Flight Details
The flight instructor and a non-instrument rated private pilot departed Pocatello, Idaho, for an instrument training flight. The instructor had filed an IFR flight plan to Rexburg, Idaho, and acknowledged an awareness of an AIRMET advising of occasional moderate rime to mixed icing in clouds below 16,000 feet.
En route to Rexburg, the aircraft entered a holding pattern at Idaho Falls, Idaho. During the hold, the aircraft accumulated ice, described as "light" by the private pilot and a "trace" by the instructor. After landing at Rexburg, both pilots reported removing ice from the aircraft.
Return Flight and Icing Encounter
The private pilot obtained an updated weather brief where icing was again discussed and filed an IFR flight plan from Rexburg back to Pocatello. The student and instructor then departed Rexburg for Pocatello. During the climb, the aircraft began picking up ice. The instructor initially attempted to divert to Idaho Falls, but upon breaking out of the clouds and noting the Rigby, Idaho, airport passing abeam, he changed his intended landing site to Rigby.
Stall and Impact
During the student's course reversal back toward Rigby, the aircraft began descending rapidly, eventually stalling prior to ground impact in a snow-covered agricultural field.
Aircraft Information
The Cessna 172N was not equipped with any anti-icing or de-icing equipment with the exception of carburetor heat. The Pilot's Operating Handbook (POH) for the aircraft cautions that "Flight into known icing conditions is prohibited" both as a placard within the aircraft and as a flight limitation.