Accident Overview
The airplane was substantially damaged when it impacted terrain following an inadvertent stall and uncontrolled descent. The instructional flight was piloted by a certified flight instructor (CFI). He was initiating a missed approach when the loss of control occurred.
Flight Details
The CFI reported that the aircraft was established in cruise flight on an Instrument Flight Rules (IFR) flight plan when it encountered light rime icing. He initially attempted to climb to avoid the icing area, however, aircraft performance had deteriorated significantly climbing through 7,400 feet mean sea level (msl). He then elected to descend. He reported that the flight "broke out of [the] clouds at 4,700 [feet] msl and leved off at 4,000 [feet msl]". He estimated that 1/4 inch of ice had accumulated on the wing leading edges at that point. The pilot decided to divert to an intermediate airport in order to remove the ice from the aircraft and evaluate the weather conditions. The flight was subsequently cleared for a visual approach.
Missed Approach and Stall
The CFI reported that after the approach, the flight was not in a position to land and he elected to execute a missed approach. He stated: "I applied full power and raised the nose to start a climb. I then banked the aircraft to the left to circle back around for landing. At this point the aircraft bucked and shook as if it was stalling. I lowered the nose to stop the stall and noticed the ground coming up quickly. I tried to slow the descent but the aircraft continued descending and impacted the ground."
Post-accident Observations
Airport personnel reported that 5/16 - 3/8 inch of ice accumulation was observed on all wing and stabilizer leading edges. An AIRMET for icing conditions was in effect at the time of the accident. Pilot reports for light rime and moderate mixed icing were on file prior to the flight's departure. Federal Aviation Administration publications note that ice accretion on an aircraft's wing can "significantly alter the aerodynamic characteristics of the wing" and that a "stall may occur with little or none of the usual cues in advance." The Cessna model 172R information manual states that flight into known icing conditions is prohibited.