Heading deviation due to malfunction of FMS. Continued flight with dead reckoning mode.

Attributes
ACN	332580
Time
Date	199604
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bhm
State Reference	AL
Altitude	agl bound lower : 0 agl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bhm
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : instrument pilot : atp pilot : commercial
Experience	flight time last 90 days : 210 flight time total : 10000 flight time type : 250
ASRS Report	332580
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

On departure from bhm, the FMS apparently began to malfunction. Departure told us that we were off course by close to 1/2 a mi. At this time the FMS gave a warning that it had gone to 'dead reckoning' mode and then showed 'FMS data invalid.' we advised ATC of the failure and continued to our destination using the jet airway system.

Original NASA ASRS Text

Title: HDG DEV DUE TO MALFUNCTION OF FMS. CONTINUED FLT WITH DEAD RECKONING MODE.

Narrative: ON DEP FROM BHM, THE FMS APPARENTLY BEGAN TO MALFUNCTION. DEP TOLD US THAT WE WERE OFF COURSE BY CLOSE TO 1/2 A MI. AT THIS TIME THE FMS GAVE A WARNING THAT IT HAD GONE TO 'DEAD RECKONING' MODE AND THEN SHOWED 'FMS DATA INVALID.' WE ADVISED ATC OF THE FAILURE AND CONTINUED TO OUR DEST USING THE JET AIRWAY SYS.

Data retrieved from NASA's ASRS site as of July 2007 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.