In the 1950s, Bell Helicopter developed a turbine-engine powered utility tactical transport helicopter for the U.S. Army. This single-engine helicopter, known as the UH-1B or “Huey,” proved to be very popular with the U.S. Army and was quickly stretched to give a bigger cabin. This stretched version became known as the UH-1D in the Army and as the Bell 205 in the civilian world. In the late 1960s, a twin-engine version of the Bell 205 was developed for the U.S. and Canadian armed forces. This model became the Bell 212 in the commercial world. In the late 1970s, in response to customer demand for a smoother ride and higher speed, Bell developed a four-bladed version of the Bell 212 with higher gross weight, an upgraded transmission and more fuel and called it the Bell 412. Over the years, several improvements were made to this helicopter. The first model to incorporate a number of system improvements was called the Bell 412 SP.
The Bell 412 SP is a medium twin-engine turbine helicopter. It has a four-bladed composite rotor. The engines used for this helicopter are the Pratt & Whitney Canada PT6T-3B or -3BF Twin-Pac. The Twin-Pac uses a front-mounted combining gearbox to allow use of an upgraded version of the standard Bell 205 main transmission. This is an upgraded version of the transmission used on the Bell 212. A two-bladed tail rotor provides directional control. The fuselage is made of conventional aluminum alloys and is mounted on a fixed skid gear. The cabin is the same as that of the Bell 205 and Bell 212 and features two pilot seats up front. Behind the pilot seats is the passenger or cargo cabin. It has a flat floor and two very large sliding doors provide ready access to every part of the cabin. When used for passenger transport, it can seat up to 13. When used for cargo, it can carry up to 5,000 pounds internally or externally.
Development of the Bell 412 started in 1978 and VFR, as well as single-pilot IFR certification, was obtained in 1981. Category A certification was also obtained. The Bell 412 SP obtained its certification at the end of 1983. When compared with the original Bell 412, it has a higher maximum takeoff gross weight (11,900 pounds) and more fuel capacity (330 gallons). The Bell 412 has been in production since 1981 and the 412 SP was produced from 1984 to 1990. During this time, 129 were produced. Production of the Bell 412 was transferred from Texas to Montreal, Canada, in 1989. Texas-built Bell 412s have serial numbers starting with 33001, while Canadian ones have serial numbers that start with 36001.