Navigation error. - NASA ASRS

Attributes
ACN	214913
Time
Date	199207
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gls
State Reference	TX
Altitude	msl bound lower : 31000 msl bound upper : 37000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Navigation In Use	other ndb
Flight Phase	cruise other
Route In Use	enroute : direct enroute airway : a766 enroute other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 20000 flight time type : 2000
ASRS Report	214913
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : commercial pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 17000 flight time type : 14000
ASRS Report	214645
Events
Anomaly	non adherence : clearance other anomaly other other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

After determining both ADF's were off by 10-12 degrees, were compensating to the error and were very near barrow intersection and made a call to ZHU and were told to fly direct to san sabine VOR. After approximately 30 mins, radar contact was established and were told we were 42 mi east of course. Corrective vector were taken. Supplemental information from acn 214645. Galveston radio beacon was the primary navigation facility. Consistently showing this flight to be on course. A766. First radar plot showed us to be 44 NM northeast of the airway. Vectors returned the flight to the airway. ADF and dead reckoning navigation should not be the only methods of navigation used for extended overwater flts. Supplemental information from acn 214912. The pilots were navigating by a radar vector from the mexican center and by means of 2 ADF's. This is the only means of navigation available over the gulf. ADF's indicated exactly on track. In my opinion, navigation facilities on this route are inadequate for aircraft not equipped with a system such as omega. ATC surveillance radar in the gulf should be a must priority.

Original NASA ASRS Text

Title: NAV ERROR.

Narrative: AFTER DETERMINING BOTH ADF'S WERE OFF BY 10-12 DEGS, WERE COMPENSATING TO THE ERROR AND WERE VERY NEAR BARROW INTXN AND MADE A CALL TO ZHU AND WERE TOLD TO FLY DIRECT TO SAN SABINE VOR. AFTER APPROX 30 MINS, RADAR CONTACT WAS ESTABLISHED AND WERE TOLD WE WERE 42 MI E OF COURSE. CORRECTIVE VECTOR WERE TAKEN. SUPPLEMENTAL INFO FROM ACN 214645. GALVESTON RADIO BEACON WAS THE PRIMARY NAV FACILITY. CONSISTENTLY SHOWING THIS FLT TO BE ON COURSE. A766. FIRST RADAR PLOT SHOWED US TO BE 44 NM NE OF THE AIRWAY. VECTORS RETURNED THE FLT TO THE AIRWAY. ADF AND DEAD RECKONING NAV SHOULD NOT BE THE ONLY METHODS OF NAV USED FOR EXTENDED OVERWATER FLTS. SUPPLEMENTAL INFO FROM ACN 214912. THE PLTS WERE NAVIGATING BY A RADAR VECTOR FROM THE MEXICAN CTR AND BY MEANS OF 2 ADF'S. THIS IS THE ONLY MEANS OF NAV AVAILABLE OVER THE GULF. ADF'S INDICATED EXACTLY ON TRACK. IN MY OPINION, NAV FACILITIES ON THIS RTE ARE INADEQUATE FOR ACFT NOT EQUIPPED WITH A SYS SUCH AS OMEGA. ATC SURVEILLANCE RADAR IN THE GULF SHOULD BE A MUST PRIORITY.

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.