Narrative:

Climbing out of dtw, entre iad, being vectored for V-103 to aco VOR. First officer flying,and approximately FL210 (cleared to FL240), I decided to turn off the seat belt sign. I stated to the first officer I was 'going off the air' to make the company required P.a. Announcement about the seat belt, then turned down my VHF volume to do so. While talking on the P.a. I noticed and pointed to converging traffic above us and to our right. I checked our altitude (just above FL240) and the altitude alert selector (now set at 26000'). Just as I finished the announcement and brought my VHF volume back up, a F/a knocked on the door and requested our ETA and asked us to 'warm it up in back.' I gave him the ETA while the first officer adjusted the temperature. Immediately thereafter, as we were passing approximately 25300', cleveland center gave us a frequency change. I acknowledged the change, then said; 'before we go, what's the altitude of that traffic at our 1 O'clock?' center said; 'he's at 260, what's your altitude? You're only cleared to 250.' (words approximately). We immediately stopped our climb at about 25800' and descended to FL250, passing approximately 1-2 mi behind and below an airlines medium large transport. While we were doing this, I told center I believed we were cleared to and had acknowledged FL260. In retrospect, this was an assumption on my part, since that clearance was issued and acknowledged while I was off the air making the announcement. The first officer later said he was fairly certain that he had received FL260. Since he is a very alert and precise first officer, I have no reason to believe otherwise. At the time of this writing, we have no knowledge of what is on the ATC tapes, but it's obvious that one of three scenarios occurred: 1) cleveland center issued an improper clearance to FL260, or 2) center issued a clearance to FL250 but the first officer misunderstood, acknowledged, and set FL260, or 3) FL250 was issued and acknowledged, but the altitude alert was mis-set to 26000', and the error was not caught, possibly due to the subsequent distrs. If scenario 1 is the case, it was an error by center that we in the cockpit have no control over. If 2 is true, the responsibility is shared by us and ATC, since center did not notice the discrepancy during the readback. In the case of 3, we alone in the cockpit are responsible. In either case 2 or 3, the chance for error would have been greatly reduced had I been 'in the loop' 100% of the time. However, with a two pilot crew, this is not always possible (ATIS, maintenance problems, required PA announcements, engine readings, etc). We've attempted to reduce the impact of these 'extra' duties by the sterile cockpit concept below 10000', but unless we return to three pilot crews or use many new automatic devices (taped announcements, uplink to cockpit printer for ATIS, automatic ACARS engine readings, etc) we have to accept the occasional periods of one pilot being 'solo'. I don't particularly like this, but then I don't know what to do about it either.

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Original NASA ASRS Text

Title: MLG OVERSHOT ALT INTENDED BY ARTCC AND HAD LESS THAN STANDARD SEPARATION WITH ANOTHER MLG.

