On 11 January 2017, control of a Cessna Citation 560 departing Oslo on a short positioning flight was lost control during flap retraction when a violent nose-down manoeuvre occurred. The First Officer took control when the Captain did not react and recovered with a 6 g pullout which left only 170 feet of ground clearance. A MAYDAY - subsequently cancelled when control was regained - was declared and the intended flight was then completed without further event. The Investigation concluded that tailplane stall after the aircraft was not de-iced prior to departure was the probable cause of the upset.