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Air carrier X unauthorized descent from assigned altitude received TCASII RA from cpr Y. Possible less than standard separation.
| Attributes | |
| ACN | 247280 |
| Time | |
| Date | 199305 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : mdw |
| State Reference | IL |
| Altitude | msl bound lower : 3800 msl bound upper : 4000 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : ord |
| Operator | common carrier : air carrier |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Flight Phase | cruise other |
| Route In Use | enroute : on vectors |
| 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 : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | other personnel other |
| Qualification | controller : radar |
| ASRS Report | 247280 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| Experience | controller radar : 8 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Miss Distance | vertical : 800 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Air carrier X was on a base leg for runway 4R at midway at 4000 ft. Cpr Y was a departure on a south heading level at 3000 ft. Traffic was exchanged to air carrier X and just as the targets were about to cross, air carrier X mode C showed 3800 ft. Air carrier X then communicated to the controller 'he had his TCASII go off.' he did not say whether he was climbing or descending, so the controller asked him if he was climbing or descending. The controller also advised him that there was traffic below him at 3000 ft and also traffic above him at 5000 ft. The controller never observed air carrier X mode C go above 4000 ft. His mode C did read 3800 ft just prior to his RA so by descending below his assigned altitude he created the whole situation. Air carrier X was being vectored into an 8 mi gap and when he had the RA, he missed 3 different radio calls to turn him in. Consequently, traffic behind him had to be turned away and resequenced.
Original NASA ASRS Text
Title: ACR X UNAUTH DSCNT FROM ASSIGNED ALT RECEIVED TCASII RA FROM CPR Y. POSSIBLE LTSS.
Narrative: ACR X WAS ON A BASE LEG FOR RWY 4R AT MIDWAY AT 4000 FT. CPR Y WAS A DEP ON A S HDG LEVEL AT 3000 FT. TFC WAS EXCHANGED TO ACR X AND JUST AS THE TARGETS WERE ABOUT TO CROSS, ACR X MODE C SHOWED 3800 FT. ACR X THEN COMMUNICATED TO THE CTLR 'HE HAD HIS TCASII GO OFF.' HE DID NOT SAY WHETHER HE WAS CLBING OR DSNDING, SO THE CTLR ASKED HIM IF HE WAS CLBING OR DSNDING. THE CTLR ALSO ADVISED HIM THAT THERE WAS TFC BELOW HIM AT 3000 FT AND ALSO TFC ABOVE HIM AT 5000 FT. THE CTLR NEVER OBSERVED ACR X MODE C GO ABOVE 4000 FT. HIS MODE C DID READ 3800 FT JUST PRIOR TO HIS RA SO BY DSNDING BELOW HIS ASSIGNED ALT HE CREATED THE WHOLE SIT. ACR X WAS BEING VECTORED INTO AN 8 MI GAP AND WHEN HE HAD THE RA, HE MISSED 3 DIFFERENT RADIO CALLS TO TURN HIM IN. CONSEQUENTLY, TFC BEHIND HIM HAD TO BE TURNED AWAY AND RESEQUENCED.
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.