Chopper comes a cropper: Chinook helicopter gets bogged down in a muddy field after mechanical failure forced it to make emergency landing 20 miles from its base at RAF Benson in Oxfordshire The 40-year-old RAF Chinook was one of the first to join the RAF's fleet in 1981 and flew in the first Gulf War The aircraft developed a technical problem returning to RAF Benson on Tuesday and was forced to land The 11-tonne chopper started sinking in the mud after being forced to perform an emergency landing