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Chapter 4
Avionics Ventilation

 4.1 Blower fault
 4.2 Extract fault
 4.3 Skin valve fault
 4.4 Avionics ventilation system fault

4.1 Blower fault

Defined as low blowing pressure or duct overheat. Unless there is a dc ess Bus fault, the blower fan should be set to ovrd. This puts the avionics ventilation into closed configuration and adds cooling air from the air conditioning system.

[ vent blower fault, fcom pro.aep.vent ]

4.2 Extract fault

Defined as low extract pressure. The extract fan should be put in ovrd. This puts the avionics ventilation into closed configuration and adds cooling air from the air conditioning system.

[ vent extract fault, fcom pro.aep.vent ]

4.3 Skin valve fault

Defined as one of three faults: the inlet valve is not fully closed in flight; the extract valve is fully open in flight; or the extract valve did not automatically close on application of take-off power. The ecam cab press page will differentiate.

If the fault is with the inlet valve, no action is required since it incorporates a non-return valve.

If the extract valve is affected, the system should be put into smoke configuration; this sends additional close signals to the extract valve. If the extract valve still remains open, the ecam directs the crew to depressurise the aircraft. The rationale for this seemingly extreme reaction to a relatively minor issue is that the ecam can only really occur immediately after the take-off inhibit ceases at 1500ft aal. The extract valve is normally held closed by the pressurisation and its motor is not sufficiently powerful to overcome this. Thus the extract valve can only be open in flight if it never closed. With the extract valve open, it will likely not be possible to complete the flight since the additional hole will make it impossible to properly pressurise the aircraft at cruise altitude, and the pressurised air rushing through the open outflow valve will cause it to be unpleasantly noisy in the cockpit. This makes depressurising the aircraft and returning for engineering attention the obvious solution.1

[ vent skin valve fault, fcom pro.aep.vent ]

4.4 Avionics ventilation system fault

Defined as either a valve not in its commanded position or the Avionics Equipment Ventilation Controller (aevc) being either unpowered or failing its power-up test. The system will automatically default to a safe configuration similar to smoke configuration. No crew action is required.

[ vent avncs sys fault, fcom pro.aep.vent ]

1The ecam procedure associated with this failure is due to be modified in an upcoming fwc update.