B737 flight crew reported the loss of both FMCs during arrival. Due to poor weather conditions at destination; flight crew returned to departure airport and landed.
Synopsis
B737 flight crew reported the loss of both FMCs during arrival. Due to poor weather conditions at destination; flight crew returned to departure airport and landed.
Narrative
During descent/arrival into ZZZ; both FMCs increased airspeed beyond the barber pole limit to an over speed. We recovered the aircraft properly. Aircraft was ok. Upon further descent into ZZZ both FMCs failed which failed both flight directors. For safety sake; we leveled the aircraft off at 16;600 feet and were given a climb to 17;000 feet to figure out the aircraft issues. ATC [declared priority handling] to give us a direct path back to ZZZ1. Discussing the minimums for the approach into ZZZ RNAV XXL was 500 feet; LOC/BC XXL was 420 feet and the ILS XYR was 230 feet; now ATC advised us that minimums were 300 feet and that two aircraft before our arrival had done a go-around on the RNAV XXL. We requested ILS XXR but we're denied for saturation. Having to fly raw data approach with winds at the time of XXX/10 gusting to 19; Captain made the decision for safety to divert back to ZZZ1. Weather was good. Upon arrival into ZZZ1; autopilot and flight directors failed again; raw data approach to ILS XZ. We broke out at 1;660 feet for a visual approach into ZZZ1 and landed without incident. Maintenance found that FCC A failed.
Second reporter narrative
During descent/arrival in to ZZZ while in VNAV 'descend now' the FMCs commanded an over speed. Disconnected autothrottles and autopilot to slow the aircraft. Leveled off at 16;600 feet and then requested a climb back up to 17;000 feet. Upon further descent in to ZZZ both FMCs and flight directors failed. We requested a level off and received a vector to keep the aircraft out of ZZZZ Airspace. At that point two aircraft in front of us performed a go around because they had not broken out. The minimums for the Localizer approach in use were 420 feet; and the minimums for XXR were 235 feet but winds were XXX@10G19. Upon discussion; we decided that with the aircraft malfunctions and in a degraded state; the safest decision would be to divert back to ZZZ1 where we knew the weather was good for a safe approach. Upon arrival in to ZZZ1 autopilot and flight directors failed again. We executed the go around and came back for a second ILS Runway XY using raw data and hand flying. The second approach was uneventful to a full stop.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.