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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Air carrier widebody transport erroneously issued a descent to occupied altitude, then corrected before commencing descent.
| Attributes | |
| ACN | 107900 |
| Time | |
| Date | 198904 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : cju |
| State Reference | FO |
| Altitude | msl bound lower : 35000 msl bound upper : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Widebody, Low Wing, 4 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute : other oceanic enroute airway : rktt enroute other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Widebody, Low Wing, 4 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute : other oceanic enroute other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 11000 flight time type : 2500 |
| ASRS Report | 107900 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 170 flight time total : 14200 flight time type : 3000 |
| ASRS Report | 108224 |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | controller : issued new clearance |
| Consequence | Other |
| Miss Distance | horizontal : 0 vertical : 2000 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
Narrative:
Departed manila IFR, destination seoul. Flight proceeded normally until approaching cju VOR northbound on B576 at FL370. Flight was clear of all clouds (on top) with good daylight visibility. At this time we were in contact with taegu control on 133.7. Taegu called our flight at approximately XX30 uct with a clearance to descend to FL350. The clearance was confirmed 3 times. During a break in the confirmation process between taego and our flight, we could hear an air carrier Y flight calling, but the transmission was of such poor quality we could not understand what was being said. After the third confirmation, the pms was programmed for the descent. Prior to the aircraft actually beginning the descent, air carrier X called and advised they were at FL310 proceeding southbound on B576. Air carrier X also indicated air carrier Y was directly above them at FL350. Our pms was immediately reprogrammed to maintain FL370. The aircraft remained at FL370. Shortly after the call from XXXX, taegu control called and cleared our flight to maintain FL370. Later we passed directly over air carrier Y. If we had both been at FL350 as assigned by taegu and had been in the clouds unable to see and avoid the other flight, we would surely have had a head on collision.
Original NASA ASRS Text
Title: ACR WDB ERRONEOUSLY ISSUED A DESCENT TO OCCUPIED ALT, THEN CORRECTED BEFORE COMMENCING DESCENT.
Narrative: DEPARTED MANILA IFR, DEST SEOUL. FLT PROCEEDED NORMALLY UNTIL APCHING CJU VOR NBOUND ON B576 AT FL370. FLT WAS CLR OF ALL CLOUDS (ON TOP) WITH GOOD DAYLIGHT VISIBILITY. AT THIS TIME WE WERE IN CONTACT WITH TAEGU CTL ON 133.7. TAEGU CALLED OUR FLT AT APPROX XX30 UCT WITH A CLRNC TO DSND TO FL350. THE CLRNC WAS CONFIRMED 3 TIMES. DURING A BREAK IN THE CONFIRMATION PROCESS BTWN TAEGO AND OUR FLT, WE COULD HEAR AN ACR Y FLT CALLING, BUT THE XMISSION WAS OF SUCH POOR QUALITY WE COULD NOT UNDERSTAND WHAT WAS BEING SAID. AFTER THE THIRD CONFIRMATION, THE PMS WAS PROGRAMMED FOR THE DSCNT. PRIOR TO THE ACFT ACTUALLY BEGINNING THE DSCNT, ACR X CALLED AND ADVISED THEY WERE AT FL310 PROCEEDING SBND ON B576. ACR X ALSO INDICATED ACR Y WAS DIRECTLY ABOVE THEM AT FL350. OUR PMS WAS IMMEDIATELY REPROGRAMMED TO MAINTAIN FL370. THE ACFT REMAINED AT FL370. SHORTLY AFTER THE CALL FROM XXXX, TAEGU CTL CALLED AND CLRED OUR FLT TO MAINTAIN FL370. LATER WE PASSED DIRECTLY OVER ACR Y. IF WE HAD BOTH BEEN AT FL350 AS ASSIGNED BY TAEGU AND HAD BEEN IN THE CLOUDS UNABLE TO SEE AND AVOID THE OTHER FLT, WE WOULD SURELY HAVE HAD A HEAD ON COLLISION.
Data retrieved from NASA's ASRS site as of August 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.