 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
A320 on approach to iad was issued ATC low altitude alert; alleges aircraft was on GS with no increased sink rate; questioned MSAW equipment calibration.
| Attributes | |
| ACN | 741597 |
| Time | |
| Date | 200706 |
| Local Time Of Day | 0001 To 0600 |
| Place | |
| Locale Reference | airport : iad.airport |
| State Reference | DC |
| Altitude | msl single value : 1400 |
| Environment | |
| Flight Conditions | IMC |
| Aircraft 1 | |
| Controlling Facilities | tower : iad.tower |
| Operator | common carrier : air carrier |
| Make Model Name | A320 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | ils localizer & glide slope : 19l |
| Flight Phase | descent : approach |
| Route In Use | approach : instrument precision |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 20 flight time total : 4800 flight time type : 1600 |
| ASRS Report | 741597 |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | atc equipment : msaw other controllera |
| Resolutory Action | none taken : anomaly accepted |
| Supplementary | |
| Problem Areas | FAA Aircraft ATC Human Performance |
| Primary Problem | Ambiguous |
Narrative:
Received a false 'altitude warning' from the iad tower at about 1100 ft afe during an ILS approach to runway 19L. This was a coupled ILS approach and the airplane had been on GS and at approach speed (stabilized) for several mi already. The runway and PAPI were in sight at the time of the altitude warning and all available cues (visual and instrument) indicated that we were on the proper vertical path. I advised tower that the ILS GS and PAPI both showed us on the proper path and they need to have their altitude warning equipment calibration checked. This caught the tower by surprise and they commented that high sink rates can also set it off. I informed them that we experienced no high sink rates and again asked them to have the calibration of their equipment checked. I don't recall exactly how they replied; but it failed to give me any assurance that they would have their equipment checked. The ability for ATC to provide 'altitude warnings' to airplanes on final is a valuable tool; if they are accurate. I just lost that confidence. (Imagine if we had been IMC; what to do?)
Original NASA ASRS Text
Title: A320 ON APCH TO IAD WAS ISSUED ATC LOW ALT ALERT; ALLEGES ACFT WAS ON GS WITH NO INCREASED SINK RATE; QUESTIONED MSAW EQUIP CALIBRATION.
Narrative: RECEIVED A FALSE 'ALT WARNING' FROM THE IAD TWR AT ABOUT 1100 FT AFE DURING AN ILS APCH TO RWY 19L. THIS WAS A COUPLED ILS APCH AND THE AIRPLANE HAD BEEN ON GS AND AT APCH SPD (STABILIZED) FOR SEVERAL MI ALREADY. THE RWY AND PAPI WERE IN SIGHT AT THE TIME OF THE ALT WARNING AND ALL AVAILABLE CUES (VISUAL AND INST) INDICATED THAT WE WERE ON THE PROPER VERT PATH. I ADVISED TWR THAT THE ILS GS AND PAPI BOTH SHOWED US ON THE PROPER PATH AND THEY NEED TO HAVE THEIR ALT WARNING EQUIP CALIBRATION CHKED. THIS CAUGHT THE TWR BY SURPRISE AND THEY COMMENTED THAT HIGH SINK RATES CAN ALSO SET IT OFF. I INFORMED THEM THAT WE EXPERIENCED NO HIGH SINK RATES AND AGAIN ASKED THEM TO HAVE THE CALIBRATION OF THEIR EQUIP CHKED. I DON'T RECALL EXACTLY HOW THEY REPLIED; BUT IT FAILED TO GIVE ME ANY ASSURANCE THAT THEY WOULD HAVE THEIR EQUIP CHKED. THE ABILITY FOR ATC TO PROVIDE 'ALT WARNINGS' TO AIRPLANES ON FINAL IS A VALUABLE TOOL; IF THEY ARE ACCURATE. I JUST LOST THAT CONFIDENCE. (IMAGINE IF WE HAD BEEN IMC; WHAT TO DO?)
Data retrieved from NASA's ASRS site as of January 2009 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.