B777. Landing Gear DO NOT USE FOR FLIGHT

Transcription

1 B777 Landing Gear DO NOT USE FOR FLIGHT

2 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 0 seconds and then blanks. With the landing gear retracted and all doors closed, the landing gear hydraulic system is automatically depressurized. Page

3 If any gear is not up and locked up after the normal transit time, the EICAS caution message GEAR DISAGREE is displayed. The EICAS gear position indication changes to the expanded non normal format, with the affected gear displayed as in transit or down, if the gear never unlocked from the down position. The EICAS advisory message GEAR DOOR is displayed if any hydraulically actuated door is not closed after normal transit time. Landing Gear Extension When the landing gear lever is moved to DN, the landing gear doors open, the gear are unlocked, and the in transit indication is displayed on the EICAS landing gear position indication. The gear free fall without hydraulic power to the down and locked position. The downlocks are powered to the locked position, all hydraulically actuated gear doors close, and the main gear trucks hydraulically tilt to the flight position. When all gear are down and locked, the EICAS gear position indication displays DOWN. The EICAS caution message GEAR DISAGREE is displayed if any gear is not locked down (side and drag brace on the same main gear not locked, or nose gear drag brace not locked) after the normal transit time. The EICAS gear position indication changes to the expanded non normal format, with the affected gear displayed as in transit (or UP if the gear never unlocked from the up position). If only one brace on a main gear is locked (either drag or side brace not locked) after the normal transit time, the EICAS caution message MAIN GEAR BRACE L or R is displayed for the affected gear. The EICAS gear position indication changes to the expanded non normal format, with the affected gear displayed as in transit. The EICAS advisory message GEAR DOOR displays if any hydraulically actuated door is not closed after the normal transit time. Landing Gear Alternate Extension The alternate landing gear extension system uses a dedicated DC powered electric hydraulic pump and center hydraulic system fluid to extend the landing gear. Selecting DOWN on the ALTERNATE GEAR switch releases all door and gear uplocks. The landing gear free fall to the down and locked position. The landing gear lever position has no effect on landing gear alternate extension. The EICAS landing gear position indication displays the expanded gear position indication when the alternate extension system is used. During alternate extension, the EICAS message GEAR DOOR is displayed because all the hydraulically powered gear doors remain open. Following an alternate extension, the landing gear can be retracted by the normal system, if it is operating. Select DN then UP to retract the landing gear using the normal system. Page 2

4 Semi-Levered Gear The semi-levered gear consists of an additional hydraulic actuator that connects the forward end of each main gear truck to the shock strut. During takeoff, the actuator locks to restrict rotation of the main gear truck and allow takeoff rotation about the aft wheel axle, thereby improving airplane performance capability. During landing, the actuator is unlocked to permit rotation of the main gear truck and provide additional damping. Nose Wheel and Main Gear Aft Axle Steering The airplane is equipped with nose wheel steering and main gear aft axle steering. Nose wheel steering is powered by the center/reserve hydraulic system. Main gear aft axle steering is powered by the center hydraulic system. Primary steering control is provided by a nose wheel steering tiller for each pilot. Limited steering control is available through the rudder pedals. The tillers can turn the nose wheels up to 70 degrees in either direction. A pointer on the tiller assembly shows tiller position relative to the neutral setting. The rudder pedals can be used to turn the nose wheels up to 7 degrees in either direction. Tiller inputs override rudder pedal inputs. Main gear aft axle steering automatically operates when the nose wheel steering angle exceeds 3 degrees to reduce tire scrubbing. The EICAS warning message CONFIG GEAR STEERING, accompanied by the takeoff configuration aural alert, is displayed if the main gear aft axles are not centered and locked when takeoff thrust is applied. The EICAS advisory message MAIN GEAR STEERING is displayed if the main gear steering actuators are not locked in the centered position when commanded to the center position. Brake System Each main gear wheel has a multiple disc carbon brake. The nose wheels have no brakes. The brake system includes: normal brake hydraulic system alternate/reserve brake hydraulic system brake accumulator Normal Brake Hydraulic System antiskid protection autobrake system parking brake. The normal brake hydraulic system is powered by the right hydraulic system. The brake pedals provide independent control of the left and right brakes. Page 3

