Chapter 7 - Wheels, Brakes, Tyres Flashcards
What are ‘ Creep Marks’?
White marks which are painted onto the tyres to show if the wheel is rotation within the hub.
If it was to move around too far, then the valve could blow the tyre.
1” width for 24” Tyres.
1.5” width for more than 24” Tyres.
What is ‘Vtyre’?
The tyre speed rating.
The maximum speed that the tyre can be used at.
- Rated in MILES PER HOUR (MPH)
What should be looked for when inspecting a tyre?
- Cuts
- Bulges
- Flat Spots
- Foreign Object Damage
- Contamination (Fluid spillage onto the tyre).
- Creep
- Wear
- Pressure
What are the correct tyre pressures? And why is it important?
Low = up too 200psi High = 200-315psi
Over Inflation leads to excess wear and possible blow out.
Under Inflation can lead to tyre creep, excess heat, wear and failure.
IF ONE TYRE IS PUNCTURED THEN THE WHOLE BOGIE IS REPLACED.
What is a Fusible Plug?
The plug/valve that goes into the tyre will melt at high temperature.
This prevents the engine exploding at high heat.
What brakes are used on a Light Aircraft?
Simple Single Discs - Passive System.
What brakes are used on a Large Transport Aircraft?
Multiple Disc Park System.
Typically using Hydraulic Power.
Active System.
787 uses electrical power.
Brakes work by converting ______ Energy into ______ Energy through Friction.
Brakes work by converting KINETIC Energy into HEAT Energy through Friction.
The brakes should be checked when…?
The brakes should be checked when the brakes are APPLIED.
How are the breaks and tyres checked?
Rule or special gauge.
Some aircraft are equipped with Break Wear Indicator Pins.
Mechanical Process of a brake activating?
Brake pressure applied to the back of the piston.
Disk loves laterally until it makes contact with the friction pad.
A return spring pulls the piston off when the pressure is released.
What is ‘Brake Fade’?
On steel brakes, when the excessive heat diminishes the braking efficiency.
- If the brakes are underperforming then try releasing the brakes temporarily, when reapplying them.
What is the purpose of a ‘Automatic Brake Adjustor’?
Ensures correct clearance between the rotating assemblies when the brakes are in the off position.
What is the purpose of a ‘Brake Wear Indicator Pin’?
As the brake pads wear down the pin starts to retract in the housing.
The pads must be replaced when the end of the pin is flush with the housing.
Carbon brakes.
Advantages
Disadvantages
Lighter, Less prone to brake fade, 30-175% improvement.
They are much more expensive.
What is ‘Minimum Brake Hold-Over’?
The minimum amount of time needed for the brakes to cool down before takeoff is permitted.
Heat is usually shown on the ECAM.
How does ‘Anti-skid’ work?
Prevents the wheels from skidding.
If skidding is detected then the brake will momentarily be released and applied.
This can be done several times a second.
What is ‘Touch Down Protection’?
Prevents the brakes from being pre-applies before touchdown.
Even if the pilots applies the brake it will not work.
What is ‘Bounce Protection’?
If the aircraft bounces, it releases the wheel brakes, until it touches down again.
This allows the wheels to spin back up, to reduce shock.
Electronic Anti-Skid System Theory of Operation? (Long and painful)
- Tacho-generator driven by a wheel generates electrical output that varies with the wheel speed.
- The anti-skid controller cross-references signals from all wheels.
- Controller determines aircraft speed & thus speed of an un-braked wheel.
- Controller determines the Slip ratio between the theoretical un-braked (idler) wheel & braked wheel.
- Controller dumps brake pressure when the measured slip ratio reaches a pre-determined ideal value.
- After dumping brake pressure the controller reapplies a lower pressure and then rises steadily back towards maximum braking force.
Changeover circuits couple valve for all brake units so that loss of speed signal from one unit does’nt affect the other.
Where is Hydroplane Prevention located? (Which wheel?)
Given to the rear wheel on the bogie trolley, as this is the first to touch down.
Difference between Hydroplaning and Aquaplaning?
Hydroplaning is the onset when the water is building.
Aquaplaning is full on ‘no friction’.
What is the purpose of ‘Autobraking’?
Brings the aircraft to a stop without input from the pilot.
The amount of brake pressure is determined by a setting on the flight deck.
Parameters for ‘Auto-brake’ to work?
- Auto brake must be ON & Serviceable.
- Anti-skid system must be ON and Serviceable.
- Power levers must be set below a certain value.
- Hydraulic system must be functional.
- Brake pedals must be depressed.
Auto brake will be automatically deactivated if?
- Brakes are manually applied.
- Power is set to TO/GA
Auto brake ‘RTO’ will activate when what parameters are met?
- Speed is greater than 90knots.
- Thrust Levers are idle.
BRAKING WILL DISARM THE SYSTEM!
If Anti-Skid has a failure what may be the consequences? How will the aircraft show you the fault?
Landing distance may double.
Amber Warning Caution will illuminate if a fault is detected.
What is the purpose of:
Brake Snubber?
Flight Brake?
Stop the wheel from rotating as it is stowed.
What happens to the brakes in the case of Hydraulic Failure?
- 2 Hydraulic systems will produce the braking force.
- If that fails a brake accumulator can be used for 6 applications of brake.
- No Anti-skid.
- No differential braking.
- Directional control problems may occur.
Parking Brake facts?
Parking brake overrides all other braking systems.
IT MUST NOT BE USED WHILE AIRBOURNE.
Cannot be set until the brakes have cooled down (Short taxi=bad)
