The Boeing Vertol CH-46 Sea Knight is a medium-lift tandem-rotor transport helicopter powered by twin turboshaft engines. It was 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 US 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 US Marine Corps (USMC), which had been studying its requirements for a medium-lift, twin-turbine cargo/troop 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 US Marine Corps’ operational environments between its introduction during the Vietnam War and its frontline retirement during 2014.
The Sea Knight was operated by the 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.
The USMC also used the helicopter for combat support, search and rescue (SAR), casualty evacuation and Tactical Recovery of Aircraft and Personnel (TRAP).
The Sea Knight also functioned as the US Navy’s standard medium-lift utility helicopter prior to the type being phased out of service in favour 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 SAR role until 2004.
Other export customers for the type included Japan, Sweden, and Saudi Arabia.
Variants
U.S Versions
Model 107
Company model number for basic prototype, one built.
Model 107M
Company model number for military transport of BV-107/II-2 for the U.S. Marine Corps.
YHC-1A
Vertol Model 107 for test and evaluation by the United States Army.
Adopted by the U.S. Marine Corps as the HRB-1.
Later redesignated YCH-46C, three built.
HRB-1
Original designation before being renamed as CH-46A before delivery under the 1962 United States Tri-Service aircraft designation system.
CH-46A
Medium-lift assault and cargo transport and SAR helicopter for the USMC, fitted with two 1,250 shp (935 kW) General Electric T58-GE-8 turbo shaft engines.
Previously designated HRB-1.
UH-46A
Medium-lift utility transport helicopter for the United States Navy.
Similar to the CH-46A.
HH-46A
Approximately 50 CH-46As were converted into SAR helicopters for the United States Navy base rescue role.
RH-46A
Planned conversion of CH-46As into minesweeping helicopters for the US Navy, none converted.
Nine SH-3As were converted to the RH-3A configuration instead.
UH-46B
Development of the CH-46A to specification HX/H2 for the United States Air Force, 12 ordered in 1962, cancelled and Sikorsky S-61R / CH-3C ordered instead.
YCH-46C
YHC-1A redesignated in 1962.
United States Army retained two, NASA used one for vertical autonomous landing trials (VALT).
CH-46D
Medium-lift assault and cargo transport helicopter for the USMC, fitted with two 1,400 shp (1,044 kW) General Electric T58-GE-10 turbo shaft engines.
HH-46D
Surviving HH-46A were upgraded and a small number of UH-46Ds were converted into SAR helicopters.
SAR upgrades included the addition of an external rescue hoist near the front crew door and an 18-inch X 18-inch Doppler RADAR system located behind the nose landing gear, which provided for automatic, day/night, over-water hovering capability for at sea rescue.
Additionally a “Loud Hailer” was installed opposite the crew entrance door for communicating with downed aviators on the ground or in the water.
UH-46D
Medium-lift utility transport helicopter for the US Navy combat supply role.
Similar to the CH-46D. Ten built and one conversion from CH-46D.
CH-46E
Approximately 275 -A, -D, and -F airframes were updated to CH-46E standards with improved avionics, hydraulics, drive train and upgraded T58-GE-16 and T58-GE-16/A engines.
HH-46E
Three CH-46Es were converted into SAR helicopters for Marine Transport Squadron One (VMR-1) at MCAS Cherry Point.
CH-46F
Improved version of CH-46D, electrical distribution, com/nav update.
Last production model in the United States.
VH-46F
Unofficial designation of standard CH-46F used by HMX-1 as VIP support transport helicopter.
CH-46X
Replacement helicopter based on the Boeing Model 360, this Advance Technology Demonstrator from the 1980s never entered production.
The aircraft relied heavily on composites for its construction and had a beefier drive train to handle the twin Avco-Lycoming AL5512 engines (4,200 shp).
XH-49
Original designation of UH-46B.
Canadian versions
CH-113 Labrador
Search and rescue version of the Model 107-II-9 for the Royal Canadian Air Force.
CH-113A Voyageur/Labrador
Assault and utility transport version of the Model 107-II-28 for the Canadian Army.
