Narrative:

My copilot and I were flying from tvf in a falcon 20. As we approached tvf, I determined that the WX was below minimums for the approach but acceptable at our WX alternate (900 ft overcast and 3/4 NM visibility). I contacted ZMP to request clearance to our alternate of gfk. At this time we were at 10000 ft MSL, cleared to gfk and given pilot's discretion to 6000 ft MSL. We turned direct to our new destination (only 75 NM ahead) and began a slow descent to 6000 ft. Once established on the new heading, I briefed my copilot (PF for this leg) on our planned approach, WX conditions at gfk, and missed approach procedures. We were IMC from about 12000 ft MSL down, with light to moderate icing. At 6000 ft MSL, we were handed off to gfk approach control and given a pilot's discretion to 2600 ft MSL. The approach plate showed an MSA of 2700 ft MSL, so I reconfirmed the altitude with gfk approach. They confirmed our clearance to 2600 ft MSL. We were 25 NM from the airport on a vector to intercept an outbound leg (downwind) for the approach to ILS runway 35L. I informed my copilot of the MSA and told him to begin a slow descent to 3000 ft and hold that altitude until established on the ILS. At approximately 3500 ft MSL, approach informed us of a new ATIS and I advised them that I would pick it up. I believe this was my mistake, because I then put my head down to tune the ATIS frequency and to write down the new WX. During this short time, my copilot continued his descent through 3000 ft MSL, past the assigned altitude (set in the alerter) of 2600 ft MSL and down to 2200 ft MSL. Passing through -200 ft, the alerter sounded off. At that moment, I looked up to see our new altitude and descent rate and firmly announced our altitude deviation and assigned altitude. By the time the descent was arrested and a climb established, we had descended 400 ft below our assigned altitude and 500 ft below the published MSA. I believe my first mistake was to take my attention away from the approach sequence. At this critical phase of flight, I should have requested the controller to update me on the new ATIS. Secondly, even though my copilot had more than 500 hours in that aircraft and over 2000 total hours and should have been capable of maintaining an assigned altitude, I should have maintained a higher level of situational awareness in that phase of flight and WX conditions.

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Original NASA ASRS Text

Title: A FALCON 20 CAPT, PNF, RPTED AN ALT OVERSHOOT DURING APCH TO GFK.

Narrative: MY COPLT AND I WERE FLYING FROM TVF IN A FALCON 20. AS WE APCHED TVF, I DETERMINED THAT THE WX WAS BELOW MINIMUMS FOR THE APCH BUT ACCEPTABLE AT OUR WX ALTERNATE (900 FT OVCST AND 3/4 NM VISIBILITY). I CONTACTED ZMP TO REQUEST CLRNC TO OUR ALTERNATE OF GFK. AT THIS TIME WE WERE AT 10000 FT MSL, CLRED TO GFK AND GIVEN PLT'S DISCRETION TO 6000 FT MSL. WE TURNED DIRECT TO OUR NEW DEST (ONLY 75 NM AHEAD) AND BEGAN A SLOW DSCNT TO 6000 FT. ONCE ESTABLISHED ON THE NEW HDG, I BRIEFED MY COPLT (PF FOR THIS LEG) ON OUR PLANNED APCH, WX CONDITIONS AT GFK, AND MISSED APCH PROCS. WE WERE IMC FROM ABOUT 12000 FT MSL DOWN, WITH LIGHT TO MODERATE ICING. AT 6000 FT MSL, WE WERE HANDED OFF TO GFK APCH CTL AND GIVEN A PLT'S DISCRETION TO 2600 FT MSL. THE APCH PLATE SHOWED AN MSA OF 2700 FT MSL, SO I RECONFIRMED THE ALT WITH GFK APCH. THEY CONFIRMED OUR CLRNC TO 2600 FT MSL. WE WERE 25 NM FROM THE ARPT ON A VECTOR TO INTERCEPT AN OUTBOUND LEG (DOWNWIND) FOR THE APCH TO ILS RWY 35L. I INFORMED MY COPLT OF THE MSA AND TOLD HIM TO BEGIN A SLOW DSCNT TO 3000 FT AND HOLD THAT ALT UNTIL ESTABLISHED ON THE ILS. AT APPROX 3500 FT MSL, APCH INFORMED US OF A NEW ATIS AND I ADVISED THEM THAT I WOULD PICK IT UP. I BELIEVE THIS WAS MY MISTAKE, BECAUSE I THEN PUT MY HEAD DOWN TO TUNE THE ATIS FREQ AND TO WRITE DOWN THE NEW WX. DURING THIS SHORT TIME, MY COPLT CONTINUED HIS DSCNT THROUGH 3000 FT MSL, PAST THE ASSIGNED ALT (SET IN THE ALERTER) OF 2600 FT MSL AND DOWN TO 2200 FT MSL. PASSING THROUGH -200 FT, THE ALERTER SOUNDED OFF. AT THAT MOMENT, I LOOKED UP TO SEE OUR NEW ALT AND DSCNT RATE AND FIRMLY ANNOUNCED OUR ALTDEV AND ASSIGNED ALT. BY THE TIME THE DSCNT WAS ARRESTED AND A CLB ESTABLISHED, WE HAD DSNDED 400 FT BELOW OUR ASSIGNED ALT AND 500 FT BELOW THE PUBLISHED MSA. I BELIEVE MY FIRST MISTAKE WAS TO TAKE MY ATTN AWAY FROM THE APCH SEQUENCE. AT THIS CRITICAL PHASE OF FLT, I SHOULD HAVE REQUESTED THE CTLR TO UPDATE ME ON THE NEW ATIS. SECONDLY, EVEN THOUGH MY COPLT HAD MORE THAN 500 HRS IN THAT ACFT AND OVER 2000 TOTAL HRS AND SHOULD HAVE BEEN CAPABLE OF MAINTAINING AN ASSIGNED ALT, I SHOULD HAVE MAINTAINED A HIGHER LEVEL OF SITUATIONAL AWARENESS IN THAT PHASE OF FLT AND WX CONDITIONS.

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.