Confusion; Situational Awareness
Aircraft Equipment Problem Critical; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action; General Declared Emergency
Aircraft; Human Factors
Many failures at once led to confusion. Most concerning was cabin altitude climbing at 400 FPM. Cabin alt passed through 7000 feet and the Capt initiated an emergency descent without departing airway. I articulated we needed to get off the airway to descend. Captain responded by pointing at the TCAS and stating there is no one below us. Reaching FL390 TCAS traffic began showing up on TCAS. When we leveled at FL360 [an aircraft] was 1;000 below us. There was an attempt somewhere in the descent to comply with my repeated statements to depart the airway. [ATC] was informed and an emergency was declared.
Just after I sat down from my break; we heard what seemed like the nose gear door rattle and a fan in the cockpit silence as our ears started popping. We also noticed a status message pop up with the gear synoptic on the EICAS and the NO APU Fire Detector checklist illuminate. We pulled up the AIR System synoptic and saw that the cabin was climbing between 400 and 500 feet per minute and was almost at 8;000 feet. The Captain decided to immediately descend out of FL400; however failed to get off the track prior to doing so. We leveled at FL360 as the pressurization started to stabilize.
Widebody flight crew reports pressurization anomalies at FL400 along with noise and vibration from unknown sources. The Captain initiates a descent without advising ATC and without turning off the airway. ATC is eventually advised and an emergency is declared. The pressurization system stabilizes at FL360 and flight continues to destination.