Narrative:

On the descent phase of a re-positioning flight; we were first cleared down to 15;000 ft. Prior to reaching 15;000 ft; we then got cleared to 12;000 ft and were asked to turn 10 degrees left to accommodate a possible departure from ZZZ. 12;000 ft was set in the pre-select and both pilots agree that the pre-select function was active during the descent. While continuing the descent; both pilot's eyes went outside to verify we had the field in sight. There was some haze in the air which made it hard to identify the airport from more than about 20 miles. When the pilot flying; who was second in command; looked back inside; we discovered the autopilot had failed to capture 12;000 ft and had descended to 10;600 ft. We then called the field in sight and were cleared by the approach controller for the visual approach. The rest of the flight went without a hitch until the tower controller advised us of a possible pilot deviation as we were exiting the runway.the factors that led to this failure to capture an assigned altitude are as follows: the pilot-flying's unfamiliarity with the auto-pilot. Both pilots attention being drawn outside to make sure we had the field in sight. A lapse in situational awareness of where the aircraft was in the descent. Modern avionics mixed with original auto-pilot which have no aural warnings for 1;000 ft to pre-selected altitude. Fatigue may have played a part in the lack of attention due to the trip being a pop-up trip; and the need to get the airplane back for another trip. These circumstances allowed for enough rest time; but made for a very early flight.the lessons I learned from this incident will make me pay a lot more attention while flying. The biggest lesson is to never allow situational awareness to slip away. I learned to trust avionics less and to be more diligent about knowing where I am vertically and horizontally. We learned that we cannot let our guard down; especially with a pilot-flying who has limited experience in the make/model of aircraft being flown.

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Original NASA ASRS Text

Title: BE20 flight crew reported an altitude deviation while trying to locate the destination airport in haze.

Narrative: On the descent phase of a re-positioning flight; we were first cleared down to 15;000 ft. Prior to reaching 15;000 ft; we then got cleared to 12;000 ft and were asked to turn 10 degrees left to accommodate a possible departure from ZZZ. 12;000 ft was set in the pre-select and both pilots agree that the pre-select function was active during the descent. While continuing the descent; both pilot's eyes went outside to verify we had the field in sight. There was some haze in the air which made it hard to identify the airport from more than about 20 miles. When the pilot flying; who was second in command; looked back inside; we discovered the autopilot had failed to capture 12;000 ft and had descended to 10;600 ft. We then called the field in sight and were cleared by the approach controller for the visual approach. The rest of the flight went without a hitch until the tower controller advised us of a possible pilot deviation as we were exiting the runway.The factors that led to this failure to capture an assigned altitude are as follows: The pilot-flying's unfamiliarity with the auto-pilot. Both pilots attention being drawn outside to make sure we had the field in sight. A lapse in situational awareness of where the aircraft was in the descent. Modern avionics mixed with original auto-pilot which have no aural warnings for 1;000 ft to pre-selected altitude. Fatigue may have played a part in the lack of attention due to the trip being a pop-up trip; and the need to get the airplane back for another trip. These circumstances allowed for enough rest time; but made for a very early flight.The lessons I learned from this incident will make me pay a lot more attention while flying. The biggest lesson is to never allow situational awareness to slip away. I learned to trust avionics less and to be more diligent about knowing where I am vertically and horizontally. We learned that we cannot let our guard down; especially with a pilot-flying who has limited experience in the make/model of aircraft being flown.

Data retrieved from NASA's ASRS site 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.