating rotors mounted next to each other on the fuselage.

    Contra-Rotating Rotors

    • Two main rotor systems mounted above and below each other on a coaxial mast, rotating in opposite directions.
    • Directional control achieved by changing pitch on one disc and decreasing pitch on the other.

    Boosted Flight Controls

    • Hydraulic system containing a pump, reservoir, relief valve, filters, accumulators, and actuators.

    Boosted Flight Controls Pumps

    • Driven by the transmission for hydraulic strength during autorotation.

    Boosted Flight Controls Reservoir

    • Contains a screen and sight gauge for fluid level inspection.

    Boosted Flight Controls Relief Valve

    • Controls system pressure, varying from 250 psi to 2000 psi.

    Boosted Flight Controls Filters

    • May have pop-out warning buttons to indicate blockage.

    Boosted Flight Controls Accumulators

    • Conventional piston type, not present on smaller systems.

    Boosted Flight Controls Actuators

    • Move pistons or cylinders, equipped with pilot and irreversible valves.

    Boosted Flight Controls Servo Actuators

    • Assist pilots with control movements and prevent rotor feedback.

    Flight Control Fly-By-Wire

    • Electronically links cockpit controls with actuators, allowing for precise maneuvering based on pilot input.
    • Reduces weight and maintenance costs, improves performance.

    Trim Controls

    • Helicopters do not have trim tabs.
    • Trimming is achieved through bias control or electronic servo systems.

    Bias Control

    • Adjust tension in linkages between pilot controls and blade control mechanisms to achieve a desired configuration.

    Electronic Servo Systems

    • Computer-based inputs to hydraulic actuators maintain desired configuration.

    Horizontal Stabilisers

    • Stabilize the fuselage, preventing follow-through pitching movements during flap-back occurrences.
    • Increase lift at the rear of the aircraft to counter nose pitch-up during forward flight.

    Stabilisers

    • Stabilisers help helicopters maintain stability and control
    • Stabilisers dampen dynamic oscillations by stabilising the fuselage and the disc
    • They're beneficial in forward flight but can cause issues in rearward flight
    • In rearward flight, the stabiliser intensifies longitudinal oscillations, increasing the risk of dangerous situations
    • Vertical stabilisers are angled based on airflow from forward flight and rotor downwash
    • Stabilisers are typically designed to function best at normal forward cruise speeds

    Synch Elevators

    • Synch elevators are a type of stabiliser that pitch up and down with fore/aft cyclic movements
    • They enhance stabiliser response across varying airspeeds

    Modern Stabilisation Systems

    • Modern helicopters use electronic stabilisation, such as gyro-controlled autopilots and computers, to provide inputs into the main control linkage system

    Tail Rotor Balancing

    • Tail rotor drive shafts are dynamically balanced during manufacturing to reduce vibration
    • Tail rotor blades are balanced against a master blade and require static and dynamic balancing
    • Static balance involves ensuring uniform weight distribution spanwise and chordwise
    • Modern blades often have weight added to the hub rather than the tips
    • Balancing equipment is usually available from the manufacturer or as universal options
    • Balancing procedures are similar for tail rotors and main rotors, but the balancing point may vary

    Tail Rotor Balancing Procedures

    • Blades are balanced in either a vertical or horizontal position using universal balancers similar to those used for main rotors
    • Balancing is done in a closed room to ensure accuracy due to sensitivity to air currents
    • Balancing involves adding weight to the blade until a perfect circle is visible between the balancer's disc and collar

    Control Rigging

    • Maintenance of control rigging typically involves removing and replacing components
    • Rigging involves adjusting components to ensure correct pitch on the collective and proper cyclic travel within tolerances
    • Initial rigging procedures can be complex due to design and manufacturing tolerances in older helicopters
    • Rigging must follow manufacturer instructions to avoid unsafe flight characteristics
    • Minor adjustments may be necessary after the initial flight, but must be done in accordance with the maintenance manual and in small increments

    Rigging Equipment

    • Rigging procedures require various equipment, including jigs, rigging pins, holding fixtures, and special tools
    • Depending on the helicopter, levelling jacks, measuring scales, universal protractors, and rigging jigs/pins are required
    • Jigs and pins hold bellcranks in place while adjusting rods

    Cyclic Control Rigging

    • The cyclic control is typically centred in a neutral position, then rods are adjusted to specific check points
    • The servo valve is set to neutral
    • The actuator is attached to the swashplate, set to a predetermined angle using a protractor
    • Control rods are then adjusted to the rotor, which might be held in place or checked for a neutral position
    • Extreme positions (stops) are set on the bellcranks or the swashplate.

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    Description

    Explore the fundamental flight control systems of helicopters, including cyclic, collective, and anti-torque controls. This quiz also covers Automatic Flight Control Systems (AFCS) and the enhanced capabilities provided by boosted flight controls. Test your knowledge on how these systems work together to manage altitude, attitude, and directional control.

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