Narrative:

My first officer and I were returning from the last of 4 consecutive nights of flying a 'stand-up overnight,' this leg being from dca to mke. I was the PF, thus, the first officer was working the radios. Company procedure dictates that, when a new altitude is given, the PNF dials the new altitude into the altitude alerter and both pilots visually and orally confirm the new altitude to which cleared. We had been cleared to start our descent from FL280 to 14000 ft (?) by ZAU and shortly thereafter, handed off to the first mke approach frequency. My recollection is that we were cleared by this controller to 7000 ft. We were then handed off to the second mke approach frequency and were given an advisory for traffic, of piper make, that would be at 8000 ft or 9000 ft MSL and approaching from the south, headed north. I noted it on the TCASII but was unable to visually locate the aircraft. As I continued our descent through 9200 ft, the approach controller told us, 'return to 10000 ft.' I glanced at the altitude alerter, saw that it said 7000 ft and noted our altitude to be 9130 ft MSL. As I started the climb, we got a single TA from the TCASII. I then heard the controller tell the pilot of the piper that his traffic (us) had 'inadvertently gone below 10000 ft' and, while I don't recall hearing it, he may have issued instructions to the piper to descend. When we'd leveled at 10000 ft, I keyed the microphone back to ATC and told him that we had been cleared down to 7000 ft. His reply, 'no, you weren't.' contributing factors to this were fatigue and possible language barrier (the first officer's native language is not english). Doing consecutive stand-up overnights is extremely tiring and, by the 4TH night/morning, fatigue definitely enters into the picture. I was somewhat tired when I began the flight the night before and had hoped to grab a few hours of sleep that night at the hotel but had trouble sleeping. The problem is, how does someone really know the level of fatigue they are at until they get into a demanding situation? It was evident to me, as we got closer to mke, that, because of my fatigue, it was increasingly difficult for me to keep my focus of attention. I remember listening to a conversation on company frequency several mins before the apparent altitude but/TA happened which could have distraction me from hearing the call to descend to 10000 ft instead of 7000 ft. I did visually and orally confirm the altitude of 7000 ft that the first officer dialed in. It is quite possible that ATC may indeed have cleared us only to 10000 ft but the first officer may have heard it as 7000 ft and, due to the first officer's heavy accent, ATC may have misunderstood him repeating back the altitude as 10000 ft (ten-thousand, not one-zero-thousand -- 'seven' and 'ten' can sound very similar depending on the speaker) and, thus, never corrected his mistake. My 'clear-cut' vision to descend to 7000 ft (as was initially set in the altitude alerter) also led me to not pay enough attention to the traffic that was headed our way. Again, I firmly believe fatigue was a factor in my not questioning ATC sooner about the closing traffic, especially since we'd been 'cleared' to an altitude below this traffic. I never did see the other aircraft. What I will do to prevent something like this from happening again is to make a better and more conservative assessment of my own fatigue level. If I am given 4 stand-up overnights in a row again, by the final night of work, I am going to take into account the amount of rest I have gotten the previous 3 days and, if it hasn't been sufficient, I will call in 'fatigue' and not work that final night. I am not the first pilot at this airline to note how things can really go downhill by the 4TH night of consecutive stand-up overnights. Responding appropriately to ATC xmissions is vital and I generally repeat back altitudes as the aim, section 4-2-8 recommends but now I am also going to brief the first officer's I fly with that I insist they do the same.

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Original NASA ASRS Text

Title: MKE APCH CHALLENGES D328 FLC AS HE OBSERVES ALT OVERSHOOT. FLC DISTR BY FATIGUE AND FO LANGUAGE CAPABILITIES.

