Cap 7 Wheels Tyre And Brakes Flashcards
Type of tyres
Ply rating> indicate tyre strength
Tread> rubber
Tubeless> internally airtight,no inner tube
Bias> plies laid in pairs ,adjacent at 90 degress
Radial >plies are laid from bead to bead
Retread > new treat heat bonded onto old carcass
Tubed tyres> use an inner tube with an infaltion valve
Tyre creep
Sudden acceleration cause the tyre to slip around the wheel.
1 inch wide for tyres of 24incg or less
1.5 inch wide for tyres over 24 diameter
Creep in monitored with creep marks
Tyres speed rating
~often rated in MPH
Tyre speed rating must match /exceed the maximum anticipated ground rolling speed of the a/c
Exceeding tyre limits>
~excess tyre heat
~excess tyre stress that damages or destroys the tyre
Tyres wear
Ribbed treads»
~min tread depth is 2mm
~may have a wear marker
~tyre is on its limit when marker is at the same height as the rib
Blocked treads»
~within limits provided that the block pattern is still visible
Tyre inspect
~damage or under inflation can lead to tyre failure or tread separation
~a burst tyre can result in loss of control
~if a tyre breaks up during use it can cause serious damage to the a/c
Tyre inspection
~Cuts>any cut the cords or sidewall require tyre replacemnt ~bulges > indicates tyre structure weaken ~flat spots>excessive wear ~FOD> ~contamination ~creep ~wear ~pressure
Tyre pressues
Large a/c»
Low pressure: up to 200psi
High pressure : 200-315 psi
Tyre overheat protection
Fusible plug
Wheel brakes
Light a/c >use single disk types
Large> mulitple disk pack systems
Some a/c are equipped with a brake wear indicator pin when it goes further in means brakes are wear (brakes need to be applied to check)
Wheel brakes
Fixed disk - Floating calliper
Floating disk - fixed calliper
Large brake systems (multiple disc brakes)
The rotor segment is physically engaged with the wheel assembly via the torque tube and so rotates with the wheel
Series of pads are arranged concentrically around both sides of a stator assembly
In between each pair of stators is a rotor segment
Automatic brake sys adjuster
Ensures correct clearance between the rotating assemblies when the brakes are in the off position
Brake wear indicator pin
When brake pads worn the pin starts to retract into the housing
Carbon braking advantages and disadvantages
Advantages> Lighter Absorbs twice as much heat as steel Less prone to brake fade Carbon brakes last longer 30% to 175% improvement
Disadvantages > more expensive
Heat dissipation
Large transport a/c equipped with brake fan units
May specify a min brake hold over time to allow cooling between landing
ATC must be informed in event of brake overheat
Brake tenmp indication
Displays the hottest brake temp
Displayed on ECAM or EICAS
ANTI SKID SYS
CONTROLLER determines if a wheel is going to stop rotating due to high braking and it releases some of the pressure to make it rotate and then reaply at lower pressure.
“Slip ration “the theoretical un-braked (idler) wheel and the braked wheel
Anti skid sys does
Touchdown protection
Incorporate a touch down protection feature:
Prevents brake pressue being applied at the wheel before touch down .
And BOUNCE PROTECTION is a protection when the wheels bounce after touch down and release the brakes until it starts to spin again ,onky then brake is reapplied
HYDROPLANE PROTECTION: as touchdown or bounce protection,
Waits until the tyre start to rotate to apply brakes.
Braking without anti skidding will double the landing distance
Autobraking
Autobrake> must be ON
ANTI SKID > MUST BE ON and servicible
power levers> must be set below a a certain value
Hydraulic sys> must befunctional
Brake pedals > must be depressed while turning ON the autobrake sys
RTO
Provides max braking ,it activities only:
~speed greater than 90 kts
~Thrust levers idle
~touching the brakes will disarm as for the AUTOLAND
Emergency braking sys
No anti skid is available
And limited braking applications with in emergency mode (6 applications)
The parking brake
Brake pressure to the wheel to be applied and held.
Overrides all other braking systems including :
Anti skid
Touch down protection