5 Alternate/Reserve Brake Hydraulic System Alternate/reserve brake hydraulic system selection is automatic. If the right hydraulic system pressure is low, the center/reserve hydraulic system automatically supplies pressure to the alternate/reserve brake hydraulic system. Pushing a brake pedal then sends hydraulic pressure through the alternate antiskid valves to the brakes. If center hydraulic system fluid quantity is low, the C primary pump is isolated from the center hydraulic system to provide a reserve braking pressure source. 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. Brake Accumulator The brake accumulator is located in the normal brake hydraulic system. If right and center/reserve brake hydraulic power is lost, the brake accumulator can provide several braking applications or parking brake application. Antiskid Protection Antiskid protection is provided in the normal and alternate/reserve brake hydraulic systems. Antiskid protection is also provided when the brake system is being supplied pressure only from the brake accumulator. The normal brake hydraulic system provides each main gear wheel with individual antiskid protection. When a wheel speed sensor detects a skid, the associated antiskid valve reduces brake pressure until skidding stops. 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. Touchdown and hydroplaning protection is provided using airplane inertial ground speed. Locked wheel protection is provided using a comparison with other wheel speeds. 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. Autobrake System The autobrake system provides automatic braking at preselected deceleration rates for landing and full pressure for rejected takeoff. The system operates only when the normal brake system is functioning. Antiskid system protection is provided during autobrake operation. Page 4

6 EICAS memo messages display the selected autobrake settings: AUTOBRAKE through 4 AUTOBRAKE MAX AUTOBRAKE RTO. The EICAS advisory message AUTOBRAKE is displayed if the autobrake system is disarmed or inoperative, or autobrake solenoid valve pressure is high when not commanded on. Rejected Takeoff Selecting RTO (rejected takeoff) prior to takeoff arms the autobrake system. The RTO mode can be selected only on the ground. The RTO autobrake setting commands maximum braking pressure if: the airplane is on the ground groundspeed is above 85 knots, and both thrust levers are retarded to idle. Maximum braking is obtained in this mode. If an RTO is initiated below 85 knots, the RTO autobrake function does not operate. Taxi Brake Release During each taxi brake application, the antiskid system releases the brakes of one axle pair of each main landing gear (if wheel speeds are less than 45 knots). The system sequences through the axle pairs at each brake application, thereby reducing the number of brake applications by each brake. This extends service life and reduces brake sensitivity during taxi. All active brakes are applied for a heavy brake application, landing rollout, RTO, or when setting the parking brake. The taxi brake release system operates only with the normal brake hydraulic system. Landing Five levels of deceleration can be selected for landing. However, on dry runways, the maximum autobrake deceleration rate in the landing mode is less than that produced by full pedal braking. After landing, autobrake application begins when: both thrust levers are retarded to idle, and the wheels have spun up. Autobrake application occurs slightly after main gear touchdown. If MAX AUTO is selected, deceleration is limited to the AUTOBRAKE 4 level until pitch angle is less than one degree, then deceleration is increased to the MAX AUTO level. The deceleration level can be changed (without disarming the system) by rotating the selector. Page 5

7 To maintain the selected airplane deceleration rate, autobrake pressure is reduced as other controls, such as thrust reversers and spoilers, contribute to total deceleration. The system provides braking to a complete stop or until it is disarmed. Autobrake Disarm The autobrake system disarms and the EICAS advisory message AUTOBRAKE is displayed if any of the following occur: pedal braking applied either thrust lever advanced after landing speedbrake lever is moved to the DOWN detent after the speedbrakes have deployed on the ground DISARM or OFF position selected on the AUTOBRAKE selector autobrake fault normal antiskid system fault loss of inertial data from the ADIRU autobrakes are applied after loss of normal brake hydraulic pressure. When the autobrake system disarms after landing, the AUTOBRAKE selector automatically moves to the DISARM position, and removes power from the autobrake system. When the autobrake system disarms during takeoff, the autobrake selector remains in the RTO position, but automatically moves to OFF after takeoff. Parking Brake The parking brake can be set with the normal or alternate brake hydraulic system pressurized. If the normal and alternate brake systems are not pressurized, parking brake pressure is maintained by the brake accumulator. The brake accumulator is pressurized by the right hydraulic system. Accumulator pressure is shown on the BRAKE ACCUMULATOR PRESSURE indicator. The parking brake is set by fully depressing both brake pedals, pulling the parking brake lever up, then releasing the pedals. This mechanically latches the pedals in the depressed position and commands the parking brake valve to close. The parking brake is released by depressing the pedals until the parking brake lever releases. When the parking brake is set, the EICAS memo message PARKING BRAKE SET is displayed. If the parking brake is set and either engine is set to takeoff thrust, the takeoff configuration aural alert sounds and the EICAS warning message CONFIG PARKING BRAKE is displayed. Page 6

