SDR ASAA2022111040740

Service difficulty report · Fmc · Boeing 737990ER

Difficulty date: November 10, 2022
Submitted: November 14, 2022
Operation: Air carrier
Aircraft: N491AS
Make and model: Boeing 737990ER
Aircraft serial: 44109
Aircraft time: 25,972 hours, 8,186 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

DURING CRUISE WITH CMD B ENGAGED, LNAV/VNAV DROPPED OFF BUT AUTOPILOT STAYED ENGAGED. SWITCHED TO CMD A, RE-ENGAGED LNAV/VNAV, NO ISSUES. GROUNDED - YES. REF B737-900 FIM 22-11 TASK 801, DFCS BITE FAUL HISTORY LOGGED CHB MSG "FMC DATA INV/NO FMC DATA" ON PREV LEG. PERFORMED DFCS FAULT MSG LRU TESTS, ALL TESTS PASSED. FMCS OPS TESTS GOOD PER B737-900 AMM TASK 34-61-00-710-801.