Narrative:

While at FL230, ZDC cleared us to climb to FL350. During the climb, we received an amended clearance to level out at FL310. After leveling out at FL310, we received and I read back a clearance to climb to FL330. The first officer thought he heard FL350 and set FL350 in the altitude selector. I did not hear the first officer's readback of 'FL350.' I was changing and identing my VOR when I looked up and saw us passing through FL333. I asked the first officer 'weren't we cleared to FL330?' he pushed the nose over and stated that he understood it to be FL350. We leveled out at FL350. At this time, ZDC called and asked us to confirm that we were leveling out at FL330. He advised us of traffic at 2 O'clock, 3 mi at FL350. We rapidly returned to FL330 and reported level. No TA or RA alert was received. When changing frequency, I asked if we needed to call, and ATC said no call was needed. Contributing factors: I failed to visually confirm the correct setting in the altitude alert selector window. (Note: on this aircraft, the altitude alert selector is located to the right, below and forward of the throttles, and is obscured by the throttles when they are at high power settings.) other airlines using this same older aircraft have placed the altitude alert selector on the glare shield in full view of both pilots at all times! This should be a required location! I also failed to be certain to hear the first officer's readback and should have asked for a verification. I also believe it would be beneficial for ATC to limit the use of nonstandard altitudes for direction of flight (ie, FL330 wbound), as pilots tend to anticipate standard altitudes. Supplemental information from acn 431884: DC9, nnwbound at FL310 requesting FL350, B737 traffic at FL350 swbound on J75. DC9 was issued a clearance to FL350 but the clearance was corrected and amended in mid transmission. DC9 read back, 'climbing to FL330.' crossing traffic was then issued. When DC9's mode C indicated FL332, I verified DC9's clearance limit. The pilot said, 'we were issued FL350.' I descended DC9 back to FL330 and reissued traffic at FL350.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC CONFUSED ALT CLRNC AND OVERSHOT ASSIGNED ALT.

Narrative: WHILE AT FL230, ZDC CLRED US TO CLB TO FL350. DURING THE CLB, WE RECEIVED AN AMENDED CLRNC TO LEVEL OUT AT FL310. AFTER LEVELING OUT AT FL310, WE RECEIVED AND I READ BACK A CLRNC TO CLB TO FL330. THE FO THOUGHT HE HEARD FL350 AND SET FL350 IN THE ALT SELECTOR. I DID NOT HEAR THE FO'S READBACK OF 'FL350.' I WAS CHANGING AND IDENTING MY VOR WHEN I LOOKED UP AND SAW US PASSING THROUGH FL333. I ASKED THE FO 'WEREN'T WE CLRED TO FL330?' HE PUSHED THE NOSE OVER AND STATED THAT HE UNDERSTOOD IT TO BE FL350. WE LEVELED OUT AT FL350. AT THIS TIME, ZDC CALLED AND ASKED US TO CONFIRM THAT WE WERE LEVELING OUT AT FL330. HE ADVISED US OF TFC AT 2 O'CLOCK, 3 MI AT FL350. WE RAPIDLY RETURNED TO FL330 AND RPTED LEVEL. NO TA OR RA ALERT WAS RECEIVED. WHEN CHANGING FREQ, I ASKED IF WE NEEDED TO CALL, AND ATC SAID NO CALL WAS NEEDED. CONTRIBUTING FACTORS: I FAILED TO VISUALLY CONFIRM THE CORRECT SETTING IN THE ALT ALERT SELECTOR WINDOW. (NOTE: ON THIS ACFT, THE ALT ALERT SELECTOR IS LOCATED TO THE R, BELOW AND FORWARD OF THE THROTTLES, AND IS OBSCURED BY THE THROTTLES WHEN THEY ARE AT HIGH PWR SETTINGS.) OTHER AIRLINES USING THIS SAME OLDER ACFT HAVE PLACED THE ALT ALERT SELECTOR ON THE GLARE SHIELD IN FULL VIEW OF BOTH PLTS AT ALL TIMES! THIS SHOULD BE A REQUIRED LOCATION! I ALSO FAILED TO BE CERTAIN TO HEAR THE FO'S READBACK AND SHOULD HAVE ASKED FOR A VERIFICATION. I ALSO BELIEVE IT WOULD BE BENEFICIAL FOR ATC TO LIMIT THE USE OF NONSTANDARD ALTS FOR DIRECTION OF FLT (IE, FL330 WBOUND), AS PLTS TEND TO ANTICIPATE STANDARD ALTS. SUPPLEMENTAL INFO FROM ACN 431884: DC9, NNWBOUND AT FL310 REQUESTING FL350, B737 TFC AT FL350 SWBOUND ON J75. DC9 WAS ISSUED A CLRNC TO FL350 BUT THE CLRNC WAS CORRECTED AND AMENDED IN MID XMISSION. DC9 READ BACK, 'CLBING TO FL330.' XING TFC WAS THEN ISSUED. WHEN DC9'S MODE C INDICATED FL332, I VERIFIED DC9'S CLRNC LIMIT. THE PLT SAID, 'WE WERE ISSUED FL350.' I DSNDED DC9 BACK TO FL330 AND REISSUED TFC AT FL350.

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.