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GLF4 at FL410 experienced TCAS RA with unreported traffic; communication with ATC facility indicated similar call sign issue may have been causal factor.
| Attributes | |
| ACN | 783579 |
| Time | |
| Date | 200804 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | msl single value : 41000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzz.artcc |
| Operator | general aviation : corporate |
| Make Model Name | Gulfstream IV |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : corporate |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 90 flight time total : 11000 flight time type : 550 |
| ASRS Report | 783579 |
| Person 2 | |
| Affiliation | company : corporate |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 14000 flight time type : 600 |
| ASRS Report | 783782 |
| Events | |
| Anomaly | conflict : airborne critical |
| Independent Detector | aircraft equipment : tcas other flight crewa |
| Resolutory Action | flight crew : took evasive action |
| Consequence | faa : reviewed incident with flight crew |
| Miss Distance | vertical : 600 |
| Supplementary | |
| Problem Areas | ATC Human Performance Flight Crew Human Performance |
| Primary Problem | Ambiguous |
Narrative:
A TA appeared at our 10 O'clock position. The aircraft was in a climb 1200 ft below and 15-20 NM laterally. We looked visually for the aircraft. The PNF made visual contact. Approximately 5 seconds after the TA; we received a 'climb' RA. The PNF stated 'he's headed right at you.' I disconnected the autoplt and autothrottles; instructed the PNF to inform ATC of the RA and followed the TCAS climb command. When the RA was issued the other aircraft was approximately 10 NM and 600 ft below our aircraft. Upon climbing through FL417; we received a 'clear of conflict' command from the TCAS. I leveled the aircraft at FL420 until instructed by ATC to return to FL410. Initially; ATC was unaware of conflict. Upon further investigation ATC discovered there were 2 aircraft with similar call signs on the frequency; and that 1 of the 2 aircraft was no longer on frequency. A conference call was made to the supervisor of the ATC facility that evening. We were informed that 1 of the 2 aircraft with similar call signs ended up on the next center frequency. This frequency change was in error and the aircraft received a climb clearance from the new controller. This frequency change error was the cause of the TA/RA. At the time this report is being filed; I do not know if the wrong aircraft was given a frequency change; or if wrong aircraft took a frequency change for the other similar tail number. Diligence and discipline must be maintained on the part of pilots and ATC when there are aircraft with similar call signs on the same frequency. This diligence and discipline includes the ATC facility receiving the aircraft via handoff from the bordering sector. Aircraft need to be informed by ATC of the similar call signs being on the same frequency; and the full call signs should be used at all times by the controllers and pilots. The controling ATC sector that is handing off the 2 aircraft with similar call signs; should inform the next sector about similar call signs when xferring aircraft to the next sector.
Original NASA ASRS Text
Title: GLF4 AT FL410 EXPERIENCED TCAS RA WITH UNREPORTED TFC; COM WITH ATC FACILITY INDICATED SIMILAR CALL SIGN ISSUE MAY HAVE BEEN CAUSAL FACTOR.
Narrative: A TA APPEARED AT OUR 10 O'CLOCK POS. THE ACFT WAS IN A CLB 1200 FT BELOW AND 15-20 NM LATERALLY. WE LOOKED VISUALLY FOR THE ACFT. THE PNF MADE VISUAL CONTACT. APPROX 5 SECONDS AFTER THE TA; WE RECEIVED A 'CLB' RA. THE PNF STATED 'HE'S HEADED RIGHT AT YOU.' I DISCONNECTED THE AUTOPLT AND AUTOTHROTTLES; INSTRUCTED THE PNF TO INFORM ATC OF THE RA AND FOLLOWED THE TCAS CLB COMMAND. WHEN THE RA WAS ISSUED THE OTHER ACFT WAS APPROX 10 NM AND 600 FT BELOW OUR ACFT. UPON CLBING THROUGH FL417; WE RECEIVED A 'CLR OF CONFLICT' COMMAND FROM THE TCAS. I LEVELED THE ACFT AT FL420 UNTIL INSTRUCTED BY ATC TO RETURN TO FL410. INITIALLY; ATC WAS UNAWARE OF CONFLICT. UPON FURTHER INVESTIGATION ATC DISCOVERED THERE WERE 2 ACFT WITH SIMILAR CALL SIGNS ON THE FREQ; AND THAT 1 OF THE 2 ACFT WAS NO LONGER ON FREQ. A CONFERENCE CALL WAS MADE TO THE SUPVR OF THE ATC FACILITY THAT EVENING. WE WERE INFORMED THAT 1 OF THE 2 ACFT WITH SIMILAR CALL SIGNS ENDED UP ON THE NEXT CTR FREQ. THIS FREQ CHANGE WAS IN ERROR AND THE ACFT RECEIVED A CLB CLRNC FROM THE NEW CTLR. THIS FREQ CHANGE ERROR WAS THE CAUSE OF THE TA/RA. AT THE TIME THIS RPT IS BEING FILED; I DO NOT KNOW IF THE WRONG ACFT WAS GIVEN A FREQ CHANGE; OR IF WRONG ACFT TOOK A FREQ CHANGE FOR THE OTHER SIMILAR TAIL NUMBER. DILIGENCE AND DISCIPLINE MUST BE MAINTAINED ON THE PART OF PLTS AND ATC WHEN THERE ARE ACFT WITH SIMILAR CALL SIGNS ON THE SAME FREQ. THIS DILIGENCE AND DISCIPLINE INCLUDES THE ATC FACILITY RECEIVING THE ACFT VIA HDOF FROM THE BORDERING SECTOR. ACFT NEED TO BE INFORMED BY ATC OF THE SIMILAR CALL SIGNS BEING ON THE SAME FREQ; AND THE FULL CALL SIGNS SHOULD BE USED AT ALL TIMES BY THE CTLRS AND PLTS. THE CTLING ATC SECTOR THAT IS HANDING OFF THE 2 ACFT WITH SIMILAR CALL SIGNS; SHOULD INFORM THE NEXT SECTOR ABOUT SIMILAR CALL SIGNS WHEN XFERRING ACFT TO THE NEXT SECTOR.
Data retrieved from NASA's ASRS site as of May 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.