Japanese versions
KV-107II-1 (CT58-110-1)
Utility transport version, one built from Boeing-supplied kits.
KV-107IIA-2 (CT58-140-1)
Improved version of the KV-107/II-2.
KV-107II-3 (CT58-110-1)
Mine sweeping version for the Japan Maritime Self-Defence Force.
KV-107IIA-3 (CT58-IHI-10-M1)
Uprated version of the KV-107/II-3.
KV-107II-4 (CT58-IHI-110-1)
Assault and utility transport version for the Japanese Ground Self Defence Force.
KV-107II-4A (CT58-IHI-110-1)
Uprated version of the KV-107/II-4.
KV-107II-5 (CT58-IHI-110-1)
Long-range SAR version for the Japan Air Self-Defence Force.
KV-107IIA-5 (CT58-IHI-104-1)
Uprated version of the KV-107II-5.
KV-107II-7 (CT58-110-1)
VIP transport version.
KV-107II-16
HKP 4C for the Swedish Navy.
It was powered by Rolls-Royce Gnome H.1200 turbo shaft engines.
KV-107IIA-17 (CT58-140-1)
Long-range transport version for the Tokyo Metropolitan Police Department.
KV-107IIA-SM-1 (CT58-IHI-140-1M1)
Firefighting helicopter for Saudi Arabia.
KV-107IIA-SM-2 (CT58-IHI-140-1M1)
Aeromedical and rescue helicopter for Saudi Arabia.
KV-107IIA-SM-3 (CT58-IHI-140-1M1)
VIP transport helicopter for Saudi Arabia.
KV-107IIA-SM-4 (CT58-IHI-140-1M1)
Air ambulance helicopter for Saudi Arabia.
Swedish versions
HKP 4A
Boeing Vertol 107-II-14, used originally by Air Force for search and rescue.
HKP 4B
Boeing Vertol 107-II-15, mine-layer/antisubmarine warfare/search and rescue helicopter for Navy.
HKP 4C
Kawasaki KV-107-II-16, advanced mine-layer/ASW/SAR helicopter for Navy.
HKP 4D
Rebuilt HKP 4A for Navy as SAR/ASW helicopter.
Specifications
Crew
5
Capacity
24 troops
Or
15 stretchers and two attendants
Or
7,000 lb (3,200 kg)
Length
44 ft 10 in (13.67 m)
(Fuselage)
83 ft 4 in (25.40 m)
(Rotors turning)
Height
16 ft 9 in (5.11 m) to top of rear rotor head
Empty weight
15,537 lb (7,047 kg)
Gross weight
24,300 lb (11,022 kg)
Max take-off weight
24,300 lb (11,022 kg)
Fuel capacity
350 US gal (290 imp gal; 1,300 l) internal
Powerplant
2 × General Electric T58-GE-16 turbo shaft engines,
1,870 shp (1,390 kW) each
Main rotor diameter
2 × 50 ft (15 m)
Main rotor area
3,926.99 sq ft (364.829 m2)
Rotor blade section
Root
Boeing VR-7
Tip
Boeing VR-8
Performance
Maximum speed
144 kn (166 mph, 267 km/h) at sea level
Cruise speed
143 kn (165 mph, 265 km/h) maximum at sea level
Range
550 nmi (630 mi, 1,020 km) with 2,400 lb (1,100 kg) payload
Ferry range
600 nmi (690 mi, 1,100 km)
Service ceiling
17,000 ft (5,200 m)
Hover ceiling IGE
9,500 ft (2,900 m)
Hover ceiling OGE
5,750 ft (1,750 m)
Rate of climb
1,715 ft/min (8.71 m/s)
Disk loading
4.43 lb/sq ft (21.6 kg/m2)
Power/mass
0.215 hp/lb (0.353 kW/kg)
Armament
Guns
Two door-mounted GAU-15/A 0.500 in (12.7 mm) machine guns
(Optional),
One ramp-mounted M240D 0.300 in (7.62 mm) machine gun
