What happened
A Beechcraft King Air 200, registration C-FCGL, was conducting an instrument flight rules medical evacuation mission from Prince George to Cranbrook, British Columbia, with the intention of transporting patients to Kelowna. The flight crew, which included two pilots and two paramedics, was cruising at 15,000 feet when the aircraft encountered icing conditions that surpassed the capacity of its onboard de-icing equipment.
As ice accumulated, the aircraft's airspeed dropped significantly. Despite the crew applying maximum engine power, the aircraft entered a power-on stall and began an uncontrolled descent. The aircraft dropped from 15,000 feet to as low as 10,800 feet, which was below the minimum altitude required to clear local terrain. During this period, the crew experienced heavy buffeting of the airframe and control surfaces. Vancouver air traffic control provided emergency vectors to guide the aircraft over the Arrow Lakes area to avoid high terrain. Eventually, the aircraft exited the clouds, the ice began to shed, and the crew was able to stabilize the flight and land safely in Keluna without further incident.
The investigation
The investigation focused on the weather briefing process and the performance of the aircraft's ice-protection systems. Investigators found that while the pilot had reviewed several weather reports, a specific graphical area forecast containing warnings of moderate icing was not reviewed. This lack of information meant the crew was unaware of the icing risks along their planned route. Additionally, the investigation examined the mechanical impact of the event, noting that both engines were removed from service because they had been operated beyond their maximum temperature and torque limits for approximately seven minutes during the emergency.
Findings
- The primary cause of the descent was severe in-flight icing that exceeded the capabilities of the aircraft's ice-protection equipment.
- The pilot-in-command did not review the graphical area forecast, which would have identified the icing conditions.
- The crew did not identify the rapid ice accumulation early enough to divert the flight and avoid the hazardous conditions.
- The aircraft entered a power-on stall and an uncontrollable descent as a direct result of the ice accumulation.
Safety action
Following the incident, the operator issued a memorandum instructing flight crews to review all available weather data prior to departure. The company also implemented a new training syllabus, examination, and emergency checklist specifically addressing severe icing conditions and exit strategies.