Helicopter Flight Control Systems Quiz

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Questions and Answers

What common components do all helicopters share in their flight control units?

Autopilot system

Emergency landing gear

Cyclic pitch control (correct)

Collective pitch control (correct)

Why is rigging considered a critical task in helicopter maintenance?

It increases fuel efficiency of the aircraft.

It helps in the cosmetic repairs of the helicopter.

It guarantees the aircraft's maximum payload capacity.

It establishes the relationship between main and tail rotor controls. (correct)

What is the first major step in the rigging process for flight control systems?

Adjusting the rotor blades for optimal performance.

Checking the hydraulic fluid levels.

Calibrating the navigation instruments.

Placing the control system in a specific position. (correct)

What tools might be used to check the angular difference between the control surface and a fixed surface?

Precision bubble protractor Signup and view all the answers

What is critical to ensure during the rigging process?

Exact adjustments, clearances, and tolerances must be maintained. Signup and view all the answers

How do the operational characteristics of flight control systems vary among different helicopter models?

Though the components are similar, each model uses unique operational mechanisms. Signup and view all the answers

What is necessary for the successful displacement of linkages during rigging?

Proper immobilization of the control systems. Signup and view all the answers

What is primarily emphasized during the rigging of the helicopter's flight control systems?

Utilization of standardized procedures outlined in manufacture manuals. Signup and view all the answers

Which parts are included in the main components of a helicopter?

Cabin, landing gear, tail boom, powerplant, transmission, main rotor, and tail rotor Signup and view all the answers

What do the vertical, lateral, and longitudinal axes in a helicopter indicate?

They are axes around which the helicopter moves and stabilizes its flight. Signup and view all the answers

Which statement accurately describes the rotorcraft classification?

Rotorcraft are also known as rotary wing aircraft due to their rotating wings. Signup and view all the answers

How do bolts, nuts, and rod ends need to be managed in helicopter maintenance?

They must be properly secured and safetied as specified. Signup and view all the answers

What does the helicopter's center of gravity indicate concerning its axes?

All axes will intersect at the helicopter’s center of gravity. Signup and view all the answers

In terms of propulsion, how can a rotating wing of a rotorcraft be described?

It can function as both a lift and a thrust producing device. Signup and view all the answers

What is the significance of the vertical axis in a helicopter?

It allows the helicopter to yaw, providing directional control. Signup and view all the answers

Which best describes how a helicopter rotates during flight?

It rotates around the longitudinal axis, which affects forward and backward movement. Signup and view all the answers

What is the purpose of setting the maximum range of travel of the various components in a rotary-wing aircraft?

To limit the physical movement of the control system Signup and view all the answers

Which of the following is NOT typically included in a functional check of the flight control system?

Checking the fuel efficiency of the engines Signup and view all the answers

What is assessed during the check of the main rotor blades' pitch angles?

The maximum and minimum pitch angles within specified limits Signup and view all the answers

In multirotor aircraft, what is crucial in relation to the rotor blades?

The synchronization of the rotor blades' movement Signup and view all the answers

What must be ensured when tabs are provided on main rotor blades?

They are correctly set Signup and view all the answers

What aspect of dual controls must be confirmed during the rigging process?

They function correctly and in synchronization Signup and view all the answers

After the completion of rigging, what should be checked thoroughly?

All attaching, securing, and pivot points Signup and view all the answers

Which part of the helicopter controls the collective pitch?

The main rotor Signup and view all the answers

What happens when the collective pitch control lever is raised?

The blade angle of all rotor blades increases uniformly. Signup and view all the answers

What is the function of the throttle located on the collective pitch control?

To increase engine power as the lever is raised. Signup and view all the answers

Which statement is true regarding the cyclic pitch control lever?

It controls the pitch change rods to change the rotor blade pitch. Signup and view all the answers

What occurs when the cyclic pitch lever is pushed forward?

The rotor blades create more lift in the back and less in the front. Signup and view all the answers

What is the effect of adjustable friction in the collective pitch lever?

It helps reduce pilot fatigue by requiring no upward pressure during flight. Signup and view all the answers

What causes the helicopter to move in the forward direction when the cyclic pitch lever is adjusted?

