Narrative:

Mistaken clearance. My understanding of the controller's descent clearance was to go direct to the aldan fix and descend to 10000 ft. I dialed in 10000 ft in the altitude selector and configured the FMS for direct to the fix. As we approached 13000 ft, the controller amended our clearance to maintain 13000 ft. Controller explained that the original clearance was to 15000 ft. We stated our understanding of the clearance and maintained 13000 ft per the controller's request. Regardless of the clearance received, a misunderstanding occurred. If the clearance was indeed to 15000 ft and we made the error, there are several reasons this could have happened: 1) 2 radios. The PF was listening to ATC through the headset in an attempt to block out the other radio and as required by company policy while the PNF listened to ATIS over the speak. The ATC clearance 'number confusion' could have easily occurred while overhearing the ATIS. 2) anticipated clearance. STAR crossing restr at aldan is 10000 ft. With the ATIS numbers in the backgnd, the altitude heard may have jumbled the real number with the expected/anticipated clearance. 3) with a very early show time (XA30 alarm) after later starts, everyone on the crew was commenting about being slow and tired. It is possible that fatigue was a factor even though ample rest was provided. In this case, fatigue could have affected perceptions of what was heard and what was expected. Suggestions to avoid this type of incident from happening again include: 1) ensuring that only 1 radio transmission can be heard at a time. ATC communications are paramount to safety, so there should be no outside interference to hearing and understanding between pilots and controllers. Additionally, all communications should be concise. 2) comply with clearance given before acting on anticipation. Clrncs should be read back as close to verbatim as possible. If there is any question about the clearance or its intention, don't hesitate to ask for clarification. Begin actions as directed, then compare against anticipated actions, then query any differences. 3) be wary of your own limitations. Be more alert of physiological effect on judgement. Teamwork in the cockpit is more important when any crew member feels the slightest impairment, regardless of the reason for the impairment. Let the other crew members know you are not operating at 100% and they will be able to watch your actions more closely. Controllers have their own unique reason for errors, the most formidable of which is shared with pilots -- we're human. Errors do occur every day and it is only through focused diligence that we can reduce the frequency of errors. By our very design, errors among humans can never be totally eliminated, though it is paramount that we try.

Related reports:

Google
 

Original NASA ASRS Text

Title: AN F100 CREW MISINTERPED A DSCNT CLRNC AND DSNDED THROUGH ASSIGNED ALT.

Narrative: MISTAKEN CLRNC. MY UNDERSTANDING OF THE CTLR'S DSCNT CLRNC WAS TO GO DIRECT TO THE ALDAN FIX AND DSND TO 10000 FT. I DIALED IN 10000 FT IN THE ALT SELECTOR AND CONFIGURED THE FMS FOR DIRECT TO THE FIX. AS WE APCHED 13000 FT, THE CTLR AMENDED OUR CLRNC TO MAINTAIN 13000 FT. CTLR EXPLAINED THAT THE ORIGINAL CLRNC WAS TO 15000 FT. WE STATED OUR UNDERSTANDING OF THE CLRNC AND MAINTAINED 13000 FT PER THE CTLR'S REQUEST. REGARDLESS OF THE CLRNC RECEIVED, A MISUNDERSTANDING OCCURRED. IF THE CLRNC WAS INDEED TO 15000 FT AND WE MADE THE ERROR, THERE ARE SEVERAL REASONS THIS COULD HAVE HAPPENED: 1) 2 RADIOS. THE PF WAS LISTENING TO ATC THROUGH THE HEADSET IN AN ATTEMPT TO BLOCK OUT THE OTHER RADIO AND AS REQUIRED BY COMPANY POLICY WHILE THE PNF LISTENED TO ATIS OVER THE SPEAK. THE ATC CLRNC 'NUMBER CONFUSION' COULD HAVE EASILY OCCURRED WHILE OVERHEARING THE ATIS. 2) ANTICIPATED CLRNC. STAR XING RESTR AT ALDAN IS 10000 FT. WITH THE ATIS NUMBERS IN THE BACKGND, THE ALT HEARD MAY HAVE JUMBLED THE REAL NUMBER WITH THE EXPECTED/ANTICIPATED CLRNC. 3) WITH A VERY EARLY SHOW TIME (XA30 ALARM) AFTER LATER STARTS, EVERYONE ON THE CREW WAS COMMENTING ABOUT BEING SLOW AND TIRED. IT IS POSSIBLE THAT FATIGUE WAS A FACTOR EVEN THOUGH AMPLE REST WAS PROVIDED. IN THIS CASE, FATIGUE COULD HAVE AFFECTED PERCEPTIONS OF WHAT WAS HEARD AND WHAT WAS EXPECTED. SUGGESTIONS TO AVOID THIS TYPE OF INCIDENT FROM HAPPENING AGAIN INCLUDE: 1) ENSURING THAT ONLY 1 RADIO XMISSION CAN BE HEARD AT A TIME. ATC COMS ARE PARAMOUNT TO SAFETY, SO THERE SHOULD BE NO OUTSIDE INTERFERENCE TO HEARING AND UNDERSTANDING BTWN PLTS AND CTLRS. ADDITIONALLY, ALL COMS SHOULD BE CONCISE. 2) COMPLY WITH CLRNC GIVEN BEFORE ACTING ON ANTICIPATION. CLRNCS SHOULD BE READ BACK AS CLOSE TO VERBATIM AS POSSIBLE. IF THERE IS ANY QUESTION ABOUT THE CLRNC OR ITS INTENTION, DON'T HESITATE TO ASK FOR CLARIFICATION. BEGIN ACTIONS AS DIRECTED, THEN COMPARE AGAINST ANTICIPATED ACTIONS, THEN QUERY ANY DIFFERENCES. 3) BE WARY OF YOUR OWN LIMITATIONS. BE MORE ALERT OF PHYSIOLOGICAL EFFECT ON JUDGEMENT. TEAMWORK IN THE COCKPIT IS MORE IMPORTANT WHEN ANY CREW MEMBER FEELS THE SLIGHTEST IMPAIRMENT, REGARDLESS OF THE REASON FOR THE IMPAIRMENT. LET THE OTHER CREW MEMBERS KNOW YOU ARE NOT OPERATING AT 100% AND THEY WILL BE ABLE TO WATCH YOUR ACTIONS MORE CLOSELY. CTLRS HAVE THEIR OWN UNIQUE REASON FOR ERRORS, THE MOST FORMIDABLE OF WHICH IS SHARED WITH PLTS -- WE'RE HUMAN. ERRORS DO OCCUR EVERY DAY AND IT IS ONLY THROUGH FOCUSED DILIGENCE THAT WE CAN REDUCE THE FREQ OF ERRORS. BY OUR VERY DESIGN, ERRORS AMONG HUMANS CAN NEVER BE TOTALLY ELIMINATED, THOUGH IT IS PARAMOUNT THAT WE TRY.

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.