FMS INS navigation system anomaly in autoflt contributed to late turn over intersection.

Attributes
ACN	298594
Time
Date	199503
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : otk
State Reference	GA
Altitude	msl bound lower : 27000 msl bound upper : 27000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx artcc : zny
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	arrival : profile descent arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : atp pilot : commercial
Experience	flight time last 90 days : 100 flight time total : 17500 flight time type : 2500
ASRS Report	298594
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 250 flight time total : 10000 flight time type : 350
ASRS Report	298698
Events
Anomaly	non adherence : published procedure other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While in cruise flight, en route from atl to mco, we were navigating on the leese 7 arrival to orlando mco airport we experienced an anomaly of unknown cause in our FMA/INS navigation system. We noticed magnetic heading difference and the aircraft on autoplt and FMS was late in turning over the eugene intersection. We overshot the turn onto track by approximately 12 mi. We tried to determine the cause but were unable in short time and needed to reintercept the proper radial by use of standard VOR navigation. Jax artc center said there was no problem although they acknowledged our deviation and corrective action. Manual navigation was continued with no further problems. Perhaps in reflecting on this, closer monitoring by myself and first officer would help. This event just reenforces need for continual xchking of all this wonderful automation.

Original NASA ASRS Text

Title: FMS INS NAV SYS ANOMALY IN AUTOFLT CONTRIBUTED TO LATE TURN OVER INTXN.

Narrative: WHILE IN CRUISE FLT, ENRTE FROM ATL TO MCO, WE WERE NAVIGATING ON THE LEESE 7 ARR TO ORLANDO MCO ARPT WE EXPERIENCED AN ANOMALY OF UNKNOWN CAUSE IN OUR FMA/INS NAV SYS. WE NOTICED MAGNETIC HDG DIFFERENCE AND THE ACFT ON AUTOPLT AND FMS WAS LATE IN TURNING OVER THE EUGENE INTXN. WE OVERSHOT THE TURN ONTO TRACK BY APPROX 12 MI. WE TRIED TO DETERMINE THE CAUSE BUT WERE UNABLE IN SHORT TIME AND NEEDED TO REINTERCEPT THE PROPER RADIAL BY USE OF STANDARD VOR NAV. JAX ARTC CTR SAID THERE WAS NO PROB ALTHOUGH THEY ACKNOWLEDGED OUR DEV AND CORRECTIVE ACTION. MANUAL NAV WAS CONTINUED WITH NO FURTHER PROBS. PERHAPS IN REFLECTING ON THIS, CLOSER MONITORING BY MYSELF AND FO WOULD HELP. THIS EVENT JUST REENFORCES NEED FOR CONTINUAL XCHKING OF ALL THIS WONDERFUL AUTOMATION.

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.