B737-800 flight crew reported a low hydraulic pressure indication during cruise. Flight crew diverted and landed using standby hydraulic system.
Synopsis
B737-800 flight crew reported a low hydraulic pressure indication during cruise. Flight crew diverted and landed using standby hydraulic system.
Narrative
HUD was placarded inop (cat 1 only) with an inop thrust reverser going to ZZZ- short runway and bad weather. Discussed this with dispatch to see if they had another aircraft. None available. Ran land app and it showed if less than braking action 5; we could not land in ZZZ. Told them if braking action was less than good in ZZZ; I would go to my alternate. Level FL 370- Eng 2 hydraulic low pressure light illuminated. Followed QRH & shut off eng driven 2 B pump. Within a short time; we got an ELEC 1 Low B pressure light and Flt Cntrl B Low Pressure light with ZERO B qty. Completed QRH for loss of B system. We were in an area with very large weather system that gave us NO nearest suitable" divert runways (all less than cat 1 with gusty winds). Called dispatch and discussed divert/ runway options. We both agreed going to ZZZ1 was best weather option/ divert option. Subsequently got Eng 1 low pressure light (A side). I knew the PTU kicks in with B fluid doing the work but did not expect ENG 1 A low pressure light. Had good A side % and pressure; so chose not to shut off that pump (as one might do as QRH checklist has for low pressure light) and risk total A & B hydraulic failure. After 10 mins; Eng 1 low pressure light went out and qty slowly decreased to 80% with good pressure.Landed ZZZ1 using stby hyd to lower flaps/ slats. ARFF checked for leaks and followed us back to gate after giving all safe.Jet had numerous previous reverser write-ups that could have been hydraulic b problems in hindsight.Recommendations: There needs to be a NOTE in the LOSS OF SYSTEM B procedure in the QRH that says if you loose complete B HYDRAULICS; the A side uses its fluid to balance out the system and you will get an A side low pressure light that comes on for 5-10 mins. Otherwise in similar situation; crews will shut off perfectly good pump on A side."
Second reporter narrative
Started with low pressure light on engine driven pump on B side. Per checklist; turned the pump off. Later; electric driven pump low pressure light also illuminated on the B side and quantity indicated 0%. Went to checklist for loss of system B which required; among other things; a flaps 15 landing. We were unable to land ZZZ due to required landing distance and opted for ZZZ1. Some time later; engine driven pump A low pressure light illuminated. CA [advised ATC]; requested clearance direct ZZZ1; worked with dispatch and informed FA and passengers while I flew the aircraft. When he was ready; he took the aircraft back to fly. Landing was uneventful. We taxied off the runway and ARFF met us. They informed us that we had a mild to moderate puddle forming at our right engine. They followed us to the gate. We taxied in under our own power.Cause: Mechanical issue; no causal factors.Suggestions: While it would not prevent this from occurring; it would be less stressful for the crew if there was a note on the checklist that stated it is normal for the A system low pressure light to illuminate.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.