The Boeing CH-46 Sea Knight is a medium-lift tandem rotor cargo helicopter, used by the United States Marine Corps (USMC) to provide all-weather, day-or-night assault transport of combat troops, supplies and equipment. Assault Support is its primary function, and the movement of supplies and equipment is secondary. Additional tasks include combat support, search and rescue, support for forward refueling and rearming points, CASEVAC and Tactical Recovery of Aircraft and Personnel (TRAP). The commercial version is the BV 107-II, commonly referred to as simply the "Vertol".
Piasecki was a pioneering developer of tandem-rotor helicopters, with the most famous previous helicopter being the Piasecki H-21 "Flying Banana". In the late 1950s, development was begun on a medium-lift tandem-rotor derivative to be marketed to both the military and commercial markets. First flight of the new helicopter, designated the Model 107, took place on October 25, 1960.
The original military version was the YHC-1A for the U.S. Army. Rejected by the Army as being too small for its needs, it was then evaluated by the U.S. Marine Corps (USMC). The YHC-1A won the design competition in 1961 and was ordered as the HRB-1 (CH-46A after 1962). It first flew in 1962, and was first delivered to the USMC in 1964.
The CH-46 Sea Knight was first procured in 1961 from the Vertol Aircraft Corporation (formerly Piasecki Helicopter) under the designation of "HRB" to meet the medium-lift requirements of the Marine Corps. The acquisition of Vertol by Boeing Aircraft Co. resulted in Boeing Vertol. In total, 625 H-46s were produced for the United States Navy and Marine Corps with the final version being the CH-46E (although an F variant was procured, the E was the later model.) Approximately 350 airframes CH-46D and CH-46F were converted to "E" models. These aircraft have improved avionics, hydraulics, drive train and upgraded 1870 shp T58-GE-16 engines, and are distinguished from earlier models by the square main engine exhausts. the dynamic Component Upgrade (DCU) incorporated starting in the mid-1990s provides for increased capabilities through strenghened drive systems and rotor controls.
The commercial variant, the BV 107-II, was first ordered by New York Airways in 1960. They took delivery of their first three aircraft, configured for 25 passengers, in July, 1962.
In 1965, Boeing Vertol sold the manufacturing rights to the commercial version to Kawasaki Heavy Industries. Prior to that, all civilian variants were built in Japan as the KV 107-II.
On December 15, 2006, Columbia Helicopters acquired all type certificates for the BV and KV 107-II, and is also in the process of acquiring all of the production certificates. Plans for actual production of the aircraft have not been announced.