Narrative:

Climbing through 17;000 feet on departure; I engaged autopilot a. The aircraft pitched down to such an extent that I had to disconnect the autopilot. The feel diff press light illuminated briefly but extinguished within a few seconds. I attempted to re-engage autopilot a but it would not engage. I engaged autopilot B but it disconnected about 5 seconds later. I flew the airplane while [the] first officer (first officer) searched for the cause of the autopilot issues. Nothing obvious; to include popped circuit breakers; was found.after leveling at FL280; I looked at the hydraulic systems page and noted that system a hydraulic quantity was about 80% and pressure was normal. [First officer] and I discussed our condition and agreed that we were ok to continue without the autopilots. A few minutes later; I checked the hydraulic systems page again to find that system a quantity was now about 66%. This started a discussion about the trend and what we might be looking at if; in fact; we were losing system a hydraulic fluid. I asked [first officer] to reference the loss of system a checklist in order to have the list of failed items fresh in our minds should we actually lose system a.a few minutes later with system a quantity at about 50%; I asked [a] deadheading captain to come to the flight deck and assist us in the event that we lost system a. [We] then sent a message to [maintenance] concerning our condition. A few minutes later; after getting no response; I sent a message to dispatch. The dispatcher immediately arranged a VHF patch via arinc. [First officer] spoke with the dispatcher while I flew the plane and handled ATC. We were about 120 miles south of [a suitable airport] so I asked [first officer] to suggest [it] as a divert airport for us. The dispatcher concurred and provided the pertinent information which would facilitate our divert including weather.with the system a quantity decreasing through about 20%; we got the left engine driven hydraulic pump low pressure light. I asked [deadheading captain] to run the hydraulic pump low pressure checklist; which he did. We secured that pump per the checklist. System a quantity continued to decrease. I directed [first officer]; who had finished his conversation with the dispatcher [to] initiate a divert to [nearby suitable airport]. We were given a descent clearance by ATC and made a normal descent; planning a visual approach and [deadheading captain] checked the non-normal landing distance chart for a loss of system a to find that we needed 4;500 feet predicted on max manual braking. The dispatcher sent us a more accurate number of 4;200 feet. [Deadheading captain] and I had a brief discussion about the use of max autobrakes. [Deadheading captain] advocated the use of max because of our non-normal situation and increased landing distance because of the loss of ground spoilers and a slow left reverser. I pointed out that we actually had normal brakes; normal autobrakes; and a nearly 12;000 feet long runway in clear VFR weather. I advocated the use of autobrakes 3 with the option to override them during the landing role and transition to max manual braking if necessary. [Deadheading captain] agreed.during the descent; I felt some unusual feedback through the control yoke as we lost hydraulic system a. I asked [deadheading captain] to run the loss of system a hydraulic checklist; which he did; confirming switch movements with me while [first officer] continued coordinating with ATC. We completed the loss of system a checklist descending through about 6;000 feet including the deferred items such as dropping the landing gear using the alternate extension method. When we were switched to tower; [first officer] confirmed that crash fire rescue equipment vehicles were standing by for us about halfway down [the] runway. We had about 3 minutes to verbalize a 'big picture' look at what we had experienced; what we had done; and all three of us agreed that we had done everything right and had completed everything we needed to for a successful outcome. We were informed of a 737 joining final at our 9 o'clock by ATC. As they joined their final; we got a 'traffic' alert from our TCAS. I asked [first officer] to switch us to TA only which silenced the alert. The flaps 40 landing was uneventful and I taxied the aircraft off to the right using the alternate nose wheel steering system. ATC cleared us to the gate; ramp cleared us in; and I lined us up at the top of the J line before shutting down the number 2 engine so as to avoid large steering inputs with only one electric hydraulic pump providing steering hydraulics. We waited there for at least 15 minutes before a crew showed up to marshal us into the gate. We shut the aircraft down; leaving all systems switches which we had manipulated in the course of running non-normal checklists where they were.

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Original NASA ASRS Text

Title: B737NG flight crew reported loss of Hydraulic System A fluid. They diverted to a nearby suitable airport.

