A B767-300 returned to the foreign departure airport after climb out because the Equipment Cooling/pressurization System was malfunctioning. The Equipment Cooling System had been MEL'ed prior to departure.
Synopsis
A B767-300 returned to the foreign departure airport after climb out because the Equipment Cooling/pressurization System was malfunctioning. The Equipment Cooling System had been MEL'ed prior to departure.
Narrative
Maintenance was performed on the Equipment Cooling system prior to departure. I reentered the cockpit after awakening early from the first break cycle. The Cockpit Crew was executing the Cabin Altitude Depressurization QRC while starting a descent. After the QRC was complete; I noticed the cabin alt indicating 11;0000' and the Cabin Altitude Alert warning illuminated. An emergency was declared for a rapid descent below 10;000'; and a return to our departure airport. The Captain handled ATC; which was challenging with the language difference and the oxygen mask on. The First Officer continued flying and landed uneventfully. I as the Relief Officer handled communications with Dispatch via ACARS; the cabin crew; passengers; and backed up the remaining pilots duties and checklist. Fuel dumping was commanded; coordinated with ATC and terminated by 7000'. Cabin advisory declared; emergency equipment requested for possible hot brakes and overweight landing. Aircraft was inspected for overweight landing; a new maintenance release was issued; refiled; refueled; and departed.
Second reporter narrative
Maintenance deferred the FORWARD EQUIPMENT COOLING EXHAUST VALVE prior to takeoff from foreign airport. Flight returned to the departure airport due to inability to maintain pressurization while climbing and while at cruise altitude. I was told soon after the return that Station maintenance failed to properly follow procedures described in the MEL.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.