Airframe Structures: Mass Balance and Control Surface Quiz

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Questions and Answers

How is aerodynamic balancing of flight controls achieved?

By placing a weight in the leading edge of the control surface

By providing a portion of the control surface ahead of the hinge point (correct)

By placing a weight ahead of the hinge point

By attaching a balance tab to the control surface

What is the primary purpose of aerodynamic balance?

To increase the aircraft's maneuverability

To reduce the control load to zero

To prevent flutter of the flying controls

To make the flying controls easier to move (correct)

What is a horn balance?

A rod projecting upward from the main control surface to which the control cables are attached

A projection of the outer edge of the control surface forward of the hinge line (correct)

A device used to measure the balance of the control surface

A rod projecting forward from the control surface with a weight on the end

How is a control surface mass balanced?

By the attachment of weights acting forward of the hinge line Signup and view all the answers

What is the purpose of anti-balance tabs?

To give more feel to the control column Signup and view all the answers

Which motion of the aircraft does the elevator control?

Pitch Signup and view all the answers

What is the purpose of mass balancing on an elevator?

To balance the mass of the elevator Signup and view all the answers

Why are the outboard ailerons on some large aircraft isolated at high speeds?

To isolate the ailerons at high speeds Signup and view all the answers

What is the effect of excessive aerodynamic balance on a control surface?

It moves the control surface center of pressure forwards, resulting in an unstable overbalance Signup and view all the answers

What is the purpose of a flying control mass balance weight?

To move the control surface center of gravity close to the hinge line Signup and view all the answers

What is attached to the rear of the vertical stabilizer?

Rudder Signup and view all the answers

What is the method employed to mass balance control surfaces?

Attach weights forward of the hinge line Signup and view all the answers

What can cause control surface flutter?

Excessive play in trim tab attachments Signup and view all the answers

Why is a 'frise' aileron incorporated?

To equalize aileron drag in a turn Signup and view all the answers

How can aerodynamic balance of a control surface be achieved?

By a horn at the extremity of the surface forward of the hinge line Signup and view all the answers

What is the purpose of providing a control surface with aerodynamic balancing?

To assist the pilot in moving the control Signup and view all the answers

What is the purpose of the extension to the rudder (shaded portion)?

To provide aerodynamic assistance for the pilot when moving the rudder Signup and view all the answers

What is the purpose of horn balance and inset hinge balance installed on control surface assembly?

Serves as a 'servo' system of balance Signup and view all the answers

In what direction does the fin help to provide stability?

Directional stability about the normal axis Signup and view all the answers

Which control surfaces are considered primary?

Elevators, ailerons, rudder Signup and view all the answers

What effect does an aerodynamic balance have?

Reduces aerodynamic loading Signup and view all the answers

How can flutter be reduced in an aircraft?

Applying mass balancing techniques Signup and view all the answers

What is the main function of roll spoilers on an aircraft?

Reduce lift and induce roll motion Signup and view all the answers

Study Notes

Flight Control Surfaces

Control surfaces are the ailerons, elevators, and rudder that control the aircraft's movement
These surfaces use aerodynamic balance to reduce the force required to move them

Aerodynamic Balance

Aerodynamic balance reduces the force required to move control surfaces
Achieved by:
- Horn balance: a projection of the outer edge of the control surface forward of the hinge line
- Inset hinge balance: a recessed area in the control surface near the hinge line
- Mass balancing: attaching weights ahead of the hinge line
Effects of aerodynamic balance:
- Reduces control column load
- Makes flying controls easier to move
- Does not affect aircraft stability

Control Surface Types

Primary control surfaces:
- Elevators: control pitch
- Ailerons: control roll
- Rudder: control yaw
Other control surfaces:
- Tabs: small, adjustable surfaces on control surfaces
- Spoilers: devices that reduce lift
- Flaps: devices that increase lift during takeoff and landing

Stability and Control

Directional stability: the aircraft's tendency to maintain direction
Longitudinal stability: the aircraft's tendency to maintain pitch
Lateral stability: the aircraft's tendency to maintain roll
Control surfaces maintain stability by:
- Providing opposition to unwanted movements
- Assisting the pilot in moving controls

Mass Balancing

Mass balancing:
- Attaches weights ahead of the hinge line
- Moves the control surface's center of gravity (C of G) closer to the hinge line
- Reduces the force required to move controls
Methods of mass balancing:
- Attaching weights forward of the hinge line
- Using bias strips on the trailing edge of the surface

Flutter

Flutter: rapid, oscillating movement of control surfaces
Causes of flutter:
- Excessive play in trim tab attachments
- High static friction in trim tab control tabs
- Incorrect angular movement of trim tabs
Methods to reduce flutter:
- Mass balancing
- Aerodynamic balancing

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Description

Test your knowledge on construction and functions of aeroplane flight control surfaces such as horn balance and inset hinge balance. Learn about balance systems and their effects on control surface assemblies.