Narrative: CLBING OUT OF DTW, ENTRE IAD, BEING VECTORED FOR V-103 TO ACO VOR. F/O FLYING,AND APPROX FL210 (CLRED TO FL240), I DECIDED TO TURN OFF THE SEAT BELT SIGN. I STATED TO THE F/O I WAS 'GOING OFF THE AIR' TO MAKE THE COMPANY REQUIRED P.A. ANNOUNCEMENT ABOUT THE SEAT BELT, THEN TURNED DOWN MY VHF VOLUME TO DO SO. WHILE TALKING ON THE P.A. I NOTICED AND POINTED TO CONVERGING TFC ABOVE US AND TO OUR R. I CHKED OUR ALT (JUST ABOVE FL240) AND THE ALT ALERT SELECTOR (NOW SET AT 26000'). JUST AS I FINISHED THE ANNOUNCEMENT AND BROUGHT MY VHF VOLUME BACK UP, A F/A KNOCKED ON THE DOOR AND REQUESTED OUR ETA AND ASKED US TO 'WARM IT UP IN BACK.' I GAVE HIM THE ETA WHILE THE F/O ADJUSTED THE TEMPERATURE. IMMEDIATELY THEREAFTER, AS WE WERE PASSING APPROX 25300', CLEVELAND CENTER GAVE US A FREQ CHANGE. I ACKNOWLEDGED THE CHANGE, THEN SAID; 'BEFORE WE GO, WHAT'S THE ALT OF THAT TFC AT OUR 1 O'CLOCK?' CENTER SAID; 'HE'S AT 260, WHAT'S YOUR ALT? YOU'RE ONLY CLRED TO 250.' (WORDS APPROX). WE IMMEDIATELY STOPPED OUR CLB AT ABOUT 25800' AND DSNDED TO FL250, PASSING APPROX 1-2 MI BEHIND AND BELOW AN AIRLINES MLG. WHILE WE WERE DOING THIS, I TOLD CENTER I BELIEVED WE WERE CLRED TO AND HAD ACKNOWLEDGED FL260. IN RETROSPECT, THIS WAS AN ASSUMPTION ON MY PART, SINCE THAT CLRNC WAS ISSUED AND ACKNOWLEDGED WHILE I WAS OFF THE AIR MAKING THE ANNOUNCEMENT. THE F/O LATER SAID HE WAS FAIRLY CERTAIN THAT HE HAD RECEIVED FL260. SINCE HE IS A VERY ALERT AND PRECISE F/O, I HAVE NO REASON TO BELIEVE OTHERWISE. AT THE TIME OF THIS WRITING, WE HAVE NO KNOWLEDGE OF WHAT IS ON THE ATC TAPES, BUT IT'S OBVIOUS THAT ONE OF THREE SCENARIOS OCCURRED: 1) CLEVELAND CENTER ISSUED AN IMPROPER CLRNC TO FL260, OR 2) CENTER ISSUED A CLRNC TO FL250 BUT THE F/O MISUNDERSTOOD, ACKNOWLEDGED, AND SET FL260, OR 3) FL250 WAS ISSUED AND ACKNOWLEDGED, BUT THE ALT ALERT WAS MIS-SET TO 26000', AND THE ERROR WAS NOT CAUGHT, POSSIBLY DUE TO THE SUBSEQUENT DISTRS. IF SCENARIO 1 IS THE CASE, IT WAS AN ERROR BY CENTER THAT WE IN THE COCKPIT HAVE NO CONTROL OVER. IF 2 IS TRUE, THE RESPONSIBILITY IS SHARED BY US AND ATC, SINCE CENTER DID NOT NOTICE THE DISCREPANCY DURING THE READBACK. IN THE CASE OF 3, WE ALONE IN THE COCKPIT ARE RESPONSIBLE. IN EITHER CASE 2 OR 3, THE CHANCE FOR ERROR WOULD HAVE BEEN GREATLY REDUCED HAD I BEEN 'IN THE LOOP' 100% OF THE TIME. HOWEVER, WITH A TWO PLT CREW, THIS IS NOT ALWAYS POSSIBLE (ATIS, MAINT PROBS, REQUIRED PA ANNOUNCEMENTS, ENG READINGS, ETC). WE'VE ATTEMPTED TO REDUCE THE IMPACT OF THESE 'EXTRA' DUTIES BY THE STERILE COCKPIT CONCEPT BELOW 10000', BUT UNLESS WE RETURN TO THREE PLT CREWS OR USE MANY NEW AUTOMATIC DEVICES (TAPED ANNOUNCEMENTS, UPLINK TO COCKPIT PRINTER FOR ATIS, AUTOMATIC ACARS ENG READINGS, ETC) WE HAVE TO ACCEPT THE OCCASIONAL PERIODS OF ONE PLT BEING 'SOLO'. I DON'T PARTICULARLY LIKE THIS, BUT THEN I DON'T KNOW WHAT TO DO ABOUT IT EITHER.

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.