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Air carrier X had less than standard separation from aircraft Y. System error. Air carrier X flight crew failed to maintain last assigned altitude. Pilot deviation.
| Attributes | |
| ACN | 156006 |
| Time | |
| Date | 199009 |
| Day | Tue |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : gmn |
| State Reference | CA |
| Altitude | msl bound lower : 23000 msl bound upper : 24000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zla |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | climbout : intermediate altitude |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| 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 : 240 flight time total : 12000 flight time type : 10000 |
| ASRS Report | 156006 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 220 flight time total : 6000 flight time type : 2000 |
| ASRS Report | 156406 |
| Events | |
| Anomaly | altitude deviation : overshoot conflict : airborne less severe non adherence : required legal separation non adherence : published procedure non adherence : clearance |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 24000 vertical : 0 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error Pilot Deviation |
Narrative:
Air carrier X cleared to FL230 with a frequency change to the high altitude controller. Checked in level FL230. Controller responded 'maintain FL330.' pilot acknowledged 'FL330 air carrier X.' after passing FL240 controller instructed a 40 degree heading change and descend to FL230. He then said he originally instructed to maintain FL230 not FL330 and a loss of sep with air carrier Y occurred. After landing I called the ATC supervisor and asked what the tapes revealed. He said the ctrl clearly said FL230. I responded that both the first officer and captain heard FL330 and acknowledged FL330 with no correction from the control. The ATC supervisor then said that our microphone was not keyed properly and the tapes only revealed '30'. Therefore, the deviation was going to be recorded as an operational error, not a pilot error, because the controller did not insure FL230 was read back. Keying the microphone properly before speaking will help prevent a reccurence. Using the call sign first in radio xmissions per aim will also help. Supplemental information from acn 156406. We were climbing to cruise altitude. We had been assigned FL230. Passing approximately FL200 we were given FL330.
Original NASA ASRS Text
Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACFT Y. SYSTEM ERROR. ACR X FLT CREW FAILED TO MAINTAIN LAST ASSIGNED ALT. PLTDEV.
Narrative: ACR X CLRED TO FL230 WITH A FREQ CHANGE TO THE HIGH ALT CTLR. CHKED IN LEVEL FL230. CTLR RESPONDED 'MAINTAIN FL330.' PLT ACKNOWLEDGED 'FL330 ACR X.' AFTER PASSING FL240 CTLR INSTRUCTED A 40 DEG HDG CHANGE AND DSND TO FL230. HE THEN SAID HE ORIGINALLY INSTRUCTED TO MAINTAIN FL230 NOT FL330 AND A LOSS OF SEP WITH ACR Y OCCURRED. AFTER LNDG I CALLED THE ATC SUPVR AND ASKED WHAT THE TAPES REVEALED. HE SAID THE CTRL CLEARLY SAID FL230. I RESPONDED THAT BOTH THE F/O AND CAPT HEARD FL330 AND ACKNOWLEDGED FL330 WITH NO CORRECTION FROM THE CTL. THE ATC SUPVR THEN SAID THAT OUR MIKE WAS NOT KEYED PROPERLY AND THE TAPES ONLY REVEALED '30'. THEREFORE, THE DEV WAS GOING TO BE RECORDED AS AN OPERROR, NOT A PLT ERROR, BECAUSE THE CTLR DID NOT INSURE FL230 WAS READ BACK. KEYING THE MIKE PROPERLY BEFORE SPEAKING WILL HELP PREVENT A RECCURENCE. USING THE CALL SIGN FIRST IN RADIO XMISSIONS PER AIM WILL ALSO HELP. SUPPLEMENTAL INFO FROM ACN 156406. WE WERE CLBING TO CRUISE ALT. WE HAD BEEN ASSIGNED FL230. PASSING APPROX FL200 WE WERE GIVEN FL330.
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.