Date: 202106
Location: ZZZ.ARTCC, US
Flight conditions: Marginal
Aircraft: B747-400
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Pressurization System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Time Pressure
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Procedure; MEL; Company Policy; Aircraft
Primary problem: Aircraft

Narrative: While in cruise at FL400; I noticed cabin altitude display illuminate Amber on upper EICAS showing cabin altitude of 8300 feet and rising at 300-400 ft/min.  Aircraft was dispatched with one pack deferred; two operating. I brought up the ECS schematic to verify Packs 2 and 3 were both supplying pressure and in High Flow. They appeared to be operating normally; but I then noticed a Status message with a Pack 2 fault; cabin altitude was already 9;000 ft. and still climbing. At this point I requested a descent from ATC to FL 360.  They gave us a vector for descent.  A minute later; with Cabin altitude of 9300 ft.; I informed ATC we had a pressurization issue and needed to descend.  We were given FL390 and then a few minutes later; FL360.  Pressurization stabilized at 8;500 ft.; but began to climb again at 100-200 ft/min. We requested and were given FL 320.  I notified Operations Control via ACARS (SATCOM inop); that we had a Pack 2 issue and that we had descended as cabin altitude had been increasing. They were given our fuel and told I would keep them advised. We were at FL 280; where cabin altitude at stabilized; but showing slight increase. I recommended to divert to ZZZ along our route of flight; but they informed me they wanted the airplane in ZZZ1.  I informed ATC that we needed to change our destination for 'maintenance' from ZZZ2 to ZZZ1.  We were given proceed direct ZZZ1; about 350 miles away; where we landed uneventfully.Cruise flight when cabin altitude appeared amber on Upper EICAS.Strictly a maintenance issue with the aircraft. We had Pack 1 deferred and any issue with the remaining Packs was going to cause pressurization issues.To assess the situation; attempt to bring pressurization under control; and descend as necessary to reduce cabin altitude.  QRH was utilized to validate what pressurization reading we should have at the various altitudes.Aircraft was dispatched to pick up freight in ZZZ2; and then proceed with a Pack deferred.


Second narrative: Pushback; taxi; takeoff and climb were completely normal. Weather on departure were calm winds and decent VFR in the terminal area. The weather became more marginal upon leveling at cruise. On this leg I myself was the First Officer and Flying Pilot. The Captain was the Pilot Not flying. We also had a Relief Pilot on board and loadmaster.  The event began somewhat early in cruise at FL400 when the Captain noticed a cabin altitude display Amber on the Upper EICAS display. He then immediately selected the ECS page and we both were made aware of a 8;300 foot cabin and rising at 300-400 fpm. The aircraft was dispatched with Pack #1 deferred; therefore packs 2 and 3 operating normally. After diagnosing the situation via the ECS page; both packs 2 and 3 appeared to be supplying pressure and in High Flow as designed when one pack is selected off.  However on the Lower EICAS we both noticed a Status message with a Pack 2 fault. Cabin altitude was still climbing and at this point showing 9;000 feet and still climbing. At this point we agreed to suggest a decent to FL360 and were given a vector for decent. About a minute later with Cabin Altitude of 9;300 feet the Captain informed ATC that we had a pressurization issue and needed to descend now; we first were given a decent to FL390 and shortly after to FL360. At FL360 we observed the cabin initially stabilizing at 8;500 feet; but shortly afterwards began again climbing at a lower rate than previously of 100-200 FPM.  We again agreed to request a lower altitude of FL320 and ATC cleared us to FL320. The Captain then notified Operations Control of the situation via ACARS (SATCOM Inop) that we had a PACK 2 issue and we were descending with a cabin altitude still slowly increasing. The Captain requested further decent to FL280 and ATC complied. At FL280 we experienced a cabin altitude almost stable at around 8;000 feet but still trying to climb at a slow interment 100 FPM. The Captain notified the rest of the crew including the Relief Pilot and load master. The Relief Pilot was taking his rest but immediately returned to the cockpit to help in CRM and dealing with the situation. I suggested the Relief Pilot pull up the cabin altitude chart showing what the cabin altitude should be for our current altitude so we would know how far off from normal we were.  All 3 crew members talked about possible diversion airports and relayed our ideas to Operations Control. After communication between Operations Control and us it was decided by Operations Control to divert to ZZZ2 to address and fix the situation. The Captain immediately requested to divert to ZZZ2 and informed ATC as to why; and I put us on a course to ZZZ2 via ATC instructions. At this point we were about 350 miles north of ZZZ2 with plenty of fuel and sufficient weather for landing. We landed at ZZZ2 uneventfully and maintenance was made aware of the present maintenance issues.While in cruise flight the cabin altitude appeared amber on the Upper EICAS.Pack 2 was failing for unknown reasons. Pack 1 was already deferred on departure so any remaining pack issues was going to cause a pressurization issue.Crew did their job in noticing the system fault and working the problem. We were dispatched with Pack 1 deferred so any further pack or pressurization faults would cause a pressurization issue.Dispatching an aircraft with a pack deferred which would and did cause a pressurization issue when any further pressurization problems would happen. In this case pack 2 also failing to perform up to specification; therefore; causing an increasing cabin altitude at a higher level cruising altitude.


Synopsis: B747-400 flight crew reported diverting after A/C Packs would not maintain cabin altitude with Number 1 pack already deferred.