The Boeing Vertol CH-46 Sea Knight is a medium-lift tandem-rotor transport helicopter powered by twin turboshaft aircraft engines designed by Vertol and manufactured by Boeing Vertol following Vertol's acquisition by Boeing.
Development of the Sea Knight, which was originally designated by the firm as the Vertol Model 107, commenced during 1956. It was envisioned as a successor to the first generation of rotorcraft, such as the H-21 "Flying Banana", that had been powered by piston engines; in its place, the V-107 made use of the emergent turboshaft engine. On 22 April 1958, the V-107 prototype performed its maiden flight. During June 1958, the U.S. Army awarded a contract for the construction of ten production-standard aircraft, designated as the YHC-1A, based on the V-107; this initial order was later cut down to three YHC-1As though. During 1961, the U.S. Marine Corps, who had been studying its requirements for a medium-lift, twin-turbine troop/cargo assault helicopter, selected Boeing Vertol's model 107M as the basis from which to manufacture a suitable rotorcraft to meet their needs. Known colloquially as the "Phrog" and formally as the "Sea Knight", it was operated across all U.S. Marine Corps' operational environments between its introduction during the Vietnam War and its frontline retirement during 2014.
The Sea Knight was operated by the United States Marine Corps (USMC) to provide all-weather, day-or-night assault transport of combat troops, supplies and equipment until it was replaced by the MV-22 Osprey during the 2010s. Additional tasks that the type was used for in USMC service included combat support, search and rescue (SAR), support for forward refueling and rearming points, CASEVAC and Tactical Recovery of Aircraft and Personnel (TRAP). The Sea Knight also functioned as the United States Navy's standard medium-lift utility helicopter prior to the type being phased out of service in favor of the MH-60S Knighthawk during the early 2000s. Several overseas operators acquired the rotorcraft as well. Canada operated the Sea Knight, designated as CH-113; the type was used predominantly in the search and rescue (SAR) role until 2004. Other export customers for the type included Japan, Sweden, and Saudi Arabia. The commercial version of the rotorcraft is the BV 107-II; it was commonly referred to simply as the "Vertol".
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Development
Origins
During the 1940s and 1950s, American rotorcraft manufacturer Piasecki Helicopter emerged as a pioneering developer of tandem-rotor helicopters; perhaps the most famous of these being the piston-powered H-21 "Flying Banana", an early utility and transport helicopter. During 1955, Piasecki was officially renamed as Vertol (standing for vertical take-off and landing); it was around this time that work commenced on the development of a new generation of tandem rotor helicopter. During 1956, the new design received the internal company designation of Vertol Model 107, or simply V-107; this rotorcraft differed from its predecessors by harnessing the newly developed turboshaft engine instead of piston-based counterparts. During that year, construction of a prototype, powered by a pair of Lycoming T53 turboshaft engines, each one being capable of producing 877 shp (640 kW), commenced.
On 22 April 1958, the V-107 prototype performed its maiden flight. In order to garner publicity for the newly developed rotorcraft, it was decided to use the prototype to conduct a series of publicised flight demonstrations during a tour across the United States and several overseas nations. During June 1958, it was announced that the U.S. Army had awarded a contract to Vertol for the construction of ten production-standard aircraft based on the V-107, which were designated as the YHC-1A. However, this order was later decreased to three helicopters; according to aviation author Jay P. Spenser, the cutback had been enacted in order that the U.S. Army would be able to divert funds for the development of the rival V-114 helicopter, which was also a turbine-powered tandem rotor design but substantially larger than the V-107. All of the U.S. Army's three YHC-1As were powered by pairs of GE-T-58 engines. During August 1959, the first YHC-1A-model rotorcraft conducted its first flight; independently, it was shortly followed by the maiden flight of an improved model intended for the commercial and export markets, designated as the 107-II.
