B747 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented
Aircraft; Human Factors
On departure; at altitude of 500 feet the relief First Officer looked up at the pressurization system and noted that the left outflow valve was fully open. At 1;000 feet he asked the Pilot Monitoring (PM) to display the Environmental Control System (ECS) page on the lower EICAS and noticed the left outflow valve was fully open. The aircraft was pressurizing at an excessive rate; so he ran the QRH procedure and tried to manually control the pressurization system but the left side was unresponsive; the right side worked on the manual mode and was able to control the pressurization at that time. During level flight we had an EICAS msg. 'Cabin Alt Auto' so we ran the QRH and complied with QRH instructions and were able to control the cabin pressurization manually. During cruise Left outflow valve would display full open; and full close indications in manual and in Auto. This was confirmed by mechanic who was onboard. The mechanic tried to troubleshoot by opening Central Monitoring Computer (CMC) on the center CDU. CMC confirmed multiple failures of the pressurization system involving both channels of pressurization system and the failure of the left outflow valve. Status messages Cabin Alt Auto B; and Cabin Alt Auto A were displayed on status page. During cruise; cabin altitude would periodically initiate excessive rates of climb for no apparent reason. Cabin was stabilized and in Manual mode; and would have to be stabilized manually. We had to be completely dedicated to monitoring the system to maintain a constant cabin altitude and differential pressure. This task was very consuming in addition to normal flight duties and other distractions; ACARS/ SATCOM failure; HF communications; redispatch flight plan; and weather avoidance. The relief pilot had flown this aircraft a week prior with the left outflow was ON MEL. He briefed the crew about it. We looked at the history of this airplane and found multiple write ups about it. The Pressurization system had been written up numerous times; and was never properly repaired.  This situation led to a complete loss of pressurization automatic control.  Manually controlling pressurization on a seven hour leg was a big distractor and a safety issue.  Maintenance needs to be properly diagnose and fixed to ensure safe operations.
A B747 First Officer experiences pressurization anomalies from right after liftoff and throughout the seven hour flight. The pressurization system will only operate in manual mode and then with occasional erratic climbs and descents of the cabin altitude. The problem had been written up numerous times and never properly repaired.