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Possible operational error in clearance for descent through occupied altitude. Potential conflict less than standard separation.
| Attributes | |
| ACN | 234699 |
| Time | |
| Date | 199302 |
| Day | Sat |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : gnv |
| State Reference | FL |
| Altitude | msl bound lower : 37000 msl bound upper : 37900 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zjx tower : mia |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 5800 flight time type : 3000 |
| ASRS Report | 234699 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 30000 flight time type : 3500 |
| ASRS Report | 235067 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation other anomaly other |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | controller : issued new clearance |
| Consequence | Other |
| Miss Distance | horizontal : 0 vertical : 900 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
| Situations | |
| ATC Facility | procedure or policy : unspecified |
Narrative:
We were descending from FL390 to FL370. We had requested descent in order to meet expected altitude restrictions on the dades 1 arrival into tampa international. Rather than initiate an idle descent, I elected to use the cruise descent capability of the FMC. At about 38000 ft MSL I saw an aircraft, air carrier about the size of an large transport, directly ahead and slightly below flashing his landing light. Shortly after that we passed directly over him at less than 1000 ft. TCASII was on but we received no RA or even a TA. Only after the fact did we receive avoidance vectors and altitude amendment. There was no indication that anything was wrong until after the fact. If I had started an idle descent instead of a cruise descent we would have collided. ATC indicated that it was their problem and they were investigating the procedure. I was very disturbed by the fact that we got no reaction of any kind from the TCASII unit on our aircraft. Self test indicated that it was working properly. The other aircraft was level at FL370, our cleared to altitude. Supplemental information from acn 235067: we were given an immediate 90 degree right turn, which again I think put us in conflict with another aircraft. We should have been climbed back to FL390, but we were kept at FL380. Very poor.
Original NASA ASRS Text
Title: POSSIBLE OPERROR IN CLRNC FOR DSCNT THROUGH OCCUPIED ALT. POTENTIAL CONFLICT LTSS.
Narrative: WE WERE DSNDING FROM FL390 TO FL370. WE HAD REQUESTED DSCNT IN ORDER TO MEET EXPECTED ALT RESTRICTIONS ON THE DADES 1 ARR INTO TAMPA INTL. RATHER THAN INITIATE AN IDLE DSCNT, I ELECTED TO USE THE CRUISE DSCNT CAPABILITY OF THE FMC. AT ABOUT 38000 FT MSL I SAW AN ACFT, ACR ABOUT THE SIZE OF AN LGT, DIRECTLY AHEAD AND SLIGHTLY BELOW FLASHING HIS LNDG LIGHT. SHORTLY AFTER THAT WE PASSED DIRECTLY OVER HIM AT LESS THAN 1000 FT. TCASII WAS ON BUT WE RECEIVED NO RA OR EVEN A TA. ONLY AFTER THE FACT DID WE RECEIVE AVOIDANCE VECTORS AND ALT AMENDMENT. THERE WAS NO INDICATION THAT ANYTHING WAS WRONG UNTIL AFTER THE FACT. IF I HAD STARTED AN IDLE DSCNT INSTEAD OF A CRUISE DSCNT WE WOULD HAVE COLLIDED. ATC INDICATED THAT IT WAS THEIR PROB AND THEY WERE INVESTIGATING THE PROC. I WAS VERY DISTURBED BY THE FACT THAT WE GOT NO REACTION OF ANY KIND FROM THE TCASII UNIT ON OUR ACFT. SELF TEST INDICATED THAT IT WAS WORKING PROPERLY. THE OTHER ACFT WAS LEVEL AT FL370, OUR CLRED TO ALT. SUPPLEMENTAL INFO FROM ACN 235067: WE WERE GIVEN AN IMMEDIATE 90 DEG R TURN, WHICH AGAIN I THINK PUT US IN CONFLICT WITH ANOTHER ACFT. WE SHOULD HAVE BEEN CLBED BACK TO FL390, BUT WE WERE KEPT AT FL380. VERY POOR.
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.