B747-800 flight crew reported the loss of the #1 Hydraulic System was caused by the loss of both System 1 hydraulic pumps. The flight crew requested priority handling and made a precautionary landing at destination airport.
Synopsis
B747-800 flight crew reported the loss of the #1 Hydraulic System was caused by the loss of both System 1 hydraulic pumps. The flight crew requested priority handling and made a precautionary landing at destination airport.
Narrative
Approaching ZZZZ2 position ZZZZZ enroute to ZZZZ1; I was in the bunk and FOs (First Officer) Name and Name 1 were at the controls. They rang me and I came up front. They told me that they had seen a brief HYD PRESS DEM 1 and then HYD PRESS ENG 1 EICAS message which both showed only momentarily; then cleared themselves. We monitored the system via the synoptic and all looked normal. Shortly thereafter we got a HYD PRESS DEM 1 EICAS followed by a HYD PRESS ENG 1 EICAS which stayed illuminated. Following the 2 EICAS and ECL Checklist procedures in turn; we turned off Engine Driven Pump 1 and then turned the Eng 1 HYD Demand Pump to the ON position. At that point; the Demand Pump was feeding the system; which indicated it was full with approximately 3;000 PSI. It appeared that the HYD fluid temperature was 20 degrees higher than the other 3 engines so I initiated a conversation with Maintenance; Dispatch and the Duty Pilot. Maintenance relayed that just running the Demand Pump constantly wouldn't cause the fluid temperature to increase since it's physically the same kind of pump as the Engine Driven Pump. We further monitored the temperature; fluid levels; and pressures; and they all appeared to stabilize at normal levels. At this point; other than having ENG Driven Pump 1 turned off; everything indicated normal. Since we were almost on top of the ETP (Equal Time Point) and all current indications were that we had a good system except for the EDP (Engine Driven Pump); I opted to proceed to ZZZZ1.As we continued on; I monitored HYD SYS 1 fluid temperature and it reduced to 66°C; down from 72°C. I was convinced things would be fine with nothing more than a failed EDP. About 1 hour from ZZZZ1 at XA:07; I was in the left seat and FO Name 1 had gotten out of the seat for a physiological break. It was while I was alone in the seat that I got the HYD PRESS SYS 1 EICAS message. I checked the synoptic and saw that HYD SYS 1 pressure had dropped to 110 PSI; indicating a Demand Pump failure. Throughout this event; HYD Quantity stayed full.I got the rest of the crew up front and we ran the Emergency Checklist for HYD PRESS SYS 1. We checked over all the lost systems and noted those. We realized we would have to manually lower the landing gear and that the Inboard Trailing Edge Flaps would be slow to move in Secondary mode. We also noted that we would have no nose wheel of body gear steering and that we'd have to stop on the runway and get towed off. We checked the weather; ran the data and continued to ZZZZ1. As early as possible; we [requested priority handling] because I knew shutting down their primary runway would be an issue and I needed to give them as much advanced notice as possible.Beginning the descent; we had approximately 23;000 lb. of fuel so I opted to configure very early in order to get the manual gear extension completed and allow for the slow flap extension. Passing about 9;000 ft. and 230 KIAS; we manually lowered the gear. I wanted the slightly higher-than-normal speed to assist providing air-load to lower and lock the gear. I also slowed and lowered flaps to 10 passing about 6;000 ft. to give them plenty of time to get into position.That all went smoothly and we got vectors to ILS XXR at ZZZZ1. I accomplished what I felt was a smooth landing using 30 flaps and autobrakes 3. Since we know we'd have no #1 reverser; I brought all 4 reversers to idle and used 2 and 3 at max reverse. We came to a stop uneventfully and stayed straight ahead on the runway where we shut down awaiting a tow. When Maintenance looked at our airplane; he told me on the intercom that the gear doors were resting on the tires and that we couldn't tow. He was able to get them off the tires and we were able to continue the tow. After shutdown and looking at the gear doors Maintenance assured me that there had been no damage to either the gear doors or the tires. I'm still not sure how they could possibly have been resting on the tires when we were stationary but [did] not touch them during the landing. I related the same story to the [governing facility] through the Maintenance Representative's interpreting and was cleared to leave.[The cause was] apparent failure of both the ENG 1 Engine Driven Hydraulic Pump and the Engine 1 Demand Pump; [and] total loss of System 1 Hydraulic Pressure. [The] quantity remained full.
Second reporter narrative
HYD PRESS ENG 1 EICAS MESSAGE" indication [appeared] for 1 second and self-cleared. Approximately 20 minutes later; "HYD PRESS DEM 1" and "HYD PRESS ENG 1 EICAS" messages occurred simultaneously and self-cleared after 1 second. The Captain was notified. No messages for approximately 20 minutes. Simultaneous Engine Indicating and Crew Alerting System messages resumed and self-cleared with shortened intervals. Captain was present. Simultaneous Engine Indicating and Crew Alerting messages reappeared and remained. Both checklists were completed. Captain spoke with Dispatch and Maintenance. Number 1 Hydraulic temp started 8 degrees Centigrade above the other 3 systems. Peak difference reached 22 degrees C.Maintenance was notified. Engine pressure pump remained off with demand pump 1 in the on position for about 2 hours. Hydraulic pressure suddenly dropped to 100 PSI. "Engine Indicating and Crew Alerting HYD PRESS SYS" message and checklist completed to a full stop on runway. Priority handling was used after completion of Engine Indicating and Crew Alerting "HYD PRESS SYS 1 step 11." Each Controller was notified of priority handling and that a full stop and tow off runway would be required. Stopped on runway; performed after landing flow and shutdown engines per ATC. Maintenance on runway said gear door was touching the tire but no damage. No fluid leaks. Maintenance secured door and towed aircraft to gate. [The] tow and secure checklists [were] completed."
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.