Podcast
Questions and Answers
What percentage of a rotor blade's span is typically occupied by the trim tab?
What percentage of a rotor blade's span is typically occupied by the trim tab?
Which of the following is true regarding the effect of an irreversible flight control system on hydraulic systems?
Which of the following is true regarding the effect of an irreversible flight control system on hydraulic systems?
A rotor blade with a uniform planform requires what to generate equal lift across the span?
A rotor blade with a uniform planform requires what to generate equal lift across the span?
Which planform is favored by manufacturers for production, and why?
Which planform is favored by manufacturers for production, and why?
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When would a special post-flight inspection be required for a rotor blade?
When would a special post-flight inspection be required for a rotor blade?
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Which of the following correctly describes a droop compensator?
Which of the following correctly describes a droop compensator?
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What is the primary function of a gradient spring within a force trim system?
What is the primary function of a gradient spring within a force trim system?
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Regarding rigging procedures on a hydraulically assisted helicopter, what is the crucial step to ensure prior to starting the rigging?
Regarding rigging procedures on a hydraulically assisted helicopter, what is the crucial step to ensure prior to starting the rigging?
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What is the purpose of the inverted airfoil design of a fixed elevator on a helicopter?
What is the purpose of the inverted airfoil design of a fixed elevator on a helicopter?
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In a bifilar vibration absorber, what component is responsible for vibration cancellation?
In a bifilar vibration absorber, what component is responsible for vibration cancellation?
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During rotor blade tracking adjustments, adding weight to the aft tracking weight will cause the blade to:
During rotor blade tracking adjustments, adding weight to the aft tracking weight will cause the blade to:
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What is the location of the chordwise mass balance weight on a rotor blade?
What is the location of the chordwise mass balance weight on a rotor blade?
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Which of the following is NOT an advantage of using a servo flap on a rotor blade?
Which of the following is NOT an advantage of using a servo flap on a rotor blade?
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Study Notes
Helicopter Components and Operation
- Droop Compensator: More complex than a correlator; a mechanical linkage between the collective and throttle.
- Vibration Dampeners: Two types: bifilar (two 4 arm disks) and a hub vibration absorber (weighted drum supported by three springs) used in force trim systems.
- Force Trim System: Returns cyclics to their previous position using gradient springs. Flight control systems may have 4 gradient actuators (2 for cyclic, 1 for collective, 1 for anti-torque).
- Servo Fap: Mounted on the trailing edge, covers 75% of the rotor blade span to take advantage of aerodynamic airflow.
- Servo Flap Advantages: Eliminates hydraulic systems, provides adjustable flight tracking, offers infinite lifespan, reduced vibration, and enhanced autorotation capabilities (reduced force required for pitch changes).
- Hydraulic Systems (Rigging): When rigging hydraulic assisted helicopters, turn off the hydraulics, bleed down residual pressure, and rig collective first, then cyclic, then anti-torque - important to ensure the throttle is correctly rigged before connecting correlator to collective.
- Elevator: Fixed elevators make for inverted airfoil designs and downwards lift direction. Moveable elevators keep a more level flight for better comfort.
- Moveable Weights: Used for vibration dampening in a bifilar system.
- Popout Float Aircrafts: Cannot take off on water; must complete ground, hover and then full flight/autorotation tests after rigging. Excess lift/torque can damage drivetrain components.
- Overspeed: A concern. Centrifugal forces on a helicopter are increased; resulting in uncontrolled amounts of force & potential damage. Ensure appropriate chordwise mass balance weights are positioned between 35-55% of the span.
- Spanwise Placement: Manufacturer and specialized repair shops can adjust the placement of span wise weights on the tip of the rotor blade.
- Tracking Weights: Located before and after the spanline on the rotorblade; forward weights lead to lower flight, after weights lead to higher flight in the plane of rotation.
- Trim Tabs: 75% blade span; bending the trim tab up will move the blade higher in the plane of rotation and bedding it lower will make it fly lower within the same plane.
- Irreversible Systems: Prevent force feedback from controls and hydraulic failure (lock hydraulic fluid in actuator), enabling manual pilot control during failure events.
- Aerodynamic Characteristics: Better aerodynamic characteristics for pitching can be achieved via asymmetrical designs (e.g., sweeping trailing edge by 3 degrees).
- Rotor Blade Materials & Design: Various materials like metal, composites, and wood are used. Some rotors use double plates at roots/tips to increase structural strength without adding weight.
- Tapered vs. Uniform Rotor Blades: Tapered designs offer even lift distribution across a whole span, while maintaining structural integrity.
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Description
This quiz explores key components and operational systems of helicopters, including droop compensators, vibration dampeners, and force trim systems. Test your knowledge on the mechanics and advantages of servo flaps and hydraulic systems in helicopter rigging. Ideal for aerospace engineering students or enthusiasts.
