The 1956 United States Army designation system was introduced by the United States Army to replace the designation system used by the United States Army Air Corps which had become the United States Air Force in 1948. It was used until the unified tri-service designation system for all services came into effect.
In 1956, the U.S. Army adopted a new, and relatively simple, designation system for its aviation assets. Aircraft were divided into three different types – 'A' for fixed-wing aircraft, 'H' for helicopters, or 'V' for V/STOL aircraft, and then were given a mission modifier, which, unlike the USAF system, came after the type code: 'C' for transports, 'O' for observation and reconnaissance aircraft, 'U' for utility types, and 'Z' for experimental aircraft. Aircraft types designated in this system were numbered sequentially.[1] For more information on the designation system, see 1956 United States Army aircraft designation system.