S Wheels, Tyres and Brakes Flashcards
What does a tyre ply rating indicate?
Strength - higher ply = higher strength
What is tyre creep?
Only relevant for tubed tyres
Sudden accelerations cause the wheel to slip around the tyre, greatest after new tyre has been fitted, monitored with creep marks
What should the dimensions of the creep marks be?
- 1 inch wide for tyres less than 24 inch diameter
- 1.5 inch wide for tyres greater than 24 inch diameter
When are the creep marks within their limit?
Whenever there is some overlap
What is Vtyre?
Aircraft tyre limiting speed on the ground, often rated in mph
What will exceeding Vtyre cause?
- Excess tyre heat
- Excess the stress causing damage
What is the minimum tread depth of a ribbed tread?
2mm
How do you know if blocked treads have sufficient depth?
Tyre wear marker bar - sits flush with grooves when tread is insufficient
What should tyres be inspected for?
- Cuts
- Bulges
- Flat spots
- FOD
- Contamination
- Creep
- Wear
- Pressure
What pressure do large aircraft tyres operate at?
High pressure - 200-315psi
What happens if one tyre is punctured on a bogie?
All tyres on the bogie must be replaced
What is a fusible plug?
Melts when the tyre overheats and allows gas inside the tyre to escape in a controlled way
How do light aircraft brakes work?
Hydraulic pressure claps friction pads tightly against a steel disk
What are the 2 types of light aircraft brakes?
- Fixed disk - Floating calliper
- Floating disk - Fixed calliper
How is break wear monitored on light aircraft wheel brakes?
Friction pads erode - special gauge can be used t measure gap between disc and brake housing
Brake wear indicator pin - as the pad wears a pin pops out indicating wear
What are the consequences of brake wear?
- Overheating
- Brake damage
- Loss of brake efficiency
What is brake fade?
On conventional steel disc brakes, excessive heating diminishes braking efficiency
What are multiple disc brakes?
Series of pads arranged around both sides of the stator assembly
What material are large aircraft brakes usually?
Steel rotors
Ceramic pads
What is the automatic brake adjuster?
Ensures correct clearance between the rotating assemblies when he brakes are in the off position
On a large transport angle how does the brake wear indicator pin work?
As the pad wears down the pin extracts into the housing, the pads must be replaced when the pin is flush with the adjuster housing
What are the advantages of the carbon braking system?
- Lighter
- Absorbs twice as much as steel
- Less prone to brake fade
- Lasts longer (30%-175% improvement)
- More expansive to fit but last longer so lower overall cost
When should you be aware of high brake temperatures?
- Hot and high landing
- High weight
- Short taxi to stand
- High speed aborted take off
How do large aircraft counter brake heating?
Brake fan units
Who needs to be informed in the event of a brake overheat?
ATC
What does the ECAM or EICAS display regarding brake temps?
Usually shows hottest brake temp
What is maximum deceleration?
Maximum brake force to a rotating wheel without stopping it
What happens if the anti-skid system detects a wheel spinning too slowly?
Releases brake pressure momentarily to allow it to get back up to speed and stop skidding
When can the anti skid provide skid protection?
Normal, dry and wet runways
What is touchdown protection?
Prevents brake pressure being applied before touchdown, even if the pilot inadvertently applies pressure to the pedals
What’s is bounce protection?
If the aircraft bounces on touch down the brakes release
What is the result of aquaplaning?
- Reduced or no braking ability
- Loss of directional control
- Damage to tyres from superheated steam
What is hydroplane protection?
Operates only on the rear wheels, when wheel speed is less than ground speed the system releases brake pressure on the rear wheels
What is auto-brake?
Can bring aircraft to a halt with no intervention from the pilot
What are the prerequisites for auto brake?
- Auto-brake selected on and deceleration level selected
- Anti-skid system on and serviceable
- Power levers set below a certain value
- Hydraulic systems functional
- Brake pedals depressed
What can override automatic braking?
- Brakes being applied manually
- Power set to TOGA
What level of braking does RTO provide?
Max braking if:
- Speed greater than 90kt
- Thrust levers idle
- Touching brakes will disarm the system
How can inoperative anti-skid effect landing distance?
Landing distance can double
What is displayed if there is an anti skid fault detected?
Amber warning caption
What operational considerations are there if anti skid is faulty?
Runway type, length and contamination
How many brake applications does the emergency brake accumulator provide?
6
What are the limitations of the emergency brake accumulator?
- No anti-skid
- No differential braking
- Directional control problems
- 6 applications
What does he parking brake do?
Allows brake pressure to be held
Why should the parking brake never be used in flight?
Overrides all other braking systems
- Disables anti-skid
- Disables touch down protection
Why are tyres inflated with nitrogen?
- It is inert
- Thermally stable
- It is dry (corrosion reduction)
What is the tyre crown?
Holds the tread pattern and makes contact with the surface
What is the tyre shoulder?
Thins from crown to side wall
What is the tyre sidewall?
Weakest part and least able to cope with damage
What is the tyre bead?
Engages with rims on the wheel o form an airtight seal
What are chined tyres?
Deflect water spray away from the sides of the tyres, minimise water spray ingestion into engines
