B767 Pneumatics

8/13/2019 B767 Pneumatics

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Copyright© Smartcockpit.comLudovic ANDRE / version 00

Smartcockpit.com BOEING 767 SYSTEMS REVIEW

PNEUMATICS

1. GENERAL

¡ Air for Ô Air conditioning & pressurizationÔ Wing & Engine anti-iceÔ Engine startÔ Cargo heatÔ 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)- 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 fornormal operation.

¡ After engine start, air is bypassed around the L & R isolation valves into the crossover manifold & theninto 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

Engine compressor section





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 insufficientpressure 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 cycledto unlatch the PRV & HPSOV and return to normal operation.

8. FAULTS

L/R ISLN

- ON (alternate action) : opens Isolation Valve- VALVE (amber) : Isolation Valve position disagrees with switch signalled position.

VALVE





APU

L/R ENG

- ON (alternate action) : opens engine bleed air valves if engine is operating- OFF (amber) : engine bleed air valve closed + EICAS msg.

- Bleed air leak in the Left, Right or engine strut pneumatic duct + EICAS msg.(amber) or

- system testÔ Bleed air and isolation switches to be selected OFFÔ in case of Bleed duct leak = back to normal when the temperature has cooledÔ if the light remain ON, a leak exists between the L and R isolation valvesÔ Strut duct leak = light remain illuminated

(amber) : Engine HPSOV (High Pressure Shutoff Valve) and/or Pressure Regulating valvesare open when they should be closed + EICAS msgÔ BLEED + Eng. HPSOV = the HPSOV is open when only low pressure is requiredÔ BLEED + Eng. PRV = the pressure regulating valve has failed open

- Engine Bleed Air over temperature + EICAS msg(amber) and

- Engine Bleed air valves are automatically closed + EICAS msgÔ OVHT gives a signal to close the engine bleed valve > idem for PRV and HPSOVÔ unless strut duct leak exist : - PRV reopens with engine anti-ice

- HPSOV and PRV reopens for Thrust reverserÔ reset = BLEED AIR SWITCH ON and OFF A only one reset recommended.

- Bleed air leak in the centre pneumatic duct + EICAS msg(amber) or

- System test + EICAS msg

VALVE

ON (amber) : APU bleed air valve disagrees with signalled position.

OF

F

ON

DUCTLEAK

BLEED

OVHT

D LU EC A

T K





PNEUMATICS SYSTEM (PW)





PNEUMATICS SYSTEM (GE)

B767 Pneumatics

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