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Descending air carrier causes TCASII RA event causing another air carrier to descend towards a third air carrier, resulting in a conflict alert at ZBW.
| Attributes | |
| ACN | 536756 |
| Time | |
| Date | 200201 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : bos.airport |
| State Reference | MA |
| Altitude | agl single value : 0 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zbw.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | Challenger CL601 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zbw.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Experience | controller radar : 11 |
| ASRS Report | 536756 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude |
| Independent Detector | atc equipment : conflict alert aircraft equipment : tcas |
| Resolutory Action | flight crew : took evasive action |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 15000 vertical : 300 |
| Supplementary | |
| Problem Areas | ATC Human Performance Airspace Structure Environmental Factor |
| Primary Problem | Environmental Factor |
Narrative:
Air carrier X level FL240, flying swbound. Air carrier Y level FL250, flying sbound. Air carrier Z descending to FL260. Air carrier Y reported 'TCASII descent.' air carrier Y descended to FL243, causing loss of separation with air carrier X.
Original NASA ASRS Text
Title: DSNDING ACR CAUSES TCASII RA EVENT CAUSING ANOTHER ACR TO DSND TOWARDS A THIRD ACR, RESULTING IN A CONFLICT ALERT AT ZBW.
Narrative: ACR X LEVEL FL240, FLYING SWBOUND. ACR Y LEVEL FL250, FLYING SBOUND. ACR Z DSNDING TO FL260. ACR Y RPTED 'TCASII DSCNT.' ACR Y DSNDED TO FL243, CAUSING LOSS OF SEPARATION WITH ACR X.
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.