B747-800 Advanced pilots reported bleed air valves malfunctioning and the loss of anti-ice capabilities while in icing conditions.
Synopsis
B747-800 Advanced pilots reported bleed air valves malfunctioning and the loss of anti-ice capabilities while in icing conditions.
Narrative
During a flight from ZZZ1 to ZZZ I was performing duties as a monitoring pilot seated in the number 4 position. I had flown this particular airplane multiple times in the previous days with the CA who was the PF. Because of this; we were extremely familiar with the MEL's on this aircraft as well as the procedures associated with them as we had briefed them multiple times. Approximately halfway between the stations at a cruise altitude of 24;000 feet; we encountered icing conditions. Per the MEL; we were required to switch the number 4 engine anti-ice from off to on which the pilot monitoring did. It was then noticed that the EAI was not displayed; we also received a EAI (Engine Anti Ice) valve 4 EICAS message; and it was noticed the number 4 engine EGT (Exhaust Gas Temperature) was significantly lower then the other 3 engines. The PM completed the NNC (Non Normal Checklist) for the EICAS message. The PM cycled the number 4 engine bleed from off to on; as it was off due to the MEL. There were no changes so the switch was selected back to off. Then we received bleeds 1; 2 and 3 EICAS messages. The PM ran the NNC for the bleeds 1 and it restored normal operation; but then the bleed 1 message returned. This was followed by WAI (Wing Anti Ice) left and right EICAS message. It was at this time we noticed the cabin pressure was increasing. The PM suggested we don oxygen masks as the pressure was approaching 10;000 feet. Shortly after donning our mask we received the Cabin Alt warning. The immediate action items were accomplished. We requested and received a descent to FL220; we couldn't go lower due to terrain. Bleeds 2 and 3 were reset and restored. The NNC checklists were the started. While completing the checklists we again lost the 2 and 3 bleeds. The decision was made to reset the bleeds again and discontinue the anti-ice NNC because the cabin altitude was being restored and we had exited icing conditions at this point. We began the approach into ZZZ and removed our masks when the cabin altitude descended below 10;000 feet. The rest of the approach and landing into ZZZ was uneventful.
Second reporter narrative
In cruise at FL240 we entered icing conditions; #4 engine anti-ice was MEL'd; as per the MEL I switched #4 engine anti-ice from off to on. We got an EAI (Engine Anti Ice) VALVE 4 EICAS message and complied with the NNC (Non Normal Checklists). We took notice that EAI was not displayed on the upper EICAS next to the engine #4 N1 like it was on engines 1; 2 and 3. Additionally the EGT (Exhaust Gas Temperature) on engine #4 was approximately 60 degrees lower than 1; 2 and 3. Bleed switch #4 was off as per the MEL and at the moment we were unsure as to whether the MEL stated that it needed to be on or off in icing conditions; and I selected the switch on without any changes; than selected it back to off. Shortly after we got BLEED 1; 2; and 3 EICAS messages. Complied with the BLEED 1 NNC and restored BLEED 1; shortly thereafter got the BLEED 1 EICAS again; followed by WAI (Wing Anti Ice) LEFT and RIGHT EICAS messages. We noticed the cabin began to climb; before it reached 10;000 feet we put oxygen masks on. We then got the CABIN ALTITUDE EICAS; complied with the IAI/NNC and requested a descent to FL220 as we could not descend any further due to the terrain. We began to comply with the WAI NNC and decided it was best to prioritize the inoperative bleeds. After resetting bleeds 2 and 3 they were restored. We then went back to the WAI NNC; but then got BLEED 2 and 3 EICAS again. After resetting bleeds 2 and 3 again; they were once again restored and the cabin began to descend. We decided not to run anymore NNCs as the cabin altitude was under control and we were out of icing conditions. Once the cabin descended below 10;000 feet oxygen masks were stored and we made an uneventful landing in ZZZ.I did not declare a Mayday or Pan; as there were no delays; and we could not descend more than what we initially did due to the terrain.Cause: The loss of cabin pressure was due to the loss of bleeds 1; 2; and 3. The loss of bleeds 1; 2 and 3 happened after bleed 4 was turned off then on; also after complying with the WAI NNC. I am uncertain as to why that happened.Suggestions: During the operations with the oxygen masks on; multiple EICAS messages and running the checklists; taking the time to slow down and take a breath would have been beneficial.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.