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E175 Systems > Landing Gear & Brakes > Flashcards

Landing Gear & Brakes Flashcards

1
Q

Describe the landing gear

A

Tricycle type, retractable, electrically activated, hydraulically actuated

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2
Q

How many Weigh on Wheel sensors are there? What type of sensor are they?

A

6 WOW proximity sensors, 2 on each landing gear

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3
Q

How many down/up lock sensors are there?

A

12 sensors (2 up and 2 down for each landing gear)

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4
Q

How is the landing gear held up?

A

Mechanical uplocks

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5
Q

How is the landing gear held down?

A

Spring-type downlocks

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6
Q

What happens if there is a disagreement between down/up lock sensors?

A

The sensor agreeing with the gear handle prevails

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7
Q

How does gear retraction work? What are the steps?

A

Gear handle down, electrical signal sent to the hydraulic system, hydraulic pressure retracts gear

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8
Q

What is the purpose of the down lock release button?

A

Allows movement of gear handle if the WOW sensor fails

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9
Q

What are the 3 ways to extend the landing gear and how do they work?

A

Normal - via gear handle (electrical signal sent to hydraulic system to release up locks), Electrical override - electric signal bypasses normal Air/Ground position sensors, Alternate - free fall method using handle to release hydraulic pressure and unlocks (gear handle must be in the down position in order to get “3 green” on EICAS)

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10
Q

What is the purpose of the Landing Gear Warning Inhibit button?

A

inhibits aural warning in the event of a dual RA Radio Altimeter failure

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11
Q

When will the gear warning (not down and locked) occur?

A

Flaps 5 or full (cannot be silenced), RA < 700’ and 1 thrust lever reduced too low (cannot be silenced when single engine), or RA Failure and flaps 4 or less and 1 thrust lever reduced too low

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12
Q

What do the towing lights mean?

A

Red - steering engaged, parking brake on or main brakes on; Green - safe to tow

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13
Q

Are the brakes FBW?

A

Yes

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14
Q

What brake protections are there?

A

Locked wheel, anti-skid, and touchdown

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15
Q

Describe the locked wheel protection

A

compares main wheel speeds and if a difference of 33% or more is detected, brake pressure is released on the slower wheel (the 33% tolerance allows for differential steering with brakes); deactivates below 30kts

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16
Q

Describe the anti-skid protection

A

prevents skidding by reducing wheel brake pressure; not available for emergency braking; deactivates below 10kts

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17
Q

Describe the touchdown protection

A

prevents landing with brakes applied or locked; deactivates 3 seconds after touchdown or when wheel speed is greater than 50kts

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18
Q

How does the emergency parking brake work?

A

powered by HYD 1 and 2; 6 full applications available

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19
Q

What are the brake wear pins?

A

4 located on each main wheel; when pin is flush, maintenance must be notified for a brake change

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20
Q

How does nose wheel steering work?

A

Electrically controlled, HYD 2 actuated; +76deg until 40kts; decreases linearly to +7deg at 100kts; pedal steering is limited to +7deg

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21
Q

When is the free wheel steering mode automatically activated?

A

Auto activated when: air/ground system failure occurs, steering angle greater than 76deg or steering system failure

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22
Q

How can the free wheel steering be disconnected?

A

disconnect switch on yokes or disconnect switch on GPU access panel

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23
Q

How is the landing gear extended and retracted?

A

Electrically commanded and hydraulically actuated

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24
Q

When will the aural warning for the landing gear sound?

A

If the gear is not down and locked and 1. <700’ RA and low TLA or 2. Any altitude with flaps set to 5 or full

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25
Q

Can the landing gear aural warning be silenced by pushing the LG WRN INHIB button?

A

Only if both radio altimeters have failed

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26
Q

What are the 3 landing gear extension modes?

A

Normal - LG lever DOWN; Electric Override - Bypasses PSEM Proximity Sensor Electronic Module to directly command selector valve; Alternate gear extension - manual uplock release opens free-fall sequencing valve

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27
Q

What is the purpose of the DN LOCK RLS button on the landing gear lever?

A

Mechanically releases the landing gear lever lock; lock protects against inadvertent landing gear retraction when WOW

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28
Q

What keeps gear locked in position?

A

Extended downlock springs

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29
Q

Describe the landing gear indications

A

Green: Down and Locked; White: Up and Locked; Amber: In Transit; Red: Gear position and lever disagreement (20sec grace period)

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30
Q

How do the landing gear doors actuate?

A

Mechanically, during landing gear extension or retraction

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31
Q

How are the brakes commanded?

A

Brake by Wire, electrically commanded and hydraulically actuated, pedal position transducers send brake requests to the BCM Brake Control Module

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32
Q

What hydraulic systems provide brake pressure?

