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An air carrier medium large transport crew had an ILS stick in the 'test' position causing the aircraft to fly through the ILS course.
| Attributes | |
| ACN | 218929 |
| Time | |
| Date | 199208 |
| Day | Sat |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : atl |
| State Reference | GA |
| Altitude | msl bound lower : 5000 msl bound upper : 5000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : atl |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | descent : approach descent other |
| Route In Use | arrival 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 : 210 flight time total : 8000 flight time type : 4000 |
| ASRS Report | 218929 |
| 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 : clearance other spatial deviation |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : overcame equipment problem other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation other |
Narrative:
Approaching atl from the northwest, set up for an ILS to 8L. Once vectoring by approach control started, I selected the ILS and left first officer on VOR to monitor position. Vectored to a 30 degree or so intercept and given a clearance to maintain 5000 until bahrr and cleared for approach. Shortly thereafter, approach control stated that we had overshot the localizer and directed us to turn left immediately, re-intercept the localizer and descend to 4500 ft. My localizer was still showing off to the right with no flags in view. I immediately complied with the instructions and switched the first officer radio to ILS. His navigation instruments showed the localizer off to the left. Confused, I tried to re-identify my ILS but could get no identify. We continued the approach using the first officer's ILS. I assumed my ILS had failed but could not figure why I had received no flags. I entered the discrepancy in the flight log and later checked with maintenance to see what they found. It seems the ILS test switch was stuck in the test position (down/right) and could not be unstuck. Apparently, me or my first officer hit the test button when we selected the ILS on my side. We had previously tuned and idented the ILS but had gone back to track the VOR. What I have since discovered is that, in the test position, no flags are in view on the HSI or ADI. In other words, it all looks perfectly normal. The only way we could have known the switch was stuck was to have been continuously monitoring the identify.
Original NASA ASRS Text
Title: AN ACR MLG CREW HAD AN ILS STICK IN THE 'TEST' POS CAUSING THE ACFT TO FLY THROUGH THE ILS COURSE.
Narrative: APCHING ATL FROM THE NW, SET UP FOR AN ILS TO 8L. ONCE VECTORING BY APCH CTL STARTED, I SELECTED THE ILS AND LEFT FO ON VOR TO MONITOR POS. VECTORED TO A 30 DEG OR SO INTERCEPT AND GIVEN A CLRNC TO MAINTAIN 5000 UNTIL BAHRR AND CLRED FOR APCH. SHORTLY THEREAFTER, APCH CTL STATED THAT WE HAD OVERSHOT THE LOC AND DIRECTED US TO TURN L IMMEDIATELY, RE-INTERCEPT THE LOC AND DSND TO 4500 FT. MY LOC WAS STILL SHOWING OFF TO THE R WITH NO FLAGS IN VIEW. I IMMEDIATELY COMPLIED WITH THE INSTRUCTIONS AND SWITCHED THE FO RADIO TO ILS. HIS NAV INSTS SHOWED THE LOC OFF TO THE L. CONFUSED, I TRIED TO RE-IDENT MY ILS BUT COULD GET NO IDENT. WE CONTINUED THE APCH USING THE FO'S ILS. I ASSUMED MY ILS HAD FAILED BUT COULD NOT FIGURE WHY I HAD RECEIVED NO FLAGS. I ENTERED THE DISCREPANCY IN THE FLT LOG AND LATER CHKED WITH MAINT TO SEE WHAT THEY FOUND. IT SEEMS THE ILS TEST SWITCH WAS STUCK IN THE TEST POS (DOWN/R) AND COULD NOT BE UNSTUCK. APPARENTLY, ME OR MY FO HIT THE TEST BUTTON WHEN WE SELECTED THE ILS ON MY SIDE. WE HAD PREVIOUSLY TUNED AND IDENTED THE ILS BUT HAD GONE BACK TO TRACK THE VOR. WHAT I HAVE SINCE DISCOVERED IS THAT, IN THE TEST POS, NO FLAGS ARE IN VIEW ON THE HSI OR ADI. IN OTHER WORDS, IT ALL LOOKS PERFECTLY NORMAL. THE ONLY WAY WE COULD HAVE KNOWN THE SWITCH WAS STUCK WAS TO HAVE BEEN CONTINUOUSLY MONITORING THE IDENT.
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.