Narrative:

First officer was PF. Bgm approach cleared our flight to descend to 9000 ft. Both of us acknowledged out of 13000 ft for 9000 ft. First officer called for the arrival checklist. At that time I began setting up the ILS and NDB frequencys, tuning the stations and verifying the approach data. During this time, bgm approach asked what our altitude was. I looked up to find the aircraft descending through 7600 ft and not level at 9000 ft as instructed. I instructed the first officer to level off immediately. I returned to bgm approach and told them we went through the altitude and were leveling at 9000 ft. Bgm approach told us to stay at 7600 ft while he coordinated our position with avp approach, who owned that sector of airspace below 9000 ft. I crosschecked TCASII to assure no traffic conflicts were present. Bgm cleared our position with avp and we continued to land without further incident. Factors involved in the incursion: inoperative autoplt on dash 8 --hand fly only. First officer's marginal situational awareness in altitude management during critical phase of flight. First officer's denial of wrongdoing, saying he thought we were cleared to a lower altitude below 9000 ft of which he didn't have a clue to as how low he thought we were cleared. My unfortunate ignorance of first officer's high rate of descent from 13000 ft to 9000 ft while setting aircraft avionics up for the approach. 'I do clearly remember saying out of 10000 ft for 9000 ft when the altitude alert chime went off.' I believe that had the autoplt functioned, this would have never occurred. This aircraft is not meant to be handflown on any great distances which results in flight crew mental fatigue. Mental fatigue was a major contributer to this incident. The aircraft MEL should be revised to prohibit flight without an operative autoflt system.

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Original NASA ASRS Text

Title: FO DSNDS THROUGH ASSIGNED ALT BY 1400 FT.

Narrative: FO WAS PF. BGM APCH CLRED OUR FLT TO DSND TO 9000 FT. BOTH OF US ACKNOWLEDGED OUT OF 13000 FT FOR 9000 FT. FO CALLED FOR THE ARR CHKLIST. AT THAT TIME I BEGAN SETTING UP THE ILS AND NDB FREQS, TUNING THE STATIONS AND VERIFYING THE APCH DATA. DURING THIS TIME, BGM APCH ASKED WHAT OUR ALT WAS. I LOOKED UP TO FIND THE ACFT DSNDING THROUGH 7600 FT AND NOT LEVEL AT 9000 FT AS INSTRUCTED. I INSTRUCTED THE FO TO LEVEL OFF IMMEDIATELY. I RETURNED TO BGM APCH AND TOLD THEM WE WENT THROUGH THE ALT AND WERE LEVELING AT 9000 FT. BGM APCH TOLD US TO STAY AT 7600 FT WHILE HE COORDINATED OUR POS WITH AVP APCH, WHO OWNED THAT SECTOR OF AIRSPACE BELOW 9000 FT. I XCHKED TCASII TO ASSURE NO TFC CONFLICTS WERE PRESENT. BGM CLRED OUR POS WITH AVP AND WE CONTINUED TO LAND WITHOUT FURTHER INCIDENT. FACTORS INVOLVED IN THE INCURSION: INOP AUTOPLT ON DASH 8 --HAND FLY ONLY. FO'S MARGINAL SITUATIONAL AWARENESS IN ALT MGMNT DURING CRITICAL PHASE OF FLT. FO'S DENIAL OF WRONGDOING, SAYING HE THOUGHT WE WERE CLRED TO A LOWER ALT BELOW 9000 FT OF WHICH HE DIDN'T HAVE A CLUE TO AS HOW LOW HE THOUGHT WE WERE CLRED. MY UNFORTUNATE IGNORANCE OF FO'S HIGH RATE OF DSCNT FROM 13000 FT TO 9000 FT WHILE SETTING ACFT AVIONICS UP FOR THE APCH. 'I DO CLRLY REMEMBER SAYING OUT OF 10000 FT FOR 9000 FT WHEN THE ALT ALERT CHIME WENT OFF.' I BELIEVE THAT HAD THE AUTOPLT FUNCTIONED, THIS WOULD HAVE NEVER OCCURRED. THIS ACFT IS NOT MEANT TO BE HANDFLOWN ON ANY GREAT DISTANCES WHICH RESULTS IN FLC MENTAL FATIGUE. MENTAL FATIGUE WAS A MAJOR CONTRIBUTER TO THIS INCIDENT. THE ACFT MEL SHOULD BE REVISED TO PROHIBIT FLT WITHOUT AN OPERATIVE AUTOFLT SYS.

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.