A

HYD 1 Outboard Brakes; HYD 2 Inboard Brakes; HYD 1 and 2 Parking/Emergency Brake

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33
Q

What protections are provided for braking?

A

Touchdown, anti-skid, locked-wheel

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34
Q

How many applications will the parking brake/emergency brake provide?

A

6 applications

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35
Q

What stops the wheels from spinning during retraction?

A

Main gear - BCM Brake Control Module applies brakes after WOffW; Nose gear - Snubbers in the nose bay stop the wheels

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36
Q

Which hydraulic system controls the NWS Nose Wheel Steering?

A

HYD 2

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37
Q

What are the limits for NWS Nose Wheel Steering?

A

Angle varies with ground speed; up to 40kts +76deg; 41-100kts Decreases linearly from 76deg to 7deg

38
Q

What is the steering limit for the nose gear?

A

76 degrees

39
Q

What kind of brakes does the E175 have? How are they controlled? How do you know if the brakes need replacement?

A

Multi-disk carbon brake assemblies. Electronically controlled and hydraulically powered carbon-composite brakes. Brake wear indicators visually show when the brakes need to be replaced.

40
Q

What is the white tube on the nose wheel?

A

The hydraulic nose wheel steering mechanism

41
Q

What is the PSEM?

A

We have 2 PSEMs, Proximity Sensor Electronics Modules, that process the information from the proximity sensors that determine WOW. The PSEM controlls the extension and retraction of the landing gear and indicates the landing gear position, the ground spoilers, and aircraft doors! Not just the WOW proximity sensors. The PSEMs then send the information to the ASCB Bus.

42
Q

What controlls the towing light?

A

The Nose Wheel Steering Control Module, NWSCM

43
Q

Is hydraulic system 3 part of the landing gear system? How about systems 1 and 2?

A

No. System 1 provides hydraulic pressure to the main brake outboard wheels and the emergency/parking brake. System 2 provides hydraulic pressure to the main brake inboard wheels, emergency/parking brake, AND LANDING GEAR EXTENSION AND RETRACTION. (This is why we have the PTU backup system.)

44
Q

What is the folding side stay, and locking stay? How are the down-lock springs associated with the folding side stay?

A

It is attached to the main landing gear holds the main landing gear in the fully extended position, and a locking stay holds the side stay in the fully extended position. THE DOWN-LOCK Springs hold the locking stay in the extended and locked position.

45
Q

What 3 peices of information do the landing gear proximity sensors send to the PSEM?

A

Landing gear down and locked (1 sensor attached to the lock stay), Landing gear up and locked (another sensor at the top by the uplock), aircraft on ground WOW (1 proximity sensor by the oleo-pneumatic strut)

46
Q

How is the landing gear retracted? Describe the steps

A

A hydraulic release actuator unlocks the locking stay, and a hydraulic retraction actuator retracts the landing gear, and the uplock holds the landing gear in the up position. Gear doors are mechanically closed and opened during extension and retraction.

47
Q

On the nose wheel, what is the piece that folds the wheel forward during retraction?

A

The folding drag brace. Like the main landing gear, the folding drag brace is held in position by a locking stay, with a pair or downlock springs holding the locking stay in the locked position.

48
Q

What sensors are on the nose wheel?

A

Proximity sensors and feedback sensors. The proximity sensors send down and locked, up and locked, and aircraft on ground WOW to the PSEM. The feedback sensors send steering angle and steering overtravel information to the nose wheel steering control module NWSCM.

49
Q

How is the nose wheel retracted? describe the steps

A

The hydraulic release actuator unlocks the locking stay, then a hydraulic retraction actuator retracts the nose gear, and an uplock holds the nose gear up. Again, like the main landing gear, the doors are mechanically opened and closed during extension and retraction.

50
Q

What are the 3 landing modes available to the crew? How do they work?

A

Normal extension/retraction (electrically actuated, hydraulically operated, the gear lever sends a signal to the PSEMs which provide hydraulic pressure to the hydraulic cylinders), electrical override (also electrically actuated and hydraulically operated, but the switch skips the PSEM and sends a signal directly to the landing gear selector valve to put the gear down), and alternate gear extension lever (mechanically actuated, gravity powered, mechanically releases all landing gear uplocks, and activates the free fall selector valve, gravity and aerodynamic forces will extend the landing gear).

51
Q

What prevents the pilot from selecting the gear up position while on the ground?

A

A locking solenoid keeps the lever from moving up based on WOW proximity sensors.

52
Q

What does the down lock release button do?

A

Pressing the down lock release button removes the locking solenoid, allowing the landing gear to be retracted even with a landing gear WOW proximity sensor disagreement (or while on the ground).

53
Q

What prevents a tire from exploding during a rejected takeoff?