During 1960, the U.S. Marine Corps evolved a requirement for a medium-lift, twin-turbine troop/cargo assault helicopter to replace the various piston-engined types that were then in widespread use with the service. That same year, American aviation company Boeing acquired Vertol, after which the group was consequently renamed Boeing Vertol. Following a competition between several competing designs, during early 1961, it was announced that Boeing Vertol had been selected to manufacture its model 107M for the U.S. Marine Corps, where it was designated as the HRB-1. During 1962, the U.S. Air Force placed its own order for 12 XCH-46B Sea Knight helicopters, which used the XH-49A designation; however, the service later decided to cancelled the order due to delays in its delivery; instead, the U.S. Air Force opted to procure the rival Sikorsky S-61R in its place.
Following the Sea Knight's first flight in August 1962, the military designation was changed to CH-46A. During November 1964, the introduction of the Marines' CH-46A and the Navy's UH-46As commenced. The UH-46A variant was a modified version of the rotorcraft to perform the vertical replenishment mission. The CH-46A was equipped with a pair of T58-GE8-8B turboshaft engines, each being rated at 1,250 shp (930 kW); these allowed the Sea Knight to carry up to 17 passengers or a maximum of 4,000 pounds (1,815 kg) of cargo.
Further developments
During 1966, production of the improved CH-46D commenced with deliveries following shortly thereafter. This model featured various improvements, including modified rotor blades and the adoption of more powerful T58-GE-10 turboshaft engines, rated at 1,400 shp (1,040 kW) each. The increased power of these new engines allowed the CH-46D to carry an increased payload, such as up to 25 troops or a maximum of 7,000 pounds (3,180 kg) of cargo. During late 1967, the improved model was introduced to the Vietnam theater, where it supplemented the U.S. Marine Corps' existing CH-46A fleet, which had proven to be relatively unreliable and problematic in service. Along with the USMC's CH-46Ds, the U.S. Navy also acquired a small number of UH-46Ds for ship resupply purposes. In addition, approximately 33 CH-46As were progressively re-manufactured to the CH-46D standard.
Between 1968 and 1971, the U.S. Marine Corps received a number of CH-46F standard rotorcraft. This model retained the T58-GE-10 engines used on the CH-46D while featuring revised avionics and featured a number of other modifications. The CH-46F was the final production model of the type. During its service life, the Sea Knight received a variety of upgrades and modifications. Over time, the majority of the U.S. Marine Corps' Sea Knights were upgraded to the improved CH-46E standard. This model featured fiberglass rotor blades, reinforcement measures throughout the airframe, along with the refitting of further uprated T58-GE-16 engines, capable of producing 1,870 shp (1,390 kW) each; in addition, several CH-46Es were modified to double their maximum fuel capacity. Starting in the mid-1990s, the Dynamic Component Upgrade (DCU) programmes was enacted, focusing on the implementation of strengthened drive systems and modified rotor controls.
The commercial variant, the BV 107-II, was first ordered by New York Airways during 1960. During July 1962, they took delivery of their first three aircraft, which was configured to seat up to 25 passengers. During 1965, Boeing Vertol sold the manufacturing rights of the 107 to Japanese conglomerate Kawasaki Heavy Industries. Under this arrangement, all Model 107 civilian and military aircraft built in Japan were referred to by the KV 107 designation. On 15 December 2006, Columbia Helicopters, Inc acquired the type certificate for the BV 107-II; at the time, the company was reportedly in the process of acquiring a Production Certificate from the Federal Aviation Administration (FAA). Plans for actual production of the aircraft were not announced.
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Design
The Boeing Vertol CH-46 Sea Knight is a medium-lift tandem-rotor transport helicopter, furnished with a set of counter-rotating main rotors in a tandem-rotor configuration. It was typically powered by a pair of General Electric T58 turboshaft engines, which were mounted on each side of the rear rotor pedestal; power to the forward rotor was transferred from the rear-mounted engines via a drive shaft. For redundancy, both engines are coupled so that either one would be capable of powering both of the main rotors in the event of a single engine failure or a similar emergency situation. Each of the rotors feature three blades, which can be folded to better facilitate storage and naval operations. The CH-46 features a fixed tricycle landing gear, complete with twin wheels on all three legs of the landing gear; this configuration results in a nose-up stance, helping to facilitate cargo loading and unloading. Two of the main landing gear were installed within protruding rear sponsons; the free interior space of the sponsons are also used to house fuel tanks, possessing a total capacity of 350 US gallons (1,438 L).