Increased lift in the back rotor blades. Signup and view all the answers

How do the rotor blades respond during the front half of their rotation when the cyclic pitch lever is pushed forward?

They create less lift. Signup and view all the answers

Which control mechanism is used to adjust the pitch of the rotor blades?

Cyclic pitch lever. Signup and view all the answers

What is required for a helicopter to achieve a hover?

The lift produced by the main rotor blades must equal the weight of the aircraft. Signup and view all the answers

How does Ground Effect influence a helicopter's ability to hover?

It can improve the lift efficiency when close to the ground. Signup and view all the answers

What is Dissymmetry of Lift in the context of helicopter flight?

An imbalance of lift due to different airspeeds experienced by rotor blades in forward flight. Signup and view all the answers

What typically happens when a helicopter attempts to transition from a hover to forward flight?

The helicopter experiences a potential rollover if not correctly managed. Signup and view all the answers

What characterizes the airflow experienced by rotor blades while in a hover?

All rotor blades experience equal velocity of airflow. Signup and view all the answers

How do rotor blade movements change as the helicopter begins to move forward?

The right side blades experience increased lift while the left side experiences decreased lift. Signup and view all the answers

What primary factor affects a helicopter's ability to hover at different altitudes?

Density altitude of the air. Signup and view all the answers

What happens to the airflow over the rotor blades when a helicopter is in forward motion?

Airflow speeds up for the blades moving towards the relative wind. Signup and view all the answers

What happens to the rotor blades if the collective is not dropped in time during autorotation?

The rotor blades will stall to an unrecoverable point. Signup and view all the answers

What is the primary benefit of lowering the blade angle with the collective pitch during autorotation?

To maintain rotor blade rotation. Signup and view all the answers

As the helicopter approaches landing after autorotation, what is the next step after flaring the helicopter?

Level the helicopter and pull full collective. Signup and view all the answers

During autorotation, what is the ideal altitude to start flaring back and reducing forward speed?

200 feet off the ground. Signup and view all the answers

What energy transition occurs as a helicopter loses altitude during autorotation?

Potential energy is transformed into kinetic energy. Signup and view all the answers

What should a pilot do immediately after experiencing a loss of power to maintain control?

Drop the collective pitch immediately. Signup and view all the answers

What role does air play in keeping the rotor blades spinning during autorotation?

It is pushed upward through the rotor disc as the helicopter descends. Signup and view all the answers

How much time does a pilot typically have to react by dropping the collective after a loss of power?

About 2 seconds. Signup and view all the answers

Study Notes

Rotary Wing Aerodynamics

Helicopters' flight control units are nearly identical across models.
All helicopters use collective pitch control, throttle grip, cyclic pitch control, and directional control pedals.
The operation of these control systems varies among helicopter models.

Rotary-Wing Aircraft Assembly and Rigging

Rigging coordinates flight controls with the main and tail rotors.
Rigging demands precision and meticulous attention to detail.
Adherence to manufacturer's manuals and service instructions is critical.
Precise adjustments, clearances, and tolerances are essential.

Rotary-Wing Aircraft Control System Steps

Step one: Position the control system with pins, clamps, or jigs, and adjust linkages for the immobile component.
Step two: Set control surfaces using a rigging jig, bubble protractor, or spirit level for correct angular differences from a fixed surface.
Step three: Set the maximum range of travel for components to limit control system movement.
Final step: Perform a functional check of the flight control system after static rigging.

Nature of Functional Check

The specifics of the functional check vary depending on the helicopter and control system.
Checks involve ensuring main and tail rotor blade movements correctly correspond with pilot controls.
The system ensures proper coordination of interconnected controls (throttle and collective pitch), as required for the type of helicopter.

Rotary-Wing Aircraft Assembly and Rigging - Additional Points

The range of movement and neutral position of pilot controls must be accurate.
Main rotor blade pitch angles must be within specified limits.
Main rotor blade tracking must be correct.
Rotor blade settings are synchronized in multirotor aircraft.
Correctly set main rotor blades (tabs) in aircraft utilizing these.
Accurate neutral, maximum, and minimum pitch angles for the tail rotor blades, as well as coning angles.
Dual controls, if present, must operate synchronously.
All attaching, securing, and pivot points must be thoroughly checked and secured correctly upon completion of rigging, complying with manufacturer's instructions.

