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Air carrier X descent through occupied altitude may have had less than standard separation from air carrier Y. Possible system error.
| Attributes | |
| ACN | 312110 |
| Time | |
| Date | 199507 |
| Day | Mon |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : air |
| State Reference | PA |
| Altitude | msl bound lower : 20600 msl bound upper : 21000 |
| Environment | |
| Flight Conditions | Marginal |
| Light | Dawn |
| Aircraft 1 | |
| Controlling Facilities | artcc : zob |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 120 flight time total : 17000 flight time type : 930 |
| ASRS Report | 312110 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : published procedure non adherence : required legal separation |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | Other |
| Miss Distance | horizontal : 30000 vertical : 500 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
Narrative:
About 80 mi west of belair (air) VOR, center suggested we should plan on crossing 30 west of air at 19000 ft. So, that was no problem. We were given a couple of step-down clrncs. And finally about 50 mi west of air, we were given 19000 ft. Somewhere in there we were cleared direct to weske, which was a small left turn. After that turn, center gave us another 10 degree left, which we did. Then, as we went through 20900 ft and descending at approximately 2500 FPM, he asked us to stop our descent at FL210, which I told him we had passed through. We stopped the descent at approximately 20500 ft, and climbed back up to FL210. We got no TCASII TA or RA, but it looked closer on the TCASII screen. Apparently, air carrier Y coming wbound was further north than the controller expected. We never saw it and probably had no conflict.
Original NASA ASRS Text
Title: ACR X DSCNT THROUGH OCCUPIED ALT MAY HAVE HAD LTSS FROM ACR Y. POSSIBLE SYS ERROR.
Narrative: ABOUT 80 MI W OF BELAIR (AIR) VOR, CTR SUGGESTED WE SHOULD PLAN ON XING 30 W OF AIR AT 19000 FT. SO, THAT WAS NO PROB. WE WERE GIVEN A COUPLE OF STEP-DOWN CLRNCS. AND FINALLY ABOUT 50 MI W OF AIR, WE WERE GIVEN 19000 FT. SOMEWHERE IN THERE WE WERE CLRED DIRECT TO WESKE, WHICH WAS A SMALL L TURN. AFTER THAT TURN, CTR GAVE US ANOTHER 10 DEG L, WHICH WE DID. THEN, AS WE WENT THROUGH 20900 FT AND DSNDING AT APPROX 2500 FPM, HE ASKED US TO STOP OUR DSCNT AT FL210, WHICH I TOLD HIM WE HAD PASSED THROUGH. WE STOPPED THE DSCNT AT APPROX 20500 FT, AND CLBED BACK UP TO FL210. WE GOT NO TCASII TA OR RA, BUT IT LOOKED CLOSER ON THE TCASII SCREEN. APPARENTLY, ACR Y COMING WBOUND WAS FURTHER N THAN THE CTLR EXPECTED. WE NEVER SAW IT AND PROBABLY HAD NO CONFLICT.
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.