The interior of the CH-46 was largely taken up by its cargo bay, complete with a rear loading ramp that could be removed or left open in flight for the carriage of extended cargoes or for parachute drops. Various furnishings were normally provided to aid in its use as a utility rotorcraft, such as an internal winch mounted within the forward cabin, which can be used to assisting loading by pulling external cargo on pallets into the aircraft via the ramp and rollers, and an optionally-attached belly-mounted cargo hook, which would be usually rated at 10,000 lb (4,500 kg) for carrying cargoes externally underneath the Sea Knight; despite the hook having been rated at 10,000 lb (4,500 kg), this was safety restricted to less payload as they got older. When operated in a typical configuration, the CH-46 would usually be operated by a crew of three; a larger crew could be accommodated when required, which would be dependent upon mission specifics. For example, a search and rescue (SAR) variant would usually carry a crew of five (Pilot, Co-Pilot, Crew Chief, Swimmer, and Medic) to facilitate all aspects of such operations. For self-defense, a pintle-mounted 0.50 in (12.7 mm) Browning machine gun could be mounted on each side of the helicopter. Service in southeast Asia resulted in the addition of armor along with the machine guns.
Operational history
United States
Known colloquially as the "Phrog", the Sea Knight was used in all U.S. Marine operational environments between its introduction during the Vietnam War and its frontline retirement in 2014. The type's longevity and reputation for reliability led to mantras such as "phrogs phorever" and "never trust a helicopter under 30". CH-46s transported personnel, evacuated wounded, supplied forward arming and refueling points (FARP), performed vertical replenishment, search and rescue, recovered downed aircraft and crews and other tasks.
During the Vietnam War, the CH-46 was one of the prime US troop transport helicopters in the theatre, slotting between the smaller Bell UH-1 Iroquois and larger Sikorsky CH-53 Sea Stallion. During the 1972 Easter Offensive, Sea Knights saw heavy use to convey US and South Vietnamese ground forces to and around the front lines. CH-46 operations were plagued by major technical problems; the engines, being prone to foreign object damage (FOD) from debris being ingested when hovering close to the ground and subsequently suffering a compressor stall, had a lifespan as low as 85 flight hours; on 21 July 1966, all CH-46s were grounded until more efficient filters had been fitted. By the end of US military operations in Vietnam, over a hundred Sea Knights had been lost to enemy fire.
In February 1968 the Marine Corps Development and Education Command obtained several CH-46s to perform herbicide dissemination tests using HIDAL (Helicopter, Insecticide Dispersal Apparatus, Liquid) systems; testing indicated the need for redesign and further study. Tandem-rotor helicopters were often used to transport nuclear warheads; the CH-46A was evaluated to deploy Naval Special Forces with the Special Atomic Demolition Munition (SADM). Nuclear Weapon Accident Exercise 1983 (NUWAX-83), simulating the crash of a Navy CH-46E carrying 3 nuclear warheads, was conducted at the Nevada Test Site on behalf of several federal agencies; the exercise, which used real radiological agents, was depicted in a Defense Nuclear Agency-produced documentary.
U.S. Marine CH-46s were used to deploy the 8th Marine Regiment into Grenada during Operation Urgent Fury, evacuated the surviving crew-member of a downed AH-1 Cobra, and then carried infantry from the 75th Ranger Regiment to secure and evacuate U.S. students at the Grand Anse campus of St. George's University, though one crashed after colliding with a palm tree.
CH-46E Sea Knights were also used by the U.S. Marine Corps during the 2003 invasion of Iraq. In one incident on 1 April 2003, Marine CH-46Es and CH-53Es carried U.S. Army Rangers and Special Operations troops on an extraction mission for captured Army Private Jessica Lynch from an Iraqi hospital. During the subsequent occupation of Iraq and counter-insurgency operations, the CH-46E was heavily used in the CASEVAC role, being required to maintain 24/7 availability regardless of conditions. According to authors Williamson Murray and Robert H Scales, the Sea Knight displayed serious reliability and maintenance problems during its deployment to Iraq, as well as "limited lift capabilities". Following the loss of numerous US helicopters in the Iraqi theatre, the Marines opted to equip their CH-46s with more advanced anti-missile countermeasures.
