Narrative:

As an first officer in a part 121 operation, the flight was at a cruising altitude of 24000 ft. Flight plan was to oma. Altitude deviation occurred 80-90 mi outside of oma. Thunderstorms were throughout the area. It seemed as if every aircraft that ZMP was controling, were requesting/assigned vectors and altitude changes with every communication. Our controller was working multiple frequencys to include some military operations which simply added to congestion on the frequency. Our flight was no longer on our original flight plan route due to vectors as previously mentioned. I believe we were on our 3RD altitude and 5TH vector by this time. With 15-20 mins left in this flight, I began calculating landing weight and performance data for our arrival into oma (to include current WX). In the middle of these calculations ZMP calls us: 'air carrier X, turn to a heading of two one zero' (this was from our current heading of I believe 160 degrees). I, the PNF respond: 'heading of two one zero for air carrier X.' I turned to the captain and repeated 'heading two one zero.' the captain replied, 'ok, two one zero -- here we go.' I continued on with my performance calculations. During my calculations, I heard center call a company flight (multiple company call signs were on our and other frequencys being operated by our controller, pretty typical). After the controller's 3RD attempt at reaching my captain (PF) queried the controller, 'sir, do you mean, company Y?' center: 'yes, air carrier X, you're at FL240, aren't you?' at this time I got this awful feeling in my stomach and as I looked up from ACARS and paused preparation per landing, I seen that our altitude preselect (which only the PNF is supposed to change, according to company profile) had been dialed down from 24000 ft to 21000 ft, and at this time we were descending through 22300 ft for 21000 ft. Captain: 'no sir, we are descending through 22300 ft for 21000 ft.' center: 'I told you to turn to a heading of two one zero not descend to two one zero.' captain: 'do you want us to climb back to two four zero?' center: 'air carrier X, turn to a heading of two one zero, descend to flight level two one zero and contact center on XXX.xx.' captain repeated back direction and continued as directed. I signed on with the next controller and he instructed us to descend to 11000 ft. After the incident, we never heard anything more from center regarding the incident. I feel responsible for this for I did not back the captain up to insure that he dialed in 210 on the heading bug versus his altitude preselect. I simply resumed getting WX and landing data into oma. Contributing factors: thunderstorms/WX, frequency congestion, multiple vectors/altitude changes, workload at the specific point of the flight, possible pilot fatigue -- only had 8 hours and 1 min off between duty days - flight time logged on previous day was 7 hours and 5 mins -- duty day was 14 hours and 45 mins. 'But it's legal.'

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION FROM ASSIGNED ALT BY AN OVERBURDENED FLT CREW ON FREQ WITH ZMP, MN.

Narrative: AS AN FO IN A PART 121 OP, THE FLT WAS AT A CRUISING ALT OF 24000 FT. FLT PLAN WAS TO OMA. ALTDEV OCCURRED 80-90 MI OUTSIDE OF OMA. TSTMS WERE THROUGHOUT THE AREA. IT SEEMED AS IF EVERY ACFT THAT ZMP WAS CTLING, WERE REQUESTING/ASSIGNED VECTORS AND ALT CHANGES WITH EVERY COM. OUR CTLR WAS WORKING MULTIPLE FREQS TO INCLUDE SOME MIL OPS WHICH SIMPLY ADDED TO CONGESTION ON THE FREQ. OUR FLT WAS NO LONGER ON OUR ORIGINAL FLT PLAN RTE DUE TO VECTORS AS PREVIOUSLY MENTIONED. I BELIEVE WE WERE ON OUR 3RD ALT AND 5TH VECTOR BY THIS TIME. WITH 15-20 MINS LEFT IN THIS FLT, I BEGAN CALCULATING LNDG WT AND PERFORMANCE DATA FOR OUR ARR INTO OMA (TO INCLUDE CURRENT WX). IN THE MIDDLE OF THESE CALCULATIONS ZMP CALLS US: 'ACR X, TURN TO A HDG OF TWO ONE ZERO' (THIS WAS FROM OUR CURRENT HDG OF I BELIEVE 160 DEGS). I, THE PNF RESPOND: 'HDG OF TWO ONE ZERO FOR ACR X.' I TURNED TO THE CAPT AND REPEATED 'HDG TWO ONE ZERO.' THE CAPT REPLIED, 'OK, TWO ONE ZERO -- HERE WE GO.' I CONTINUED ON WITH MY PERFORMANCE CALCULATIONS. DURING MY CALCULATIONS, I HEARD CTR CALL A COMPANY FLT (MULTIPLE COMPANY CALL SIGNS WERE ON OUR AND OTHER FREQS BEING OPERATED BY OUR CTLR, PRETTY TYPICAL). AFTER THE CTLR'S 3RD ATTEMPT AT REACHING MY CAPT (PF) QUERIED THE CTLR, 'SIR, DO YOU MEAN, COMPANY Y?' CTR: 'YES, ACR X, YOU'RE AT FL240, AREN'T YOU?' AT THIS TIME I GOT THIS AWFUL FEELING IN MY STOMACH AND AS I LOOKED UP FROM ACARS AND PAUSED PREPARATION PER LNDG, I SEEN THAT OUR ALT PRESELECT (WHICH ONLY THE PNF IS SUPPOSED TO CHANGE, ACCORDING TO COMPANY PROFILE) HAD BEEN DIALED DOWN FROM 24000 FT TO 21000 FT, AND AT THIS TIME WE WERE DSNDING THROUGH 22300 FT FOR 21000 FT. CAPT: 'NO SIR, WE ARE DSNDING THROUGH 22300 FT FOR 21000 FT.' CTR: 'I TOLD YOU TO TURN TO A HDG OF TWO ONE ZERO NOT DSND TO TWO ONE ZERO.' CAPT: 'DO YOU WANT US TO CLB BACK TO TWO FOUR ZERO?' CTR: 'ACR X, TURN TO A HDG OF TWO ONE ZERO, DSND TO FLT LEVEL TWO ONE ZERO AND CONTACT CTR ON XXX.XX.' CAPT REPEATED BACK DIRECTION AND CONTINUED AS DIRECTED. I SIGNED ON WITH THE NEXT CTLR AND HE INSTRUCTED US TO DSND TO 11000 FT. AFTER THE INCIDENT, WE NEVER HEARD ANYTHING MORE FROM CTR REGARDING THE INCIDENT. I FEEL RESPONSIBLE FOR THIS FOR I DID NOT BACK THE CAPT UP TO INSURE THAT HE DIALED IN 210 ON THE HDG BUG VERSUS HIS ALT PRESELECT. I SIMPLY RESUMED GETTING WX AND LNDG DATA INTO OMA. CONTRIBUTING FACTORS: TSTMS/WX, FREQ CONGESTION, MULTIPLE VECTORS/ALT CHANGES, WORKLOAD AT THE SPECIFIC POINT OF THE FLT, POSSIBLE PLT FATIGUE -- ONLY HAD 8 HRS AND 1 MIN OFF BTWN DUTY DAYS - FLT TIME LOGGED ON PREVIOUS DAY WAS 7 HRS AND 5 MINS -- DUTY DAY WAS 14 HRS AND 45 MINS. 'BUT IT'S LEGAL.'

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.