Narrative:

I was flying as first officer on a lear jet 25D, on a flight from pocatello, identification, to salt lake city, ut. The captain was the PF and I was the PNF. We were operating under far part 91, with the aircraft owner, his business associates, and friends aboard. During the arrival to salt lake city, I was responding to radio instructions and reading the checklist items. We accomplished the descent check while being controled by ZLC. We were handed off to slc approach and given several altitude assignments. With each new altitude assignment I read back the altitude to the controller, set the new altitude in the altitude alerter, and confirmed the new altitude with the captain. The last altitude assignment prior to the incident was 8000 ft. I repeated the altitude to slc approach, set 8000 ft in the altitude alerter, and told the captain '8000 ft.' he acknowledged the altitude. At 9000 ft I called '1000 ft to go.' he acknowledged the call, then called for the approach check. While I was heads down reading the checklist, I heard the altitude alerter sound, and looked up at the altimeter. I saw 7500 ft. I told the captain that we were cleared to 8000 ft, and he responded 'no, we are now cleared to 7000 ft.' I had been calling checklist items and thought that I must have missed a radio transmission clearing us to 7000 ft while I was reading the checklist and calling out items. I noted that the altitude alerter was still set for 8000 ft which seemed strange because if the captain had received a new altitude assignment, and had answered the radio for me, he should have changed the altitude alerter and confirmed the change with me. I was about to query the captain about the discrepancy between the altitude to which he thought we were cleared and the altitude alerter, when slc approach told us that we were not cleared below 8000 ft. The captain returned to 8000 ft. We had a brief discussion about the altitude alerter, the fact that we had made a deviation, then returned to our duties and continued the approach into slc. The remainder of the flight was uneventful. The problem was caused by the captain failing to use proper crew procedures with the radio and altitude alerter. To prevent recurrence, the captain and I have discussed crew procedures and use of the altitude alerter to prevent deviations. We have agreed that if the PNF misses an altitude call, that the pilot who hears the call must immediately inform the other pilot.

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Original NASA ASRS Text

Title: ALTDEV, DSCNT.

Narrative: I WAS FLYING AS FO ON A LEAR JET 25D, ON A FLT FROM POCATELLO, ID, TO SALT LAKE CITY, UT. THE CAPT WAS THE PF AND I WAS THE PNF. WE WERE OPERATING UNDER FAR PART 91, WITH THE ACFT OWNER, HIS BUSINESS ASSOCIATES, AND FRIENDS ABOARD. DURING THE ARR TO SALT LAKE CITY, I WAS RESPONDING TO RADIO INSTRUCTIONS AND READING THE CHKLIST ITEMS. WE ACCOMPLISHED THE DSCNT CHK WHILE BEING CTLED BY ZLC. WE WERE HANDED OFF TO SLC APCH AND GIVEN SEVERAL ALT ASSIGNMENTS. WITH EACH NEW ALT ASSIGNMENT I READ BACK THE ALT TO THE CTLR, SET THE NEW ALT IN THE ALT ALERTER, AND CONFIRMED THE NEW ALT WITH THE CAPT. THE LAST ALT ASSIGNMENT PRIOR TO THE INCIDENT WAS 8000 FT. I REPEATED THE ALT TO SLC APCH, SET 8000 FT IN THE ALT ALERTER, AND TOLD THE CAPT '8000 FT.' HE ACKNOWLEDGED THE ALT. AT 9000 FT I CALLED '1000 FT TO GO.' HE ACKNOWLEDGED THE CALL, THEN CALLED FOR THE APCH CHK. WHILE I WAS HEADS DOWN READING THE CHKLIST, I HEARD THE ALT ALERTER SOUND, AND LOOKED UP AT THE ALTIMETER. I SAW 7500 FT. I TOLD THE CAPT THAT WE WERE CLRED TO 8000 FT, AND HE RESPONDED 'NO, WE ARE NOW CLRED TO 7000 FT.' I HAD BEEN CALLING CHKLIST ITEMS AND THOUGHT THAT I MUST HAVE MISSED A RADIO XMISSION CLRING US TO 7000 FT WHILE I WAS READING THE CHKLIST AND CALLING OUT ITEMS. I NOTED THAT THE ALT ALERTER WAS STILL SET FOR 8000 FT WHICH SEEMED STRANGE BECAUSE IF THE CAPT HAD RECEIVED A NEW ALT ASSIGNMENT, AND HAD ANSWERED THE RADIO FOR ME, HE SHOULD HAVE CHANGED THE ALT ALERTER AND CONFIRMED THE CHANGE WITH ME. I WAS ABOUT TO QUERY THE CAPT ABOUT THE DISCREPANCY BTWN THE ALT TO WHICH HE THOUGHT WE WERE CLRED AND THE ALT ALERTER, WHEN SLC APCH TOLD US THAT WE WERE NOT CLRED BELOW 8000 FT. THE CAPT RETURNED TO 8000 FT. WE HAD A BRIEF DISCUSSION ABOUT THE ALT ALERTER, THE FACT THAT WE HAD MADE A DEV, THEN RETURNED TO OUR DUTIES AND CONTINUED THE APCH INTO SLC. THE REMAINDER OF THE FLT WAS UNEVENTFUL. THE PROB WAS CAUSED BY THE CAPT FAILING TO USE PROPER CREW PROCS WITH THE RADIO AND ALT ALERTER. TO PREVENT RECURRENCE, THE CAPT AND I HAVE DISCUSSED CREW PROCS AND USE OF THE ALT ALERTER TO PREVENT DEVS. WE HAVE AGREED THAT IF THE PNF MISSES AN ALT CALL, THAT THE PLT WHO HEARS THE CALL MUST IMMEDIATELY INFORM THE OTHER PLT.

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.