The U.S. Navy retired the type on 24 September 2004, replacing it with the MH-60S Seahawk; the Marine Corps maintained its fleet as the MV-22 Osprey was fielded. In March 2006 Marine Medium Helicopter Squadron 263 (HMM-263) was deactivated and redesignated VMM-263 to serve as the first MV-22 squadron. The replacement process continued through the other medium helicopter squadrons into 2014. On 5 October 2014, the Sea Knight performed its final service flight with the U.S. Marine Corps at Marine Corps Air Station Miramar. HMM-364 was the last squadron to use it outside the United States, landing it aboard the USS America (LHA-6) on her maiden transit. On 9 April 2015, the CH-46 was retired by the Marine Medium Helicopter Training Squadron 164, the last Marine Corps squadron to transition to the MV-22. The USMC retired the CH-46 on 1 August 2015 in a ceremony at the Udvar-Hazy Center near Washington DC. The HH-46E variant continued to operate in a Search and Rescue capacity at Marine Corps Air Station Cherry Point. The last flight of a Marine Corps H-46 took place on 25 September 2015 at MCAS Cherry Point and ended the 57-year Cherry Point Search and Rescue program.
Canada
The Royal Canadian Air Force procured six CH-113 Labrador helicopters for the SAR role and the Canadian Army acquired 12 of the similar CH-113A Voyageur for the medium-lift transport role. The RCAF Labradors were delivered first with the first one entering service on 11 October 1963. When the larger CH-147 Chinook was procured by the Canadian Forces in the mid-1970s, the Voyageur fleet was converted to Labrador specifications to undertake SAR missions. The refurbished Voyageurs were re-designated as CH-113A Labradors, thus a total of 15 Labradors were ultimately in service.
The Labrador was fitted with a watertight hull for marine landings, a 5,000 kilogram cargo hook and an external rescue hoist mounted over the right front door. It featured a 1,110 kilometer flying range, emergency medical equipment and an 18-person passenger capacity. By the 1990s, heavy use and hostile weather conditions had taken their toll on the Labrador fleet, resulting in increasing maintenance costs and the need for prompt replacement. In 1981, a mid-life upgrade of the fleet was carried out by Boeing Canada in Arnprior, Ontario. Known as the SAR-CUP (Search and Rescue Capability Upgrade Program), the refit scheme included new instrumentation, a nose-mounted weather radar, a tail-mounted auxiliary power unit, a new high-speed rescue hoist mounted over the side door and front-mounted searchlights. A total of six CH-113s and five CH-113As were upgraded with the last delivered in 1984.
In 1992, it was announced that the Labradors were to be replaced by 15 new helicopters, a variant of the AgustaWestland EH101, designated CH-149 Chimo. The order was subsequently cancelled by the Jean Chrétien Liberal government in 1993, resulting in cancellation penalties, as well as extending the service life of the Labrador fleet. However, in 1998, a CH-113 from CFB Greenwood crashed on Quebec's Gaspé Peninsula while returning from a SAR mission, resulting in the deaths of all crewmembers on board. The crash placed pressure upon the government to procure a replacement, thus an order was placed with the manufacturers of the EH101 for 15 aircraft to perform the search-and-rescue mission, designated CH-149 Cormorant. CH-149 deliveries began in 2003, allowing the last CH-113 to be retired in 2004. In October 2005 Columbia Helicopters of Aurora, Oregon purchased eight of the retired CH-113 Labradors to add to their fleet of 15 Vertol 107-II helicopters.
