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Smartcockpit.com
BOEING 767 SYSTEMS REVIEW
Page 1
PNEUMATICS
1. GENERAL ¡ Air for Ô Air conditioning & pressurization Ô Wing & Engine anti-ice Ô Engine start Ô Cargo heat Ô Center hydraulic system ADP (Air Driven Pump) Ô Hydraulic Reservoir Pressure
2. ENGINE BLEED AIR SUPPLY ¡ Left & Right engine bleed air supplies are similar & pneumatics energy comes either from : - High Pressure (HP) Engine compressor section - Low Pressure (LP) ¡ Low thrust = HP valve open. High thrust = HP valve closed. ¡ Bleed Air valves are used for pressure control and : - are electrically commanded - are pressure actuated - close during period of low air demand.
3. PNEUMATIC DUCTING ¡ Normal flight procedures require isolation between Left and Right systems after engine start : - Each engine supplies air to its corresponding Air Cond. Pack, Wing Anti-ice, Thrust reverser & Hydraulic reservoir. - Both engines supply air to the Center pneumatic duct. - Separation of the system is controlled by the L & R isolation valves controlled by the L & R Isol. Switches. - A bypass around each isolation valve allows airflow from the engine for FWD cargo compartment heat & to supply the Center pneumatic duct. ¡ The pressures read on the Pneumatic Duct Pressure Indicator should be approximately equal ¡ Center Isolation switch controls Bleed airflow into or out of the Center pneumatic duct. The switch is ON for normal operation. ¡ After engine start, air is bypassed around the L & R isolation valves into the crossover manifold & then into the Center pneumatic duct for distribution to the using systems : - Center hydraulic system demand Air Driven Pump (ADP) - Aft cargo compartment heat - Bulk cargo compartment heat - Center hydraulic reservoir
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BOEING 767 SYSTEMS REVIEW
Page 2
4. APU BLEED AIR SUPPLY ¡ APU is connected to the pneumatic system through the APU Bleed Air Valve : - VALVE light illuminates momentarily indicating a disagreement while the valve is in transit. - Opens with APU at normal speed through the Center pneumatic duct. - Closes after the first engine start. - Reopens during the start cycle of the other engine. - With engines running, cannot be opened unless Center isolation valve closed & both engine bleed valves closed (Check valve in the center duct + APU bleed Air Valve). ¡ Barometric control of APU components automatically reduces APU pneumatic pressure and results in insufficient pressure for cabin pressurization > 20.000 ft.
5. GROUND PNEUMATIC SUPPLY ¡ 2 ground connectors on the Left side of the a/c permit 2 Packs operation or engine start. ¡ L + R ISLN switches should be ON for : - air conditioning pack - engine starting
6.
DUCT LEAK TEST
¡ Checks the continuity of the leak detector loops. ¡ Illumination of the three DUCT LEAK + EICAS Caution messages = no fault ¡ BODY DUCT LEAK msg is a leak in the CENTER duct.
7. ENG STRUT LEAK TEST ¡ Checks the continuity of the detectors and simulate a strut leak. ¡ Illumination of L&R DUCT LEAK lights + EICAS Caution message = no fault. ¡ Releasing the switch terminates the test. For resetting the system, Engine Bleed Air switches must be cycled to unlatch the PRV & HPSOV and return to normal operation.
8.
FAULTS L/R ISLN VALVE
- ON (alternate action) : opens Isolation Valve - VALVE (amber) : Isolation Valve position disagrees with switch signalled position.
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BOEING 767 SYSTEMS REVIEW
Page 3
APU V A L V E
ON
(amber) : APU bleed air valve disagrees with signalled position.
L/R ENG
O F F
DUCT LEAK
BLEED
OVHT
D U C T
L E A K
- ON (alternate action) : opens engine bleed air valves if engine is operating - OFF (amber) : engine bleed air valve closed + EICAS msg.
ON
(amber)
- Bleed air leak in the Left, Right or engine strut pneumatic duct + EICAS msg. or - system test Ô Bleed air and isolation switches to be selected OFF Ô in case of Bleed duct leak = back to normal when the temperature has cooled Ô if the light remain ON, a leak exists between the L and R isolation valves Ô Strut duct leak = light remain illuminated
(amber) : Engine HPSOV (High Pressure Shutoff Valve) and/or Pressure Regulating valves are open when they should be closed + EICAS msg Ô BLEED + Eng. HPSOV = the HPSOV is open when only low pressure is required Ô BLEED + Eng. PRV = the pressure regulating valve has failed open
(amber)
(amber)
- Engine Bleed Air over temperature + EICAS msg and - Engine Bleed air valves are automatically closed + EICAS msg Ô OVHT gives a signal to close the engine bleed valve > idem for PRV and HPSOV Ô unless strut duct leak exist : - PRV reopens with engine anti-ice - HPSOV and PRV reopens for Thrust reverser Ô reset = BLEED AIR SWITCH ON and OFF A only one reset recommended.
- Bleed air leak in the centre pneumatic duct + EICAS msg or - System test + EICAS msg
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BOEING 767 SYSTEMS REVIEW
PNEUMATICS SYSTEM (PW)
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Page 4
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BOEING 767 SYSTEMS REVIEW
PNEUMATICS SYSTEM (GE)
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Page 5
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BOEING 767 SYSTEMS REVIEW
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