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B737 accepts B757 clearance and descends into conflict with other aircraft. ATC misses incorrect readback.
| Attributes | |
| ACN | 470784 |
| Time | |
| Date | 200004 |
| Day | Tue |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : tay.vortac |
| State Reference | FL |
| Altitude | msl bound lower : 33600 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zjx.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other |
| Flight Phase | cruise : enroute altitude change |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zjx.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 180 flight time total : 13000 flight time type : 2700 |
| ASRS Report | 470784 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : multi engine pilot : atp pilot : cfi pilot : commercial pilot : instrument |
| Experience | flight time last 90 days : 100 flight time total : 13000 flight time type : 7500 |
| ASRS Report | 470397 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : published procedure |
| Independent Detector | other controllera other flight crewa other flight crewb |
| Resolutory Action | controller : issued new clearance controller : issued advisory flight crew : returned to assigned altitude |
| Miss Distance | horizontal : 29400 vertical : 700 |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Flight in cruise at FL370. ATC advised 'for traffic, descend and maintain FL310.' descending through FL337, ATC (ZJX) asked 'what is your altitude?' replied with 'descending through FL337 for FL310 assigned.' ATC claimed our flight was 'cleared to FL350 even though I may have replied FL310.' aircraft bottomed out at FL336 before climbing back up to FL350. Another aircraft was level at FL330, 3-5 NM horizontal and 500-700 ft vertical closest point of conversion. Supplemental information from acn 470397: the captain informed the controller that he had initially cleared us to FL310 and that he, the captain, had read back 'FL310.' the controller then responded with something to the effect of 'you might have read back FL310, but I cleared you to FL350.' meanwhile, a B757 passed off our right at FL330 at the 5 NM ring on the TCASII scope. 6 mins later, there was obviously a controller change. The new controller started off very confused and issued clrncs to the B757 which were, ultimately, meant for us. A subsequent check with ZJX revealed that the problem 'was with the controller.'
Original NASA ASRS Text
Title: B737 ACCEPTS B757 CLRNC AND DSNDS INTO CONFLICT WITH OTHER ACFT. ATC MISSES INCORRECT READBACK.
Narrative: FLT IN CRUISE AT FL370. ATC ADVISED 'FOR TFC, DSND AND MAINTAIN FL310.' DSNDING THROUGH FL337, ATC (ZJX) ASKED 'WHAT IS YOUR ALT?' REPLIED WITH 'DSNDING THROUGH FL337 FOR FL310 ASSIGNED.' ATC CLAIMED OUR FLT WAS 'CLRED TO FL350 EVEN THOUGH I MAY HAVE REPLIED FL310.' ACFT BOTTOMED OUT AT FL336 BEFORE CLBING BACK UP TO FL350. ANOTHER ACFT WAS LEVEL AT FL330, 3-5 NM HORIZ AND 500-700 FT VERT CLOSEST POINT OF CONVERSION. SUPPLEMENTAL INFO FROM ACN 470397: THE CAPT INFORMED THE CTLR THAT HE HAD INITIALLY CLRED US TO FL310 AND THAT HE, THE CAPT, HAD READ BACK 'FL310.' THE CTLR THEN RESPONDED WITH SOMETHING TO THE EFFECT OF 'YOU MIGHT HAVE READ BACK FL310, BUT I CLRED YOU TO FL350.' MEANWHILE, A B757 PASSED OFF OUR R AT FL330 AT THE 5 NM RING ON THE TCASII SCOPE. 6 MINS LATER, THERE WAS OBVIOUSLY A CTLR CHANGE. THE NEW CTLR STARTED OFF VERY CONFUSED AND ISSUED CLRNCS TO THE B757 WHICH WERE, ULTIMATELY, MEANT FOR US. A SUBSEQUENT CHK WITH ZJX REVEALED THAT THE PROB 'WAS WITH THE CTLR.'
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.