Sweden
In 1963, Sweden procured ten UH-46B from the US as a transport and anti-submarine helicopter for the Swedish armed forces, designated Hkp 4A. In 1973, a further eight Kawasaki-built KV-107, which were accordingly designated Hkp 4B, were acquired to replace the older Piasecki H-21. During the Cold War, the fleet's primary missions were anti-submarine warfare and troop transportation, they were also frequently employed in the search and rescue role. In the 1980s, the Hkp 4A was phased out, having been replaced by the Eurocopter AS332 Super Puma; the later Kawasaki-built Sea Knights continued in operational service until 2011, they were replaced by the UH-60 Black Hawk & NH90.
Civilian
The civilian version, designated as the BV 107-II Vertol, was developed prior to the military CH-46. It was operated commercially by New York Airways, Pan American World Airways and later on by Columbia Helicopters. Among the diversity of tasks was pulling a hover barge, and constructing transmission towers for overhead power lines.
In December 2006, Columbia Helicopters purchased the type certificate of the Model 107 from Boeing, with the aim of eventually producing new-build aircraft themselves.
Variants
American versions
Canadian versions
Swedish versions
Japanese versions
Source:
Operators
Military and government
- United States Department of State
Civil
- Helifor Canada
- Columbia Helicopters
- Sky Aviation Corp
Former operators
- Canadian Land Force Command
- Royal Canadian Air Force
- Japan Air Self-Defense Force
- Japan Ground Self-Defense Force
- Japan Maritime Self-Defense Force
- Tokyo Metropolitan Police Department
- Ministry of Interior
- Swedish Air Force
- Swedish Navy
Thailand
- Royal Thai Army
- New York Airways
- Pan American Airways
- United States Marine Corps
- HMX-1
- HMM-262
- HMM-265
- HMM-268
- HMM-364
- HMM-764
- HMM-774
- HMMT-164
- VMR-1
- United States Navy
Notable accidents and incidents
- On 15 July 1966 during Operation Hastings, two CH-46As BuNo 151930 and BuNo 151936 of HMM-164 collided at LZ Crow while another, BuNo 151961, crashed into a tree avoiding the first two, resulting in 2 Marines killed. Another CH-46 BuNo 152500 of HMM-265 was shot down at the LZ later that day resulting in 13 Marines killed.
- On 4 June 1968 CH-46D BuNo 152533 of HMM-165 was hit by anti-aircraft fire at Landing Zone Loon and crashed killing 13 Marines
- On 14 March 1969 CH-46D BuNo 154841 of HMM-161 was hit by a B-40 rocket as it conducted a resupply and medevac mission at Landing Zone Sierra, killing 12 Marines and 1 Navy corpsman.
- On 10 May 1996, a CH-46E collided in mid-air with an AH-1W, killing fourteen soldiers (twelve Marines, one Navy sailor, and one Army soldier) aboard the two helicopters. The pilots of the CH-46E were injured. Both helicopters, of HMM-266, were operating from USS Saipan and were participating in Operation Purple Star, a joint exercise involving troops from the United States and the United Kingdom in North Carolina at Camp Lejeune.
- On 9 December 1999, a CH-46D Sea Knight BuNo 154790 of HMM-166 crashed during a boarding exercise off the coast of San Diego, California, killing seven U.S. Marines. The pilot landed the CH-46 short on the deck of the USNS Pecos, causing the left rear tire and strut to become entangled in the safety netting at the back of the ship, which caused it to plunge into the ocean.
Aircraft on display
- Canada Aviation and Space Museum - Labrador 11301
- Comox Air Force Museum - Labrador 11310
- National Air Force Museum of Canada - Labrador 11315
- Greenwood Military Aviation Museum - Labrador 11308
- Japan Air Self Defense Force Hamamatsu Air Base Publication Center, Hamamatsu, Shizuoka, Japan
- Kakamigahara Aerospace Science Museum, Kakamigahara, Gifu, Japan
- Kawasaki Vertol 107-II - Kawasaki Good Times World, within Kobe Maritime Museum, Kobe, Hy?go, Japan.
- Aeroseum, Gothenburg, Sweden - Boeing Vertol/Kawasaki KV-107-II (CH-46), Hkp 4C, c/n 4093, Fv 04072 "72"
- Swedish Air Force Museum, Linköping Sweden. Prototype BV-107-II N6679D Bought used from Boeing in 1970.
