The Kaman HH-43 Huskie is a helicopter developed and produced by the American rotorcraft manufacturer Kaman Aircraft. It is perhaps most distinctive for its use of twin intermeshing rotors, having been largely designed by the German aeronautical engineer Anton Flettner.

First flown on 21 April 1953, the HH-43 went into production and was operated by several military air services, including the United States Air Force, the United States Navy and the United States Marine Corps. It was primarily intended for use in aircraft firefighting and rescue in the close vicinity of air bases, but was extensively deployed during the Vietnam War. It was used as a search and rescue platform, having often been enhanced with makeshift modification and new apparatus to better suit the tropical conditions. Under the aircraft designation system used by the U.S. Navy pre-1962, Navy and U.S. Marine Corps versions were originally designated as the HTK, HOK or HUK, for their use as training, observation or utility aircraft, respectively. In American service, it was retired during the 1970s, having been rendered obsolete by the arrival of larger, more capable rotorcraft.

Development
In 1947, the German aeronautical engineer Anton Flettner was brought to the United States as part of Operation Paperclip. He was the developer of the two earlier synchropter designs from Germany during the Second World War: the Flettner Fl 265 which pioneered the synchropter layout, and the slightly later Flettner Fl 282 Kolibri ("Hummingbird"), intended for eventual production. Both designs used the principle of counter-rotating side-by-side intermeshing rotors, as the means to solve the problem of torque compensation, normally countered in single–rotor helicopters by a tail rotor, fenestron, NOTAR, or vented blower exhaust. Flettner remained in the United States and became the chief designer of the Kaman company. In this capacity, he designed numerous new helicopters that used the Flettner double rotor.

On 21 April 1953, the first prototype, referred to by the manufacturer as the K-225, made its maiden flight. It was later adopted by the United States Navy as the HTK-1, by which point it was outfitted with a single  Lycoming O-435-4 flat-six piston engine, producing . During 1954, for an experiment jointly conducted by Kaman and the U.S. Navy, a single HTK-1 was modified and flown with its piston engine having been replaced by a pair of turbine engines, becoming the world's first twin-turbine helicopter in the process.

Subsequently, a much more powerful Pratt & Whitney R-1340 Wasp radial piston engine, capable of producing , powered for the far heavier HOK-1, HUK-1, and H-43A versions for the United States Marines, U.S. Navy, and the United States Air Force, respectively. The U.S. Air Force also opted to procure two models that were powered by a single turboshaft engine: the HH-43B and HH-43F. The HH-43B variant established several world records for helicopters in its class during the early 1960s, including for rate of climb, altitude, and distance traveled.

Design
The HH-43 had an unusual intermeshing contra-rotating twin-rotor arrangement. Flight control was primarily effected by a series of servo-flaps, or large tabs, that was located on the trailing edge of each rotor blade; the actuation of these flaps would cause the rotors to warp and thus cause the helicopter to either rise or descend as desired. The rotor blades were composed of laminated wood; these restricted the aircraft's use in heavy rains as it could cause blade delamination. There was no conventional tail rotor, its absence gave the rotorcraft a somewhat unusual look. The contra-rotating twin rotors posed a particular hazard on the ground; crews were instructed to avoid approaching or departing the vehicle from the sides, but to instead advance or leave the vehicle from the front, as the blades would be at their highest at this position.

The interior of the HH-43 was divided in two somewhat cramped compartments, the cockpit at the front and an aft crew compartment, which were connected by a small opening that was too narrow for most personnel to pass through. Dependent on the mission being performed, the aft compartment would be used to house firefighters, medics, mechanics, and/or rescued personnel; folding sidewall-mounted seats were provided for up to four personnel in this space, while the cockpit normally housed the pilot and co-pilot alone. In a typical configuration, a pair of clamshall doors would be fitted that could open up into the aft area of the rear compartment; in tropical conditions, these doors would often be removed to help cool the interior; in such a configuration, an aft net would be installed to prevent any personnel from falling out of the aircraft. No weapons mounts were officially approved, but some improvised arrangements did see the use of a Browning Automatic Rifle at the aft ramp position.

