40 Questions
What is the primary purpose of aircraft tyres?
To absorb shocks and roughness of landings and take-offs
What should be checked on a new component before it is fitted to an aircraft?
The serviceable label and the maintenance publication
Why should fluid be discarded after being bled or drained from the system?
Because it is contaminated and unusable
What precaution should be taken when handling fluids?
Prevent spillage to avoid damage to aircraft components
Why is it essential to release air pressure slowly?
To ensure safe operation in confined spaces
What should be inspected before installing a new component?
The component's cleanliness
What should be isolated prior to plug removal and installation?
The electrical systems
What are the two major assemblies that make up a wheel assembly?
Hub and tyre
What is the primary purpose of multiple disc brakes in large aircraft?
To provide increased friction surfaces for braking purposes
How do the operating cylinders move in a multiple disc brake system?
Through hydraulic pressure
What is the purpose of the stators in a multiple disc brake system?
To provide additional friction surfaces
What is the main difference between multiple disc brakes and segmented rotor disc brakes?
The construction of the rotor and stator plates
What happens when the brakes are applied in a multiple disc brake system?
The operating pistons move against the pressure plate
What is the primary advantage of using hydraulic pressure in multiple disc brake systems?
Increased braking power
What is the purpose of the thrust plate in a multiple disc brake system?
To clamp the rotors and stators
What is the primary characteristic of segmented rotor disc brakes?
The use of multiple rotor segments joined together
What is the primary function of the drag link or drag strut?
To stabilise the landing gear assembly longitudinally
Why must the side link or side brace strut be hinged?
To enable the gear to retract sideways
What is the function of the over-centre link or down lock?
To prevent the link from pivoting at the centre pivot joint
What is the purpose of the uplock?
To positively lock the landing gear in the retracted position
What is the main function of the shock strut?
To contain the shock absorbing mechanism
Where is the top of the shock strut attached?
To the trunnions or is an integral part of the trunnions
What is free to move in or out of the shock strut?
The piston
What type of loads do side links bear during certain operations?
Side loads
What happens when the emergency brake switch is selected to the 'off' position?
The brake system returns to the normal system pressure.
What is the primary function of the spool valve in the priority change over valve?
To connect the No 2 Emergency Brakes system to the brake units.
What is the purpose of the park brake valve?
To compensate for thermal expansion and contraction of the brake fluid.
What should be considered before setting the park brake?
The brake assembly temperature.
What is the result of setting the park brake when the main brakes are hot?
Serious damage such as welding or warping may occur.
What is the sequence of operations to apply the park brake?
Depress the brake pedals, then apply the park brake handle.
What is the purpose of depressing the brake pedals when releasing the park brake?
To build up pressure to unseat the park brake valve.
What happens when the park brake valve is unseated?
The park brake is released.
What is the primary function of the compensating port in a brake master cylinder?
To relieve pressure and volume of fluid back to the reservoir
What is the purpose of the spool valve in a boosted brake master cylinder?
To direct hydraulic system pressure behind the piston to assist the pilot
What happens to the brakes when the pedal is released in a boosted brake master cylinder?
The brakes are vented to the reservoir to allow for thermal expansion
What is the purpose of the toggle mechanism in a boosted brake master cylinder?
To move the spool valve and assist the pilot in applying more braking force
Why is a boosted brake master cylinder used in an aircraft?
To provide more braking force than can be applied with an independent master cylinder
What happens when the pilot pushes the pedal in a boosted brake master cylinder?
The piston is moved to apply braking force to the brake cylinder
What is the purpose of the master cylinder in a brake system?
To convert non-hydraulic pressure into hydraulic pressure
What is the benefit of using a boosted brake master cylinder over an independent master cylinder?
It provides more braking force when needed
Study Notes
Landing Gear Components
- Drag link (also known as drag strut) stabilizes the landing gear assembly longitudinally and must be hinged to enable gear retraction.
- Side link (or side brace strut) stabilizes the landing gear assembly laterally and bears side loads during skidding, crosswind landings, and take-offs.
- Over-centre link (or down lock) applies pressure to the centre pivot joint in a drag or side brace link to prevent gear collapse during ground operation.
- Uplocks positively lock the landing gear in the retracted (up) position, removing the need for constant hydraulic or electrical actuator input.
Shock Strut
- The shock strut is the main vertical member of the landing gear assembly and contains the shock absorbing mechanism.
- The top of the strut can be attached to, or be an integral part of, the trunnions.
Safety Precautions
- New components should be examined and cross-checked with the appropriate maintenance publication to ensure correct fitting.
- New components should be inspected for cleanliness before installation, and components containing fluid should be primed before installation and bled after installation.
- Fluid bled or drained from the system should be discarded, and care should be taken to prevent spillage, which may have detrimental effects on paint, rubber, cable insulation, etc.
- Air pressure should be released slowly, particularly in confined spaces.
Wheel Assemblies
- Wheel assemblies consist of two major assemblies: tyre and hub.
- Aircraft tyres provide a cushion of air to absorb shocks and roughness during landings and take-offs, support the aircraft's weight, and provide traction for braking and stopping.
Braking Systems
- Multiple disc brakes are heavy-duty brakes designed to provide increased friction surfaces for braking purposes in large aircraft.
- Segmented rotor disc brakes are heavy-duty brakes adapted for use with high-pressure hydraulic systems.
- Boosted brake master cylinders utilize hydraulic system pressure to assist the pilot in applying braking force when needed.
- GenFly brake system emergency operation allows for continued braking in the event of No 1 system failure.
Park Brakes
- The park brake is a sub-assembly of the normal hydraulic brake system, located in the cockpit.
- Applying the park brake depends on the type of system used, and brake assembly temperature should be considered before setting the park brake.
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