Deviation from track 20 miles 130 miles south of VOR.

Attributes
ACN	87057
Time
Date	198805
Day	Sat
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : bka
State Reference	AK
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zan
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute airway : zan
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 180 flight time total : 20400 flight time type : 4200
ASRS Report	87057
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 160 flight time total : 6500 flight time type : 130
ASRS Report	87056
Events
Anomaly	other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	Pilot Deviation

Narrative:

Copilot's leg on trip from seattle to anchorage. Both VOR's tuned to biorka island VOR (bka) and tracking inbound on J501 with autoplt engaged using VOR-localizer mode. No 1 ADF tuned to situation and no 2 to zp. Initially the autoplt captured the course and tracked normally for several minutes. Shortly thereafter I noticed that the aircraft was in a right bank and no longer in the VOR localizer mode and to the right of course. I immediately mentioned this to the copilot who started making correction to the left at which time center called to say we were 20 miles to the right of course. At this time the course deviation bar was fluctuating as much as 6 to 7 degree left to right although the identify was still good and center was advised of this. A flight in the vicinity also mentioned to center that they had experienced similar fluctuations for over a year. When the bka VOR settled down and we had our course deviation bars centered we checked with center and were advised we were 6 miles to the right of course. Outbound from bka we checked again with center and although our course bars were centered we were 5 miles to right of course when we were 100 DME northwest. Inbound to joh and anc we checked our navaids and everything appeared to be normal. Closer checking of our ADF's and an early call to anc center for a radar fix would have alleviated much of the problem.

Original NASA ASRS Text

Title: DEVIATION FROM TRACK 20 MILES 130 MILES SOUTH OF VOR.

Narrative: COPLT'S LEG ON TRIP FROM SEATTLE TO ANCHORAGE. BOTH VOR'S TUNED TO BIORKA ISLAND VOR (BKA) AND TRACKING INBOUND ON J501 WITH AUTOPLT ENGAGED USING VOR-LOC MODE. NO 1 ADF TUNED TO SIT AND NO 2 TO ZP. INITIALLY THE AUTOPLT CAPTURED THE COURSE AND TRACKED NORMALLY FOR SEVERAL MINUTES. SHORTLY THEREAFTER I NOTICED THAT THE ACFT WAS IN A RIGHT BANK AND NO LONGER IN THE VOR LOC MODE AND TO THE RIGHT OF COURSE. I IMMEDIATELY MENTIONED THIS TO THE COPLT WHO STARTED MAKING CORRECTION TO THE LEFT AT WHICH TIME CENTER CALLED TO SAY WE WERE 20 MILES TO THE RIGHT OF COURSE. AT THIS TIME THE COURSE DEVIATION BAR WAS FLUCTUATING AS MUCH AS 6 TO 7 DEG LEFT TO RIGHT ALTHOUGH THE IDENT WAS STILL GOOD AND CENTER WAS ADVISED OF THIS. A FLT IN THE VICINITY ALSO MENTIONED TO CENTER THAT THEY HAD EXPERIENCED SIMILAR FLUCTUATIONS FOR OVER A YEAR. WHEN THE BKA VOR SETTLED DOWN AND WE HAD OUR COURSE DEVIATION BARS CENTERED WE CHECKED WITH CENTER AND WERE ADVISED WE WERE 6 MILES TO THE RIGHT OF COURSE. OUTBOUND FROM BKA WE CHECKED AGAIN WITH CENTER AND ALTHOUGH OUR COURSE BARS WERE CENTERED WE WERE 5 MILES TO RIGHT OF COURSE WHEN WE WERE 100 DME NW. INBOUND TO JOH AND ANC WE CHECKED OUR NAVAIDS AND EVERYTHING APPEARED TO BE NORMAL. CLOSER CHECKING OF OUR ADF'S AND AN EARLY CALL TO ANC CTR FOR A RADAR FIX WOULD HAVE ALLEVIATED MUCH OF THE PROBLEM.

Data retrieved from NASA's ASRS site as of August 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.