On the exterior of the rotorcraft, a motorised hoist that was typically used for rescue missions was commonly fitted; control of the hoist was normally exercised from within the aft compartment, but the pilot could also directly control the hoist via the cyclic stick. For rescues at sea, a padded sling, nicknamed the 'horse collar', was fitted to the end of the hoist to aid in retrieval operations. Due to unsatisfactory performance in the field, other devices were usually fitted, including the wire basket "Stokes litter" and a heavy "forest penetrator".

Operational history
The HH-43 Huskie was procured by the U.S. Air Force; the first H-43As were delivered to the service in November 1958 while the first H-43Bs were accepted in June 1959. The U.S. Air Force primarily procured the type to perform local base rescue operations and to fight aircraft fires. For the latter capacity, the H-43 was commonly outfitted with an airborne fire suppression kit that hung beneath it; this kit, which was developed at Wright-Patterson AFB, weighed only 1,000 pounds yet could output almost 700 gallons of fire-fighting foam. Huskies were usually capable of reaching crash sites before ground vehicles could, saving often-critical time in the rescue. During 1962, the USAF opted to change the H-43 designation to HH-43 to reflect the rotorcraft's role as a rescue vehicle. The HH-43F was the first model delivered to the U.S. Air Force , these differed from earlier models primarily by engine modifications that produced greater lift.

The Huskie was deployed overseas during the Vietnam War; several detachments of the Pacific Air Rescue Center, the 33d, 36th, 37th, and 38th Air Rescue Squadrons, and the 40th Aerospace Rescue and Recovery Squadron operated the type. Personnel came to commonly refer to the aircraft by its call sign "Pedro". Early on, the rotorcraft's limited range proved to be a hindrance to operations; some crews resorted to an improvised additional fuel tank housed within the aft compartment, increasing fuel capacity by roughly 75 percent. During the conflict, the HH-43 flew more rescue missions than all other rotorcraft combined, largely due to its unique hovering capability; between 1966 and 1970, the type performed a total of 888 combat rescue, comprising 343 aircrew rescues and 545 non-aircrew rescues. The type was also occasionally used as a firefighting vehicle in the theatre as well. Noting the shortcomings of the HH-43, the procurement of newer aircraft, such as the Sikorsky SH-3 Sea King, was accelerated; their arrival in quantity supplanted the type and saw its being entirely replaced during the early 1970s.

Variants

K-240 company designation from HTK-1/TH-43E
K-600 proposed civilian counterpart of HOK-1
K-600-3 civilian counterpart of H-43B
K-600-4 company designation of HOK-3 development
K-600-5 HH-43F
XHTK-1 two two-seat aircraft for evaluation
HTK-1 three-seat production version powered by a  Lycoming O-435-4 flat-six piston engine for the United States Navy, later became TH-43E, 29 built
XHTK-1G one example for evaluation by the United States Coast Guard
HTK-1K one example for static tests as a drone
XHOK-1 prototype of United States Marine Corps version, two built
HOK-1 United States Marine Corps version powered by a  R-1340-48 Wasp radial piston engine; later became OH-43D, 81 built
HOK-3 proposed development powered by a Blackburn-Turbomeca Twin Turmo 600 turboshaft powerplant.
HUK-1 United States Navy version of the HOK-1 with R-1340-52 radial piston engine; later became UH-43C, 24 built
H-43A USAF version of the HOK-1; later became the HH-43A, 18 built
HH-43A post-1962 designation of the H-43A
H-43B H-43A powered by an  Lycoming T53-L-1B turboshaft engine, three-seats and full rescue equipment; later became HH-43B, 200-built
HH-43B post-1962 designation of the H-43B
UH-43C post-1962 designation of the HUK-1
OH-43D post-1962 designation of the HOK-1
TH-43E post-1962 designation of the HTK-1
HH-43F HH-43B powered by an  Lycoming T53-L-11A turboshaft engine with reduced diameter rotors, 42 built and conversions from HH-43B
QH-43G One OH-43D converted to drone configuration

Operators

 
Burmese Air Force

Colombian Air Force
 Iran
Imperial Iranian Air Force

Royal Moroccan Air Force

Pakistan Air Force
Pakistan Navy

Royal Thai Air Force

 United States Air Force
 United States Marine Corps
 United States Navy

Surviving aircraft
In addition to those on static display and the airworthy example at the Olympic Flight Museum, many H-43s are still in use with private owners.

Burma
 UB6166 – HH-43B is on display at the Defence Services Museum in Naypyidaw, Mandalay.

