23 Questions
How is aerodynamic balancing of flight controls achieved?
By providing a portion of the control surface ahead of the hinge point
What is the primary purpose of aerodynamic balance?
To make the flying controls easier to move
What is a horn balance?
A projection of the outer edge of the control surface forward of the hinge line
How is a control surface mass balanced?
By the attachment of weights acting forward of the hinge line
What is the purpose of anti-balance tabs?
To give more feel to the control column
Which motion of the aircraft does the elevator control?
Pitch
What is the purpose of mass balancing on an elevator?
To balance the mass of the elevator
Why are the outboard ailerons on some large aircraft isolated at high speeds?
To isolate the ailerons at high speeds
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
What is the purpose of a flying control mass balance weight?
To move the control surface center of gravity close to the hinge line
What is attached to the rear of the vertical stabilizer?
Rudder
What is the method employed to mass balance control surfaces?
Attach weights forward of the hinge line
What can cause control surface flutter?
Excessive play in trim tab attachments
Why is a 'frise' aileron incorporated?
To equalize aileron drag in a turn
How can aerodynamic balance of a control surface be achieved?
By a horn at the extremity of the surface forward of the hinge line
What is the purpose of providing a control surface with aerodynamic balancing?
To assist the pilot in moving the control
What is the purpose of the extension to the rudder (shaded portion)?
To provide aerodynamic assistance for the pilot when moving the rudder
What is the purpose of horn balance and inset hinge balance installed on control surface assembly?
Serves as a 'servo' system of balance
In what direction does the fin help to provide stability?
Directional stability about the normal axis
Which control surfaces are considered primary?
Elevators, ailerons, rudder
What effect does an aerodynamic balance have?
Reduces aerodynamic loading
How can flutter be reduced in an aircraft?
Applying mass balancing techniques
What is the main function of roll spoilers on an aircraft?
Reduce lift and induce roll motion
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
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.
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