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Similar numbers in call sign air carrier X. Unauthorized descent to occupied altitude. TCASII RA. Had less than standard separation from air carrier Y.
| Attributes | |
| ACN | 277948 |
| Time | |
| Date | 199407 |
| Day | Fri |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : cxr |
| State Reference | OH |
| Altitude | msl bound lower : 29000 msl bound upper : 30000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zob |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller radar : 7 |
| ASRS Report | 277948 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Experience | flight time last 90 days : 210 flight time total : 6000 flight time type : 210 |
| ASRS Report | 277849 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : required legal separation non adherence : clearance |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | faa : assigned or threatened penalties faa : investigated |
| Miss Distance | horizontal : 15000 vertical : 1000 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Air carrier X level FL310 swbound. Air carrier Y level FL290 nebound. These 2 aircraft were head-on, approximately 12 mi apart. I issued a clearance to air carrier Z to maintain FL290. Z read back the clearance. I then issued WX rerouting to Z. I then observed X descending and separation was lost with air carrier Y. I issued a clearance to X to climb immediately to FL310. X complied and said I had cleared him to FL290. After listening to a tape of the incident the only readback heard is that of Z. All aircraft TCASII equipped. Supplemental information from acn 277849: while cruising at FL310 ZOB (on frequency 119.87) directed us to descend to FL290. We acknowledged and started a descent. At FL300 we observed a TCASII conflict and ATC (simultaneously) called telling us to 'climb immediately to FL310,' which we did. The other aircraft passed behind and below us. I feel that ATC did precisely what they should have in response and that TCASII worked well. I can only suggest that the ATC controller be sure we are the aircraft he wanted to descend.
Original NASA ASRS Text
Title: SIMILAR NUMBERS IN CALL SIGN ACR X. UNAUTH DSCNT TO OCCUPIED ALT. TCASII RA. HAD LTSS FROM ACR Y.
Narrative: ACR X LEVEL FL310 SWBOUND. ACR Y LEVEL FL290 NEBOUND. THESE 2 ACFT WERE HEAD-ON, APPROX 12 MI APART. I ISSUED A CLRNC TO ACR Z TO MAINTAIN FL290. Z READ BACK THE CLRNC. I THEN ISSUED WX REROUTING TO Z. I THEN OBSERVED X DSNDING AND SEPARATION WAS LOST WITH ACR Y. I ISSUED A CLRNC TO X TO CLB IMMEDIATELY TO FL310. X COMPLIED AND SAID I HAD CLRED HIM TO FL290. AFTER LISTENING TO A TAPE OF THE INCIDENT THE ONLY READBACK HEARD IS THAT OF Z. ALL ACFT TCASII EQUIPPED. SUPPLEMENTAL INFO FROM ACN 277849: WHILE CRUISING AT FL310 ZOB (ON FREQ 119.87) DIRECTED US TO DSND TO FL290. WE ACKNOWLEDGED AND STARTED A DSCNT. AT FL300 WE OBSERVED A TCASII CONFLICT AND ATC (SIMULTANEOUSLY) CALLED TELLING US TO 'CLB IMMEDIATELY TO FL310,' WHICH WE DID. THE OTHER ACFT PASSED BEHIND AND BELOW US. I FEEL THAT ATC DID PRECISELY WHAT THEY SHOULD HAVE IN RESPONSE AND THAT TCASII WORKED WELL. I CAN ONLY SUGGEST THAT THE ATC CTLR BE SURE WE ARE THE ACFT HE WANTED TO DSND.
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.