Landing Gear Flashcards
The 322 incorporates a more robust main gear strut and truck than earlier 777
models as well as semi-levered gear.
The semi-levered gear consists of
a hydraulic actuator that connects the forward side of the main gear strut
to the gear truck.
The semi-levered gear has
locked, tilt and stow positions.
On take-off, the aircraft effectively rotates around
the aft wheel pairs as the hydraulic actuator locks the main gear truck.
This facilitates a greater Angle Of Attack and better take-off performance.
In flight with the wheels down and locked,
the hydraulic actuator positions
the main gear truck with
a wheels up tilt
to provide damping during touchdown.
The hydraulic actuator also positions the main gear truck to
a forward wheels down position
for retraction into the wheel wells.
he Boeing 777 is steered on the ground through
nose wheel and main gear aft axle steering.
Hydraulic power for the normal brake
hydraulic system is supplied by
the Right Hydraulic system.
The brake accumulator is pressurized by
the Right Hydraulic system.
In the normal brake system (and with accumulator braking),
each wheel has individual antiskid protection.
The alternate / reserve brake system only provides individual antiskid
to the aft axle wheels;
forward and middle axles are protected as wheel pairs.
The parking brake can be set with
normal or alternate brake system pressure.
If neither is available,
it can be set using brake accumulator pressure.
The normal range for the brake temperatures are
For values between 3 and 4.9,
the symbol for the hottest brake, on each main gear, becomes
between 0 and 4.9.
solid white.
Brake temperature values between 5.0 and 9.9 will be
shown in amber and
the solid amber box for any brake
indicates an overheat condition.
There are two weight-on-wheels landing sensors located
on each main landing gear beam.
The maximum airspeed for normal gear extension and retraction is
270 KIAS or Mach .82.
White crosshatches indicate
A closed door is indicated by
the door is not closed.
“CLOSED” boxed in white.
Once the uplocks are released,
the gear freefalls into the down and locked position
and the downlocks are
powered to the downlock position.
The hydraulically actuated gear doors close and the main gear tilt to the flight position.
Main gear aft axle steering automatically operates when
the nose gear steering angle exceeds 13 °.
The aft axles move up to 6.5 ° in each direction
reaching full deflection when the nose wheel reaches 70 °.
This movement of the aft axles reduces
tire scrubbing and the turning radius of the aircraft.
on dry runways, deceleration rate for MAX AUTO is
less than that produced by full manual pedal braking.
With AUTOBRAKE 1 or 2 selected, brake application is
With 3, 4 or MAX AUTO selected, autobrakes are
delayed until slightly after touchdown.
applied immediately upon touchdown.
Autobrakes disarm and the EICAS advisory message AUTOBRAKE is
displayed if:
pedal braking is applied,
either thrust lever is advanced after landing,
the speedbrake lever is moved to the DOWN detent,
disarm or OFF is selected,
an autobrake fault, or there is a normal antiskid system fault.
The Autobrakes disarm and the EICAS message also displays if there is loss of inertial data from the ADIRU,
or autobrakes are applied after loss of normal brake hydraulics.
The RTO setting commands maximum braking pressure if:
the airplane is on the ground,
ground speed is above 85 kt and both thrust levers are retarded to idle.
If a Rejected Take-off (RTO) is initiated below 85 kt the RTO autobrake function does not operate.
After take-off, the AUTOBRAKE selector automatically
disarms and moves to the OFF position.
touchdown and hydroplaning protection is provided
using airplane inertial ground speed.
If the gear lever is locked down after take-off,
there is a malfunction with the air / ground sensing system.
System inputs indicate (incorrectly)
that the aircraft is on the ground.
The alternate gear extension system
uses a dedicated DC powered motor and fluid from
the Center Hydraulic system to extend the landing gear.
Selecting the alternate gear switch releases all door and gear uplocks.
Like normal gear extension, the gear free falls to the down and locked position.
Landing gear lever position has
no effect on the alternate system.
When the alternate gear system is used,
the EICAS changes to the expanded gear indication.
The advisory message “GEAR DOOR” will also display on the EICAS because
all gear doors remain in the open position.
If either the drag brace or side brace is not locked after the normal gear transit
time, the EICAS caution message
“MAIN GEAR BRACE L” or “MAIN GEAR BRACE R” will be displayed.
A white box indicates failure of any gear or door position indicator.
Failure of all gear position indicators is indicated
by a single white box on the EICAS.
If the main gear aft axles are not centered when commanded to the center
position, the EICAS advisory message
“MAIN GEAR STEERING” will be displayed.
If take-off thrust is applied without
the main gear aft axles centered and locked,
the take-off configuration aural alert will sound
and the EICAS warning
“CONFIG GEAR STEERING” will be displayed.
If Right Hydraulic system pressure is low,
the Center / Reserve Hydraulic system
automatically supplies pressure to the alternate / reserve
brake hydraulic system via the alternate antiskid valves.
In the event center system quantity is low,
the C1 hydraulic pump is isolated to
provide pressure to the alternate brakes.
It uses reserve fluid in the center reservoir
to provide reserve braking.
Loss of the right and center / reserve hydraulic systems causes
the “BRAKE SOURCE”
light to illuminate
and the EICAS advisory message
“BRAKE SOURCE” to display.
If right and center / reserve brake hydraulic power is lost,
the brake accumulator can
provide several braking applications
or parking brake application.
The alternate / reserve brake hydraulic system
provides antiskid protection to tandem wheel pairs
for the forward and middle axle wheels.
The aft axle wheels
remain individually controlled.
The EICAS advisory message “ANTISKID” is displayed if
an antiskid fault affecting the brake hydraulic system in use is detected,
or if the parking brake valve is not fully open with the parking brake released,
or if the system is completely inoperative.
The EICAS advisory message “AUTOBRAKE” is displayed if
the autobrake system is disarmed or has failed.
Brake temperature values of
5.0 and above are displayed in amber and
the EICAS advisory message “BRAKE TEMP” is displayed.
