BRAKES 1. NORMAL OPERATION & INDICATION ¡ Landing gear is powered by the RIGHT hydraulic system. ¡ LEFT & RIGHT brake pedals provide independent control of pressure to the LEFT & MAIN brakes ¡ Pushing a brake pedal opens the respective brake metering valve allowing pressure to pass through antiskid valves provided for each wheel. ¡ ACCUMULATOR pressure = RIGHT system pressure = Brake pressure without active hydraulic power (RIGHT & CENTER) Ô Amber band = initial precharge (a reading at or below amber band indicates no accumulator brake pressure is available). Ô Accumulator pressure maintained during alternate operation by closing an accumulator isolation valve. Ô ONLY source of braking with amber BRAKE SOURCE light. ¡ AUTOBRAKE is only available on Normal brakes (antiskid protection is provided during autobrake operation) Ô Max Autobrake = less than full manual braking Ô Autobrake operation starts if : 1) System armed (AUTOBRAKE selector on RTO) 2) T/L to IDLE 3) MAIN landing gear truck untilt 4) Wheel spin-up Ô Autobrake disarms when : 1) System fault 2) Normal antiskid system fault 3) Manual braking 4) Advancing T/L after landing 5) Speedbrake Lever > DOWN 6) Selecting DISARM or OFF Ô RTO = MAX Manual braking Ô It is activated on ground with : - Average wheel speed > 85 kt. and - both T/L retarded to IDLE Ô Selector trips to OFF on liftoff
2. ALTERNATE OPERATION ¡ Alternate brake system is powered by the CENTER hydraulic system ¡ When RIGHT hydraulic system is LOW, the ALTERNATE source selector valve opens automatically to provide CENTER hydraulic pressure to the ALTERNATE METERING valves. ¡ Same antiskid controller & light as normal brakes are used during ALTERNATE operation. Antiskid Controller regulates pressure through each alternate antiskid valve to a set of laterally paired wheels based on 8 separate wheel speed transducer inputs
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BOEING 767 SYSTEMS REVIEW
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¡ When the ALTERNATE brake system is powered, the ANTISKID light monitors the alternate brake system. This light illuminates with a power loss or system malfunction. The Brake system is summarized below :
PRIORITY
BRAKE SYSTEM
1 2 3 4
HYDRAULIC POWER
Normal brakes Right system Alternate brakes Center system Reserve brakes & steering Reserve qty of Center system Accumulator (Normal brakes) Accumulator
ANTISKID AUTOBRAKES OK OK OK OK
OK INOP INOP INOP
3. ANTISKID ¡ Pushing a brake pedal opens the respective brake metering valve allowing pressure to pass through antiskid valves provided for each wheel. ¡ Antiskid Controller regulates pressure through each valve based on 8 separate wheel speed transducer inputs. It is a protection for : - Skid - Locked wheel - Hydroplane - Touchdown ¡ ANTISKID light = partial antiskid failure but autobrake may be selected. if not operative, the selector will trip to disarm ¡ ANTISKID OFF light = complete failure (computer) > Do not use autobrake ! ¡ ANTISKID OFF light + Parking brake ON = the parking brake valve does not OPEN to release the brakes pressure.
4. BRAKE TEMPERATURE ¡ Brake temperature conditions – for each MAIN gear – are displayed on the EICAS status page (option) ¡ Temperature values tend to build for 10 min. to 15 min after braking 0-2 INITIAL range 3-4 NORMAL range 5-9 HIGH range
indications are BLUE values are BLUE and box is WHITE Indications are WHITE and BRAKE TEMP light ON
5. FAULTS PARK BRAKE
BRAKE SOURCE
(amber) : Parking brake valve not open.
(amber) :
- Normal & Alternate brake system pressure low or - Accumulator is power source to brakes.
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ANTISKID
(amber) : Antiskid fault detected in the active brake system (NORMAL or ALTERNATE)
AUTO BRAKES
(amber) : Auto brakes system disarmed
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BOEING 767 SYSTEMS REVIEW
BRAKES SYSTEM
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BOEING 767 SYSTEMS REVIEW
NORMAL BRAKES
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BOEING 767 SYSTEMS REVIEW
ALTERNATE BRAKES
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