Helicopter Structures and Airfoils

Key components of a helicopter include the cabin, landing gear, tail boom, powerplant, transmission, main rotor, and tail rotor.

Helicopter Axes of Flight

Helicopters, like airplanes, possess vertical, lateral, and longitudinal axes, all passing through the center of gravity.
Helicopters experience yaw around the vertical axis, pitch around the lateral axis, and rotate about the longitudinal axis.
These axes intersect at the helicopter's center of gravity.
The vertical axis usually passes near the center of the main rotor, given the center of gravity placement concern.

Control around the Vertical Axis

Anti-torque rotor (tail rotor) or fan airflow manages vertical axis control in single main rotor helicopters.
Pilots use anti-torque pedals on the cockpit floor to control yaw, similarly to rudder pedals on airplanes.
Correct anti-torque pedal input aligns the helicopter's nose in the desired direction.
Pilots push on the correct anti-torque pedal to counteract the main rotor's counterclockwise spin (when viewed from above), as required for a clockwise turn or rotational counteraction.
Vertical stabilizers on some helicopters help counteract main rotor torque in forward flight.

Control Around the Longitudinal and Lateral Axes

Collective pitch controls the rotor blades' angles and lift.
Increased collective pitch on the lever increases engine throttle power.
Cyclic pitch adjustments cause lift variations over different portions of the rotor disk, directing movement within the lateral and longitudinal axes.
The collective pitch lever may have built-in adjustable friction.
The cyclic pitch lever facilitates forward, backward, sideways movement, and side-to-side bank changes.
Forward movement results from increased back lift from the rotor.
Lateral movement results from lift variation between the left and right sides of the rotor.

Hovering

Hovering is the stable, non-moving (altitude-wise only) flight condition maintained by the helicopter.
Maintaining the same altitude requires a lift produced by the main rotor equal to the aircraft weight.
The engine supplies the power needed to drive the main rotor and any anti-torque features for equilibrium.
Hovering operation stability is impacted by various factors, including ground proximity, air density, and load.

Forward Flight

Achieving forward movement from hovering requires mastering changes in rotor blade airflow velocity with relative wind.
Understanding how rotor blade positions (advancing/retreating) affect lift (directional) changes during forward movement is crucial.
Rotor blade flapping is necessary for effective control during forward movement despite variations in airflow over advancing and retreating blades..

Blade Flapping Flight

Rotor blade flapping adjustments respond to varying lift conditions for forward flight, maintaining equilibrium.
Semi-rigid and fully articulated rotor systems have flapping hinges for automatic blade adjustments.
Rigid rotor systems rely on sufficient blade flexibility for lift adjustments.

Problems of Blade Flapping Flight

Increased forward speed can result in sonic velocity, which could cause the blade to stall during forward flight, resulting in the aircraft losing control.
A shock wave forms and air separates from the rotor blade during high forward speed, leading to an unstable high-speed stall.
The blade tip frequently stalls first, and this progresses towards the blade root.

Autorotation

Autorotation occurs when the main rotor blades are driven by the force of relative wind in the event of an engine failure in helicopters.
The helicopter needs to maintain forward speed to create lift while decreasing altitude.
The collective pitch control lowers the blade angle.
A properly executed autorotation landing has a smooth transition to a normal landing.

Autogyro

A free-spinning horizontal rotor that turns due to airflow passing through it is an autogyro.
Forward motion produces the airflow needed to spin the rotor for use in an autogyro aircraft.

Single Rotor Helicopter

A single horizontal main rotor provides lift and directional control, with a secondary tail rotor compensating for rotational forces (torque).

Dual Rotor Helicopter

Two counter-rotating horizontal rotors produce both lift and directional control.
Counter-rotating rotors eliminate the need for a separate tail rotor for torque control.

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Description

Test your knowledge on the common components of helicopter flight control systems, the rigging process, and maintenance tasks. This quiz covers essentials such as operational characteristics, tools used in rigging, and critical procedures for ensuring safety and efficiency. Perfect for anyone studying aviation maintenance or helicopter operations.