B787 flight crew reported misdiagnosing a hydraulic system failure as flap and slat systems failure. The flight crew continued to destination airport and made a precautionary landing.
Synopsis
B787 flight crew reported misdiagnosing a hydraulic system failure as flap and slat systems failure. The flight crew continued to destination airport and made a precautionary landing.
Narrative
During flap extension the center hydraulic system failed. Initially the ECL (Electronic Checklist) presented 'FLAPS PRIMARY FAIL' and 'SLATS PRIMARY FAIL'. After delegating the First Officer to flying and communicating; I began those checklists. Shortly thereafter; ECL presented 'HYD PRESS SYSTEM C' and that checklist was accomplished as well. We asked for delay vectors to accomplish all the required tasks. We requested priority handling with ATC; contacted Dispatch with the situation notification as well. Flight Attendants were briefed with no need to prepare for evacuation. Notified passengers with multiple announcements. We requested the longest runway; and asked that the fire equipment be standing by. We extended the gear with the alternate system and used the secondary system for flap extension. After landing; nose wheel steering was available and we taxied to the gate. I debriefed with the flight attendants and then the other pilots. An area for improvement in my performance was accomplishing the first two checklists in the order they presented; rather than waiting for the 'HYD PRESS SYSTEM C' that presented after a period of time. That would have made things easier.
Second reporter narrative
I was beginning to configure and perform my first landing in the 787 on my first IOE trip. After our attempt to lower flaps 1; we saw and heard the master caution alarm. The right flap had fully extended and the left had not. The FLAPS PRIMARY FAIL and SLATS PRIMARY FAIL ECLs appeared. The Captain transferred radios to me while he addressed the ECLs. Several more ECLs appeared and it became clear the primary issue was that the center hydraulic tank quantity and pressure were extremely low. We decided to request priority handling; which I told ZZZ Tower and that we would need to use [Runway] XXL and to send crash fire and rescue trucks. We received vectors and ATC asked if it was a flap issue which the Captain agreed it was; and I told ATC that it was. The Captain discussed and performed the ECLs with the relief pilot and LCA (Line Check Airman) / Instructor in the jump seats. I focused on flying the aircraft using autopilot and monitored for any abnormalities. There were no observable differences in aerodynamics or performance. After we completed the ECLs and discussed our fuel on board; the Captain took control of the aircraft for the approach and I became pilot monitoring. We received vectors to fly the ILS approach to XXL. Landing gear and flaps 20 extended without issue and the approach and landing were normal. After landing we were able to taxi normally using nose wheel steering and we proceeded to taxi to the gate and park normally.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.