Large transport over water flight has NDB malfunction, course deviation.

Attributes
ACN	260372
Time
Date	199401
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : gls
State Reference	TX
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : cvg
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Navigation In Use	other ndb
Flight Phase	cruise other
Route In Use	enroute : direct enroute : other oceanic enroute airway : zhu
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 : 220 flight time total : 4800 flight time type : 1050
ASRS Report	260372
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 240 flight time total : 4250 flight time type : 620
ASRS Report	260368
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : became reoriented other
Consequence	Other Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

En route from dallas/ft worth, tx (dfw) to montego bay, jamaica (mkjs) on the sbound leg from gls NDB on A766, our aircraft ADF's were receiving erratic signals from gls NDB and showing slightly west of course (139 degree bearing from the station). ZHU called on the radio and reported that we were 11.8 mi east of A766 over barow intersection. Immediately we made a course correction to the west. When in range of cozumel (czm) NDB, we found that the #2 ADF was operating normally, but the #1 ADF was erratic and unreliable. The #1 ADF was promptly entered into the maintenance log as inoperative and placarded by the MEL. We believe the gls NDB was unreliable and caused the deviation.

Original NASA ASRS Text

Title: LGT OVER WATER FLT HAS NDB MALFUNCTION, COURSE DEV.

Narrative: ENRTE FROM DALLAS/FT WORTH, TX (DFW) TO MONTEGO BAY, JAMAICA (MKJS) ON THE SBOUND LEG FROM GLS NDB ON A766, OUR ACFT ADF'S WERE RECEIVING ERRATIC SIGNALS FROM GLS NDB AND SHOWING SLIGHTLY W OF COURSE (139 DEG BEARING FROM THE STATION). ZHU CALLED ON THE RADIO AND RPTED THAT WE WERE 11.8 MI E OF A766 OVER BAROW INTXN. IMMEDIATELY WE MADE A COURSE CORRECTION TO THE W. WHEN IN RANGE OF COZUMEL (CZM) NDB, WE FOUND THAT THE #2 ADF WAS OPERATING NORMALLY, BUT THE #1 ADF WAS ERRATIC AND UNRELIABLE. THE #1 ADF WAS PROMPTLY ENTERED INTO THE MAINT LOG AS INOP AND PLACARDED BY THE MEL. WE BELIEVE THE GLS NDB WAS UNRELIABLE AND CAUSED THE DEV.

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.