Control Flashcards
What is a trim tab?
Device which can be used by the pilot to reduce and neutralise forces acting on the flight controls
What are ground adjustable trim tabs?
Set by maintenance on the ground and cannot be adjusted in flight
What is a trimmable horizontal stabiliser?
The incidence of the entire horizontal stabiliser is adjusted
What is aerodynamic balancing?
It is used to keep control forces to a manageable level
What is a control horn balance?
A section of the control surface is placed in front of the hinge line
This provides a small force that tries to increase control deflection, reducing the input needed by the pilot
What are aileron spades?
A spade sticks out when the surface is deflected, which provides a small force that tries to increase deflection, reducing the input needed by the pilot
What is an issue with the CoG of a control surface being behind the hinge line?
Vibrations can cause the control surface to deflect
What is flutter?
Deflections combine with vibrations which overcomes the control surfaces dampening ability. This can lead to structural failure
What does mass balancing prevent?
Control surface flutter
What is mass balancing?
A mass balance is placed on the control surface to move the CoG as close to the hinge line as possible
What is a balance tab?
Designed to reduce the force required to deflect a control surface
How does a balance tab work?
It is linked to the control surface and moves in the opposite direction to the surface
What is an anti-balance tab?
Works in the opposite sense to a balance tab so moves in the direction of the control surface
What is an anti-balance tab used for?
Used to increase control force required and stop over-controlling
What are servo (or control) tabs?
Instead of controlling the control surface, the pilot controls the servo tab
How does a servo tab work?
Deflection of the servo tab provides an aerodynamic force which drives the control surface in the opposite direction to the correct position
What is a stabilator?
An “all flying tail”
The entire horizontal stabiliser is used for pitch control
What is a stabilator usually fitted with?
An anti-balance tab
What is adverse yaw?
The tendency for the aircraft to yaw in the opposite direction of the roll
What is adverse yaw caused by?
Increase in induced drag on the down-going aileron
What design features reduce the adverse yaw effect?
Differential ailerons
Frise type ailerons
Coupling the rudder
What are differential ailerons?
The down-going aileron travels less distance
Why do differential ailerons help?
Reduces the induced drag produced by down-going aileron, reducing adverse yaw
What are frise type ailerons?
Part of the up-going aileron is deflected into the airflow
Why do frise type ailerons help?
Creates extra drag on the up-going aileron which balances the drag on the down going aileron
What is rudder coupling?
As the ailerons are deflected the rudder moves to counter the adverse yaw
What are spoilers?
Small panels on the upper surface of a wing which can deflect into the airflow
What do spoilers do?
Decrease lift and increase drag
What happens when spoilers are used symmetrical?
Speed brakes
What happens when spoilers are used asymmetrically?
Aids roll control