- 150954 - USS Midway Museum in San Diego, California displays HH-46A (c/n 2040) as U.S. Navy SA-46 of HC-3 on one side and VR-46 of HC-11 on the other.
- 151952 - National Museum of Naval Aviation in Pensacola, FL displays HH-46D (c/n 2102) as U.S Navy HW-00 of HC-6.
- 153389 - Carolinas Aviation Museum, Charlotte, North Carolina, has Raymond Clausen's Medal of Honor mission CH-46E (c/n 2287) as HMM-263 EG-16. The rear fuselage of BuNo 153335 was used in restoration.
- 153986 - National Museum of the Marine Corps Quantico, Virginia has a walk-through exhibit containing the rear half of a CH-46D displayed as the former BuNo 153986 (c/n 2337) YK-13 from HMM-364 with their logo, The Purple Fox. The front half of the aircraft was used as a training aid display for HMX-1.
- 153402 - New River Aviation Memorial at the front gate of Marine Corps Air Station New River, (part of Camp Lejeune) in Jacksonville, North Carolina - CH46E (c/n 2300) as YS-02 of HMM-162 on one side and HMM-261 on the other.
- 154009 - Patriots Point Naval and Maritime Museum in Mount Pleasant, South Carolina, has CH-46E (c/n 2360) of HMM-164.
- 154803 - Flying Leatherneck Aviation Museum, San Diego, California, USA has CH-46E (c/n 2410) as YS-09 Lady Ace 09 of HMM-165. The CH-46 took part in Operation Frequent Wind and was used to evacuate Ambassador Graham Martin, the last United States Ambassador to South Vietnam from the United States Embassy, Saigon on 30 April 1975.
- 156427 - Veterans Museum Dyersburg Army Air Base in Halls, Tennessee.
- 153369 - National Air and Space Museum at the Steven F. Udvar-Hazy Center in Chantilly, Virginia has CH-46D (c/n 2265) displayed as MQ-400 of HMM-774. This aircraft is on loan from National Museum of the Marine Corps, Quantico, Virginia. The aircraft was last flown on August 1, 2015 at the Marine Corps' formal sunset ceremony for the type which was the last public showing of an airworthy Marine Corps CH-46.
- 157688 - Classic Rotors Rotorcraft Museum in Ramona, CA. displays HH-46E '02' from VMR-1 Cherry Point MCAS N.C.
Specifications (CH-46E)
Data from Frawley, Donald
General characteristics
- Crew: five: two pilots, one crew chief, one aerial gunner/observer, one tail gunner
- Capacity: ** 24 troops or
- 15 stretchers and two attendants or
- 5,000 lb (2,270 kg)
- Length: 44 ft 10 in fuselage (13.66 m
- Fuselage width: 7 ft 3 in (2.2 m))
- Rotor diameter: 50 ft (15.24 m)
- Height: 16 ft 9 in (5.09 m)
- Disc area: 3,927 ft² (364.8 m²)
- Empty weight: 11,585 lb (5,255 kg)
- Loaded weight: 17,396 lb (7,891 kg)
- Max. takeoff weight: 24,300 lb (11,000 kg)
- Powerplant: 2 × General Electric T58-GE-16 turboshafts, 1,870 shp (1,400 kW) each
Performance
- Maximum speed: 166 mph (144 knots, 267 km/h)
- Range: 633 mi (550 nmi, 1,020 km)
- Ferry range: 690 mi (600 nmi, 1,110 km)
- Service ceiling: 17,000 ft (5,180 m)
- Rate of climb: 1,715 ft/min (8.71 m/s)
- Disc loading: 4.43 lb/ft² (21.6 kg/m²)
- Power/mass: 0.215 hp/lb (354 W/kg)
Armament
- Guns: Two door-mounted GAU-15/A .50 BMG (12.7×99 mm) machine guns (optional), one ramp-mounted M240D 7.62×51 mm machine gun (optional)
Source of the article : Wikipedia
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