Narrative:

My trainer and I had just split the high sectors from the low sector. Traffic was just starting to pick up and when we split the sector I had radar control of approximately 9 aircraft. An air carrier requested an altitude change for rides. I climbed him. Other aircraft called on and I issued a clearance to climb; another air carrier off of lex going to ord. I had traffic for him at FL290 so I climbed him to FL280. An aircraft called on from area 4 at FL330 and I took the handoff on air carrier X FL330 from ZKC. Air carrier X was the only aircraft that hadn't called on my frequency. These xmissions were very garbled and mixed with what I thought was more than 1 aircraft calling. I looked at my trainer as we were listening to determine if he'd heard any more detail than I had. At that point I stated; 'it sounds like someone said something about a climb.' when the transmission started; I heard 'air carrier X garble...(climb)...garble....' this transmission was mixed and blocked by air carrier Y reading back his climb clearance. My trainer said; 'well; air carrier checked on;' pointing to air carrier X. I'd also heard the word air carrier transmitted; 'air carrier X I have you at flight level three-three-zero.' I heard a reply; 'air carrier X; three-three-zero.' I replied; 'roger; who else called?' and waited. I got no answer and scanned my data blocks wondering who said the word 'climb' and was verifying no one was climbing other than the 2 aircraft I had previously cleared for climbs. He reported back the correct assigned altitude. No other aircraft said anything about requesting a climb or anything else. Approximately 10 mins later; I was paged and told I worked an aircraft that may have gotten with another aircraft in ZKC or zmc's airspace. We went to the e-desk and the manager told me I probably had an airspace violation. He said that the ZME controller saw that a plane was climbing and turned his traffic so the 2 aircraft didn't lose separation. ZKC was also listening to tapes and this is when I found out air carrier X had mistakenly called on my frequency. The operations manager told us that the ZKC controller had both air carrier Y and air carrier Z on his frequencys. The ZKC controller never advised the 2 aircraft that he had them both and to use caution with similar sounding call signs. We listened to the recordings several times but they sound very different from what the frequencys sounded like. I asked about this and they told me that the frequencys are recorded separately at the console. This recording is not what is coming through the controller's headset. The recordings were digitally replayed and run at the same time. On 'tape;' they are very clear because neither aircraft is canceled by another transmission. The mgrs acted as if they did not believe my description of what I had heard. But there were 3 people plugged in and none of us heard the exact exchange because of the canceled xmissions. On the recording; air carrier X checks O 'climbing out of 22X for flight level two-seven-oh.' at the same time on the other frequency; the air carrier Y was reading back his clearance to climb to FL310. The recordings are not blocked and are very strong and clear. Also; it sounded like air carrier X recording was more prominent than the air carrier Y. This also was opposite in my headset. So; after a pause on the frequency when my trainer and I were discussing who called; my next transmission is 'air carrier X; I have you at flight level three-three-zero.' air carrier X reply is 'roger; air carrier X climbing to flight level three-three-zero.' I reply; 'roger; who else called?' there was no reply. I was told a few hours after this by the controller working the pxv/imp sector that after I left; about 10 mins or so later he was called 'out of the blue' by an air carrier Z asking if he was on the right frequency. The controller said the pilot sounded very unsure of himself. The controller looked him up in uret and gave him the correct ZME frequency. In all; several things happened here besides the mistake of dual expectations. The recording equipment and the live broadcasts were very different. I also should have followed my instincts when I heard 'climb;' I should have asked again specifically who said something about climbing. I thought I'd covered my bases when I knew the air carrier Y read his clearance back and I verified with the only other aircraft in my airspace that I knew of; the air carrier was climbing to his assigned altitude. The air carrier X pilot should have questioned me when I said an altitude different from what he had just reported to me. Maybe he also should have said something when air carrier X called on and I answered that aircraft and additionally never told them to use caution because of similar sounding call signs. My trainer also commented after hearing the recordings that maybe he led me to believe that the air carrier looking for was the one that called. He said maybe I should have just waited for the aircraft to call again. This is correct but given the information that we had; the only plane we were waiting for was air carrier X; that is what we went with.

