Vertol CH-46 Sea Knight
Design and Development

Piasecki was a pioneering developer of tandem-rotor helicopters, with the most famous previous helicopter being the H-21 "Flying Banana". Piasecki's former company Vertol began work on a new tandem rotor helicopter designated the Vertol Model 107 or V-107 in 1957. The V-107 had two Lycoming T53 turboshaft engines, producing 860 shp (640 kW) each. The first flight of the V-107 took place on April 22, 1958. The V-107 was then put through a flight demonstration tour in the US and overseas. In June 1958, the US Army awarded a contract to Vertol for ten production aircraft designated "YHC-1A".

The order was later decreased to three, so the Army could divert funds to the V-114, a larger version of the V-107. The Army's three YHC-1As were powered by GE-T-58 engines. The YHC-1As first flew in August 1959, and were followed by an improved commercial/export model, the 107-II. During 1960, the U.S. Marine Corps (USMC) evolved a requirement for a twin-turbine troop/cargo assault helicopter to replace the piston engine types then in use. Following a design competition, Boeing Vertol was selected to build its model 107M as the HRB-1, early in 1961. Boeing had acquired Vertol in 1960 and renamed the group Boeing Vertol.

The helicopter was first procured in 1961 to meet the medium-lift requirements of the Marine Corps. Its first flight in August 1962 was followed by a change in designation to CH-46A. Fleet introduction of CH-46As with the Marines and the Navy's UH-46As in November 1964. The UH-46A variant was modified for use in the vertical replenishment role.

The CH-46A had tandem contrarotating rotors that were powered by two T58-GE8-8B turboshaft engines rated at 1,250 shp (930 kW) each. The engines were mounted on each side of the rear rotor pedestal with a driveshaft to the forward rotor. The engines were coupled so either could power both rotors in an emergency. The rotors featured three blades and could be folded for on ship operations.

The CH-46A had a cargo bay with a rear loading ramp that could be removed or left open in flight for extended cargo or for parachute drops. A belly sling hook could be attached for carrying external cargo. It has a crew of three and could carry 17 passengers or 4,000 pounds (1,815 kg) of cargo. A pintle-mounted 0.50 in (12.7 mm) Browning machine gun was mounted on each side of the helicopter for self-defense.

The CH-46A had fixed tricycle landing gear, with twin wheels on all three units. The gear configuration caused a nose-up stance to facilitate cargo loading and unloading. The main gear was fitted in rear sponsons that also contained fuel tanks with a total capacity of 350 US gallons (1,438 L). The USMC received 160 CH-46As and the US Navy acquired 24 UH-46As.

Approximately 350 CH-46D and CH-46F Sea Knights were converted to "E" models. These aircraft have improved avionics, hydraulics, drive train and upgraded 1770 shp (normal) and 1870 shp (military) T58-GE-16 and 16A engines,[citation needed] and are distinguished from earlier models by the square main engine exhausts. A total of 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 before the E). The Dynamic Component Upgrade (DCU) incorporated starting in the mid-1990s provides for increased capabilities through strengthened 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 of the 107 to Kawasaki Heavy Industries. Under this arrangement, all Model 107 civilian and military aircraft built in Japan are known as KV 107.

On December 15, 2006, Columbia Helicopters, Inc acquired the type certificate for the Boeing Vertol 107-II, and is in the process of acquiring a Production Certificate from the FAA. Plans for actual production of the aircraft have not been announced.

Wikipedia: H-46 Sea Knight