B757-Landing_Gear_and_Brakes

                  B757    Landing Gear & Brakes DO NOT USE FOR FLIGHT  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 four wheels in tandem pairs. Hydraulic power for retraction, extension, and steering is supplied by the left hydraulic system. An alternate extension system is also provided. The normal/reserve brake hydraulic system is powered by the right hydraulic system. The alternate brake hydraulic system is powered by the left hydraulic system. Antiskid protection is provided with both systems, but the auto brake system is available only through the normal system. [B757 with Brake Temp EICAS display] A brake temperature monitor system displays each brake temperature on the EICAS status display. Air/Ground Sensing System In–flight and ground operation of various airplane systems are controlled by the air/ground sensing system and the nose air/ground sensing system. The air/ground sensing system receives air/ground logic signals from tilt sensors located on each main landing gear. These signals are used to configure the airplane systems to the appropriate air or ground status. A nose air/ground sensing system receives air/ground logic signals from nose gear strut compression sensors. These signals are for controlling stall warning and portions of the caution and warning system. An EICAS advisory message AIR/GND SYS or NOSE A/G SYS indicates that some portion of the sensing system failed. Affected equipment and systems will not operate normally and therefore takeoff is not allowed. 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 controlled by the main gear tilt sensors. When the gear is not tilted (aircraft on the ground) the lock is engaged. The lever lock can be manually overridden by pushing and holding the landing gear lever LOCK OVRD switch. In flight, the lever lock is automatically released through air/ground sensing. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 1 Ludo Tampon Landing Gear Retraction After takeoff both main gear tilt, releasing the lever lock. When the landing gear lever is positioned to UP, the landing gear begins to retract. The gear down green lights extinguish, the GEAR and DOORS lights illuminate showing gear is in transit (gear, doors and lever position disagree).The landing gear doors open and the tilted main gear and nose gear move to the retract position. Automatic wheel braking occurs during gear retraction. After retraction, all three landing gear and their doors are held up by uplocks. The GEAR and DOORS lights extinguish. The landing gear lever is placed in the OFF position to depressurize the landing gear system. The GEAR light remains illuminated and the EICAS caution message GEAR DISAGREE display if any gear is not up and locked up after the normal transit time. The affected gear’s, gear down light, remains illuminated if the gear never unlocked from the down position. The DOORS light remains illuminated and the EICAS advisory message GEAR DOORS display 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 GEAR and DOORS lights illuminate. The gear are hydraulically powered 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 gear down lights illuminate and the GEAR and DOORS lights extinguish. The GEAR light remains illuminated and the EICAS caution message GEAR DISAGREE display if any gear is not locked down after the normal transit time. The extinguished gear down light indicates the affected gear. The DOORS light remains illuminated and the EICAS advisory message GEAR DOORS display 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. Fluid within the supply line to the pump is sufficient for alternate gear extension operation. This fluid is isolated from the left hydraulic system. Selecting the ALTN GEAR EXTEND switch releases all door and gear uplocks. The landing gear free–fall to the down and locked position. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 2 Ludo Tampon When all gear are down and locked, the gear down lights illuminate and the GEAR light extinguishes. During alternate extension, the DOORS light remains illuminated and the EICAS advisory message GEAR DOORS display because all the hydraulically powered gear doors remain open. Nose Wheel Steering Nose wheel steering is powered by the left hydraulic system. Primary steering control is provided by the left sidewall nose wheel steering tiller. Limited steering control is available through the rudder pedals. The tiller can turn the nose wheel up to 65 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 seven degrees in either direction. Tiller inputs override rudder pedal inputs. Brake System Each main gear wheel has a multiple disc brake. The nose wheels have no brakes. The brake system includes: • normal/reserve brake hydraulic system • alternate brake hydraulic system • brake accumulator • antiskid protection • auto brake system • parking brake Normal Brake Hydraulic System The normal brake hydraulic system is powered by the right hydraulic system. The brake pedals provide independent control of the left and right brakes. Alternate Brake Hydraulic System Alternate brake hydraulic system selection is automatic. If the right hydraulic system pressure is low, the left hydraulic system automatically supplies pressure to the alternate brake system. Pushing a brake pedal then sends hydraulic pressure through the alternate antiskid valves to the brakes. The BRAKE SOURCE light illuminates and the EICAS advisory message BRAKE SOURCE displays if both the normal and the alternate brake system pressures are low. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 3 Ludo Tampon Reserve Brakes Pressing the RESERVE BRAKES switch provides reserve hydraulic fluid to the right system electric pump. Pump pressure is then supplied exclusively to the normal brakes system. The BRAKE SOURCE light extinguishes when pressure is available. Brake Accumulator If right/reserve, and alternate 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/reserve and alternate brake hydraulic systems. The normal/reserve 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 brake hydraulic system provides antiskid protection to laterally paired wheels. Touchdown, hydroplaning, and locked wheel protection is provided. The ANTISKID light illuminates and the EICAS advisory message ANTISKID displays to indicate a fault is detected in the antiskid system. Auto Brake System The auto brake system provides automatic braking at pre–selected deceleration rates for landing. The system operates only when the normal/reserve brake system is functioning. Antiskid system protection is provided during auto brake operation. The AUTO BRAKES light illuminates and the EICAS advisory message AUTOBRAKES displays if the auto brake system is disarmed or inoperative. Rejected Takeoff Selecting RTO prior to takeoff arms the auto brake system. The RTO mode can be selected only on the ground. The RTO auto brake 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 auto brake function does not operate. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 4 Ludo Tampon Landing Five levels of deceleration can be selected for landing. However, on dry runways, the maximum auto brake deceleration rate in the landing mode is less than that produced by full pedal braking. After landing, auto brake application begins when: • both thrust levers are retarded to idle, and • the wheels have spun up Auto brake application occurs slightly after main gear touchdown. Deceleration is limited until the pitch angle is less than one degree, then deceleration increases to the selected level. The deceleration level can be changed (without disarming the system) by rotating the selector. To maintain the selected airplane deceleration rate, auto brake 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. Auto Brake – Disarm The system disarms immediately, the AUTO BRAKES light illuminates and the EICAS advisory message AUTOBRAKES displays if any of the following occur: • pedal braking applied • either thrust lever advanced after landing • speedbrake lever is moved from the full up position after the speedbrakes have deployed on the ground • DISARM or OFF position selected on the AUTO BRAKES selector • auto brake fault • normal antiskid system fault When the auto brake system disarms after landing, the auto brakes selector automatically moves to the DISARM position, the AUTO BRAKES light illuminates, and power is removed from the auto brake system. When the auto brake system disarms during takeoff, the auto brakes selector remains in the RTO position. After takeoff, the AUTO BRAKES selector automatically moves to OFF. Parking Brake The parking brake can be set with the normal/reserve or alternate brake hydraulic system. If the normal/reserve 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 PRESS indicator. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 5 Ludo Tampon The parking brake is set by fully depressing both brake pedals, pulling the parking brake handle 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 handle releases. The PARK BRAKE light illuminates and the EICAS advisory message PARKING BRAKE displays when the parking brake is set. Brake Temperature Indication [B757 with Brake Temp EICAS display] Wheel brake temperatures are displayed on the EICAS status page. Numerical values related to wheel brake temperature are displayed for each main gear brake. Brake temperature values range from 0 to 9. Temperature values are not instantaneous and tend to build for 10 to 15 minutes after brakes are applied. Initial range values of 0 to 2 are cyan numbers in a cyan box. For normal range values of 3 and 4, the number is cyan and the box is white for the first per truck that exceeds 2. Values in the high range of 5 to 9 have a white number and box. The BRAKE TEMP light illuminates for values of 5 and above. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 6 Ludo Tampon Landing Gear EICAS Messages The following EICAS messages can be displayed.te: Configuration warning messages are covered in Chapter 15, Warning Systems. The following EICAS messages can be displayed. Brakes Landing Gear Message Level Light Aural Condition ANTISKID Advisory ANTISKID A fault is detected in the antiskid system. AUTOBRAKES Advisory AUTO BRAKES Auto brakes are disarmed or inoperative. BRAKE SOURCE Advisory BRAKE SOURCE Normal and alternate brake system pressures are low. PARKING BRAKE Advisory PARK BRAKE The parking brake is set. Message Level Light Aural Condition AIR/GND SYS Advisory Air/ground sensing system failed. GEAR DISAGREE Caution GEAR Beeper Gear position disagrees with landing gear lever position. GEAR DOORS Advisory DOORS One or more gear doors are not closed. NOSE A/G SYS Advisory Nose air/ground sensing system failed. