 The final report was issued on 15 June 2014.The AIC found that the pilot in command pulled the power levers beyond the flight idle gate and into the ground beta range, while attempting to slow the aircraft down during descent in bad weather.Ground beta (the propeller's reverse pitch range) should only be used for decelerating or reversing on the ground, as in flight it can cause uncontrollable propeller overspeed and damage to the engines.