LG and brakes Flashcards
Brakes general
16 Carbon brakes (one per WLG and the 4 front wheels of the BLGs)
Brakes modes
Normal
Alt
Emer
Ultimate
Parking
Each set of wheels can be in a different braking mode, e.g. 1 can be in normal, 1 in alt and the rest in emer
Hyd sources for different braking modes
Norm:
Green supplies WLG
Yellow supplies BLG
Alt/Emer/Ultimate:
2 LEHGS (Local Electro-Hydro Generation Systems) - 1 for WLG and 1 for BLG
Each LEHGS is an independent hydraulic generation system. Each has its own hydraulic reservoir and generates pressure via an hydraulic electro pump. The LEHGS reservoir is automatically filled on ground by the G or Y system
BCS - Brake control systems
EBCU (Emer BCU)
2 which control Normal and Alternate braking (1 active 1 back-up) based on brake-pedals, Auto-brake selection and LG lever)
It computes and sends elec orders to hydraulic brake units to actuate braking
Also an EBCU which controls emer braking and part of ultimate braking (WLG only)
Normal and Alt braking
Norm: WLG on green and BLG on yellow
Alt: LEHGS and accumulators
No limitation on brake applications
Diff braking available
Auto-brake and anti-skid available
No perf degradation in ALT mode (full pressure applied)
Emer and Ultimate mode control (ECBU)
Controlled by EBCU (WLG only for Ultimate)
Source input:
Brake pedals only for Emer
Park brake only for Ultimate
EBCU sends message to alternate hydraulic brake actuators in accordance with these inputs
Emer braking
Flight crew use pedals
If LEHGS available, unlimited brake applications
If LEHGS unavailable, accumulator so brake applications limited
No auto-brake
No anti-skid
Ultimate braking
Flight crew use park brake
Pedals unavailable
No auto-brake
No anti-skid
ECBU controls WLG and park brake controls BLG
Parking brake
Controls BLGs if all engines shut down
Supplied by LEHGS or accumulators
ACCUS Reinflate button
Next to Park brake
When pressed:
Activates BLG and WLG LEHGS
Pressurizes BLG and WLG accumulators
Brake to vacate (BTV) dry and wet computations
Dry and Wet lines calculated at descent prep with max braking distances (regardless of brake mode used) from an ILS autoland (reverse idle Dry, Full reverse wet)
These remain until below 600’ RA where they are calculated in real time by ROW/ROPS system
BCS commands deceleration to reach 10 kt 65 m before exit
ROW/ROP basics
ROW, active:
From 500/300 ft AGL to the start of braking (Classic autobrake/BTV, respectively)
ROP:
From start of braking to 30 kt/ RW vacation
Both computes LD real time according to:
Speed
Configuration
AC position/weight
Temp/wind
ROW/ROPs warnings
ROW:
Amber “If wet, Rnw too short”: GA if wet
Red “Rwn too short”: GA
ROP - manual braking:
“BRAKE, MAX BRAKING, MAX REVERSE” - Apply full brake and reverse - Red bar flashes on OANS until overrun no longer detected
ROP - Autobrake:
ROP triggers Max braking (via BCS) to give max hydraulic braking (like an RTO). “SET MAX REVERSE”
ROP can only be disarmed once overrun no longer a threat, in which case braking reverts to old autobrake setting
Both cases below 80 kt if overrun still detected “KEEP MAX REVERSE”
ROW ROP failures
If a failure occurs that degrades LD, ROW no longer available (no Dry/Wet magenta lines
But On Ground computation still accurate to ROP still active
LGERS Landing Gear Extension Retraction System
Normal: Elec controlled, Hyd actuated (Green and yellow)
BLG Yellow; WLG/NLG Green
Abnormal: Elec controlled, Mechanically (gravity) actuated
