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A commuter flight crew read back a clearance for pilot's discretion to a lower altitude, but the clearance was for another aircraft. When the descent was begun, the ARTCC radar controller intervened. Altitude deviation altitude excursion.
| Attributes | |
| ACN | 327020 |
| Time | |
| Date | 199601 |
| Day | Sat |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : fca |
| State Reference | MT |
| Altitude | msl bound lower : 13700 msl bound upper : 17000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Night |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 135 |
| Flight Phase | descent other |
| Route In Use | enroute airway : zlc |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 9400 flight time type : 1400 |
| ASRS Report | 327020 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 7000 flight time type : 4500 |
| ASRS Report | 326838 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were checking the ASOS at our destination, fca, and received a clearance from ZSE to 'descend at pilot's discretion to 9000 ft.' after checking the ASOS, I called out of 17000 ft. We were then instructed to contact ZLC. On initial contact I reported at 14000 ft descending 9000 ft. Salt lake said 'where did you get the 9000 ft?' I replied, 'from ZSE.' we immediately leveled off and there was a pause where apparently salt lake was checking with seattle. Salt lake came back and said that the clearance was for another aircraft. We questioned this due to the fact we had read it back, and asked if there was a problem, and salt lake said 'no there is not a problem, you are over lower terrain now, descend and maintain 9000 ft.' the minimum obstruction clearance altitude on the airway is 9600 ft, and we never went below 13400 ft before being reclred by salt lake. Apparently there were no conflicts. After reviewing this event in the cockpit, we still believe we were cleared to 9000 ft by ZSE. At this point on the airway, it is routine to receive a lower clearance, unless there is a conflict with lower traffic. There was no traffic conflict. We would have to hear the tape to be convinced that we responded to someone's clearance. It is common for controllers to work multiple sectors however, and not being able to hear aircraft in those other sectors definitely sets up a situation ripe for confusion. Supplemental information from acn 326838: the first officer acknowledged the call, repeated it completely with our call sign.
Original NASA ASRS Text
Title: A COMMUTER FLC READ BACK A CLRNC FOR PLT'S DISCRETION TO A LOWER ALT, BUT THE CLRNC WAS FOR ANOTHER ACFT. WHEN THE DSCNT WAS BEGUN, THE ARTCC RADAR CTLR INTERVENED. ALTDEV ALT EXCURSION.
Narrative: WE WERE CHKING THE ASOS AT OUR DEST, FCA, AND RECEIVED A CLRNC FROM ZSE TO 'DSND AT PLT'S DISCRETION TO 9000 FT.' AFTER CHKING THE ASOS, I CALLED OUT OF 17000 FT. WE WERE THEN INSTRUCTED TO CONTACT ZLC. ON INITIAL CONTACT I RPTED AT 14000 FT DSNDING 9000 FT. SALT LAKE SAID 'WHERE DID YOU GET THE 9000 FT?' I REPLIED, 'FROM ZSE.' WE IMMEDIATELY LEVELED OFF AND THERE WAS A PAUSE WHERE APPARENTLY SALT LAKE WAS CHKING WITH SEATTLE. SALT LAKE CAME BACK AND SAID THAT THE CLRNC WAS FOR ANOTHER ACFT. WE QUESTIONED THIS DUE TO THE FACT WE HAD READ IT BACK, AND ASKED IF THERE WAS A PROB, AND SALT LAKE SAID 'NO THERE IS NOT A PROB, YOU ARE OVER LOWER TERRAIN NOW, DSND AND MAINTAIN 9000 FT.' THE MINIMUM OBSTRUCTION CLRNC ALT ON THE AIRWAY IS 9600 FT, AND WE NEVER WENT BELOW 13400 FT BEFORE BEING RECLRED BY SALT LAKE. APPARENTLY THERE WERE NO CONFLICTS. AFTER REVIEWING THIS EVENT IN THE COCKPIT, WE STILL BELIEVE WE WERE CLRED TO 9000 FT BY ZSE. AT THIS POINT ON THE AIRWAY, IT IS ROUTINE TO RECEIVE A LOWER CLRNC, UNLESS THERE IS A CONFLICT WITH LOWER TFC. THERE WAS NO TFC CONFLICT. WE WOULD HAVE TO HEAR THE TAPE TO BE CONVINCED THAT WE RESPONDED TO SOMEONE'S CLRNC. IT IS COMMON FOR CTLRS TO WORK MULTIPLE SECTORS HOWEVER, AND NOT BEING ABLE TO HEAR ACFT IN THOSE OTHER SECTORS DEFINITELY SETS UP A SIT RIPE FOR CONFUSION. SUPPLEMENTAL INFO FROM ACN 326838: THE FO ACKNOWLEDGED THE CALL, REPEATED IT COMPLETELY WITH OUR CALL SIGN.
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.