Narrative:

We departed sln. We were given clearance during the climb to 'climb and maintain FL310.' we replied with a 'maintain FL310.' while continuing the slow climb; at FL285; we received the following instructions -- or what we both believed to be the following instructions: 'advise FL300 for FL310 for traffic above.' we responded with something like 'ok...advise FL300' or 'ok...check with you at FL300' (not completely clear without tape confirmation). We are sure; however; there was no mention of 'maintain' in our readback. Since the controller never questioned our readback nor did he respond; we assumed we had heard the instruction clearly and thus responded correctly. Our perception of the ATC instruction was that the controller was being proactive in possibly allowing us to continue the slower climb once traffic was clear; thus his request to 'advise FL300 for FL310 for traffic.' we thought this was just for his information to get us to a higher altitude. The problem arose prior to leveling off at FL310. One mistake made by this crew was the late call going through FL300. We had mistakenly not remembered to 'advise FL300' until FL304. From what we can recall; the controller was giving instructions to someone else until we were at FL308. Immediately after talking with the other aircraft; he began to inquire about our altitude as previously mentioned. As we were capturing our altitude; the controller came on and asked us what altitude we were at. We reported to him that we were capturing FL310. He then told us that we were supposed to be at FL300 due to traffic and that he instructed us to do so earlier during the radio transmission at FL285 in the climb. At this point; he said to disregard and maintain FL310 because we were clear of traffic. We mentioned to him that there must have been a misunderstanding; however; after a brief pause we were given a phone number to call ZKC. After the flight; we immediately called ZKC and spoke with the supervisor. We talked about numerous issues including: what was heard on the tapes; the process to expect; and why they are required to report this. She was very helpful and gave us the contact names and numbers we would need. Discussion of the tapes: she discussed the information the tapes contained. Our (the pilot's) conclusion is that there was a huge misunderstanding with the initial call from ATC and then with the subsequent readback. She told us that the initial call was something along the lines of 'revise and maintain FL300 for FL310 for traffic.' this is when we did not hear the word 'maintain' and misconstrued 'revise' for 'advise.' once again she said the tapes indicated we did not read back the word 'maintain.' however; because the aircraft separation occurred they have to process possible pilot deviation action. This problem occurred due to a misunderstood clearance and readback. We (the pilots) thought we had heard one thing and responded. At that point; the controller took that readback as an acknowledgement. Unfortunately; we both perceived the instruction/readback differently.

Google
 

Original NASA ASRS Text

Title: AN HS125-700 CREW MISUNDERSTOOD AN ATC RADAR CTLR'S INSTRUCTION TO LEVEL AT FL300 AND LEVELED AT FL310 CAUSING A PLTDEV FOR TFC SEPARATION.

Narrative: WE DEPARTED SLN. WE WERE GIVEN CLRNC DURING THE CLB TO 'CLB AND MAINTAIN FL310.' WE REPLIED WITH A 'MAINTAIN FL310.' WHILE CONTINUING THE SLOW CLB; AT FL285; WE RECEIVED THE FOLLOWING INSTRUCTIONS -- OR WHAT WE BOTH BELIEVED TO BE THE FOLLOWING INSTRUCTIONS: 'ADVISE FL300 FOR FL310 FOR TFC ABOVE.' WE RESPONDED WITH SOMETHING LIKE 'OK...ADVISE FL300' OR 'OK...CHK WITH YOU AT FL300' (NOT COMPLETELY CLR WITHOUT TAPE CONFIRMATION). WE ARE SURE; HOWEVER; THERE WAS NO MENTION OF 'MAINTAIN' IN OUR READBACK. SINCE THE CTLR NEVER QUESTIONED OUR READBACK NOR DID HE RESPOND; WE ASSUMED WE HAD HEARD THE INSTRUCTION CLRLY AND THUS RESPONDED CORRECTLY. OUR PERCEPTION OF THE ATC INSTRUCTION WAS THAT THE CTLR WAS BEING PROACTIVE IN POSSIBLY ALLOWING US TO CONTINUE THE SLOWER CLB ONCE TFC WAS CLR; THUS HIS REQUEST TO 'ADVISE FL300 FOR FL310 FOR TFC.' WE THOUGHT THIS WAS JUST FOR HIS INFO TO GET US TO A HIGHER ALT. THE PROB AROSE PRIOR TO LEVELING OFF AT FL310. ONE MISTAKE MADE BY THIS CREW WAS THE LATE CALL GOING THROUGH FL300. WE HAD MISTAKENLY NOT REMEMBERED TO 'ADVISE FL300' UNTIL FL304. FROM WHAT WE CAN RECALL; THE CTLR WAS GIVING INSTRUCTIONS TO SOMEONE ELSE UNTIL WE WERE AT FL308. IMMEDIATELY AFTER TALKING WITH THE OTHER ACFT; HE BEGAN TO INQUIRE ABOUT OUR ALT AS PREVIOUSLY MENTIONED. AS WE WERE CAPTURING OUR ALT; THE CTLR CAME ON AND ASKED US WHAT ALT WE WERE AT. WE RPTED TO HIM THAT WE WERE CAPTURING FL310. HE THEN TOLD US THAT WE WERE SUPPOSED TO BE AT FL300 DUE TO TFC AND THAT HE INSTRUCTED US TO DO SO EARLIER DURING THE RADIO XMISSION AT FL285 IN THE CLB. AT THIS POINT; HE SAID TO DISREGARD AND MAINTAIN FL310 BECAUSE WE WERE CLR OF TFC. WE MENTIONED TO HIM THAT THERE MUST HAVE BEEN A MISUNDERSTANDING; HOWEVER; AFTER A BRIEF PAUSE WE WERE GIVEN A PHONE NUMBER TO CALL ZKC. AFTER THE FLT; WE IMMEDIATELY CALLED ZKC AND SPOKE WITH THE SUPVR. WE TALKED ABOUT NUMEROUS ISSUES INCLUDING: WHAT WAS HEARD ON THE TAPES; THE PROCESS TO EXPECT; AND WHY THEY ARE REQUIRED TO RPT THIS. SHE WAS VERY HELPFUL AND GAVE US THE CONTACT NAMES AND NUMBERS WE WOULD NEED. DISCUSSION OF THE TAPES: SHE DISCUSSED THE INFO THE TAPES CONTAINED. OUR (THE PLT'S) CONCLUSION IS THAT THERE WAS A HUGE MISUNDERSTANDING WITH THE INITIAL CALL FROM ATC AND THEN WITH THE SUBSEQUENT READBACK. SHE TOLD US THAT THE INITIAL CALL WAS SOMETHING ALONG THE LINES OF 'REVISE AND MAINTAIN FL300 FOR FL310 FOR TFC.' THIS IS WHEN WE DID NOT HEAR THE WORD 'MAINTAIN' AND MISCONSTRUED 'REVISE' FOR 'ADVISE.' ONCE AGAIN SHE SAID THE TAPES INDICATED WE DID NOT READ BACK THE WORD 'MAINTAIN.' HOWEVER; BECAUSE THE ACFT SEPARATION OCCURRED THEY HAVE TO PROCESS POSSIBLE PLTDEV ACTION. THIS PROB OCCURRED DUE TO A MISUNDERSTOOD CLRNC AND READBACK. WE (THE PLTS) THOUGHT WE HAD HEARD ONE THING AND RESPONDED. AT THAT POINT; THE CTLR TOOK THAT READBACK AS AN ACKNOWLEDGEMENT. UNFORTUNATELY; WE BOTH PERCEIVED THE INSTRUCTION/READBACK DIFFERENTLY.

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.