ATC detects a potential navigation error of 8 mi by an omega equipped widebody transport.

Attributes
ACN	224646
Time
Date	199210
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zla
State Reference	CA
Altitude	msl bound lower : 18000 msl bound upper : 18000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other descent other
Route In Use	enroute : direct enroute other
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 : 117 flight time total : 14225 flight time type : 117
ASRS Report	224646
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe non adherence : published procedure non adherence : clearance non adherence other other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Prior to tuba city center cleared us to civet intersection which is 52 NM out on the lax 25L localizer. We were equipped with dual omegas and accepted the clearance. Just passing hector VOR, center said our heading was going to take us 8 mi west of civit intersection. We accepted a heading change from center and checked the civit coordinates. Both sets checked good with one showing a xtrack error of 1 mi the other 8/10 of a mi. My point in reporting is that I will be very careful about accepting clrncs to fixes I cannot xchk, ie, had civet been a VOR I would have been receiving radial information long before an error could occur. Obviously the omegas were not doing the job in a precise manner. The only explanation I have is that they had been correcting for a 75 KT direct crosswind at altitude and still had a heading correction indicated as we descended.

Original NASA ASRS Text

Title: ATC DETECTS A POTENTIAL NAV ERROR OF 8 MI BY AN OMEGA EQUIPPED WDB.

Narrative: PRIOR TO TUBA CITY CTR CLRED US TO CIVET INTXN WHICH IS 52 NM OUT ON THE LAX 25L LOC. WE WERE EQUIPPED WITH DUAL OMEGAS AND ACCEPTED THE CLRNC. JUST PASSING HECTOR VOR, CTR SAID OUR HDG WAS GOING TO TAKE US 8 MI W OF CIVIT INTXN. WE ACCEPTED A HDG CHANGE FROM CTR AND CHKED THE CIVIT COORDINATES. BOTH SETS CHKED GOOD WITH ONE SHOWING A XTRACK ERROR OF 1 MI THE OTHER 8/10 OF A MI. MY POINT IN RPTING IS THAT I WILL BE VERY CAREFUL ABOUT ACCEPTING CLRNCS TO FIXES I CANNOT XCHK, IE, HAD CIVET BEEN A VOR I WOULD HAVE BEEN RECEIVING RADIAL INFO LONG BEFORE AN ERROR COULD OCCUR. OBVIOUSLY THE OMEGAS WERE NOT DOING THE JOB IN A PRECISE MANNER. THE ONLY EXPLANATION I HAVE IS THAT THEY HAD BEEN CORRECTING FOR A 75 KT DIRECT XWIND AT ALT AND STILL HAD A HDG CORRECTION INDICATED AS WE DSNDED.

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.