Narrative: Climbing through 17;000 feet on departure; I engaged Autopilot A. The aircraft pitched down to such an extent that I had to disconnect the autopilot. The Feel Diff Press light illuminated briefly but extinguished within a few seconds. I attempted to re-engage Autopilot A but it would not engage. I engaged Autopilot B but it disconnected about 5 seconds later. I flew the airplane while [the] F/O (First Officer) searched for the cause of the autopilot issues. Nothing obvious; to include popped circuit breakers; was found.After leveling at FL280; I looked at the hydraulic systems page and noted that System A Hydraulic quantity was about 80% and pressure was normal. [F/O] and I discussed our condition and agreed that we were OK to continue without the autopilots. A few minutes later; I checked the hydraulic systems page again to find that System A quantity was now about 66%. This started a discussion about the trend and what we might be looking at if; in fact; we were losing System A hydraulic fluid. I asked [F/O] to reference the loss of System A checklist in order to have the list of failed items fresh in our minds should we actually lose System A.A few minutes later with System A quantity at about 50%; I asked [a] deadheading Captain to come to the flight deck and assist us in the event that we lost System A. [We] then sent a message to [Maintenance] concerning our condition. A few minutes later; after getting no response; I sent a message to Dispatch. The Dispatcher immediately arranged a VHF patch via ARINC. [F/O] spoke with the dispatcher while I flew the plane and handled ATC. We were about 120 miles south of [a suitable airport] so I asked [F/O] to suggest [it] as a divert airport for us. The dispatcher concurred and provided the pertinent information which would facilitate our divert including weather.With the System A quantity decreasing through about 20%; we got the left engine driven hydraulic pump low pressure light. I asked [deadheading Captain] to run the hydraulic pump low pressure checklist; which he did. We secured that pump per the checklist. System A quantity continued to decrease. I directed [F/O]; who had finished his conversation with the dispatcher [to] initiate a divert to [nearby suitable airport]. We were given a descent clearance by ATC and made a normal descent; planning a visual approach and [Deadheading Captain] checked the non-normal landing distance chart for a loss of System A to find that we needed 4;500 feet predicted on max manual braking. The dispatcher sent us a more accurate number of 4;200 feet. [Deadheading Captain] and I had a brief discussion about the use of max autobrakes. [Deadheading Captain] advocated the use of max because of our non-normal situation and increased landing distance because of the loss of ground spoilers and a slow left reverser. I pointed out that we actually had normal brakes; normal autobrakes; and a nearly 12;000 feet long runway in clear VFR weather. I advocated the use of autobrakes 3 with the option to override them during the landing role and transition to max manual braking if necessary. [Deadheading Captain] agreed.During the descent; I felt some unusual feedback through the control yoke as we lost hydraulic System A. I asked [Deadheading Captain] to run the loss of System A hydraulic checklist; which he did; confirming switch movements with me while [F/O] continued coordinating with ATC. We completed the loss of System A checklist descending through about 6;000 feet including the deferred items such as dropping the landing gear using the alternate extension method. When we were switched to Tower; [F/O] confirmed that CFR vehicles were standing by for us about halfway down [the] runway. We had about 3 minutes to verbalize a 'big picture' look at what we had experienced; what we had done; and all three of us agreed that we had done everything right and had completed everything we needed to for a successful outcome. We were informed of a 737 joining final at our 9 o'clock by ATC. As they joined their final; we got a 'traffic' alert from our TCAS. I asked [F/O] to switch us to TA only which silenced the alert. The flaps 40 landing was uneventful and I taxied the aircraft off to the right using the alternate nose wheel steering system. ATC cleared us to the gate; ramp cleared us in; and I lined us up at the top of the J line before shutting down the number 2 engine so as to avoid large steering inputs with only one electric hydraulic pump providing steering hydraulics. We waited there for at least 15 minutes before a crew showed up to marshal us into the gate. We shut the aircraft down; leaving all systems switches which we had manipulated in the course of running non-normal checklists where they were.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.