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ZFW controller described loss of separation event at 6100 during holding when aircraft descended below assigned altitude.
| Attributes | |
| ACN | 733181 |
| Time | |
| Date | 200703 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : csi.vortac |
| State Reference | TX |
| Altitude | msl bound lower : 5800 msl bound upper : 6100 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zhu.artcc |
| Operator | general aviation : personal |
| Make Model Name | Light Transport Low Wing 2 Turboprop Eng |
| Operating Under FAR Part | Part 91 |
| Flight Phase | cruise : holding |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zhu.artcc |
| Operator | general aviation : personal |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Flight Phase | cruise : holding |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar controller : military |
| Experience | controller military : 4 controller radar : 1 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : required legal separation non adherence : clearance |
| Independent Detector | atc equipment : conflict alert other controllera |
| Resolutory Action | controller : issued alert controller : issued new clearance |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 22200 vertical : 600 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Aircraft #1 was holding at 6100 ft over csi VORTAC. Aircraft #2 was holding at 5100 ft over csi VORTAC. I was working the skf low sector at ZHU. I keyed the microphone to give aircraft #1 a descent clearance. I said the call sign; descend and maintain 4000 ft. I unkeyed; keyed the microphone again and said disregard. The aircraft never read back anything. I then gave the descent clearance to aircraft #2. About this time; we were splitting the sector because of volume. The receiving controller just took over the frequencys when we noticed aircraft #1 descending out of 5800 ft. I tried to key the microphone to stop him; but I was already off the frequencys. By the time the relieving controller recognized the situation; it was too late and separation was lost.
Original NASA ASRS Text
Title: ZFW CTLR DESCRIBED LOSS OF SEPARATION EVENT AT 6100 DURING HOLDING WHEN ACFT DESCENDED BELOW ASSIGNED ALT.
Narrative: ACFT #1 WAS HOLDING AT 6100 FT OVER CSI VORTAC. ACFT #2 WAS HOLDING AT 5100 FT OVER CSI VORTAC. I WAS WORKING THE SKF LOW SECTOR AT ZHU. I KEYED THE MIKE TO GIVE ACFT #1 A DSCNT CLRNC. I SAID THE CALL SIGN; DSND AND MAINTAIN 4000 FT. I UNKEYED; KEYED THE MIKE AGAIN AND SAID DISREGARD. THE ACFT NEVER READ BACK ANYTHING. I THEN GAVE THE DSCNT CLRNC TO ACFT #2. ABOUT THIS TIME; WE WERE SPLITTING THE SECTOR BECAUSE OF VOLUME. THE RECEIVING CTLR JUST TOOK OVER THE FREQS WHEN WE NOTICED ACFT #1 DSNDING OUT OF 5800 FT. I TRIED TO KEY THE MIKE TO STOP HIM; BUT I WAS ALREADY OFF THE FREQS. BY THE TIME THE RELIEVING CTLR RECOGNIZED THE SITUATION; IT WAS TOO LATE AND SEPARATION WAS LOST.
Data retrieved from NASA's ASRS site as of January 2009 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.