HISTORIC U.S. ARMY HELICOPTERS

World War II thru early Vietnam era helicopters (Page 1 of 3)

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Early Platt-LePage models (1940-1942). First to use the VTOL axiom, Platt-LePage Aircraft Co. was also first to experiment with the tilt-rotor. At the time, the industry was not ready for the concept, but Platt-LePage patented the idea that would eventually lead to the evolution of such VTOL aircraft as Bell-Boeing V-22 Osprey. This information was contributed by courtesy of Mr. Jay Hendrickson, Platt-LePage Aircraft Archives RotaryResearchJBH@att.net

Platt-LePage (model PL-3) XR-1 (1941). The XR-1 and XR-1A were two-seat twin-rotor prototypes submitted for evalation under the very first U.S. Army Air Corps (USAAC) helicopter program in July 1940. The XR-1 was powered by a Pratt & Whitney R-985-21 450hp engine mounted within the fuselage.
Platt-LePage XR-1 (Serial No. 41-001) (J. Hendrickson collection)

Platt-LePage (model PL-5) XR-1A (1942). The XR-1A featured two counter-rotating rotors mounted on faired outriggers. The XR-1A, with 31'6" rotors (about 33' between pylon centers) and a length of 29'10", was powered by a Pratt & Whitney R-985-AN-1 450hp engine. While the Platt-LePage machines did not go into service, the work carried-out by Platt-Lepage Aircraft Co. spurred Igor Sikorsky to speed-up development of the VS-300 and the XR-4.
Platt-LePage XR-1A (Serial No. 42-6581) (J. Hendrickson collection)

Platt-LePage (model PL-4) (1940) was the first design study for an armed attack helicopter, along the lines of the model PL-3, but with four nose-mounted machine guns. Along with engineering data, several renderings of operational use of a Helicopter Scout were produced, that anticipated the modern gunship by two decades. It is interesting that the renderings showed armed helicopters operating from battleships, in night and bad-weather attacks, and the helicopter outmaneuvering a pursuit plane. Offered to USAAC and U.S. Navy in 1940, both services turned down the idea as impractical.

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Early model Sikorsky military helicopters (1942-1943). The United Aircraft (Vought-Sikorsky) VS-300 was an experimental helicopter designed and piloted by Igor Sikorsky. Igor's nightmare, constructed of struts, metal tubing, sheet metal, and a pulley belt system, could be radically redesigned overnight. The final version bares little resemblance to the original. Using this craft, Sikorsky perfected cyclic pitch control of the main rotor and the use of the tail rotor to balance torque and provide logitudinal control, the method of control used in all modern helicopters. The VS-300 made the first true controlled flight of a helicopter December 8, 1941. The VS-300 was the prototype for three Sikorsky R-series helicopters. The R-series helicopters each had a three-bladed main rotor and a three-bladed vertical controllable-pitch anti-torque and steering tail rotor. In 1948, the U.S. Army Air Force (USAAF) changed the designation from R (Rotorcraft) to H (Helicopter). See Igor Sikorsky Historical Archives, Inc. for a rich tribute to the man and his aircraft.

Sikorsky R-4 (1942). The Sikorsky (model S-47) R-4 (British name Hoverfly MK I), was the first mass-produced military helicopter. The XR-4 (VS-316A), first flown in 14 January 1942, had a fabric covered tubular steel fuselage. Model numbers ranged from A through C. The YR-4B was a two-place side-by-side, observation, reconnaissance, and MedEvac helicopter, with one external litter. The R-4 was first used in combat in May 1944. The model R4-B entered service in 1945. Many were fitted with twin pontoons for use aboard ships or over water. A YR-4, equipped with pontoons, made the first helicopter deck landing on the S.S. Bunker Hill on May 6, 1943. An Army YR-4B performed the first military/MedEvac rescue behind enemy lines in Burma on April 25-26, 1944. Taxed-to-the-limit, powered by only a 185 hp Warner R550-1 engine, it required the YR-4B pilot four trips over a two day period to rescue the downed Stinson L-1 Vigilant pilot and three British casualties. R-4Bs were used by the U.S. Army Air Force, U.S. Navy (as the HNS-1), U.S. Coast Guard, as well as the British Royal Air Force and the Royal Navy (as the Hoverfly MK I). The R-4B was replaced by the versatile Sikorsky (model S-51) R-5D shortly after World War II.
YR-4 equipped with pontoons for shipboard operation
Royal Navy R-4 Hoverfly MK I
U.S. Air Force Museum R-4B helicopter

