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Air carrier X possible descent to wrong altitude had less than standard separation from aircraft Y. Possible system error.
| Attributes | |
| ACN | 294383 |
| Time | |
| Date | 199501 |
| Day | Fri |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : atl |
| State Reference | GA |
| Altitude | msl bound lower : 24000 msl bound upper : 24000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : ztl |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | other : unknown |
| Flight Phase | descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : commercial |
| Experience | flight time last 90 days : 210 flight time total : 20000 flight time type : 7000 |
| ASRS Report | 294383 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation non adherence : published procedure |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 18000 vertical : 100 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Air carrier X cleared to descend to FL240. Approaching FL245 center called and said maintain FL250. The captain replied that we were descending to FL240 and did they want us to climb back to FL250. Center replied affirmative. Autoplt was disconnected and a positive transition from descent to a climb was initiated at FL244. Aircraft began climbing approximately FL241. As aircraft began climbing a TCASII display aircraft Y was noted at our 6 O'clock position, descending out of FL240 about 3 mi astern. Although other TCASII replies were observed and noted, none was observed in our immediate vicinity until climb was underway as stated earlier. At no time did the TCASII system issue a TA or RA. Aircraft continued to destination without further incident.
Original NASA ASRS Text
Title: ACR X POSSIBLE DSCNT TO WRONG ALT HAD LTSS FROM ACFT Y. POSSIBLE SYS ERROR.
Narrative: ACR X CLRED TO DSND TO FL240. APCHING FL245 CTR CALLED AND SAID MAINTAIN FL250. THE CAPT REPLIED THAT WE WERE DSNDING TO FL240 AND DID THEY WANT US TO CLB BACK TO FL250. CTR REPLIED AFFIRMATIVE. AUTOPLT WAS DISCONNECTED AND A POSITIVE TRANSITION FROM DSCNT TO A CLB WAS INITIATED AT FL244. ACFT BEGAN CLBING APPROX FL241. AS ACFT BEGAN CLBING A TCASII DISPLAY ACFT Y WAS NOTED AT OUR 6 O'CLOCK POS, DSNDING OUT OF FL240 ABOUT 3 MI ASTERN. ALTHOUGH OTHER TCASII REPLIES WERE OBSERVED AND NOTED, NONE WAS OBSERVED IN OUR IMMEDIATE VICINITY UNTIL CLB WAS UNDERWAY AS STATED EARLIER. AT NO TIME DID THE TCASII SYS ISSUE A TA OR RA. ACFT CONTINUED TO DEST WITHOUT FURTHER INCIDENT.
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.