A

Fuseable plugs are installed in the tire which melt and reduce tire pressure safely.

54
Q

How are the aircraft brakes controlled?

A

Electonic modules (2 BCM Brake Control Modules (1 for inboard and 1 for outboard) and 1 ABM Autobrake module, sensors, and hydraulic valves controll the hydraulic pressure to the inboard (hyd sys 2) and outboard brakes (hyd sys 1).

55
Q

How to the autobrakes work?

A

The ABM Autobrake Module will automatically apply the brakes.

56
Q

How does the anti-skid braking system work?

A

TBD not in the CBT video

57
Q

Does the emergency/parking brake work with a loss of hydraulic pressure?

A

Yes.

58
Q

How does the BCM know the wheel speeds if there is one going faster than another?

A

Transducers in the hub cap send the speed to the BCM.

59
Q

What are the braking high-level functions provided by the BCMs? How do they work?

A

Antiskid control, touchdown protection, and locked wheel protection. Antiskid control (compares wheel speed signals so BCMs can adjust braking pressure to each wheel) ACTIVE ABOVE 10kts, touchdown protection (prohibits a pressure command for any wheel if the aircraft is in flight or on ground for less than 3 seconds, except a spin-up override function allows braking when wheel speed is above 50kts). Locked wheel protection adjusts brake pressure by comparing wheel speeds activates if one wheel in the pair turns at less than 33% of its partner speed while over 30kts

60
Q

Why do the BCMs send a pressure command to all wheels for 4 seconds after takeoff? What happens after? How are the brakes activated for landing?

A

To keep the wheels from spinning in the wheel well causing heat. Once wheel speed is zero, the BCMs send signals to the 2 SOVs to isolate hydraulic supply to the brake control valves, so the brake hydraulic system is depressurized in flight. When the landing gear lever is moved down for landing a brake pressure test occurs and if successful, the 2 SOVs are energized again

61
Q

Can the autobrake switch be moved while landing, if you meant it to be high, but it was in the low position?

A

Yes. The autobrake will not turn off. It will adjust accordingly.

62
Q

When will the autobrakes apply brake pressure? When will they deactivate?

A

When armed, average wheel speed is above 60kts, WOW indicates on the ground for more than 2 seconds, and BOTH thrust levers are in idle or reverse position. They will deactivate when thrust levers are moved out of idle, it is turned off, or when brake pressure is applied.

63
Q

Will autobrakes work for a rejected takeoff below 60kts?

A

No.

64
Q

How does the emergency/parking brake work?

A

Mechanicalluy actuated handle, will lock at 60deg for parking brake and ON light on the EMERG/Parkbrake light, one side of the valve is connected to hyd sys 1 for the outboard brakes, the other side of the valve is connected to hyd sys 2 for the inboard brakes, ilsolated from the normal hydraulic supply by check valves, still available in the event of a total hydraulic system (1 and 2) failure through the accumulators.

65
Q

What does brake temperature in green mean?

A

The brakes can absorb maximum kinetic energy. at and above 252deg C the brakes are in the amber (verify) which indicates cooling is required.

66
Q

How does the nose wheel steering system work? What is it composed of?

A

Steer-by-wire system with 2 modes: Normal or Free-Wheel Steering Mode. The Nose wheel steering control module NWSCM, Steering manifold, steering motor, hydraulic system 2, turning angle sensor, over-steer angle sensor, rudders for high-speed steering control, steering handle for low-speed steering control, disarming switches on the yokes and outside on the AC GPU panel

67
Q

What is the steer off switch on the AC GPU panel for?

A

It puts the nose wheel steering in either normal mode or bypass mode allowing towing.

68
Q

How does the steering handle work?

A

There is a switch and a RVDT Rotary Variable Displacement Transducer. To turn the airplane, push the handle down, which activates the switch and the RVDT sends the steering angle desired to the NWSCM.

69
Q

What is the maximum steering angle using the steering handle?

A

76 degrees

70
Q

What is the nose wheel angle limited to when airspeed increases? Is the steering handle movement linear?

A

At taxi speeds from 40-100kts, the angle is gradually reduced from 76deg to 7degrees. THE STEERING HANDLE IS NOT LINEAR. When you turn the handle from 0 to 40deg, the nose wheel only turns 10degrees. When you turn the handle from 40-80deg, the nose wheel turns from 10deg to 76deg

71
Q

In the freewheel steering mode, what happens?

A

The nose wheel is controlled by an outside force (like towing), not by the steering handle or the rudders. This mode is activated (or normal is disengaged) by pressing the steering disarm switch or via the outside steering switch. STEER OFF will be displayed on the EICAS. If the airplane is turned more than 76deg, the STEER OFF message will also appear.

72
Q

What happens to the nosewheel angle after takeoff?

