Narrative:

At the time I was leveling at 12000 ft I heard clearance to 350. The captain took the call then resumed reentering en route winds that had been previously dumped. I selected 350 in the altitude alerter. Just prior to 13000 ft approach control asked about our altitude. I told the controller climbing to 35000. Controller responded return immediately to 12000 ft which was done in approximately 5-10 seconds at most. Altitude did not exceed 13000 ft. Approach controller then turned us over to ZJX. After discussing the incident with the captain the clearance was turned to heading 350. All I heard was 350, not, heading by either the captain or the controller. The captain verified heading was given and he read it back as such. When I heard 350 the captain, busy reentering data in the FMC, didn't turn the heading selector or altitude alerter so I said 350 and entered it in the alerter. The captain later said he didn't hear me say 350. I assume even if he had, he would've thought I was just repeating heading information. As a result the altitude information was not verified by both pilots. This could have been avoided by using correct company procedures that are as follows: the PNF or pilot acknowledging the clearance sets the altitude in the alerter and points to it, repeating the clearance. The other pilot responds in kind, verifying the clearance and selection. This was the last leg of a 4-DAY trip. Possibly the FMC failure, late departure, last leg the commute back home, maybe some fatigue played some part in the deviation from procedure of verifying altitude. These procedures are in place for exactly this reason. If followed, this incident would not have occurred. By not acknowledging the clearance when given by the controller and only hearing it in part and taking action, I, in effect, cut the captain out of the loop. My fault entirely. The controller used proper terminology and was quick to point out the deviation in a timely and concise manner. Possibly if the controller had said turn to a heading of 3 'fifty' instead of 350, but how was he to know I had my head up my APU. I have been flying this model of aircraft for 4 yrs. I didn't expect to make this kind of mistake and I'm sure the captain didn't either. This aircraft was TCASII equipped. It was operating during the entire flight. No conflict on TCASII. Please excuse this spelling and neatness -- it's been a long day.

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Original NASA ASRS Text

Title: FLC OF MLG OVERSHOT ASSIGNED ALT OF 12000.

Narrative: AT THE TIME I WAS LEVELING AT 12000 FT I HEARD CLRNC TO 350. THE CAPT TOOK THE CALL THEN RESUMED REENTERING ENRTE WINDS THAT HAD BEEN PREVIOUSLY DUMPED. I SELECTED 350 IN THE ALT ALERTER. JUST PRIOR TO 13000 FT APCH CTL ASKED ABOUT OUR ALT. I TOLD THE CTLR CLBING TO 35000. CTLR RESPONDED RETURN IMMEDIATELY TO 12000 FT WHICH WAS DONE IN APPROX 5-10 SECONDS AT MOST. ALT DID NOT EXCEED 13000 FT. APCH CTLR THEN TURNED US OVER TO ZJX. AFTER DISCUSSING THE INCIDENT WITH THE CAPT THE CLRNC WAS TURNED TO HDG 350. ALL I HEARD WAS 350, NOT, HDG BY EITHER THE CAPT OR THE CTLR. THE CAPT VERIFIED HDG WAS GIVEN AND HE READ IT BACK AS SUCH. WHEN I HEARD 350 THE CAPT, BUSY REENTERING DATA IN THE FMC, DIDN'T TURN THE HDG SELECTOR OR ALT ALERTER SO I SAID 350 AND ENTERED IT IN THE ALERTER. THE CAPT LATER SAID HE DIDN'T HEAR ME SAY 350. I ASSUME EVEN IF HE HAD, HE WOULD'VE THOUGHT I WAS JUST REPEATING HDG INFO. AS A RESULT THE ALT INFO WAS NOT VERIFIED BY BOTH PLTS. THIS COULD HAVE BEEN AVOIDED BY USING CORRECT COMPANY PROCS THAT ARE AS FOLLOWS: THE PNF OR PLT ACKNOWLEDGING THE CLRNC SETS THE ALT IN THE ALERTER AND POINTS TO IT, REPEATING THE CLRNC. THE OTHER PLT RESPONDS IN KIND, VERIFYING THE CLRNC AND SELECTION. THIS WAS THE LAST LEG OF A 4-DAY TRIP. POSSIBLY THE FMC FAILURE, LATE DEP, LAST LEG THE COMMUTE BACK HOME, MAYBE SOME FATIGUE PLAYED SOME PART IN THE DEV FROM PROC OF VERIFYING ALT. THESE PROCS ARE IN PLACE FOR EXACTLY THIS REASON. IF FOLLOWED, THIS INCIDENT WOULD NOT HAVE OCCURRED. BY NOT ACKNOWLEDGING THE CLRNC WHEN GIVEN BY THE CTLR AND ONLY HEARING IT IN PART AND TAKING ACTION, I, IN EFFECT, CUT THE CAPT OUT OF THE LOOP. MY FAULT ENTIRELY. THE CTLR USED PROPER TERMINOLOGY AND WAS QUICK TO POINT OUT THE DEV IN A TIMELY AND CONCISE MANNER. POSSIBLY IF THE CTLR HAD SAID TURN TO A HDG OF 3 'FIFTY' INSTEAD OF 350, BUT HOW WAS HE TO KNOW I HAD MY HEAD UP MY APU. I HAVE BEEN FLYING THIS MODEL OF ACFT FOR 4 YRS. I DIDN'T EXPECT TO MAKE THIS KIND OF MISTAKE AND I'M SURE THE CAPT DIDN'T EITHER. THIS ACFT WAS TCASII EQUIPPED. IT WAS OPERATING DURING THE ENTIRE FLT. NO CONFLICT ON TCASII. PLEASE EXCUSE THIS SPELLING AND NEATNESS -- IT'S BEEN A LONG DAY.

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.