2024-12 · NASA ASRS report 2197352
B737 air carrier flight crew reported a hydraulic system malfunction during cruise. Flight crew returned to departure airport.
Normal operations leaving ZZZ. After reaching top of climb we got an ENG HYD 1 LOW PRESSURE light. Ran the checklists which guides us to turn it off. We spoke with Maintenance Control and they directed a cycle of the system to off and then on. No change and light remained illuminated. Therefore left in OFF. Maintenance Control said the aircraft systems were ok and it was our decision what to do next. After consideration with my First Officer (FO) we both decided that we were uncomfortable with going Class 2 nav to ZZZ1 on the backup electrical system. As we were deliberately where to divert; Dispatch sent a message to return to ZZZ. We established with Dispatch that no Maintenance would be available in ZZZ1 and agreed with their decision.Immediately after this decision an ENG OIL FILTER BYPASS light illuminated. I ran the checklist which leads to disconnecting the auto throttles and bringing the power back until light extinguishes or idle power. We got to idle power with the light still on. The checklist leads to the eng failure or shutdown checklist. After going through the conditions we decided that we did not have any of them so decided to leave ENG 1 running at idle power. We completed the checklist with the caveat of the Eng running at idle power so many of the steps were not relevant. We [requested priority handling] and requested immediate vectors for ZZZ.We decided to complete the one Eng inoperative landing checklist to make sure we had everything covered as we made the decision to leave ENG 1 at idle but setting up the approach as if the Engine had been shut down. Weather was not ideal at ZZZ but still good for a Cat 1 ILS. I completed a brief with the lead Flight Attendant (FA) and informed the passengers of our return to ZZZ.We now noticed that the HYD SYSTEM A was emptying to 10% but did not have the indications of a complete System A loss so did not run the checklist. We requested a 20 mile final to Runway XXC with emergency equipment standing by. We were concerned with being overweight and the brake temperatures. We made the decision that due to the pressing situation with a HYD leak and potential ENG failure to land overweight.We configured normally giving ourselves plenty of time to be fully configured and stable. The cloud bases had reduced to approximately 500ft and a successful flap 15; overweight landing was completed by myself. After vacating the runway we had the emergency services check our engine and the brakes. After they confirmed that everything appeared normal we shut down ENG 1 and parked at gate XX.
Soon after reaching top of climb; I was the pilot flying and we got a HYD1 LOW PRESSURE light. The Captain ran the non normal checklist; we got in contact with Maintenance and Dispatch and the decision was made to return to ZZZ. Before we could turn back to ZZZ we got an OIL FILTER BYPASS light on the number 1 engine. Again the Captain ran the non normal checklist which tells you to reduce the thrust lever until the indication is gone or idle. We reduced the thrust lever to idle and the indication was still present. The number 1 engine indications were showing normal other than the FILTER BYPASS light; so we decided to leave the thrust lever at idle and not shut the engine off. While I remained the pilot flying; the Captain continued with the single engine landing non normal checklist and after all checklist were complete and we were ready for the approach; I gave the Captain control of the airplane and he made an uneventful ILS approach and landing on XXC. After vacating the runway we stopped and had the Fire and Rescue crews check our brakes for smoke. Once we received confirmation from fire and rescue; we proceeded to the gate without further incident.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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