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B737 flight crew with ZID experienced TCAS TA when given descent clearance; through occupied altitude; from FL360 to FL250.
| Attributes | |
| ACN | 687115 |
| Time | |
| Date | 200602 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : iiu.vortac |
| State Reference | KY |
| Altitude | msl bound lower : 34400 msl bound upper : 35000 |
| Aircraft 1 | |
| Controlling Facilities | artcc : zid.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : enroute altitude change cruise : level |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zid.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 175 flight time total : 10300 flight time type : 3250 |
| ASRS Report | 687115 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Experience | flight time last 90 days : 160 flight time total : 20000 flight time type : 7300 |
| ASRS Report | 687115 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | aircraft equipment : tcas other flight crewa other flight crewb |
| Resolutory Action | controller : issued new clearance flight crew : took precautionary avoidance action |
| Consequence | faa : investigated |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Flying at cruise at FL360; ZID requested us to descend to FL250. In accordance with SOP; I set FL250 in the MCP altitude setting; confirmed it with the captain; and read back the clearance to ATC. As we began our descent through FL345 we got a TCAS 'traffic' warning at FL340. We leveled off at FL344 and began a return to FL350. At this same time ZID requested our current altitude. I read back FL345 and said that we had a TCAS warning. ZID requested that we return to FL350 and we accomplished a climb back to the requested altitude. The captain and I had the air carrier Y traffic in sight during the entire incident. I confirmed that we were initially cleared to FL250 and we got no response from ZID. We leveled at FL350 and given a frequency change to another ZID center frequency.
Original NASA ASRS Text
Title: B737 FLT CREW WITH ZID EXPERIENCED TCAS TA WHEN GIVEN DSCNT CLRNC; THROUGH OCCUPIED ALT; FROM FL360 TO FL250.
Narrative: FLYING AT CRUISE AT FL360; ZID REQUESTED US TO DSND TO FL250. IN ACCORDANCE WITH SOP; I SET FL250 IN THE MCP ALT SETTING; CONFIRMED IT WITH THE CAPT; AND READ BACK THE CLRNC TO ATC. AS WE BEGAN OUR DSCNT THROUGH FL345 WE GOT A TCAS 'TFC' WARNING AT FL340. WE LEVELED OFF AT FL344 AND BEGAN A RETURN TO FL350. AT THIS SAME TIME ZID REQUESTED OUR CURRENT ALT. I READ BACK FL345 AND SAID THAT WE HAD A TCAS WARNING. ZID REQUESTED THAT WE RETURN TO FL350 AND WE ACCOMPLISHED A CLB BACK TO THE REQUESTED ALT. THE CAPT AND I HAD THE ACR Y TFC IN SIGHT DURING THE ENTIRE INCIDENT. I CONFIRMED THAT WE WERE INITIALLY CLRED TO FL250 AND WE GOT NO RESPONSE FROM ZID. WE LEVELED AT FL350 AND GIVEN A FREQ CHANGE TO ANOTHER ZID CTR FREQ.
Data retrieved from NASA's ASRS site as of January 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.