Chief Technician (CT or Ch Tech) is a non_commissioned rank in the Royal Air Force which is only held by airmen in technical trades and by musicians. It is between Sergeant and Flight Sergeant and like the latter has a NATO code of OR-7. Airmen in non-technical trades progress directly from sergeant to flight sergeant. Along with Junior Technician this is the only survivor of a separate ranking system for technicians introduced in 1950 and abolished in 1964. During that period it was equivalent to flight sergeant, but was made junior to that rank in 1964. The rank badge is three chevrons below a four_bladed propeller. Between 1950 and 1964 the badge was three point up chevrons below a crown. Chief technicians are usually addressed as Chief.