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Air carrier in level flight receives TCASII alert and descends without ATC authority/authorized. TCASII traffic was level flight above.
| Attributes | |
| ACN | 200629 |
| Time | |
| Date | 199202 |
| Day | Mon |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : yqo |
| State Reference | ON |
| Altitude | msl bound lower : 27000 msl bound upper : 28000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zob |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : corporate |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : developmental |
| Experience | controller radar : 5 |
| ASRS Report | 200629 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa |
| Resolutory Action | none taken : detected after the fact |
| Consequence | Other |
| Miss Distance | horizontal : 9000 vertical : 600 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Air carrier X indicated TCASII alert set off by aircraft immediately behind him with mode C indicating 400 ft below assigned altitude. ATC assigned altitude: air carrier X, FL280. Cga Y, FL290. Cga Y reported level at FL290. Air carrier X descended to FL270 without ATC clearance.
Original NASA ASRS Text
Title: ACR IN LEVEL FLT RECEIVES TCASII ALERT AND DSNDS WITHOUT ATC AUTH. TCASII TFC WAS LEVEL FLT ABOVE.
Narrative: ACR X INDICATED TCASII ALERT SET OFF BY ACFT IMMEDIATELY BEHIND HIM WITH MODE C INDICATING 400 FT BELOW ASSIGNED ALT. ATC ASSIGNED ALT: ACR X, FL280. CGA Y, FL290. CGA Y RPTED LEVEL AT FL290. ACR X DSNDED TO FL270 WITHOUT ATC CLRNC.
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.