Narrative: MY FO AND I WERE RETURNING FROM THE LAST OF 4 CONSECUTIVE NIGHTS OF FLYING A 'STAND-UP OVERNIGHT,' THIS LEG BEING FROM DCA TO MKE. I WAS THE PF, THUS, THE FO WAS WORKING THE RADIOS. COMPANY PROC DICTATES THAT, WHEN A NEW ALT IS GIVEN, THE PNF DIALS THE NEW ALT INTO THE ALT ALERTER AND BOTH PLTS VISUALLY AND ORALLY CONFIRM THE NEW ALT TO WHICH CLRED. WE HAD BEEN CLRED TO START OUR DSCNT FROM FL280 TO 14000 FT (?) BY ZAU AND SHORTLY THEREAFTER, HANDED OFF TO THE FIRST MKE APCH FREQ. MY RECOLLECTION IS THAT WE WERE CLRED BY THIS CTLR TO 7000 FT. WE WERE THEN HANDED OFF TO THE SECOND MKE APCH FREQ AND WERE GIVEN AN ADVISORY FOR TFC, OF PIPER MAKE, THAT WOULD BE AT 8000 FT OR 9000 FT MSL AND APCHING FROM THE S, HEADED N. I NOTED IT ON THE TCASII BUT WAS UNABLE TO VISUALLY LOCATE THE ACFT. AS I CONTINUED OUR DSCNT THROUGH 9200 FT, THE APCH CTLR TOLD US, 'RETURN TO 10000 FT.' I GLANCED AT THE ALT ALERTER, SAW THAT IT SAID 7000 FT AND NOTED OUR ALT TO BE 9130 FT MSL. AS I STARTED THE CLB, WE GOT A SINGLE TA FROM THE TCASII. I THEN HEARD THE CTLR TELL THE PLT OF THE PIPER THAT HIS TFC (US) HAD 'INADVERTENTLY GONE BELOW 10000 FT' AND, WHILE I DON'T RECALL HEARING IT, HE MAY HAVE ISSUED INSTRUCTIONS TO THE PIPER TO DSND. WHEN WE'D LEVELED AT 10000 FT, I KEYED THE MIKE BACK TO ATC AND TOLD HIM THAT WE HAD BEEN CLRED DOWN TO 7000 FT. HIS REPLY, 'NO, YOU WEREN'T.' CONTRIBUTING FACTORS TO THIS WERE FATIGUE AND POSSIBLE LANGUAGE BARRIER (THE FO'S NATIVE LANGUAGE IS NOT ENGLISH). DOING CONSECUTIVE STAND-UP OVERNIGHTS IS EXTREMELY TIRING AND, BY THE 4TH NIGHT/MORNING, FATIGUE DEFINITELY ENTERS INTO THE PICTURE. I WAS SOMEWHAT TIRED WHEN I BEGAN THE FLT THE NIGHT BEFORE AND HAD HOPED TO GRAB A FEW HRS OF SLEEP THAT NIGHT AT THE HOTEL BUT HAD TROUBLE SLEEPING. THE PROB IS, HOW DOES SOMEONE REALLY KNOW THE LEVEL OF FATIGUE THEY ARE AT UNTIL THEY GET INTO A DEMANDING SIT? IT WAS EVIDENT TO ME, AS WE GOT CLOSER TO MKE, THAT, BECAUSE OF MY FATIGUE, IT WAS INCREASINGLY DIFFICULT FOR ME TO KEEP MY FOCUS OF ATTN. I REMEMBER LISTENING TO A CONVERSATION ON COMPANY FREQ SEVERAL MINS BEFORE THE APPARENT ALT BUT/TA HAPPENED WHICH COULD HAVE DISTR ME FROM HEARING THE CALL TO DSND TO 10000 FT INSTEAD OF 7000 FT. I DID VISUALLY AND ORALLY CONFIRM THE ALT OF 7000 FT THAT THE FO DIALED IN. IT IS QUITE POSSIBLE THAT ATC MAY INDEED HAVE CLRED US ONLY TO 10000 FT BUT THE FO MAY HAVE HEARD IT AS 7000 FT AND, DUE TO THE FO'S HVY ACCENT, ATC MAY HAVE MISUNDERSTOOD HIM REPEATING BACK THE ALT AS 10000 FT (TEN-THOUSAND, NOT ONE-ZERO-THOUSAND -- 'SEVEN' AND 'TEN' CAN SOUND VERY SIMILAR DEPENDING ON THE SPEAKER) AND, THUS, NEVER CORRECTED HIS MISTAKE. MY 'CLEAR-CUT' VISION TO DSND TO 7000 FT (AS WAS INITIALLY SET IN THE ALT ALERTER) ALSO LED ME TO NOT PAY ENOUGH ATTN TO THE TFC THAT WAS HEADED OUR WAY. AGAIN, I FIRMLY BELIEVE FATIGUE WAS A FACTOR IN MY NOT QUESTIONING ATC SOONER ABOUT THE CLOSING TFC, ESPECIALLY SINCE WE'D BEEN 'CLRED' TO AN ALT BELOW THIS TFC. I NEVER DID SEE THE OTHER ACFT. WHAT I WILL DO TO PREVENT SOMETHING LIKE THIS FROM HAPPENING AGAIN IS TO MAKE A BETTER AND MORE CONSERVATIVE ASSESSMENT OF MY OWN FATIGUE LEVEL. IF I AM GIVEN 4 STAND-UP OVERNIGHTS IN A ROW AGAIN, BY THE FINAL NIGHT OF WORK, I AM GOING TO TAKE INTO ACCOUNT THE AMOUNT OF REST I HAVE GOTTEN THE PREVIOUS 3 DAYS AND, IF IT HASN'T BEEN SUFFICIENT, I WILL CALL IN 'FATIGUE' AND NOT WORK THAT FINAL NIGHT. I AM NOT THE FIRST PLT AT THIS AIRLINE TO NOTE HOW THINGS CAN REALLY GO DOWNHILL BY THE 4TH NIGHT OF CONSECUTIVE STAND-UP OVERNIGHTS. RESPONDING APPROPRIATELY TO ATC XMISSIONS IS VITAL AND I GENERALLY REPEAT BACK ALTS AS THE AIM, SECTION 4-2-8 RECOMMENDS BUT NOW I AM ALSO GOING TO BRIEF THE FO'S I FLY WITH THAT I INSIST THEY DO THE SAME.

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.