Almost insignificant track deviation occurred when, in-flight, navigation data based expired.

Attributes
ACN	435154
Time
Date	199904
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : lbv.vortac
State Reference	FL
Altitude	msl single value : 21000
Aircraft 1
Controlling Facilities	artcc : zma.artcc
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other other
Route In Use	departure sid : mia.3
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	435154
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe maintenance problem : improper maintenance non adherence : published procedure non adherence : company policies non adherence : far other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : overrode automation
Supplementary
Problem Areas	Flight Crew Human Performance Maintenance Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

Captain flying autoplt on coupled up to gfms to intercept winco transition out of dhp. Gfms initially intercepted departure course perfectly at XA00Z, a gfms navigation data out of date message appeared on both gfms displays. The aircraft began a slow but initially unperceived turn toward the west, off course. At this time ATC cleared us after climbing through FL210 proceed direct nepta then flight planned route. At this time noting our turn and course displacement, I immediately turned to reintercept our route and notified ATC of our navigation error. ZMA said no problem and that he showed that we remained within our course corridor. Apparently when the gfms clock hit XA00Z and the navigation data message appeared, our route data dumped. The only navigation points remaining were from the STAR we loaded. The autoplt coupled to the gfms was taking us to the first fix on the STAR. I have not experienced this navigation data problem before.

Original NASA ASRS Text

Title: ALMOST INSIGNIFICANT TRACK DEV OCCURRED WHEN, INFLT, NAV DATA BASED EXPIRED.

Narrative: CAPT FLYING AUTOPLT ON COUPLED UP TO GFMS TO INTERCEPT WINCO TRANSITION OUT OF DHP. GFMS INITIALLY INTERCEPTED DEP COURSE PERFECTLY AT XA00Z, A GFMS NAV DATA OUT OF DATE MESSAGE APPEARED ON BOTH GFMS DISPLAYS. THE ACFT BEGAN A SLOW BUT INITIALLY UNPERCEIVED TURN TOWARD THE W, OFF COURSE. AT THIS TIME ATC CLRED US AFTER CLBING THROUGH FL210 PROCEED DIRECT NEPTA THEN FLT PLANNED RTE. AT THIS TIME NOTING OUR TURN AND COURSE DISPLACEMENT, I IMMEDIATELY TURNED TO REINTERCEPT OUR RTE AND NOTIFIED ATC OF OUR NAV ERROR. ZMA SAID NO PROB AND THAT HE SHOWED THAT WE REMAINED WITHIN OUR COURSE CORRIDOR. APPARENTLY WHEN THE GFMS CLOCK HIT XA00Z AND THE NAV DATA MESSAGE APPEARED, OUR RTE DATA DUMPED. THE ONLY NAV POINTS REMAINING WERE FROM THE STAR WE LOADED. THE AUTOPLT COUPLED TO THE GFMS WAS TAKING US TO THE FIRST FIX ON THE STAR. I HAVE NOT EXPERIENCED THIS NAV DATA PROB BEFORE.

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.