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Large transport on oceanic route has ADF malfunction plus WX avoidance. Off course 40-50 mi.
| Attributes | |
| ACN | 162829 |
| Time | |
| Date | 199011 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : gls |
| State Reference | TX |
| Altitude | msl bound lower : 28000 msl bound upper : 28000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zhu |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | cruise other |
| Route In Use | enroute : other oceanic enroute other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 240 flight time total : 18000 |
| ASRS Report | 162829 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : critical non adherence : clearance non adherence : far other spatial deviation |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : became reoriented flight crew : returned to intended course or assigned course none taken : detected after the fact |
| Consequence | faa : reviewed incident with flight crew |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
Flight cozumel-iah. First officer navigating by #1 ADF A766. When making contact with houston center approaching barow intersection ATC advised we were 40-50 mi to right or north of A766. Gave estimate of barow intersection at ab:45 zulu. Our ADF gave the proper relative bearing of 316 degree to gls radio beacon. We were unable to obtain DME from leeville VOR to establish accurate position of barow. I wrote the #1 ADF bearing needle as indicating 10-15 degree off course from relative bearing desired. Also #1 ADF bearing indicator fluctuated either side of desired course by 20 degree approximately 30 mi out of houston international contacted on 326 radio frequency. We believed #1 ADF to be more accurate than #2 ADF as I navigated to cozumel on the way down and it appeared to be relatively accurate. We had to circumnav around thunderstorms in the middle of the gulf of mexico west/O use of any navaids to accurately pinpoint our position. I made an error in my computations of nuley intersection time by 20 mins. I was to have contacted houston on 132.65 at nuley estimate; however, because of incorrectly writing down our nuley estimate as ab:53 rather than ab:33 I was late contacting houston. Merida center only ATC instructions was to contact houston center at nuley intersection. No time estimates were asked or given for nuley or barow intxns. I believe our off course was caused by an unreliable bearing indicator.
Original NASA ASRS Text
Title: LGT ON OCEANIC ROUTE HAS ADF MALFUNCTION PLUS WX AVOIDANCE. OFF COURSE 40-50 MI.
Narrative: FLT COZUMEL-IAH. F/O NAVIGATING BY #1 ADF A766. WHEN MAKING CONTACT WITH HOUSTON CTR APCHING BAROW INTXN ATC ADVISED WE WERE 40-50 MI TO R OR N OF A766. GAVE ESTIMATE OF BAROW INTXN AT AB:45 ZULU. OUR ADF GAVE THE PROPER RELATIVE BEARING OF 316 DEG TO GLS RADIO BEACON. WE WERE UNABLE TO OBTAIN DME FROM LEEVILLE VOR TO ESTABLISH ACCURATE POS OF BAROW. I WROTE THE #1 ADF BEARING NEEDLE AS INDICATING 10-15 DEG OFF COURSE FROM RELATIVE BEARING DESIRED. ALSO #1 ADF BEARING INDICATOR FLUCTUATED EITHER SIDE OF DESIRED COURSE BY 20 DEG APPROX 30 MI OUT OF HOUSTON INTL CONTACTED ON 326 RADIO FREQ. WE BELIEVED #1 ADF TO BE MORE ACCURATE THAN #2 ADF AS I NAVIGATED TO COZUMEL ON THE WAY DOWN AND IT APPEARED TO BE RELATIVELY ACCURATE. WE HAD TO CIRCUMNAV AROUND TSTMS IN THE MIDDLE OF THE GULF OF MEXICO W/O USE OF ANY NAVAIDS TO ACCURATELY PINPOINT OUR POS. I MADE AN ERROR IN MY COMPUTATIONS OF NULEY INTXN TIME BY 20 MINS. I WAS TO HAVE CONTACTED HOUSTON ON 132.65 AT NULEY ESTIMATE; HOWEVER, BECAUSE OF INCORRECTLY WRITING DOWN OUR NULEY ESTIMATE AS AB:53 RATHER THAN AB:33 I WAS LATE CONTACTING HOUSTON. MERIDA CTR ONLY ATC INSTRUCTIONS WAS TO CONTACT HOUSTON CTR AT NULEY INTXN. NO TIME ESTIMATES WERE ASKED OR GIVEN FOR NULEY OR BAROW INTXNS. I BELIEVE OUR OFF COURSE WAS CAUSED BY AN UNRELIABLE BEARING INDICATOR.
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.