Brakes + Tyres Flashcards
Ply Rating
Tyre strength
Tyre Tread is…
Patterns (ribbed etc)
Types of tyre
Bias - Plies laid in pairs 90 degrees
Radial - Laid from bead to bead
Tubeless - No inner tube to contain gas (reduction in weight/cool running)
Retreading a tyre
Can be remoulded several times with new crown as long as wheel structure is sound
Tyre Creep
Creep marks - 1 inch for 24 inch or 1.5 inch for tyres over 24 inch
Most likely on first landings/needs to be monitored
Tyre Overheat Protection
Fusible plug - Bursts before tyre fails
X3 Wheel Construction
Well Based - Light AC (Tubed)
Detachable Flange - Easy to replace
Split - Large AC tubeless
Light AC Wheel Brakes
Fixed - Floating calliper mounted to landing gear/disc bolted to wheel
Floating - Calliper bolted to landing gear via torque plate/disc keyed not bolted to main wheel
Brake Fade
Affects conventional steel brakes
Result of brakes overheating
Cannot absorb any further energy causing retardation issues
Judder/stick to disc
Automatic Brake Adjuster
Ensures correct clearance between rotating assemblies when brakes are off
Advantages of carbon brakes
Lighter
Absorb twice as much heat as steel - less brake fade
Carbon brakes last longer
More expensive but last longer
Heat Dissipation
Read SOP regarding break cooling time and let ATC know
Tyre Speed rating
Limiting speed for tyre must match or exceed this rating
Anti Skid role
To relief brake pressure on normal/dry/wet/contaminated runway to prevent skidding when wheel is turning slower
Controller predict slip ratio based on speed and reduces pressure to wheel to let it spin back up then reapply.
Functions of Anti Skid
Skid Protection
Bounce Protection
Touch down protection
Hydroplane protection (ops on boogie)
Auto brake system function
“Armed” sense certain conditions when brakes are needed.
- power needs to below a certain level
- deactivated if brake pedals applied/switched off/throttle action
Auto Retract
After TO brakes forced to stop turning before entering wheel well.
Rubber snubbers
Parking Brake
Brake pressure applied and held
! Overrides other braking systems anti skid systems
! Do not set in flight
! Do not set if brakes are excessively hot
Weakest Part Of Wheel
The side wall
Conditions needed to check for brake wear
Brakes must be applied
Auto brake Condition For disarming
Manual Braking
Advancing thrust
Moving speed brake lever down
Moving auto brake selector to disarm
Not activated below 85kts
Too Low tyre pressure
Excessive wear on shoulders
Too high tyre pressure
Excessive wear on the crown
RTO mode Auto Brakes
Provides fixed level of deacceleration until stand still
Primary element for automatic ground spoiler deployment
Weight on wheels on touch down
Shimmy preventions
Hydraulically locking steering piston
Hydraulic dampers
Self centring springs
Double nose wheels
Tyre Wear Limits for ribbed treads
Minimum tread depth is 2mm measured from bottom of groove
Tyre Wear limits of blocked treats
Within limits provided block pattern is still visible
Auto Brakes conditions needed are..
Armed
Thrust levers set to idle or reverse
Brake pedals not touched
Wheels speed average 88kt
Anti skid system must be on and serviceable
Hydraulic system must be functional
4 types of anti skid protection
Hydroplane - applied to rear wheels on a bogie
Skid Protection - reduce brake pressure
Bounce - system release pressure if bounce occurs on touchdown
Touchdown - prevent any brake pressure prior to touchdown
Carbon Brakes - Limiting Wear
Dependent on total number of brake applications
One firm brake causes less wear than several light applications
Like working when brakes are HOT
Less sensitive to weight and speed than steel
Steel brake - Limiting wEAR
Using large number of small light brake application to allow brakes to cool between applications
Weight/speed reduce brake life on steel due to kinetic energy increase
Tillter
Large deflection up to 78 degrees nose wheel steering on large ac
Rudder pedal steering
Max 7 degrees
What are the input data of the anti skid system
Wheel speed
Ground speed
Wheel speed of all wheels on boogie
Definition of nose wheel shimmy
As oscillatory lateral movement of the nose wheel about the longitudinal axis of the aircraft when the nose wheel is in contact with the runway during the take off and landing rung
Anti Retract Latch
Prevent inadvertent up selection of landing gear on ground.
Can be overridden for maintenance etc
Most stress is carried by a torsion link…
Between the inner and outer cylinder of the main oleo leg during a small radius turn
Pressurised nitrogen bottle system
Activated by pulling red gear control handle giving one shot extension of the landing great.
Thermal Plugs
Operate a safety valve when excessive temperature reached in wheel assembly allowing controlled tyre deflation
Nose wheel shimmy
Lateral movement about the longitudinal axis in contact with the runway
When the pilot forget to arm the auto brake system what happens
Nothing there will be no warning generated during take off
RTO applies the maximum possible deceleration not constant
