What happened
During the return portion of a round trip flight, the aircraft was on final approach to an alternate airport following a weather-induced diversion. While conducting an instrument approach, the pilot descended to the prescribed minimum descent altitude approximately 0.5 miles from the missed approach point. At this stage, the aircraft's speed had gradually decreased from a recommended 140 knots to approximately 75 knots. As the airplane began to vibrate, the pilot increased engine power, but the action was not timely enough to prevent a stall. The Cessna (type not specified in source) rolled left and entered an uncontrolled descent, colliding with a commercial building located 0.96 nautical miles from the runway's displaced threshold. There were no fatalities or injuries reported in the source text.
The weather at the time of the accident consisted of moderate intensity snow showers and freezing fog. During the initial approach, visibility was reported at 1.5 miles; however, by the time the pilot passed the final approach fix, visibility had decreased to 0.5 mile. The pilot was not informed that visibility had dropped below the required 1-mile minimum.
The investigation
The investigation focused on the mechanical condition of the aircraft and its deicing systems. It was noted that company mechanics had previously maintained the airplane, and during prior operations, overheat conditions had occurred where environmental ducting melted and transferred heat to the adjacent pneumatic tube responsible for providing deice air to the empennage boots. During this investigation, the deice tube was found to be completely melted closed, which rendered all of the empennage deice boots dysfunctional.