B747-400
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Total 15000; Flight Crew Type 4800
Physiological - Other
Aircraft Equipment Problem Critical
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
[We got an] EICAS 'trim valve' message. Procedure is to reset once; then; if unsuccessful; turn off 'Trim Air.' The reset was unsuccessful and we turned the trim air off. Cabin temperature was uncontrollable; with Maintenance Control guidance used Captain's Emergency Authority to reset associated circuit breakers but this was unsuccessful. We continued with two pack operation in auto and/or manual as required to warm the cabin. This was acceptable but the cabin remained very cool and the passengers used blankets and coats as a supplemental source of warmth.
When the automatic air conditioning system malfunctioned enroute; the flight crew of a B747-400 utilized alternative methods to mitigate the loss of temperature control.