SDR ASAA2015081812923

Service difficulty report · Autopilot Sys · Boeing 737890

Difficulty date: August 18, 2015
Submitted: August 20, 2015
Operation: Air carrier
Aircraft: N579AS
Make and model: Boeing 737890
Aircraft serial: 35187
Aircraft time: 32,463 hours, 9,723 cycles
System (JASC): 2210 · Autopilot System
Part: Autopilot Sys
Condition: Unknown
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

WHILE IN THE FOLOWING MODE; LNAV, MCP SPEED, ALT HOLD, LEVEL AT FL390, F/E IAS/MACH WINDOW OPEN WITH .79 MACH COMMANDED ON A/T, THE COMMANDED SPEED CHANGED FROM .79 TO .80 ON MORE THAN 1 OCCASION AUTONOMOUSLY. NO KNOBS WERE TURNED OR TOUCHED, NOR BUTTONS PUSHED OR MODE CHANGED. ACFT GROUNDED. PERFORMED DFCF BITE PROCEDURE, FAULT HISTORY SORTED BY FAULT LEG, REF FIM 22-11, TASK 801, NO FAULTS FOUND, PERFORMED FIM 22-32 TASK 803, ALL SYSTEMS CHECKED NORMAL, NO FAULTS NOTED. ACFT OK FOR SERVICE.