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Flight crew of a lear jet 35 descended in response to a similar sounding call sign. The other aircraft was also a learjet with a similar call sound.
| Attributes | |
| ACN | 432580 |
| Time | |
| Date | 199903 |
| Day | Wed |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | navaid : bzn.vortac |
| State Reference | MT |
| Altitude | msl bound lower : 35000 msl bound upper : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zlc.artcc |
| Operator | common carrier : air taxi |
| Make Model Name | Learjet 35 |
| Operating Under FAR Part | Part 135 |
| Navigation In Use | other vortac |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zlc.artcc |
| Operator | common carrier : air taxi |
| Make Model Name | Gates Learjet Corp Undifferentiated or Other Model |
| Operating Under FAR Part | Part 135 |
| Flight Phase | cruise : enroute altitude change |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air taxi |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument pilot : multi engine |
| Experience | flight time last 90 days : 150 flight time total : 1500 flight time type : 800 |
| ASRS Report | 432580 |
| Person 2 | |
| Affiliation | company : air taxi |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 10000 |
| ASRS Report | 432562 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued alert controller : issued new clearance |
| Supplementary | |
| Problem Areas | ATC Human Performance Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Approximately 100 NM from bzn VOR. ZLC cleared atx X to 12000 ft pilot's discretion. I read back the clearance followed by complete call sign. At approximately XX10, we were at FL350 and center replied, 'atx X it looks like you have begun your descent. I did not clear you to descend. Descend now and maintain 15000 ft.' I read back his clearance followed by full call sign and the advised the controller that our last clearance received was to descend at pilot's discretion to 12000 ft. The controller replied, 'you must have read back someone else's clearance and I did not catch it.' I apologized and we were handed off to a new controller. There was another lear on same frequency being called lifeguard atx Y. This may have been the cause of the problem. The controller should have cautioned both aircraft of similar tail numbers on frequency, as do most other controllers. That way full call signs could have been used.
Original NASA ASRS Text
Title: FLC OF A LEAR JET 35 DSNDED IN RESPONSE TO A SIMILAR SOUNDING CALL SIGN. THE OTHER ACFT WAS ALSO A LEARJET WITH A SIMILAR CALL SOUND.
Narrative: APPROX 100 NM FROM BZN VOR. ZLC CLRED ATX X TO 12000 FT PLT'S DISCRETION. I READ BACK THE CLRNC FOLLOWED BY COMPLETE CALL SIGN. AT APPROX XX10, WE WERE AT FL350 AND CTR REPLIED, 'ATX X IT LOOKS LIKE YOU HAVE BEGUN YOUR DSCNT. I DID NOT CLR YOU TO DSND. DSND NOW AND MAINTAIN 15000 FT.' I READ BACK HIS CLRNC FOLLOWED BY FULL CALL SIGN AND THE ADVISED THE CTLR THAT OUR LAST CLRNC RECEIVED WAS TO DSND AT PLT'S DISCRETION TO 12000 FT. THE CTLR REPLIED, 'YOU MUST HAVE READ BACK SOMEONE ELSE'S CLRNC AND I DID NOT CATCH IT.' I APOLOGIZED AND WE WERE HANDED OFF TO A NEW CTLR. THERE WAS ANOTHER LEAR ON SAME FREQ BEING CALLED LIFEGUARD ATX Y. THIS MAY HAVE BEEN THE CAUSE OF THE PROB. THE CTLR SHOULD HAVE CAUTIONED BOTH ACFT OF SIMILAR TAIL NUMBERS ON FREQ, AS DO MOST OTHER CTLRS. THAT WAY FULL CALL SIGNS COULD HAVE BEEN USED.
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.