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A first officer reports the B737-900 has an altitude alert warning audio set too high and interferes with ATC communications.
| Attributes | |
| ACN | 543414 |
| Time | |
| Date | 200204 |
| Day | Fri |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : atp technician : powerplant technician : airframe |
| Experience | fss specialist : 543414 flight time last 90 days : 250 flight time total : 16000 flight time type : 1000 |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | aircraft equipment : altitude alert other flight crewa |
| Resolutory Action | none taken : unable |
| Consequence | other Other |
| Supplementary | |
| Problem Areas | Environmental Factor Flight Crew Human Performance Aircraft |
| Primary Problem | Aircraft |
Narrative:
This report doesn't address a particular flight, rather it addresses a hazardous situation. We have various models of the B737. The B737-900 altitude alerter system incorporates an aural warning that is heard through the pilot's headset as well as through the aircraft's speakers. The volume is loud enough to blank out ATC communications when it is activated by approaching leveloff. I consider this hazardous to safety, and it adds to frequency congestion when missed ATC instructions must be repeated. It is also a distraction during approach to landing, because the radio altimeter voice says 100 ft, 50 ft, 30 ft, 20 ft, 10 ft during the most critical phase of flight. If instructed by ATC to go around, I doubt seriously that we would hear it due to volume level. I strongly recommend that boeing redesign this system to coincide with older models of B737's that only broadcast the altitude alerter signal through the speaker system.
Original NASA ASRS Text
Title: A FO RPTS THE B737-900 HAS AN ALT ALERT WARNING AUDIO SET TOO HIGH AND INTERFERES WITH ATC COMS.
Narrative: THIS RPT DOESN'T ADDRESS A PARTICULAR FLT, RATHER IT ADDRESSES A HAZARDOUS SIT. WE HAVE VARIOUS MODELS OF THE B737. THE B737-900 ALT ALERTER SYS INCORPORATES AN AURAL WARNING THAT IS HEARD THROUGH THE PLT'S HEADSET AS WELL AS THROUGH THE ACFT'S SPEAKERS. THE VOLUME IS LOUD ENOUGH TO BLANK OUT ATC COMS WHEN IT IS ACTIVATED BY APCHING LEVELOFF. I CONSIDER THIS HAZARDOUS TO SAFETY, AND IT ADDS TO FREQ CONGESTION WHEN MISSED ATC INSTRUCTIONS MUST BE REPEATED. IT IS ALSO A DISTR DURING APCH TO LNDG, BECAUSE THE RADIO ALTIMETER VOICE SAYS 100 FT, 50 FT, 30 FT, 20 FT, 10 FT DURING THE MOST CRITICAL PHASE OF FLT. IF INSTRUCTED BY ATC TO GO AROUND, I DOUBT SERIOUSLY THAT WE WOULD HEAR IT DUE TO VOLUME LEVEL. I STRONGLY RECOMMEND THAT BOEING REDESIGN THIS SYS TO COINCIDE WITH OLDER MODELS OF B737'S THAT ONLY BROADCAST THE ALT ALERTER SIGNAL THROUGH THE SPEAKER SYS.
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.