A

The nosewheel is centered by the self-centering mechanism once the shock strut extends.

73
Q

If the ground crew says the towing light is red, but the steer off switch was pressed, why might the light still be on?

A

The brakes are not released so it is still not safe to tow.

74
Q

If there is a nosewheel steering failure STEER FAIL EICAS in flight, what will happen when you land? Will the nose wheel be sideways?

A

No. The nosewheel will go into the free castor mode. This mode lets the nose wheel move freely in the direction of ground run. Steering can be accomplished using differential braking or rudder inputs.

75
Q

How is the landing gear warning gear system incorporated into the landing gear system?

A

The landing gear warning system gets information from the ASCB from the PSEMs - from the proximity sensors, GROUND SPOILER proximity sensors, and AIRCRAFT DOORS proximity sensors.

76
Q

In what 2 situations will the landing gear warning system annunciate “LANDING GEAR” and cannot be silenced?

A

If at least one landing gear is not locked down and there is an intention to land the aircraft. The intention to land the aircraft is based on TLA, Flap Setting, and RA. Cannot be silenced if:

  1. slat/flaps 5/full regardless of TLA or RA
  2. slat/flap 1/2/3/4, RA<700’AGL, TLA less than 45deg (or below 59deg if SE)
77
Q

When is the landing gear warning inhib button used? When can it not silence the landing gear warning?

A

In the event of dual RA failure, the warning inhib button will silence the aural warning only if the slat/flap lever is in the 1/2/3/4 position

In the event of a faulty RA signal, the button can be pushed and illumunated white, but once slat/flap 5/full OR TLA ABOVE 45deg (or ABOVE 59deg if SE) OR when all landing gear is down and locked, the red light will appear allowing a new warning activation

Cannot be silenced if:

  1. slat/flaps 5/full regardless of TLA or RA
  2. slat/flap 1/2/3/4, RA<700’AGL, TLA less than 45deg (or below 59deg if SE)
78
Q

Towing is not allowed when

A

Steering motor is pressurized, when operation is in active mode, and if any of the brakes are pressurized.

79
Q

In the event of a failure of both electronic and electrical override system, the landing gear should be extended by means of

A

the alternate gear extension lever

80
Q

During normal operation, the landing gear system is

A

electronically controlled and hydraulically operated

81
Q

Which BCM protections are still available during auto-brake control?

A

Anti-skid, touchdown protection, and locked wheel protection

82
Q

In the event of a failure in the PSEM electronics, the landing gear should be extended by means of

A

The electrical override switch

83
Q

Should the parking brake be set during Icing Conditons?

A

The use of Emergency/Parking Brakes may result in brakes freezing in certain conditions. Emergency/Parking Brakes should only be applied in the case of sloping and/or icy ramps. Snow or ice may be melted by the heat retained in the brakes.

Parking main tires in a layer of sand or mat may prevent tires from freezing on pavement surfaces. Wheel chocks should be placed against the Landing Gear wheels.

84
Q

ABM

A

Auto Brake Control Module

85
Q

BCM

A

Brake Control Module

86
Q

PSEM

A

Proximity Sensor Electronic Module

87
Q

PSEU

A

Proximity Sensor Electronic Unit

88
Q

PSS

A

Proximity Sensor System

89
Q

How are the carbon brakes different in general from normal brakes?

A

The carbon brake assembly on the E-JETs family has a carbon brake heat sink. This differs from traditional steel brakes since carbon brake wear is strongly affected by brake temperature. Carbon brakes wear less when operated at high temperatures while steel brakes wear less when operated at low temperatures.

90
Q

What considerations must be made for carbon brake use?

A

A. Overnight or Long Period Parking in Cold Weather
Avoid leaving the parking brake set. This decreases the chances of having brake stacks frozen together in case moisture was present before brake application.

B. General Rules for Carbon Brakes

  1. During taxi, minimize the duration of each brake application when practical by using shorter applications with higher pressure on the pedals.
  2. Avoid using brakes asymmetrically.

C. Number of Brake Applications
Minimize the number of brake applications when practical. The number of brake applications governs carbon brake wear.

D. Taxi when Brakes are Cold

  1. Do not intentionally use the brakes solely to heat them.
  2. Carefully manage taxi Speed. Let airplane accelerate to a maximum safe Speed, then use the brakes in one increasingly firm application to slow the airplane. Then release the brakes and allow the airplane to accelerate again. Less frequent use of brakes with higher braking pressure improves brake life.

E. Taxi when Brakes are Warm
1. Carefully manage taxi Speed. Let airplane accelerate to a maximum safe Speed then use brakes in a short but firm application. This helps to keep the brake within operating temperature range limits by allowing more cooling time and less brake friction time.

E175 Systems (18 decks)

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