Skyfire77 last edited by
In the late 1950s, Vertol Corporation, which had been founded as Piasecki Helicopter in 1940, began work on a new generation of twin-rotor medium and heavy helicopters based on designs such as the H-21 'Flying Banana', which powered by piston engines, were limited in their utility. Rapid evolution of jet engines during the late 40's and 1950s had pointed to turboshaft engines for improving the power available to helicopters, and two Lycoming T53 engines were incorporated into the Model 107 prototype, which first flew in 1958.
The Model 107 prototype in 1958. The fuselage was covered in air flow and direction indicator tufts for testing purposes
After completing test flights, the Model 107 embarked on a number of demonstrations across the country, as well as in select countries overseas, in order to drum up business, and in June of that year the US Army had signed a contract for 10 (later cut to three) production-standard V-107, which were given the provisional designation YHC-1A. The Army's version differed from the V-107 in that they were powered by GE-T-58 turboshafts. The YHC-1A's first flight was in August of 1959, though during the flight test program the Army judged that the chopper was too heavy for assault missions, but too light for transport, and pressed Vertol to design an enlarged version of the design. Vertol responded with the Model 114, which was later accepted as the CH-47 Chinook. Vertol continued to offer the Model 107, and in 1961 the US Marine Corps selected the design for their new cargo/troop transport as the HRB-1 Sea Knight. The USAF placed an order for its own version of the HRB-1 under the designation XH-49 (later changed to CH-46B), but canceled the order in favor of the Sikorsky S-61R/CH-3C. The following year, as part of the 1962 Tri-Service Designation System realignment, the Sea Knight was redesignated the CH-46A. The US Navy was interested in acquiring its own helicopter based on the V-107 for Vertical Replenishment, and placed an order for the generally similar UH-46A. Deliveries of both types began in 1964.
An early CH-46A Sea Knight
The Model 107/H-46's engines were mounted in the large "sail" on the aft fuselage, which also housed the second rotor, and the main landing gear were placed into two sponsons, which also contained 350 gallons of fuel, on either side. These measures gave the cylindrical fuselage the maximum volume possible, with early models capable of holding 17-25 fully equipped troops or 5,000lbs of cargo. The 107 has a pronounced squat to the rear landing legs, which assists in loading and unloading the heli, and the interior is fitted with rollers in the floor and an internal winch to allow pallets to be pulled in. An optional belly-mounted hook allowed up to 10,000lbs of cargo to be carried externally, though loads were restricted to lighter weights as the Sea Knights aged. The aft ramp could be opened in flight to allow for parachute drops, or left off entirely for outsized cargo. Up to three .50 cal machine guns could be mounted, one on either side firing out through the hull, and a third on the ramp. The rotor blades were capable of folding to minimize the footprint of the helicopter while being stored aboard ships and land bases.
Marines being evacuated in a CH-46 during the Vietnam War
Marine Sea Knights saw extensive use during the Vietnam War, transporting troops and cargo into combat, and evac'ing same afterwards, as well as performing Search And Rescue (SAR) missions, recovering downed aircraft, and resupplying forward arming and refueling points (FARP), among other tasks. Marine soldiers were fond of the CH-46, nicknaming it the "Phrog".
UH-46D Sea Knight helicopter of Helicopter Combat Support Squadron 3 (HC-3) "Merlins" lowers mail to the fantail of the guided missile destroyer USS Decatur (DDG-31), during operations in the South China Sea, December 1968.
The engines on early CH-46s suffered greatly from foreign object damage (FOD) due to debris kicked up during hover, takeoff, and landing, and in 1966 the type was grounded until better filters could be fitted. Sea Knights were grounded again the following year following a series of accidents and crashes revealed structural weaknesses in the aft sail, including the transmission brackets and rotor attachment points. Eighty CH-46As were transported to MCAS Futenma in Japan, where a joint force of USMC and Boeing Vertol technicians received numerous structural modifications and upgrades, and the Knights began to return to service beginning in December of '67, with full return by February of '68. The CH-46 also proved to be vulnerable to NVA anti-aircraft fire, with over 100 lost to enemy action by the end of the war.
A CH-46A, hit by AAA, burns as it falls in the Song Ngan Valley on 15 July 1966. The craft exploded on impact, killing 13 of the 16 Marines on board.
The Marines retained their Sea Knights after Vietnam, with the type serving during Operation URGENT FURY in Grenada in 1983, and again during the 1991 and 2003 Gulf Wars. Despite upgrades and conversions over the years, the type began to show their advancing age, with the USN retiring their UH-46Ds in 2004 in favor of the MH-60S Seahawk. Ongoing delays with the V-22 Osprey program saw the USMC flying their CH-46s into the 2010s, though the last Phrog was finally retired on 25 September 2015.
U.S. Marine CH-46 as it swoops over Huntington Beach Pier in 2011
The US Department of State operates a number of CH-46Ds, under the unofficial designation VH-46F, as VIP transports and for utility purposes.
A VH-46 from HMX-1 in the squadron's traditional glossy olive drab color.
The US military was not the only customer for the Model 107, as the type was also used by the Canadian Air Force as the CH-113 Labrador and by the Canadian Army as the CH-113A Voyageur until 2004. In 1965, Boeing Vertol entered into a licensing agreement with Kawasaki Heavy Industries, who produced Model 107s under the designation KV-107 for the Japanese Self-Defense Forces, as well as for the civilian market. The Swedish Armed Forces flew a mix of UH-46Bs and KV-107s until 2011.
JSDF KV-107 on display
A CH-113 on display
A Swedish Hkp 4 in flight
New York Airways and Pan Am offered service from the heliport at the East Pier #6 starting in 1962, and beginning in 1965 through 1968, and then again for a short time in 1977, from the Pan Am building (now the MetLife Building) in NYC to to JFK on Model 107s. Rising fuel prices and two fatal accidents, one in 1977 and another in 1979, saw the end first of helicopter service from the Pan Am building, then NY Airlines entirely.
A V-107 II in Pan Am's colors
A NY Airways 107-II unloading at JFK
A number of Model 107 IIs remain in service with civil operators such as Columbia Helicopters, Sky Aviation Corp, and Helifor Canada, acting as aerial firefighters or assisting with logging or construction projects.
CB last edited by
Good read. You suckered me in with a Canadian search and rescue one on the thumbnail.
Skyfire77 last edited by
BicycleBuck last edited by
@skyfire77 Whirlybirds! I really wish I had the funds to get my rotary wing endorsement.