machine gun aboard a Marine CH-46 in Iraq, August 2006
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 retirement in 2015. 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.
Vietnam War ", 15 July 1966 During the Vietnam War, the CH-46 was one of the prime US Marine troop transport helicopters in the theater, slotting between the smaller
Bell UH-1 Iroquois and larger
Sikorsky CH-53 Sea Stallion and progressively replacing the
UH-34. 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. On 3 May 1967, a CH-46D at
Marine Corps Air Facility Santa Ana crashed, killing all four members of the crew. Within three days the accident investigators had determined that the mounting brackets of the main transmission had failed, allowing the front and rear overlapping rotors to intermesh. All CH-46s were temporarily grounded for inspection. On 13 May, a CH-46A crashed off the coast of Vietnam when the tail pylon containing the engines, main transmission and aft rotors broke off in flight. All four crew members were killed. On 20 June, another CH-46A crashed, though two of the four-man crew survived. Once again, even though the aircraft was not recovered from the water, failure of some sort in the rear pylon was suspected. On 30 June a CH-46D at Santa Ana crashed when a rotor blade separated from the aircraft, all three of the crew survived. As a result of this latest accident, all CH-46Ds were immediately grounded, but the CH-46As continued flying. On 3 July another CH-46A crashed in Vietnam, killing all four Marines of its crew. The cause of the crash again was traced to failure of the main transmission. On 31 August 1967, a CH-46A on a medical evacuation mission to disintegrated in midair killing all its occupants. The following day another CH-46A experienced a similar incident at
Marble Mountain Air Facility leading to the type being grounded for all except emergency situations and cutting Marine airlift capacity in half. An investigation conducted by a joint Naval Air Systems Command/Boeing Vertol accident investigation team revealed that structural failures were occurring in the area of the rear pylon resulting in the rear rotor tearing off in flight and may have been the cause of several earlier losses. The team recommended structural and systems modifications to reinforce the rear rotor mount as well as installation of an indicator to detect excessive strain on critical parts of the aircraft. 80 CH-46As were shipped to
Marine Corps Air Station Futenma,
Okinawa where they received the necessary modifications by a combined force of Marine and Boeing Vertol personnel. The modified CH-46As began returning to service in December 1967 and all had been returned to service by February 1968. Marine CH-46s participated in
Operation Frequent Wind, the evacuation of
Saigon, in April 1975 and the last helicopter to leave the roof of the
US embassy was a CH-46 of
HMM-164. By the end of US military operations in Vietnam, over a hundred Sea Knights had been lost to enemy fire.
Post-Vietnam board a Marine Corps CH-46E helicopter from
VMM-261 before the rescue of American students at St. George's University during Operation Urgent Fury in 1983. 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 crewmember of a downed AH-1 Cobra, and then carried infantry from the
75th Ranger Regiment to secure and evacuate U.S. students at
St. George's University, though one crashed after colliding with a palm tree. in South Central Afghanistan, 2004 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 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. A number of CH-46s from
HMX-1 were transferred to the Air Wing in late 2014. In Afghanistan the CH-46s were used by Embassy Air for secure transport of State Department personnel. The CH-46s were equipped with missile warning sensors and flare dispensers and could be armed with M240D or M2 Browning machine guns. A report in September 2019 by the
State Department Inspector General found that a seat on a CH-46 for a seven-minute flight cost US$1,500 (~$ in ).
Evacuation of Afghanistan CH-46E, 2012 Seven of the State Department Air Wing CH-46s took part in the
2021 Kabul Airlift. Prior to the complete withdrawal of U.S. forces, all seven were rendered unusable and abandoned at
Kabul International Airport and are seen in many videos and pictures online. One of the CH-46s that was abandoned (BuNo 154038, c/n 2389) also took part in
Operation Frequent Wind 46 years earlier. The U.S. State Department drew criticism for leaving behind the aircraft. Commenting on the issue, the U.S. State Department claimed that the helicopters were already being phased out of State Department Air Wing due to their age and the inability to support them. The seven CH-46s left behind were the only U.S. State Department aircraft left behind at Kabul International Airport.
Canada off the tip of
Bell Island in Newfoundland 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. 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. Nonetheless, as a search and rescue helicopter it endured heavy use and hostile weather conditions; which had begun to take their toll on the Labrador fleet by the 1990s, resulting in increasing maintenance costs and the need for prompt replacement.
Sweden In 1963, Sweden procured ten UH-46Bs 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-107s, 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, most famously during the rescue operation of the
MS Estonia after it
sank in the Baltic Sea on 28 September 1994. 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 and
NH90.
Argentina On 15 September 2023,
Argentina's
Air Force chief Gen.
Xavier Issac briefed the media that Argentina had sent a letter requesting the US to approve the refurbishment of surplus CH-46s currently stored with the
309th Aerospace Maintenance and Regeneration Group in
Arizona. The availability of civilian-operated CH-46s was also being explored. They would be used to support
Argentina's Antarctic bases. The CH-46s would replace two
Mil Mi-171E helicopters acquired in 2010, but now not able to be repaired by
Russia due to sanctions from the
Russian invasion of Ukraine.
Civilian and others 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. 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. In 2023, Columbia Helicopters began a program of purchasing older Model 107-II and CH-46E airframes, and refurbishing them into Model 107-IIs for sale. Columbia Helicopters has also updated old airframes into the
Model 107-III. ==Variants==