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 7 Ludo Tampon 14.10 Landing Gear-Controls and Indicators Landing Gear Panel Gear Indications [B757 with Gear panel without Brake Temp light] [B757 with Gear panel with Brake Temp light] 1 DOORS Light Illuminated (amber) – a door is not closed. 2 Landing GEAR Disagree Light Illuminated (amber) – the gear position disagrees with the lever position. 3 Landing Gear Down Lights (NOSE, LEFT, and RIGHT) Illuminated (green) – the associated landing gear is down and locked. CENTER FORWARD PANEL NOSE LEFT D O O R S G E A R RIGHT 1 CENTER FORWARD PANEL NOSE LEFT D O O R S G E A R RIGHT BRAKE TEMP 4 4 Brake Temperature (BRAKE TEMP) Light [B757 with Gear panel with Brake Temp light] Illuminated (white) – a wheel brake temperature is in high range (a value of 5 or above on the status page). Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 8 Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon 1 Landing Gear Lever UP – the landing gear retracts. OFF – hydraulic pressure is removed from landing gear system. DN – the landing gear extends. 2 Alternate Gear Extend (ALTN GEAR EXTEND) Switch OFF – the landing gear lever operates normally. DN (down) – the landing gear extends by the alternate extension system. DN UP RETRACT 270K OFF LOCK OVRD EXTEND OR EXTENDED 270K-.82M CENTER FORWARD PANEL OFF DN ALTN GEAR EXTEND 250K-.75M 1 2 3 Gear Extension/Retraction 3 Landing Gear Lever Lock Override (LOCK OVRD) Switch Push – releases the landing gear lever lock. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 9 Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Nose Wheel Steering Tiller A nose wheel steering tiller is installed on the left sidewall. 1 Nose Wheel Steering Tiller Rotate – • turns the nose wheels up to 65 degrees in either direction • overrides rudder pedal steering 2 Tiller Position Indicator Shows tiller displacement from the straight–ahead, neutral position. Brake System Rudder/Brake Pedals 1 Rudder Pedal Adjust Crank Pull and Rotate – adjusts the rudder pedals forward or aft. SIDEWALL 1 2 2 1 2 Rudder/Brake Pedals Push the full pedal – turns the nose wheel up to seven degrees in either direction. Push the top of the pedals – actuates the wheel brakes. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 10 Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon 1 AUTO BRAKES Light Illuminated (amber) – the auto brakes are disarmed or inoperative. 2 AUTO BRAKES Selector OFF – deactivates the autobrake system. DISARM – • disengages the auto brake system • releases brake pressure 1,2,3,4, MAX AUTO – selects the desired deceleration rate. RTO – automatically applies maximum brake pressure when the thrust levers are retarded to idle above 85 knots. Parking Brake Handle CENTER FORWARD PANEL AUTO BRAKES AUTO BRAKES 1 2 3 4 MAX AUTO DISARM OFF RTO 2 1 PARK BRAKE A R B R K A K E P CONTROL STAND 1 2 Auto Brakes Selector 1 Parking Brake (PARK BRAKE) Light Illuminated (amber) – the parking brake is set. 2 Parking Brake (PARK BRAKE) Handle Pull – sets parking brake when both brake pedals are simultaneously depressed. Release – simultaneously depress both brake pedals. Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 11 Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon 1 Brake Accumulator Pressure (BRAKE PRESS) Indicator Indicates brake accumulator pressure (psi x 1000). Brake Source Light 1 BRAKE SOURCE Light Illuminated (amber) – both normal and alternate brake system pressures are low. Reserve Brakes 4 3 2 1 0 PRESS BRAKE PSIX1000 CENTER FORWARD PANEL 1 BRAKE SOURCE CENTER FORWARD PANEL 1 RESERVE BRAKES ON CENTER FORWARD PANEL 1 Brake Accumulator Pressure Indicator 1 RESERVE BRAKES Switch ON – • allows use of reserve hydraulic fluid • activates right electric hydraulic pump • isolates the right electric hydraulic pump power to the normal brake system OFF (ON not visible) – • allows the right electric hydraulic pump switch to control the pump • does not allow use of the reserve hydraulic fluid • removes isolation of the right electric hydraulic pump power to only the normal brakes Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 12 Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Antiskid Light 1 ANTISKID Light Illuminated (amber) – a fault is detected in the antiskid system. Brake Temperature [Aircraft with EICAS Display Brake Temp] ANTISKID OVERHEAD PANEL 1 BRAKE TEMP 2 2 2 2 21 11 EICAS STATUS DISPLAY 1 1 Brake Temperature (BRAKE TEMP) Indicates a relative value of wheel brake temperature. • values range from 0 to 9 • 0 to 2 – initial range, box and number are cyan • 3 and 4 – normal range, box is white for the first brake per truck that exceeds the value of two and number cyan • 5 to 9 – high range, box and number are white for each brake with a value of 5 or above Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 13 Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon Boeing B757 - Systems Summary [Landing Gear & Brakes] Page 14 Ludo Tampon Ludo Tampon Ludo Tampon Ludo Tampon