Download B777 Landing Gear PDF

TitleB777 Landing Gear
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Total Pages17
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B777

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Introduction
The airplane has two main landing gear and a single nose gear. The nose gear is a
conventional steerable two–wheel unit. Each main gear has six wheels in tandem
pairs. To improve turning radius, the aft axle of each main gear is steerable.
Hydraulic power for retraction, extension, and steering is supplied by the center
hydraulic system. An alternate extension system is also provided.

[Option – Synoptic Tire Pressure Indication]
The normal brake hydraulic system is powered by the right hydraulic system. The
alternate/reserve brake hydraulic system is powered by the center hydraulic
system. Antiskid protection is provided with both systems, but the autobrake
system is available only through the normal system. A brake temperature monitor
system and tire pressure indication system displays each brake temperature and
tire pressure on the GEAR synoptic display.

Air/Ground Sensing System
In–flight and ground operation of various airplane systems are controlled by the
air/ground sensing system.
The system receives air/ground logic signals from sensors located on each main
landing gear beam. These signals are used to configure the airplane systems to the
appropriate air or ground status.

Landing Gear Operation
The landing gear are normally controlled by the landing gear lever. On the ground,
the lever is held in the DN position by an automatic lever lock. The lever lock can
be manually overridden by pushing and holding the landing gear lever LOCK
OVERRIDE switch. In flight, the lever lock is automatically released through
air/ground sensing.

Landing Gear Retraction
When the landing gear lever is moved to UP, the landing gear begins to retract.
The landing gear doors open and the main gear wheels tilt to the retract position.
The EICAS landing gear position indication display changes from a green DOWN
indication to a white crosshatch in–transit indication as the landing gear retract
into the wheel wells. After retraction, the landing gear are held up by uplocks. The
EICAS landing gear position indication changes to UP for 10 seconds and then
blanks. With the landing gear retracted and all doors closed, the landing gear
hydraulic system is automatically depressurized.

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Brake Temperature Indication
Wheel brake temperatures are displayed on the GEAR synoptic display.
Numerical values related to wheel brake temperature are displayed adjacent to
each wheel/brake symbol. These values range from 0.0 to 9.9 in increments of 0.1.
The values tend to increase after the brakes are used.
Normal range values of 0 to 4.9 are white. For values of 3.0 to 4.9, the brake
symbol for the hottest brake becomes solid white. Values of 5.0 and above are
amber. For values of 5.0 and above, the EICAS advisory message BRAKE TEMP
is displayed.

Tire Pressure Indication
[Option]
Individual tire pressures, from 0 to 400 PSI, are displayed inside the individual
wheel symbols on the GEAR synoptic display.
The EICAS advisory message TIRE PRESS is displayed if any tire pressure is
above or below the normal range, or there is an excessive pressure difference
between two tires on the same axle.

Tail Skid
[777-300 and 777-300ER]
The airplane is equipped with a tail skid system. The tail skid extends for takeoff
and landing and retracts during flight. It helps protect the pressurized part of the
airplane from contact with the runway. The tail skid uses the main landing gear
actuation system.
The EICAS advisory message TAIL SKID is displayed when the tail skid is not in
the correct position.

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Landing Gear EICAS Messages
The following EICAS messages can be displayed.

Note: Configuration warning messages are covered in Chapter 15, Warning
Systems.

Brakes

Landing Gear

Message Level Aural Condition

ANTISKID Advisory A fault is detected in the antiskid system.

AUTOBRAKE Advisory Autobrake is disarmed or inoperative.

AUTOBRAKE 1,
2, 3, 4, MAX, RTO

Memo Indicates selected autobrake level.

BRAKE SOURCE Advisory Normal, alternate, and reserve brakes are
not available.

BRAKE TEMP Advisory Temperature of one or more brakes is
excessive.

PARKING
BRAKE SET

Memo The parking brake lever is up and the
parking brake valve is closed

RESERVE
BRAKES/STRG

Advisory Reserve brakes, normal nose gear
extension, and nose wheel steering may
not be available.

Message Level Aural Condition

GEAR DISAGREE Caution Beeper Gear position disagrees with landing gear
lever position.

GEAR DOOR Advisory One or more gear doors are not closed.

MAIN GEAR
BRACE L, R

Caution Beeper Affected main gear is down with one brace
unlocked.

MAIN GEAR
STEERING

Advisory Main gear steering is unlocked when
centered.

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Gear Synoptic Display
The landing gear synoptic is displayed by pushing the GEAR synoptic display
switch on the display select panel. Display select panel operation is described in
Chapter 10, Flight Instruments, Displays.

[Option – Tire Pressure Indication]

1 Brake Temperature
Indicates a relative value of wheel brake temperature:
• values range from 0.0 to 9.9
• white – normal range
• amber – high range.

2 Brake Symbol
Blank box indicates any brake less than 3.0.
Solid white box indicates hottest brake on each main gear within range of 3.0 to
4.9.
Solid amber box indicates brake overheat condition on each wheel within range of
5.0 to 9.9.

3 Gear Door Status
Crosshatched – the door is not closed.
CLOSED (white) – the door is closed.

CLOSEDDOOR

160 160

160160

160160

160 160

160160

160160

BRAKE
0.0

2.4

3.4

3.1

3.3

2.8

2.2

ASKID
1.7

8.3

7.1

ASKID
3.3

2.8

DOOR

160 160

MULTIFUNCTION DISPLAY

1

2

3

4

5

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Empty box(es) (white) – the associated landing gear door position indicators are
inoperative.

4 Fault Indication (amber)
BRAKE – indicates brake deactivation on the associated wheel.
ASKID – indicates antiskid fault on the associated wheel.

5 Tire Pressure Indication
Displays individual tire pressures:
• white – normal range
• amber – abnormal high or low range.

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