Narrative:

Air carrier X departs sju for jfk and was issued FL280. X reads back FL280. Later X was advised FL280 would be final altitude. Air carrier X readback was FL310. I, as the controller, did not hear the FL310 readback. Air carrier X reports level, I thought I heard FL280. I terminated radar service and charged X frequency to enroute commercial radio. Air carrier X leaves radar coverage to nonradar enroute at FL310. Three to four minutes in front on same routing is air carrier Y, also at FL310 separation needed at this time is 15 min. When air carrier X reports to comm radio the sector 4 non radar controller is made aware of air carrier X's aircraft, and he reroutes X to achieve standard separation. Callback conversation with reporter revealed the following: reporter states that operation error review did not reveal the reason that flight crew of air carrier X thought they were clrd to FL310. He had told X twice that altitude assignment was FL280. Were getting ready for daily sbound and all altitude on A300 were occupied so when error noted they moved air carrier X over to airway A-23. Believes air carrier X and air carrier Y were at same altitude for just a few minutes as his d-man caught it when communication radio gave report. Reporter says that he did a poor job of listening to readback and also failed to check mode C altitude readout prior to changing aircraft over to communication radio.

Related reports:

Google
 

Original NASA ASRS Text

Title: FOREIGN ACR AND ANOTHER ACR WERE AT SAME ALT WITH LESS THAN STANDARD SEPARATION. OPERATIONAL ERROR.

Narrative: ACR X DEPARTS SJU FOR JFK AND WAS ISSUED FL280. X READS BACK FL280. LATER X WAS ADVISED FL280 WOULD BE FINAL ALT. ACR X READBACK WAS FL310. I, AS THE CTLR, DID NOT HEAR THE FL310 READBACK. ACR X REPORTS LEVEL, I THOUGHT I HEARD FL280. I TERMINATED RADAR SERVICE AND CHARGED X FREQ TO ENROUTE COMMERCIAL RADIO. ACR X LEAVES RADAR COVERAGE TO NONRADAR ENROUTE AT FL310. THREE TO FOUR MINUTES IN FRONT ON SAME ROUTING IS ACR Y, ALSO AT FL310 SEPARATION NEEDED AT THIS TIME IS 15 MIN. WHEN ACR X REPORTS TO COMM RADIO THE SECTOR 4 NON RADAR CTLR IS MADE AWARE OF ACR X'S ACFT, AND HE REROUTES X TO ACHIEVE STANDARD SEPARATION. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: RPTR STATES THAT OP ERROR REVIEW DID NOT REVEAL THE REASON THAT FLT CREW OF ACR X THOUGHT THEY WERE CLRD TO FL310. HE HAD TOLD X TWICE THAT ALT ASSIGNMENT WAS FL280. WERE GETTING READY FOR DAILY SBOUND AND ALL ALT ON A300 WERE OCCUPIED SO WHEN ERROR NOTED THEY MOVED ACR X OVER TO AIRWAY A-23. BELIEVES ACR X AND ACR Y WERE AT SAME ALT FOR JUST A FEW MINUTES AS HIS D-MAN CAUGHT IT WHEN COM RADIO GAVE REPORT. RPTR SAYS THAT HE DID A POOR JOB OF LISTENING TO READBACK AND ALSO FAILED TO CHECK MODE C ALT READOUT PRIOR TO CHANGING ACFT OVER TO COM RADIO.

Data retrieved from NASA's ASRS site as of August 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.