Narrative:

While working the south arrival/departure position, aircraft X, a B767, departed iln climbing to 3000 ft. I radar idented him and issued traffic on a PA28 overflt at 4000 ft at his 2 O'clock position, and 4 mi crossing his flight path, and told him to expect higher passing the traffic. Traffic was also issued to the PA28. Aircraft Z, another B767, that departed iln prior to aircraft X, was also on frequency level at 8000 ft and awaiting climb to 10000 ft. I transmitted to aircraft Z to climb and maintain 10000 ft and contact center. I received a readback acknowledging the climb and frequency change. I then answered a landline and while on the line, heard aircraft Z ask if that transmission was for him. I immediately came off the landline and transmitted for aircraft X to maintain 3000 ft and that transmission was not for him. I then reissued the traffic to the PA28 who advised the H/B767 in sight and was instructed to maintain visual separation. Aircraft X had already switched to center. The center controller advised him to return to approach frequency and the center controller also advised that he had a TA. I told him I thought he had taken instructions for another aircraft. He stated that both he and the other pilot thought the call was for them. At the time, I wasn't sure if I had used the wrong call sign or not. After listening to the tape, the proper call sign aircraft Z was used, but in the heat of the battle, I didn't notice that the readback did not include the use of any call sign, and I assumed it was from aircraft Z until aircraft Z called back for confirmation. I was lucky to hear this since I was on a landline trying to listen to another controller. A couple things I feel I could've done to possibly avoid this: 1) ensure or confirm that the correct aircraft acknowledges using a call sign if none is used in a readback of critical instructions and, 2) use caution when issuing an altitude change and frequency change in same transmission. As far as the flight crew, if the pilots would've used their call sign when reading back the clearance, it would've given me a chance to catch and correct the error. Also, the pilot, with the verbal picture and information on the traffic along with TCASII information in the cockpit, could've and should've questioned the climb through traffic that was never called in sight by him or advised no longer a factor by me. Thank goodness it was VMC.

Related reports:

Google
 

Original NASA ASRS Text

Title: DAY TRACON CTLR EXPERIENCED LOSS OF SEPARATION WITH CLBING B767 AND PA28 OVER FLT AT APPROX 3000 FT BECAUSE OF A READBACK WITHOUT USE OF A CALL SIGN.

Narrative: WHILE WORKING THE S ARR/DEP POS, ACFT X, A B767, DEPARTED ILN CLBING TO 3000 FT. I RADAR IDENTED HIM AND ISSUED TFC ON A PA28 OVERFLT AT 4000 FT AT HIS 2 O'CLOCK POS, AND 4 MI XING HIS FLT PATH, AND TOLD HIM TO EXPECT HIGHER PASSING THE TFC. TFC WAS ALSO ISSUED TO THE PA28. ACFT Z, ANOTHER B767, THAT DEPARTED ILN PRIOR TO ACFT X, WAS ALSO ON FREQ LEVEL AT 8000 FT AND AWAITING CLB TO 10000 FT. I XMITTED TO ACFT Z TO CLB AND MAINTAIN 10000 FT AND CONTACT CTR. I RECEIVED A READBACK ACKNOWLEDGING THE CLB AND FREQ CHANGE. I THEN ANSWERED A LANDLINE AND WHILE ON THE LINE, HEARD ACFT Z ASK IF THAT XMISSION WAS FOR HIM. I IMMEDIATELY CAME OFF THE LANDLINE AND XMITTED FOR ACFT X TO MAINTAIN 3000 FT AND THAT XMISSION WAS NOT FOR HIM. I THEN REISSUED THE TFC TO THE PA28 WHO ADVISED THE H/B767 IN SIGHT AND WAS INSTRUCTED TO MAINTAIN VISUAL SEPARATION. ACFT X HAD ALREADY SWITCHED TO CTR. THE CTR CTLR ADVISED HIM TO RETURN TO APCH FREQ AND THE CTR CTLR ALSO ADVISED THAT HE HAD A TA. I TOLD HIM I THOUGHT HE HAD TAKEN INSTRUCTIONS FOR ANOTHER ACFT. HE STATED THAT BOTH HE AND THE OTHER PLT THOUGHT THE CALL WAS FOR THEM. AT THE TIME, I WASN'T SURE IF I HAD USED THE WRONG CALL SIGN OR NOT. AFTER LISTENING TO THE TAPE, THE PROPER CALL SIGN ACFT Z WAS USED, BUT IN THE HEAT OF THE BATTLE, I DIDN'T NOTICE THAT THE READBACK DID NOT INCLUDE THE USE OF ANY CALL SIGN, AND I ASSUMED IT WAS FROM ACFT Z UNTIL ACFT Z CALLED BACK FOR CONFIRMATION. I WAS LUCKY TO HEAR THIS SINCE I WAS ON A LANDLINE TRYING TO LISTEN TO ANOTHER CTLR. A COUPLE THINGS I FEEL I COULD'VE DONE TO POSSIBLY AVOID THIS: 1) ENSURE OR CONFIRM THAT THE CORRECT ACFT ACKNOWLEDGES USING A CALL SIGN IF NONE IS USED IN A READBACK OF CRITICAL INSTRUCTIONS AND, 2) USE CAUTION WHEN ISSUING AN ALT CHANGE AND FREQ CHANGE IN SAME XMISSION. AS FAR AS THE FLT CREW, IF THE PLTS WOULD'VE USED THEIR CALL SIGN WHEN READING BACK THE CLRNC, IT WOULD'VE GIVEN ME A CHANCE TO CATCH AND CORRECT THE ERROR. ALSO, THE PLT, WITH THE VERBAL PICTURE AND INFO ON THE TFC ALONG WITH TCASII INFO IN THE COCKPIT, COULD'VE AND SHOULD'VE QUESTIONED THE CLB THROUGH TFC THAT WAS NEVER CALLED IN SIGHT BY HIM OR ADVISED NO LONGER A FACTOR BY ME. THANK GOODNESS IT WAS VMC.

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.