A B757 flight crew is off course, but gets back on when they turn off the FMS.

Attributes
ACN	526270
Time
Date	200110
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : cvg.airport
State Reference	KY
Altitude	msl single value : 13000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Flight Phase	climbout : initial climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : commercial pilot : private pilot : multi engine pilot : atp pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 16000 flight time type : 2000
ASRS Report	526270
Events
Anomaly	aircraft equipment problem : less severe other spatial deviation
Resolutory Action	controller : issued advisory flight crew : returned to intended or assigned course
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

FMS showed us turning to intercept outbound radial, cvg 221 degrees. Controller stated we were 2 mi west off course. We increased our rate of turn and corrected back to course after disconnecting LNAV.

Original NASA ASRS Text

Title: A B757 FLT CREW IS OFF COURSE, BUT GETS BACK ON WHEN THEY TURN OFF THE FMS.

Narrative: FMS SHOWED US TURNING TO INTERCEPT OUTBOUND RADIAL, CVG 221 DEGS. CTLR STATED WE WERE 2 MI W OFF COURSE. WE INCREASED OUR RATE OF TURN AND CORRECTED BACK TO COURSE AFTER DISCONNECTING LNAV.

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.