SDR ASAA2020080432982

Service difficulty report · Fmc · Boeing 737990ER

Difficulty date: August 3, 2020
Submitted: August 4, 2020
Operation: Air carrier
Aircraft: N471AS
Make and model: Boeing 737990ER
Aircraft serial: 41703
Aircraft time: 22,624 hours, 7,228 cycles
System (JASC): 3460 · Flight Management Computing Hardware System
Part: Fmc
Condition: Faulted
Stage of operation: CR
How discovered: O
Nature of condition: J
Precautionary procedure: O

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

IN CRUISE LNAV AND VNAV DISENGAGED FOLLOWED BY VTK FLAG ON LEFT MAP AND BOTH FMCS LOST FMC PROMPT AFTER ABOUT 10 SECONDS FMC RESTORED AND LNAV/VNAV REENGAGED. GROUNDED - YES. ACCOMPLISHED FIM 34-61, TASK 837. FMC LT SHOWS FAULT FOR PRES POS LAT RATE, FAULT FOR PREV LEG. THIS SHOWS INTERMITTENT FAULT. ACCOMPLISHED SYS RESET IAW FIM 34-61 TASK 836. OPS CHECKED NORMAL. GROUND VERIFICATION NORMAL.