Brakes & NWS Flashcards
Do we manually have to select alternate brakes?
Usually not, just in case of loss of braking.
Is anti-skid available on the alternate brakes?
Antiskid may be available, depending on:
* Electric supply (A/SKID & N/W STRG switch OFF, or power supply failure, or BSCU failure), or
* Hydraulic supply (Y + G system low pressure, the brakes are supplied by the brake accumulator only).
Name four different types of braking:
- Normal Braking
- Alternate braking with anti-skid
- Alternate braking without anti-skid (Accumulator pressure: max 7 applications)
- Parking Brake
N.B: Autobrake always lost when on alternate brake!
Describe Normal Braking:
Braking is normal when:
* Green hydraulic pressure is available.
* The A/SKID & N/W STRG switch is ON.
During normal braking, antiskid is operative and autobrake is available. Braking is electrically-controlled through the BSCU from:
* The pilot’s pedals, or
* Automatically:
a) On ground by the autobrake system, or
b) In flight when the landing gear lever is up
The antiskid system is controlled by the BSCU and there is no brake pressure indication in the cockpit.
Describe Alternate Braking WITH anti-skid:
Braking uses this mode when green hydraulic pressure is insufficient, and:
* Yellow hydraulic pressure is available
* The A/SKID & N/W STRG switch is ON
* The parking brake is NOT ON.
Antiskid is controlled by the BSCU.
Brake pressure, as well as accumulator pressure, are indicated on a triple indicator located on the center instrument panel.
Autobrake is inoperative.
Describe Alternate Braking WITHOUT anti-skid:
The antiskid system is either deactivated:
* Electrically (A/SKID & N/W STRG sw OFF, or power supply failure, or BSCU failure), or
* Hydraulically (Y + G system low pressure, the brakes are supplied by the brake accumulator only).
Brake pressure and accumulator pressure are indicated on a triple indicator, located on the center instrument panel. To avoid wheel locking and limit the risk of tire burst, brake pressure is automatically limited to 1 000 PSI.
Accumulators are designed to supply at least 7 full brake applications.
Autobrake and antiskid are inoperative.
Describe the Parking Brake:
Brakes are supplied by the yellow hydraulic system, or by accumulator pressure via the parking brake control valve, which opens allowing full pressure application on the main gear wheel brakes.
The accumulator maintains the parking pressure for at least 12 h.
If the parking brake is activated and no yellow hydraulic or accumulator brake pressure is available, then the normal braking system can be applied via the brake pedals.
Yellow accumulators can be pressurized by pressing the yellow electrical pump switch.
Brake pressure and accumulator pressure are indicated on a triple indicator, located on the center instrument panel.
When does antiskid become available (eg above what ground speed)?
The speed of each main gear wheel (given by a tachometer) is compared to the aircraft speed (reference speed). When the speed of a wheel decreases below approximately 0.87 times (depending on conditions) reference speed, brake release orders are given to maintain the wheel slip at that value (best braking efficiency).
In normal operations, the reference speed is determined by the BSCU from the horizontal acceleration of ADIRU 1, or ADIRU 2, or ADIRU 3.
In case all ADIRUs fail, reference speed equals the maximum of either main landing gear wheel speeds.
Is autobrake available on the alternate braking system?
No, autobrake is always lost when on alternate brake.
What speed on takeoff does nose wheel steering stop?
130 kts
BRAKES and ACCU PRESS Indicator, how to read it?
Brake pressure is only indicated when the yellow hydraulic system controls the brake pressure. This is when:
* Alternate braking system is activated, or
* Parking brake is applied.
ACCU PRESS: Indicates the pressure in the yellow brake accumulator.
BRAKES: Indicates the yellow pressure delivered to the left and right brakes, as measured
upstream of the alternate servo valves.
What happens in the event of a shear pin failure during pushback?
In the event of a shear pin failure during pushback:
* If the pushback stops immediately after the failure of the shear pin, inspection is not necessary.
* The nose gear must be inspected after the failure of the towbar shear pin (during forward or rearward towing) with subsequent separation and overrun of the towbar by the aircraft, or Push-turn operations, when the towbar arm touches the tractor after the failure of the turning towbar shear pin only.
When does the green arc above the brakes appear on the ECAM WHEEL page?
The green arc appears on the wheel ECAM page when the hottest brake temperature is above 100°C.
Brake temperature requiring maintenance actions:
OM B 2.3.21
* The temperature difference between the 2 brakes on the same gear is > 150˚C, and the temperature of either one of these brakes is ≥ 600˚C, or
* The temperature difference between the 2 brakes on the same gear is > 150˚C, and the temperature of one brake is ≤ 60˚C, or
* The difference between the average temperature of the left gear brakes and the average temperature of the right gear brakes is ≥ 200˚C, or
* One brake’s temperature > 900ºC.
Explain the autobrake functions:
- LO mode sends progressive pressure to the brakes 2 seconds after the ground spoilers deploy, in order to decelerate the aircraft at 2 m/s2 (or 4 seconds and 1.7m/s2 in some MSN)
- MED mode sends progressive pressure to the brakes 2 seconds after the ground spoilers deploy, in order to decelerate the aircraft at 3 m/s2.
- MAX: In the case of an aborted takeoff, maximum pressure goes to the brakes, as soon as the system generates the ground spoiler deployment order.
