Landing Gear And Brakes Flashcards
PSEU
Proximity Sensing Electronic Unit
How does the PSEU work?
Uses sensors to determine gear and gear door position and supplies this to the Data Concentrator Unit (DCU) for display on the EICAS primary page
What controls the nose wheel?
Controlled by a steering Electronic Control Unit (ECU)
Which way does the NLG retract?
Forward into nosewheel bay.
How does NLG lock?
In both extended and retracted positions via spring-loaded, over-center locking mechanism.
Which way do the MLGs retract?
Inboard to the fuselage.
Proximity Sensor System components
- PSEU
2. Proximity sensors and switches
What landing gear related functions does the PSS provide?
Normal landing gear positioning control, landing gear position indication and weight on wheels monitoring.
When is the landing gear position indication removed?
30 seconds after the gear is up and locked position with flaps at 0
If gear and handle positions disagree, what will happen?
Warning message displays and aural sounds
How is the PSS tested?
Continuously through the PSEU
“PROX SYS CHAN” caution
1 PSEU channel loss
“PROX SYS” caution
Loss of both PSEU channels
WOW
Weight on Wheels sensor
What is the purpose of the solenoid lock in the landing gear control handle?
Prevents the lever from being moved to UP position on the ground
Weight Off Wheels signal from PSEU is sent to _______ the landing gear lock
Unlock
If the landing gear handle solenoid lock malfunctions, what can we do?
DN LCK REL button will allow us to override the solenoid lock.
What is the purpose of the tire spin-down assembly in the NLG bay?
Stops nosewheel rotation when NLG is retracted
Which hydraulic system powers the landing gear?
Number 3.
What retracts and extends the landing gear?
A retract/extend actuator
If a failure occurs in the landing gear control system or in the hydraulic system number 3, the _______ will allow for alternate gear lowering
Landing gear manual release
What happens when the landing gear manual release handle is pulled and held to its full extension?
MLG unlocks are released
Bypass valve dumps number 3 hydraulic pressure which permits the gear to partially extend under its own weight.
Hydraulic system 2 will pressure MLG auxiliary actuators and NLG uplock manual release actuator
MLG auxiliary actuators
Assist the gear to the down and locked position
When can the Landing gear Manual Release be released during a manual extension of the landing gear?
Once EICAS indicates NLG and MLG are down and locked
When will the landing gear warning horn sound?
Incorrect configuration during landing phase of flight:
Can the gear warning horn always be muted?
Only in certain configurations.
What hydraulic system powers the NWS?
Hydraulic system number 3.
When is NWS enabled?
System armed, on the ground (WOW) and gear down and locked.
What is the maximum angle either side of center for the nosewheel using the tiller?
80 degrees
How much can the rudder pedals move the nosewheel?
8 degrees either side of center.
What straightens the nosewheel prior to extraction and what keeps it centered?
Prior to retraction: ECU
Keeps centered: centering cam on nosewheel strut.
How is directional control maintained in the shimmy dampening mode?
Differential braking
Differential thrust
When will the NWS enter the shimmy dampening mode?
- Failure detected by the steering control system or…
2. Hydraulic system number 3 is lost
What may cause the “STEERING INOP” caution to display prior to landing?
Moving the nosewheel steering tiller more than 2 degrees
How are the main wheel disc brakes actuated?
2 independent systems, No. 2 and No. 3 hydraulic system
Fusible plugs
Fitted to main gear wheels which prevent against tire burst in the event of overheat
How do you check the wear pin indicators?
With the brakes applied and No. 2 and No. 3 hydraulic systems pressurized
Inboard brakes are powered by hydraulic system number _____ and the outboard by number ______.
3; 2
During landing gear retraction, hydraulic pressure is applied to the main brakes to ________.
Stop the main wheels from spinning
If a leak occurs in a brake line, what will happen?
The associated hydraulic fuse will close off the hydraulic line
With loss of 1 hydraulic system, the aircraft has ______ symmetric braking capability and ____ anti-skid braking on operative brakes.
50%; FULL
If Hydraulic No. 2 and 3 fail, what will happen to the braking system?
Accumulators in each system will provide reserve pressure for braking
When will anti skid engage?
- Anti Skid switch is ARMED
- Parking brake is not engaged
- Both main landing gear are down and locked
- WOW signal is received
- 35 knot wheel spin-up signal is present
How does the anti-skid system work?
Monitors each wheel speed individually to detect skidding. If detected, the ASCU reduces brake pressure at the skidding wheel by modulating pressure outputs of the appropriate anti-skid control valve
When is a “A/SKID FAULT” status message generated?
- Loss of redundancy of ASCU
- Loss of WOW input
- Spin down failure
- Loss of internal communication
When will a “A/SKID OUTBD” caution display?
When that anti skid channel has failed.
What provides braking when aircraft is parked?
The inboard brakes and the parking brake shutoff valve
How do we set the parking brake?
Pull the parking brake handle and turn it 90 degrees while fully depressing the brakes.
When is the parking brake on advisory message displayed?
- On the ground
- Both engines not at take-off power
- Inboard brake pressure greater than 800 psi
When will the parking brake SOV caution be generated?
Parking brake shutoff valve fails open
Inboard brake pressure greater than 800 psi
BTMS
Brake Temperature Monitoring System
What makes up the BTMS?
Four temperature sensors
ASCU
BTMS OVHT WARN RESET switch
BTMS Temp indications:
Green: normal
White: caution
Red: Exceeded
Amber: sensor failure
NLG consists of:
2 forward and one aft door
MLG is held in the up and locked position by:
A mechanical lock
“PROX SYS FAULT 2” status message indicates:
Any one non-critical sensor or input or output has failed
Retraction and extension of the landing gear is normally powered using:
Hydraulic system No. 3
When the aircraft is configured for takeoff, but the parking brake is set, what will happen?
A “PARKING BRAKE” WARNING will sound.
Landing gear is _____ controlled and ______ actuated
Electronically / hydraulically
The normal hydraulic system for retracting and extending the landing gear is…
Hydraulic system 3
Turn limit for the NLG is?
80 Degrees
What can absorb side loads during landing?
Side stay
How is the MLG held in the retracted position?
Mechanical uplock
How is main wheel rotation stopped on MLG retraction?
Hydraulic system 3 brake application
Without #2 hydraulic pressure, nose gear ______
Cannot be extended
When can you no longer silence the gear horn?
160 KIAS
When will EGPWS say “Too Low, Gear”
Less than 500’ and airspeed is less than 190 KIAS with the gear not down.
PSS
Proximity sensing unit, senses location of the gear, electro magnetic, no mechanical parts. Takes place of squat switches
Each digit on the BTMS is how many degrees?
35 degrees
How long will a RED BTMS indicator stay?
Forever until… maintenance resets. Requires an inspection of the fuse plugs on the wheel wells
What is the maximum BTMS indication?
20
PSEU
Proximity sensor electronic unit. Monitors position of unlocks and down locks, controls valve position for landing gear.
Maximum tire limit speed:
182 - 700
192 - 900
Do we disable NWS in flight?
No
What is the purpose of the electronic control unit?
To command the NLG to turn based on the Tiller.
How do you reset the Electronic Control Unit when “STEERING INOP” caution is displayed?
Turn NWS OFF and ON again.
When are landing gear indications removed from EICAS?
30 seconds after the gear is up and locked, the flaps are at 0 degrees and the BTMS indications are normal.
What do we have to do in order to get an accurate brake wear test?
Pressurize inboard and outboard brakes and set the parking brake
