B737 flight crew reported Flight Director and Navigation Displays failure on initial climb.
Synopsis
B737 flight crew reported Flight Director and Navigation Displays failure on initial climb.
Narrative
During the ZZZZZ SID out of ZZZ; FO was hand-flying as PF and in the turn from ZZZZZ to ZZZZZ1 when his FD (Flight Director) dropped off; then we noticed LNAV and VNAV had disengaged; and my FD then dropped off as well. As PM; I automation managed my next actions of trying to cycle the FD switches off and back on again and try to re-engage LNAV & VNAV; but to no avail. Then the FO's ND (Navigation Display) lost all navigation guidance / display and he got a momentary 'bank angle' audio call during the initial steeper part of the SID turn; which we corrected promptly. However; I still had a valid ND display; so we quickly swapped me to PF and the FO took PM duties. I continued to fly the lateral path and appropriate climb speed; even without the FD. We were then cleared direct to ZZZZZ2 on the SID and the FO loaded and executed this in his FMC. Right after this; his ND was restored; we were able to re-engage LNAV and VNAV; and our FD's came back on. All of this occurred without any caution lights or observed ND/PFD (Primary Flight Display); or FMC scratchpad messages. Once everything was restored; we swapped back to our original PF and PM roles; and the flight continued without further incident. I wrote up an ELB (Electronic Log Book) en-route; called ZZZ1 Ops/MX (Maintenance) upon arrival; and further explained what happened. The next morning; I looked up the logbook updates. I am not familiar with their term 'FMC 2 DISCRETE WORD INVALID.'; but I don't know how they could find the NAV data out of date; as the currently loaded Nav database end date was Day 0; and this event occurred around XA10 on the Day 0. Given the lack of apparent reason on why this occurred and the seemingly inconclusive maintenance write-up; I thought it would be good if the FOQA team could tag this event on the FDR (Flight Data Recorder) if still possible; for further analysis.
Second reporter narrative
On climbout of ZZZ I was pilot of flying; captain was pilot monitoring. ZZZZZ arrival; ZZZZZ2 transition; before reaching ZZZZZ we lost both flight directors at the same it. I announced I have lost my flight director; and I looked over left side of the cockpit and 'you've lost yours.'I do believe there are some startle factor on his end but he immediately started to look around for any abnormal caution lights. I focused on maintaining flight path first; maintain magenta line the turn; continuing the climb. The bank angle announced over the speaker; and I announce correcting; shallowed my bank and continued my climb while maintaining heading ; altitude by continuing the climb and airspeed. Captain announced he was cycling both flight directors trying to reengage LNAV and VNAV. Then I then loss my PFD (Primary Flight Display) I continue to fly using the Captains PFD map for lateral guidance to stay on SID and cross referencing my altitude and heading while climbing direct ZZZZZ2. After realizing I had no; flight Directors; lateral or vertical mode; and no MFD (Multi-function Flight Display) because I was using the captains MFD. I made the decision to announce to the Captain that he had the flight controls. Feeling it would be better for him to fly since I was using his instruments to fly. He announced; he had the flight controls; and there was a positive transfer of controls. When looking at the MCP (Mode Control Panel); both flight directors had already been cycled and were on; I reengaged LNAV; and then VNAV. Flight directors re-engaged; moving map with magenta line came back on. With instrumentation MFD and FD (Flight Director) working on my side; I asked for the flight controls back and there was a positive transfer of controls. I do not believe there was a lateral deviation off of the SID or altitude deviation. There might of be a slight increase in air speed below 10;000 (263) while captain was flight but I'm not sure. Everything happened so fast. We maintain positive control of the aircraft and the safety of flight was never an issue. We immediately debriefed and talked about what happened. If we are comfortable continuing to fly? yes. If it was safe to continue? yes. Captain and I discussed and decided to continue the flight.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.