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Original NASA ASRS Text

Title: ZID DEVELOPMENT CTLR DESCRIBED CONFUSED SIT WHEN AN ACR; ON THE WRONG FREQ WITH SIMILAR CALL SIGN; RESPONDED TO ATC'S INQUIRIES.

Narrative: MY TRAINER AND I HAD JUST SPLIT THE HIGH SECTORS FROM THE LOW SECTOR. TFC WAS JUST STARTING TO PICK UP AND WHEN WE SPLIT THE SECTOR I HAD RADAR CTL OF APPROX 9 ACFT. AN ACR REQUESTED AN ALT CHANGE FOR RIDES. I CLBED HIM. OTHER ACFT CALLED ON AND I ISSUED A CLRNC TO CLB; ANOTHER ACR OFF OF LEX GOING TO ORD. I HAD TFC FOR HIM AT FL290 SO I CLBED HIM TO FL280. AN ACFT CALLED ON FROM AREA 4 AT FL330 AND I TOOK THE HDOF ON ACR X FL330 FROM ZKC. ACR X WAS THE ONLY ACFT THAT HADN'T CALLED ON MY FREQ. THESE XMISSIONS WERE VERY GARBLED AND MIXED WITH WHAT I THOUGHT WAS MORE THAN 1 ACFT CALLING. I LOOKED AT MY TRAINER AS WE WERE LISTENING TO DETERMINE IF HE'D HEARD ANY MORE DETAIL THAN I HAD. AT THAT POINT I STATED; 'IT SOUNDS LIKE SOMEONE SAID SOMETHING ABOUT A CLB.' WHEN THE XMISSION STARTED; I HEARD 'ACR X GARBLE...(CLB)...GARBLE....' THIS XMISSION WAS MIXED AND BLOCKED BY ACR Y READING BACK HIS CLB CLRNC. MY TRAINER SAID; 'WELL; ACR CHKED ON;' POINTING TO ACR X. I'D ALSO HEARD THE WORD ACR XMITTED; 'ACR X I HAVE YOU AT FLT LEVEL THREE-THREE-ZERO.' I HEARD A REPLY; 'ACR X; THREE-THREE-ZERO.' I REPLIED; 'ROGER; WHO ELSE CALLED?' AND WAITED. I GOT NO ANSWER AND SCANNED MY DATA BLOCKS WONDERING WHO SAID THE WORD 'CLB' AND WAS VERIFYING NO ONE WAS CLBING OTHER THAN THE 2 ACFT I HAD PREVIOUSLY CLRED FOR CLBS. HE RPTED BACK THE CORRECT ASSIGNED ALT. NO OTHER ACFT SAID ANYTHING ABOUT REQUESTING A CLB OR ANYTHING ELSE. APPROX 10 MINS LATER; I WAS PAGED AND TOLD I WORKED AN ACFT THAT MAY HAVE GOTTEN WITH ANOTHER ACFT IN ZKC OR ZMC'S AIRSPACE. WE WENT TO THE E-DESK AND THE MGR TOLD ME I PROBABLY HAD AN AIRSPACE VIOLATION. HE SAID THAT THE ZME CTLR SAW THAT A PLANE WAS CLBING AND TURNED HIS TFC SO THE 2 ACFT DIDN'T LOSE SEPARATION. ZKC WAS ALSO LISTENING TO TAPES AND THIS IS WHEN I FOUND OUT ACR X HAD MISTAKENLY CALLED ON MY FREQ. THE OPS MGR TOLD US THAT THE ZKC CTLR HAD BOTH ACR Y AND ACR Z ON HIS FREQS. THE ZKC CTLR NEVER ADVISED THE 2 ACFT THAT HE HAD THEM BOTH AND TO USE CAUTION WITH SIMILAR SOUNDING CALL SIGNS. WE LISTENED TO THE RECORDINGS SEVERAL TIMES BUT THEY SOUND VERY DIFFERENT FROM WHAT THE FREQS SOUNDED LIKE. I ASKED ABOUT THIS AND THEY TOLD ME THAT THE FREQS ARE RECORDED SEPARATELY AT THE