8 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.. 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 [ and ER] 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. Page 7

9 Landing Gear EICAS Messages The following EICAS messages can be displayed. Note: Configuration warning messages are covered in Chapter 5, Warning Systems. Brakes Message Level Aural Condition ANTISKID Advisory A fault is detected in the antiskid system. AUTOBRAKE Advisory Autobrake is disarmed or inoperative. AUTOBRAKE, 2, 3, 4, MAX, RTO Landing Gear 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 RESERVE BRAKES/STRG Memo Advisory The parking brake lever is up and the parking brake valve is closed 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 MAIN GEAR STEERING Caution Beeper Affected main gear is down with one brace unlocked. Advisory Main gear steering is unlocked when centered. Page 8

10 Tail Skid [ and ER] Tires [Option] Message Level Aural Condition TAIL SKID Advisory Tail skid position disagrees with landing gear lever position. Message Level Aural Condition TIRE PRESS Advisory One or more tire pressures are not normal. Page 9

11 4.0 Landing Gear-Controls and Indicators Landing Gear Panel GND PROX G/S FLAP GEAR GND PROX G/S INHB OVRD OVRD RETRACT 270K-.82M UP LOCK OVRD TERR OVRD OVRD DN ALTN GEAR NORM 4 EXTEND 270K-.82M DOWN 3 AUTOBRAKE 2 3 DISARM OFF 4 MAX AUTO 2 RTO CENTER FORWARD PANEL Landing Gear Lever UP the landing gear retracts. DN the landing gear extends. 2 AUTOBRAKE Selector OFF deactivates and resets the autobrake system. DISARM disengages the autobrake system releases brake pressure., 2, 3, 4, MAX AUTO selects the desired deceleration rate. RTO automatically applies maximum brake pressure when the thrust levers are retarded to idle above 85 knots. Page 0

12 3 Alternate Gear (ALTN GEAR) Switch NORM the landing gear lever operates normally. DOWN the landing gear extends by the alternate extension system. Note: Alternate extension may be selected with the landing gear lever in any position. 4 Landing Gear Lever Lock Override (LOCK OVRD) Switch Push releases the landing gear lever lock. Nose Wheel Steering Tiller 2 LEFT AND RIGHT SIDEWALLS Nose Wheel Steering Tiller Rotate turns the nose wheels up to 70 degrees in either direction overrides rudder pedal steering main gear aft axle steering is slaved to nose wheel steering. 2 Tiller Position Indicator Shows tiller displacement from the straight ahead, neutral position. Page

13 Brake System Rudder/Brake Pedals 2 Rudder Pedal Adjust Crank Adjusts the rudder pedals forward or aft. Note: To avoid inadvertent rudder pedal movement, the crank handle should be stowed when not in use. 2 Rudder/Brake Pedals Push the full pedal turns the nose wheel up to 7 degrees in either direction does not activate main gear steering. Push the top of the pedals actuates the wheel brakes. Parking Brake Lever PARKING BRAKE PULL CONTROL STAND Page 2

14 Parking Brake Lever Pull sets the parking brake when both brake pedals are simultaneously depressed. Release simultaneously depress both brake pedals. Brake Accumulator Pressure Indicator BRAKE SOURCE 2 4 BRAKE ACCUM 3 0 P SI X 2 00 LEFT FORWARD PANEL BRAKE SOURCE Light Illuminated (amber) both active brake hydraulic sources (right and center/reserve hydraulic systems) have low pressure. 2 BRAKE ACCUMULATOR PRESSURE Indicator Indicates brake accumulator pressure. Landing Gear System Indications Landing Gear Position Indications DOWN GEAR 2 DN GEAR DN EICAS DISPLAY Page 3

15 Gear Position Indication (Normal Display) DOWN (green) all landing gear are down and locked. Crosshatched (white) one or more landing gear are in transit. UP (white) all landing gear are up and locked (blanks after 0 seconds). Empty box (white) all landing gear position indicators are inoperative. 2 Expanded Gear Position Indication (Non Normal Display) DN (green) the associated landing gear is down and locked. Crosshatched (white) the associated landing gear is in transit. UP (white) the associated landing gear is up and locked. Empty box(es) (white) the associated landing gear position indicators are inoperative. Page 4

16 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 0, Flight Instruments, Displays. [Option Tire Pressure Indication] DOOR CLOSED BRAKE ASKID ASKID DOOR MULTIFUNCTION DISPLAY 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 Gear Door Status Crosshatched the door is not closed. CLOSED (white) the door is closed. Page 5

17 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. Page 6