FMS malfunction causes 90 degree heading error for BA4100 flight crew in roa, va.

Attributes
ACN	424513
Time
Date	199812
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : roa.tracon
State Reference	VA
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Navigation In Use	Other
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 200 flight time total : 10000 flight time type : 500
ASRS Report	424513
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial
Events
Anomaly	aircraft equipment problem : critical non adherence : clearance other spatial deviation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

We were given direct mol. The FMS showed direct mol then gave erroneous information. The controller said we were 90 degrees off our heading, then gave us a vector. We wrote up the problem when we landed in iad, and had the FMS deferred.

Original NASA ASRS Text

Title: FMS MALFUNCTION CAUSES 90 DEG HDG ERROR FOR BA4100 FLC IN ROA, VA.

Narrative: WE WERE GIVEN DIRECT MOL. THE FMS SHOWED DIRECT MOL THEN GAVE ERRONEOUS INFO. THE CTLR SAID WE WERE 90 DEGS OFF OUR HDG, THEN GAVE US A VECTOR. WE WROTE UP THE PROB WHEN WE LANDED IN IAD, AND HAD THE FMS DEFERRED.

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.