Heading track deviation.

Attributes
ACN	218806
Time
Date	199208
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zid
State Reference	IN
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 10 flight time total : 10000 flight time type : 2000
ASRS Report	218806
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe non adherence : far non adherence : published procedure non adherence : clearance other anomaly other other spatial deviation
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

During cruise flight, my copilot noticed that the FMS display was calculating the wind speed at almost 300 KTS, obviously too high to be correct. We then spent several mins 'playing' with the FMS computer, trying to determine and correct the problem. During this time, the autoplt was flying and navigating. After several mins of involvement with the computer, center queried us on our route of flight. Upon checking our flight instruments, we realized that the FMS had reverted to 'dead reckoning' and that the aircraft had drifted off the airway. We explained our navigational problem to center, while we returned to tracking the correct radial with the VOR and CDI. Next time that the FMS is giving us winds of 300 KTS, we will immediately think about returning to basic navigation, before we worry about what's wrong with the computer!

Original NASA ASRS Text

Title: HDG TRACK DEV.

Narrative: DURING CRUISE FLT, MY COPLT NOTICED THAT THE FMS DISPLAY WAS CALCULATING THE WIND SPD AT ALMOST 300 KTS, OBVIOUSLY TOO HIGH TO BE CORRECT. WE THEN SPENT SEVERAL MINS 'PLAYING' WITH THE FMS COMPUTER, TRYING TO DETERMINE AND CORRECT THE PROBLEM. DURING THIS TIME, THE AUTOPLT WAS FLYING AND NAVING. AFTER SEVERAL MINS OF INVOLVEMENT WITH THE COMPUTER, CTR QUERIED US ON OUR RTE OF FLT. UPON CHKING OUR FLT INSTS, WE REALIZED THAT THE FMS HAD REVERTED TO 'DEAD RECKONING' AND THAT THE ACFT HAD DRIFTED OFF THE AIRWAY. WE EXPLAINED OUR NAVIGATIONAL PROBLEM TO CTR, WHILE WE RETURNED TO TRACKING THE CORRECT RADIAL WITH THE VOR AND CDI. NEXT TIME THAT THE FMS IS GIVING US WINDS OF 300 KTS, WE WILL IMMEDIATELY THINK ABOUT RETURNING TO BASIC NAV, BEFORE WE WORRY ABOUT WHAT'S WRONG WITH THE COMPUTER!

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.