Germany
 62-4547 – HH-43F on static display at the Hubschraubermuseum Bückeburg in Bückeburg, Lower Saxony.

Pakistan
 62-4556 – HH-43P on static display at the Pakistan Air Force Museum in Karachi, Sindh.

Thailand
 H5-2/05 – Type 5 on static display at the Royal Thai Air Force Museum in Bangkok.

United Kingdom
 62-4535 – HH-43B under restoration at the Midland Air Museum in Baginton, Warwickshire. This airframe is one of only two examples on display in the United Kingdom.

United States
 Composite – HH-43F on static display at the New England Air Museum in Windsor Locks, Connecticut. This airframe is painted as 60-0289, but was built up from parts of various HH-43s.
 129313 – HTK-1/TH-43E on static display at the Tillamook Air Museum in Tillamook, Oregon. This airframe is painted in Navy markings.

 129801 – HOK-1/OH-43S in storage at the New England Air Museum in Windsor Locks, Connecticut.
 138101 – HOK-1/OH-43D in storage at the United States Army Aviation Museum at Fort Rucker near Daleville, Alabama. BuNo 138101 was formerly displayed indoors at the National Naval Aviation Museum at NAS Pensacola, Florida (circa 1986-2001) in a dark blue finish with USMC markings. It was repainted from its original USMC markings to pre-Vietnam U.S. Army colors when it was loaned to the Army by the National Naval Aviation Museum.
 139974 – OH-43D on static display at the Pima Air & Space Museum, adjacent to Davis-Monthan AFB in Tucson, Arizona. This airframe is painted in USMC markings.
 139982 – HOK-1/OH-43D in storage at the Carolinas Aviation Museum in Charlotte, North Carolina. This airframe is painted in Marine Corps markings.
 139990 – HOK-1/OH-43D in storage at the Flying Leatherneck Aviation Museum at MCAS Miramar in San Diego, California. This airframe is painted in USMC markings. It was previously on display at MCAS Tustin in Tustin, California; but was moved to MCAS Miramar after MCAS Tustin was closed and NAS Miramar was transferred from control of the Navy to the Marine Corps.
 58-1837 – HH-43A in storage at the New England Air Museum in Windsor Locks, Connecticut.
 58-1841 – HH-43F on static display at the Military Firefighter Heritage Display at Goodfellow Air Force Base in San Angelo, Texas. It is incorrectly painted with Air Force Serial Number 58-1481. This Huskie was a ground trainer (circa 1962–1976) at Sheppard Air Force Base, so it retained the square-tail empennage that was removed from almost all other Huskies after repeated rotor strikes in heavy winds. After being sold by the military, but before arriving at its current location, it was on display at the Pate Museum of Transportation in Cresson, Texas.
 58-1853 – HH-43F on static display at the Museum of Aviation at Robins Air Force Base in Warner Robins, Georgia.
 59-1578 – HH-43F on static display at Kirtland Air Force Base in Albuquerque, New Mexico. This may be the same airframe listed on other sites as being located at the National Museum of Nuclear Science & History, which has since moved off-base, but adjacent to, Kirtland Air Force Base.
 60-0263 – HH-43B on static display at the National Museum of the United States Air Force at Wright-Patterson AFB in Dayton, Ohio.
 62-4513 – HH-43F on static display at the Castle Air Museum at the former Castle AFB in Atwater, California.
 62-4531 – HH-43F on static display at the Pima Air & Space Museum adjacent to Davis-Monthan AFB in Tucson, Arizona.
 62-4532 – HH-43B on static display at the Air Mobility Command Museum at Dover AFB in Dover, Delaware.
 62-4561 – HH-43B on static display at the Hill Aerospace Museum at Hill AFB in Roy, Utah.
 64-17558 – HH-43F airworthy at the Olympic Flight Museum in Olympia, Washington. This airframe is painted in USAF markings.

Specifications (HH-43F / K-600-5)

See also

References

Citations

Bibliography

External links

 HH-43 page at the National Museum of the United States Air Force
 HH-43 Huskie Reference at Cybermodeler.com
 HH-43 Page at GlobalSecurity.org

Kaman aircraft
Firefighting equipment
Kaman HH-43 Huskie
H-43 Huskie
1950s United States helicopters
Search and rescue helicopters
Synchropters
Kaman HH-43 Huskie
Single-turbine helicopters
Aircraft first flown in 1953