CONSOLE. THIS RECORDING IS NOT WHAT IS COMING THROUGH THE CTLR'S HEADSET. THE RECORDINGS WERE DIGITALLY REPLAYED AND RUN AT THE SAME TIME. ON 'TAPE;' THEY ARE VERY CLR BECAUSE NEITHER ACFT IS CANCELED BY ANOTHER XMISSION. THE MGRS ACTED AS IF THEY DID NOT BELIEVE MY DESCRIPTION OF WHAT I HAD HEARD. BUT THERE WERE 3 PEOPLE PLUGGED IN AND NONE OF US HEARD THE EXACT EXCHANGE BECAUSE OF THE CANCELED XMISSIONS. ON THE RECORDING; ACR X CHKS O 'CLBING OUT OF 22X FOR FLT LEVEL TWO-SEVEN-OH.' AT THE SAME TIME ON THE OTHER FREQ; THE ACR Y WAS READING BACK HIS CLRNC TO CLB TO FL310. THE RECORDINGS ARE NOT BLOCKED AND ARE VERY STRONG AND CLR. ALSO; IT SOUNDED LIKE ACR X RECORDING WAS MORE PROMINENT THAN THE ACR Y. THIS ALSO WAS OPPOSITE IN MY HEADSET. SO; AFTER A PAUSE ON THE FREQ WHEN MY TRAINER AND I WERE DISCUSSING WHO CALLED; MY NEXT XMISSION IS 'ACR X; I HAVE YOU AT FLT LEVEL THREE-THREE-ZERO.' ACR X REPLY IS 'ROGER; ACR X CLBING TO FLT LEVEL THREE-THREE-ZERO.' I REPLY; 'ROGER; WHO ELSE CALLED?' THERE WAS NO REPLY. I WAS TOLD A FEW HRS AFTER THIS BY THE CTLR WORKING THE PXV/IMP SECTOR THAT AFTER I LEFT; ABOUT 10 MINS OR SO LATER HE WAS CALLED 'OUT OF THE BLUE' BY AN ACR Z ASKING IF HE WAS ON THE RIGHT FREQ. THE CTLR SAID THE PLT SOUNDED VERY UNSURE OF HIMSELF. THE CTLR LOOKED HIM UP IN URET AND GAVE HIM THE CORRECT ZME FREQ. IN ALL; SEVERAL THINGS HAPPENED HERE BESIDES THE MISTAKE OF DUAL EXPECTATIONS. THE RECORDING EQUIPMENT AND THE LIVE BROADCASTS WERE VERY DIFFERENT. I ALSO SHOULD HAVE FOLLOWED MY INSTINCTS WHEN I HEARD 'CLB;' I SHOULD HAVE ASKED AGAIN SPECIFICALLY WHO SAID SOMETHING ABOUT CLBING. I THOUGHT I'D COVERED MY BASES WHEN I KNEW THE ACR Y READ HIS CLRNC BACK AND I VERIFIED WITH THE ONLY OTHER ACFT IN MY AIRSPACE THAT I KNEW OF; THE ACR WAS CLBING TO HIS ASSIGNED ALT. THE ACR X PLT SHOULD HAVE QUESTIONED ME WHEN I SAID AN ALT DIFFERENT FROM WHAT HE HAD JUST RPTED TO ME. MAYBE HE ALSO SHOULD HAVE SAID SOMETHING WHEN ACR X CALLED ON AND I ANSWERED THAT ACFT AND ADDITIONALLY NEVER TOLD THEM TO USE CAUTION BECAUSE OF SIMILAR SOUNDING CALL SIGNS. MY TRAINER ALSO COMMENTED AFTER HEARING THE RECORDINGS THAT MAYBE HE LED ME TO BELIEVE THAT THE ACR LOOKING FOR WAS THE ONE THAT CALLED. HE SAID MAYBE I SHOULD HAVE JUST WAITED FOR THE ACFT TO CALL AGAIN. THIS IS CORRECT BUT GIVEN THE INFO THAT WE HAD; THE ONLY PLANE WE WERE WAITING FOR WAS ACR X; THAT IS WHAT WE WENT WITH.

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.