A copilot in training and the flying pilot aboard a Bombardier Challenger are being blamed in a report by Finnish safety investigators for the uncontrolled pitch oscillations the aircraft encountered shortly after takeoff on a familiarization flight from Moscow to St. Petersburg on Dec. 23, 2010. The Finnish-registered aircraft carried three passengers and three crewmembers. Two passengers were injured and the cabin interior sustained an uncategorized level of damage. The aircraft returned to Moscow’s Sheremetyevo Airport, where the injured were transported to a local hospital.

The incident began as the aircraft climbed away from Moscow, when an Eicas message indicated an “autopilot stabilizer trim failure.” Although he was not the pilot flying, the captain disengaged the autopilot, which resulted in porpoising oscillations that the new pilot initially was unable to stop.

Investigators listed as contributing factors the pilots’ unfamiliarity with the characteristics and operating principle of the aircraft’s artificial pitch feel system as well as shortcomings in system training. Further shortcomings were also observed in the flight crew’s checks and in cooperation between the pilots. High airspeed was another contributing factor to the considerable acceleration forces experienced during the upset.