Air carrier cargo flight has omega navigation problem, drifts off course.

Attributes
ACN	237568
Time
Date	199303
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : yay
State Reference	NF
Altitude	msl bound lower : 35000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : czqx
Operator	common carrier : air carrier
Make Model Name	Heavy Transport, Low Wing, 4 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute : other oceanic enroute : atlantic
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp pilot : instrument
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 1000
ASRS Report	237568
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 11000 flight time type : 1000
ASRS Report	237305
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance 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 other
Consequence	faa : reviewed incident with flight crew faa : investigated
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

Flight licz to kbgr: had no problems with omega operation until 53N 50W. After 53N 50W noted discrepancy in omegas. Notified gander radio of the problem. When in VOR reception noted #2 omega (navigation system in use) had drifted. Resumed navigation on #1 omega system and VOR navigation. When in radar contact, asked controller and he said we had drifted about 6 mi off course. Don't know how far off course we were prior to that. Wrote up #2 omega in logbook when we landed in kbgr. Don't know what caused the problem. Supplemental information from acn 237305: disconnected #2 from the autoplt and continued fpr to yay (N5130 W5655.0). This is a repeat of omega navigation variation in the gander area. Cause unknown (total variation estimated 18 NM). Additional factor/ possible contributing factor of slower than normal crew discrepancy recognition: crew fatigue. Crew had been on duty (without any rest whatsoever) for 17 hour 30 mins of a duty day of 24 hours 10 mins. This included total flight time of 15 hours 5 mins. The part 91 international FARS are ludicrous and demand (in the interest of safety) a revision.

Original NASA ASRS Text

Title: ACR CARGO FLT HAS OMEGA NAV PROB, DRIFTS OFF COURSE.

Narrative: FLT LICZ TO KBGR: HAD NO PROBS WITH OMEGA OP UNTIL 53N 50W. AFTER 53N 50W NOTED DISCREPANCY IN OMEGAS. NOTIFIED GANDER RADIO OF THE PROB. WHEN IN VOR RECEPTION NOTED #2 OMEGA (NAV SYS IN USE) HAD DRIFTED. RESUMED NAV ON #1 OMEGA SYS AND VOR NAV. WHEN IN RADAR CONTACT, ASKED CTLR AND HE SAID WE HAD DRIFTED ABOUT 6 MI OFF COURSE. DON'T KNOW HOW FAR OFF COURSE WE WERE PRIOR TO THAT. WROTE UP #2 OMEGA IN LOGBOOK WHEN WE LANDED IN KBGR. DON'T KNOW WHAT CAUSED THE PROB. SUPPLEMENTAL INFO FROM ACN 237305: DISCONNECTED #2 FROM THE AUTOPLT AND CONTINUED FPR TO YAY (N5130 W5655.0). THIS IS A REPEAT OF OMEGA NAV VARIATION IN THE GANDER AREA. CAUSE UNKNOWN (TOTAL VARIATION ESTIMATED 18 NM). ADDITIONAL FACTOR/ POSSIBLE CONTRIBUTING FACTOR OF SLOWER THAN NORMAL CREW DISCREPANCY RECOGNITION: CREW FATIGUE. CREW HAD BEEN ON DUTY (WITHOUT ANY REST WHATSOEVER) FOR 17 HR 30 MINS OF A DUTY DAY OF 24 HRS 10 MINS. THIS INCLUDED TOTAL FLT TIME OF 15 HRS 5 MINS. THE PART 91 INTL FARS ARE LUDICROUS AND DEMAND (IN THE INTEREST OF SAFETY) A REVISION.

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.