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Air carrier X responded to air carrier Y clearance unauthorized descent. Pilot deviation. Air carrier X had less than standard separation from air carrier Y. System error.
| Attributes | |
| ACN | 188022 |
| Time | |
| Date | 199108 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : srp |
| State Reference | AZ |
| Altitude | msl bound lower : 31000 msl bound upper : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zab |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : flight data |
| Qualification | controller : radar |
| Experience | controller radar : 20 |
| ASRS Report | 188023 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance 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 : 20400 vertical : 1000 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Pilot Deviation Operational Error |
Narrative:
Air carrier X and Y were inbound flts to phx. The night time conditions were thunderstorms in area with aircraft deviating throughout the sector because of WX on both inbound and outbound rtes. Air carrier Y was at FL310 and air carrier X almost directly above at FL330. Both aircraft needed to be spaced for descent and arrival to phx. Accordingly, the radar controller issued clearance for air carrier Y to turn right to a heading of 260 and descend to 12000. The readback of this clearance (the tapes later showed) was correct except that the call sign at the end (not the beginning) was air carrier X. Air carrier X descended into conflict with air carrier Y after taking air carrier Y's clearance. The controllers (both right and D) were held at fault because they did not catch the 'air carrier X' at the end of the readback. As the radar controller saw air carrier X descend (no report leaving the altitude) he issued instructions to keep the incident from turning into an accident. Whoever was to blame, this points up the need for pilots as well as controllers to listen to the radio with care. 3 crew members in the air carrier Y cockpit should have heard air carrier X answer their clearance. They said nothing. Both pilots in air carrier X took action on a clearance not directed to them.
Original NASA ASRS Text
Title: ACR X RESPONDED TO ACR Y CLRNC UNAUTHORIZED DSCNT. PLTDEV. ACR X HAD LTSS FROM ACR Y. SYS ERROR.
Narrative: ACR X AND Y WERE INBOUND FLTS TO PHX. THE NIGHT TIME CONDITIONS WERE TSTMS IN AREA WITH ACFT DEVIATING THROUGHOUT THE SECTOR BECAUSE OF WX ON BOTH INBOUND AND OUTBOUND RTES. ACR Y WAS AT FL310 AND ACR X ALMOST DIRECTLY ABOVE AT FL330. BOTH ACFT NEEDED TO BE SPACED FOR DSCNT AND ARR TO PHX. ACCORDINGLY, THE RADAR CTLR ISSUED CLRNC FOR ACR Y TO TURN R TO A HDG OF 260 AND DSND TO 12000. THE READBACK OF THIS CLRNC (THE TAPES LATER SHOWED) WAS CORRECT EXCEPT THAT THE CALL SIGN AT THE END (NOT THE BEGINNING) WAS ACR X. ACR X DSNDED INTO CONFLICT WITH ACR Y AFTER TAKING ACR Y'S CLRNC. THE CTLRS (BOTH R AND D) WERE HELD AT FAULT BECAUSE THEY DID NOT CATCH THE 'ACR X' AT THE END OF THE READBACK. AS THE RADAR CTLR SAW ACR X DSND (NO RPT LEAVING THE ALT) HE ISSUED INSTRUCTIONS TO KEEP THE INCIDENT FROM TURNING INTO AN ACCIDENT. WHOEVER WAS TO BLAME, THIS POINTS UP THE NEED FOR PLTS AS WELL AS CTLRS TO LISTEN TO THE RADIO WITH CARE. 3 CREW MEMBERS IN THE ACR Y COCKPIT SHOULD HAVE HEARD ACR X ANSWER THEIR CLRNC. THEY SAID NOTHING. BOTH PLTS IN ACR X TOOK ACTION ON A CLRNC NOT DIRECTED TO THEM.
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.