B767 Equipment Cooling

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BOEING 767 SYSTEMS REVIEW

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EQUIPMENT COOLING 1. GENERAL ¡ Equipment cooling system supplies cooling air for cockpit instrument & Electrical/Electronic (E/E) compartment ¡ Early airplane = heat exchanger system utilises airplane skin to cool air discharged from E/E ¡ Later airplane = cooling by circulating the air throughout the lower compartment ¡ Equipment cooling selector = 3 positions

- AUTO (normal position for ground & flight ops - STBY under specific conditions - OVERRIDE under specific conditions.

2. AUTO OPERATION 1) GROUND : auto configuration dependent on engine ops, pack ops, air/ground logic, airplane temperature and ambient temperature. (dependent on these conditions, system will configure itself to provide adequate E/E cooling. 2) FLIGHT : Only the bypass valve opens and the EXHAUST fan operates. If EXHAUST fan fails, the SUPPLY fan operates as a backup.

3. STBY OPERATION ¡ STBY Operation is used when : - an overheat is observed during auto operation or - a VALVE light is illuminated after both engines started ¡ Positioning the Equipment Cooling Selector to STBY signals ALL valves closes except the bypass valve (TO OPEN) and - on ground, both fans to ON - in flight, SUPPLY fan is signaled ON (with EXHAUST fan as a backup)

4. OVERRIDE OPERATION ¡ OVERRIDE (OVRD) Operation is used when : - an overheat is detected after STBY is selected or - if smoke is detected in the equipment cooling system ¡ Selecting OVRD : - opens the SMOKE/OVRD valve and positions the air conditioning manifold valve to provide cond.air for cockpit equipment cooling - all other valve close - both fans are turned OFF - diff. pressure causes reverse airflow through the cockpit instrument panels & E/E compartment avionics. - the NO COOLING light will illuminate if no reverse airflow is detected. - Ground Crew horn will sound if OVRD is selected on the ground ¡ Activation of the fuel jettison switch automatically selects the override cooling mode regardless of the equipment cooling selector position. (When fuel jettison switch is selected OFF, equipment cooling system reverts to the selected equipment cooling mode.

Copyright  Smartcockpit.com Ludovic ANDRE / version 00

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5. AFT EQUIPMENT COOLING ¡ Aft equipment rack is cooled by a continuously operating EXHAUST fan that draws air through the equipment and then exhausts it near the pressurization outflow valve. ¡ There are 2 EXHAUST fans : - 1 operating - 1 alternate which automatically starts if the operating fan fails. ¡ Aft equipment cooling system is also used to vent the lavatories & galleys.

6. FAULTS

VALVE

OVHT

(amber)

(amber)

SMOKE

(amber)

NO COOLING

(amber)

Overboard valves or inboard valves not in their commanded position + EICAS msg After illumination of the VALVE light, selecting STBY signals the valves to the Inboard configuration. If the Overboard valves close and the Inboard valves open the VALVE light extinguishes and the EICAS msg. disappears

- Overheat or - Low airflow in the equipment cooling system or - Equipment cooling test Ô inhibited for 5' after selecting STBY to provide a cooling period Ô deactivated after selecting OVRD

- Smoke in the equipment cooling system + EICAS msg. or - Equipment cooling test Ô smoke is detected by a sensor in the equipment cooling air exhaust duct. Ô selecting OVRD reverses the flow of cooling air for the cockpit avionics and the E/E compartment avionics and exhausts the air overboard through the smoke. Ô extinguishes when the smoke clears. Ô STBY to be used if NO COOLING light.

- No reverse air flow through the E/E compartment avionics + EICAS msg. Ô active only in OVRD Ô To allow a period of time to establish reverse airflow, the NO COOLING light is inhibited for 1 minute after OVRD is selected.


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EQUIPMENT COOLING


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B767 Equipment Cooling

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