B737NG captain reported a track error occurred following loss of both fmcs in cruise flight. A few m...

Attributes
ACN	1665976
Time
Date	201907
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 208 Flight Crew Total 14976
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Clearance Deviation - Track / Heading All Types

Narrative:

At cruise; both fmcs failed with no annunciators except for momentary vtk annunciator on captain's instruments. FMC prompt disappeared from both cdus. A few seconds later; aircraft went into cws for roll and auto throttles attempted to go to full idle. Crew began to execute checklist and troubleshoot the problem. Because aircraft went into cws for roll; and heading select would not function; aircraft drifted slightly off course as crew analyzed the various failures. ATC noticed and asked us where we were going. I informed ATC of our failures. He gave us a heading to correct. Three minutes later all systems self-restored and we continued without further anomalies. Captain made a [logbook] entry. ATC was advised immediately of our restored systems and that we needed no further assistance. Captain was about to inform ATC of our system failure when ATC noticed our slight course deviation.

Original NASA ASRS Text

Title: B737NG Captain reported a track error occurred following loss of both FMCs in cruise flight. A few minutes later; all systems returning to normal with no action taken by the crew.

Narrative: At cruise; both FMCs failed with no annunciators except for momentary VTK annunciator on Captain's instruments. FMC prompt disappeared from both CDUs. A few seconds later; aircraft went into CWS for roll and auto throttles attempted to go to full idle. Crew began to execute checklist and troubleshoot the problem. Because aircraft went into CWS for roll; and heading select would not function; aircraft drifted slightly off course as crew analyzed the various failures. ATC noticed and asked us where we were going. I informed ATC of our failures. He gave us a heading to correct. Three minutes later all systems self-restored and we continued without further anomalies. Captain made a [logbook] entry. ATC was advised immediately of our restored systems and that we needed no further assistance. Captain was about to inform ATC of our system failure when ATC noticed our slight course deviation.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

B737NG captain reported a track error occurred following loss of both fmcs in cruise flight. A few minutes later; all systems returning to normal with no action taken by the crew.