A B767 departed an airport not in the FMS database and subsequently became 8 miles off course while following FMS navigation guidance.

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Attributes
ACN	750405
Time
Date	200708
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : dbn.vortac
State Reference	GA
Altitude	msl single value : 41000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : ztl.artcc tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B767 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	instruction : trainee oversight : pic
Qualification	pilot : flight engineer pilot : instrument pilot : atp pilot : multi engine pilot : private pilot : commercial
Experience	flight time last 90 days : 181 flight time total : 15500 flight time type : 4310
ASRS Report	750405
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 10000 flight time type : 3000
ASRS Report	750404
Events
Anomaly	aircraft equipment problem : less severe non adherence : company policies non adherence : published procedure other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued advisory flight crew : returned to intended or assigned course
Supplementary
Problem Areas	Company Flight Crew Human Performance Aircraft
Primary Problem	Ambiguous

Narrative:

Our leg entailed a charter flight departing an offline airport. We programmed the FMS and followed all procedures as prescribed by air carrier's operating procedures manual; supplemental section 'FMS preflight for origins/destinations not contained in FMS database.' we departed and climbed up to our cruise altitude of FL410. We were cleared direct dbn by center. After switching to next center; the controller asked if we were proceeding direct dbn. We told him we were. He responded that we were approximately 8 mi off course. We doublechked our FMS. It showed us on course direct dbn. However; as we checked the raw data on the VOR we realized the FMS was off. Either the FMS drifted or we had a map shift. Being unsure of our navigation accuracy; we requested vectors to complete our flight. Rest of flight was uneventful. Supplemental information from acn 750404: map shift/off-line alignment/aircraft malfunction.

Original NASA ASRS Text

Title: A B767 DEPARTED AN ARPT NOT IN THE FMS DATABASE AND SUBSEQUENTLY BECAME 8 MILES OFF COURSE WHILE FOLLOWING FMS NAV GUIDANCE.

Narrative: OUR LEG ENTAILED A CHARTER FLT DEPARTING AN OFFLINE ARPT. WE PROGRAMMED THE FMS AND FOLLOWED ALL PROCS AS PRESCRIBED BY ACR'S OPERATING PROCS MANUAL; SUPPLEMENTAL SECTION 'FMS PREFLT FOR ORIGINS/DESTS NOT CONTAINED IN FMS DATABASE.' WE DEPARTED AND CLBED UP TO OUR CRUISE ALT OF FL410. WE WERE CLRED DIRECT DBN BY CTR. AFTER SWITCHING TO NEXT CTR; THE CTLR ASKED IF WE WERE PROCEEDING DIRECT DBN. WE TOLD HIM WE WERE. HE RESPONDED THAT WE WERE APPROX 8 MI OFF COURSE. WE DOUBLECHKED OUR FMS. IT SHOWED US ON COURSE DIRECT DBN. HOWEVER; AS WE CHKED THE RAW DATA ON THE VOR WE REALIZED THE FMS WAS OFF. EITHER THE FMS DRIFTED OR WE HAD A MAP SHIFT. BEING UNSURE OF OUR NAV ACCURACY; WE REQUESTED VECTORS TO COMPLETE OUR FLT. REST OF FLT WAS UNEVENTFUL. SUPPLEMENTAL INFO FROM ACN 750404: MAP SHIFT/OFF-LINE ALIGNMENT/ACFT MALFUNCTION.

Data retrieved from NASA's ASRS site as of January 2009 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.