11.9 Flight Controls Flashcards
What is the function of roll spoilers?
To extend on the wing with upward aileron deflection (down going wing) to give a more accurate turn on larger aircraft
How do ruddervator surfaces on V-tail aircraft provide pitch and yaw control?
- Both deflect up or down to control pitch
- One deflect up and one down to control yaw
What is the advantage and disadvantages of V-tail controls?
+Less weight as no vertical stab is required
- More surface area is required
- Cannot have full rudder and elevator extension at the same time
- Aircraft less stable
- Control surface adjustment more complicated due to combined inputs
How do elevons on delta wing aircraft control pitch and roll?
- Both surfaces move up or down simultaneously to control pitch
- One moves up and one down to control roll (aileron function)
What do secondary flight controls consist of?
- Lift Devices
- Drag Devices
- Trim systems
What 3 things can all flight control systems be divided into?
- Control Inputs
- Control transmissions
- Control surface outputs
What component is required to combine inputs from the rudder pedals and control column in a ruddervator (V-tail) system?
A mixer unit containing a gimbal
What does the flap lever control?
Flaps and slats
What are 2 the main components in a mechanical control run?
- Cables
- Rods
What 2 types of components do Hydraulic control systems use?
- Mechanical components
- Hydraulic components
What 3 types of components do electrical control transmissions use?
- Mechanical components
- Hydraulic components
- Electrical components
Through what 3 properties is a control cable identified?
- Diameter
- Number of strands
- Number of wires in each strand
Where are extra flexible control cables used?
In sections that require several changes of direction
What is the advantage and disadvantage of cables compared to rods?
+Less weight
-Cannot transmit push forces
What is the disadvantage of a mechanical control system with many connections?
There will be greater total play in the system from all the connectors so the transmission will be less accurate
What is an advantage of cables over rods when under excessive stress?
Cables will show evidence of failing before it fails completely (broken wires/strands etc) whereas a rod will fail suddenly
What can be used to remove old lubrication, grease and dirt from the surface of control cables?
A lint free cloth
What 3 things must cables be inspected for?
- Broken wires
- Worn areas
- Corrosion
What are the 3 main type of quadrants used to transmit push-pull rod forces to cables?
- Normal quadrants
- Single quadrants
- Tension regulators
What are single quadrants used for?
To transmit movement from a cable to several outputs simultaneously
What 3 things make up a tension regulator?
- 2 quadrant halves mounted on a common axle
- A spring loaded cross head mounted on a guide
- Pull rods
How does a cable tension regulator compensate for increased tension in a warm aircraft?
The quadrant halves rotate the pull rods, moves the cross head and compresses the springs
How does the cable tension regulator compensate for reduced cable tension in cold aircraft?
The springs press against the cross head and this force is transferred via the pull rods and the quadrant halves to the cables. The cable tension is restored to normal.
What are the six cable wear patterns that can be found on pulleys?
- Cable tension too high
- Cable misaligned
- Pulley misaligned
- Cable too small for pulley
- Blocked pulley
- Normal wear
What is used to maintain an airtight seal around cables that pass through a pressure bulkhead?
Pressure seals
What is the purpose of fairleads?
To guide and support the cable along its routing, allowing a maximum direction change of 3 degrees
What are the 3 key components of an adjustable rod?
- Inner and outer lock washers
- A lock nut
- An inspection hole to check for minimum screw penetration
What are the 3 main components of a chain installation?
- The chain
- The wheel
- The protection guards
What is the purpose of torque shafts?
To transmit torque for linear movements
What is the purpose of torque tubes?
To transmit torque for rotary movements
What must the couplings between torque tubes in a torque tube system be capable of and what do they allow?
- Compensating for axial movement and change of alignment
- Allow torque tube rotation during wing bending
What are the 4 types of gearbox that can be found in a torque tube system?
- Angle gearbox
- Offset gearbox
- Rotary actuators
- Differential gearing
What does an Angle gearbox (aka bevel gearbox) do?
Facilitates change in direction when power is transmitted from one torque tube to another
What does an Offset gearbox do?
Moves the drive path forward and back
What is a rotary actuator used for?
To transmit torque tube rotation to an output lever (changes a low torque, high speed input into a high torque, low speed output)
What does a differential gear box do?
Connects 1 output shaft with 2 independently operating motors
What are the 3 main components of a screw jack transmission?
- A transmission gearbox
- The screwjack
- The ball nut
What are ball screwjack transmissions used for?
High torque transmissions with minimal friction such as in flap or stabiliser operation
What 2 safety measures are incorporated into a ball screwjack transmission?
- Stops to restrict total ball screw travel
- A safety rod to secure the transmission if the screwjack breaks
What is a disadvantage of a screwjack transmission and how can it be counteracted?
- Strong aerodynamic loads can drive the screwjack backwards
- A No-Back brake can be used to prevent flaps being pushed back by airflow
What are the 3 main components of a No-back brake?
- A ratchet wheel
- Pawl
- A brake disc
What happens to the No-back brake during flap retraction?
The retraction force overrides the brake disc friction, allow the surface to move in the airflow direction
Excessive torque can damage the torque tube system and aircraft structure, what is used to prevent this?
A torque limiter
What are the 3 main components of a torque limiter?
- A friction brake
- A ball and ramp device with input and output members
- Springs which are preloaded to approx 120% of the maximum operating torque
An over-torque indicator is included in the torque limiter, what is its function?
It extends when an over torque has occurred and must be manually reset to ensure an over torque does not go unnoticed
Override devices prevent the entire flight control system jamming when 1 component is jammed, what are the 3 main types?
- Force detents
- Shear rivets
- Force limiting struts