Sikorsky R-5 (H-5D) (1943). The Sikorsky (model S-48) R-5 (British name Dragonfly) was first flown on August 18, 1943. The first XR-5, in 1944, was a tandem rotor model, the VS-272; all others, VS-327s, were single rotor. The R-5, developed concurrently with the R-6, with a crew of two seated in tandem, had an all-metal fuselage. It was designed to have a greater useful load, range, speed, and service ceiling than the R-4. The R-5, produced in 11 models through 1951, could be rigged to carry four external litters, two per side, in the MedEvac role. It had provisions for cameras and a radio. The R-5D model added a third seat, nosewheel, external hoist, and an external fuel tank. The R-5D was the basis for the four-seat Sikorsky (model S-51) which gained fame in Korea with the U.S. Naval Air Rescue Service. The R-5 (H-5D) served with the U.S. Army Air Force, U.S. Navy (as the HO2S-1), and U.S. Marine Corps. The R-5/H-5D was build under license to Great Britain as the Dragonfly. The Westland Dragonfly served with the Royal Navy and a few saw service with the Royal Air Force. The R5-A was powered by a 450 hp Pratt & Whitney R-985-AN-5 Wasp Junior engine.
Sikorsky XR-5 in flight

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Sikorsky R-6 (1943). The Sikorsky (model S-49) R-6 (British name Hoverfly MK II) was first flown on October 15, 1943. A refinement of the R-4, the R-6 (VS-316B) featured a larger, improved, streamlined metal fuselage with improved pilot visibility. This was a joint U.S. Army/U.S. Navy program. It had the same rotor and transmission as the R-4, but a more powerful 245 hp Franklin O-405-9 engine. It had a crew of two, seated side-by-side. It was equipped with a high-frequency radio. In the MedEvac role it could be equipped with two external capsules to carry litters. Bomb racks could be installed to carry 650 lbs. of bombs externally. The R-6A could also be equipped with pontoons for use over water. The R-6A was the first USAAF helicopter to serve in combat in May 1944. The initial XR-6 and all five XR-6As were produced by Sikorsky. All R-6As were produced in 1944 and 1945 by Nash-Kelvinator under license to Sikorsky. The R-6A was used primarily by the U.S. Navy (as the HOS-1) and the U.S. Coast Guard, as well as the Royal Navy (as the Hoverfly MK II). Models A thru C were powered by a Pratt & Whitney R-985-AN-5 450 hp engine. The D model was powered by a Pratt & Whitney R-1340 600 hp engine.
Sikorsky XR-6 in flight
U.S. Army Air Force R-6A parked on a road in China, 1945
U.S. Air Force Museum R-6A helicopter

YR-13/H-13/OH-13 Series Sioux light observation helicopter (1946). The Bell (model 47) H-13 Sioux, with a crew of three, was one of the most popular light utility helicopters ever built. The Bell model 47 was produced continuously from 1946 to 1973, and by Agusta, in Italy, through 1976. Produced in 20 different configurations, with model numbers ranging from A to T, the Bell model 47 was used in 40 countries. The combined total of commercial and military versions of this series was 5,000. The U.S. Army Air Force procured it's first YR-13 (model 47B) in December 1946. The OH-13 had a cruising speed of 85 mph (75 knots), with a range of 255 miles.
OH-13 Sioux used for pilot training at Ft. Wolters, TX in 1966 (Copyright Jerry Barnes, baron67@airmail.net )
OH-13H Sioux light observation helicopter (Source US Army AMCOM)

An important Bell inovation during the early development of the helicopter was the use of short weighted gyro-stabilizer bar at 90° to, and beneath, the main rotor. The gyro-stabilizer bar, with streamlined counterweights at both tips, was linked to the rotor in such a way that it determined the plane of the rotor, and maintained it generally in the horizontal, regardless of the angle of the mast. The stabilizer bar, connected to the cyclic pitch control, acted as a hinged flywheel utlizing gyroscopic inertia to keep the teetering rotor blades in-plane and independent of fuselage movement due to gusts of wind, providing stability during flight. Arthur Young, Bell's designer, ensured the system had high enough inertia so sufficient energy would be stored in the rotor to permit safe autorotation in event of engine failure, an important safety consideration.

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The H-13 was used for observation, reconnaissance and in the MedEvac role as a litter carrier in Korea, following initial fielding in 1951. In the MedEvac role a cacoon-like stretcher pod could be mounted on each skid. A distinctive feature of the Bell (model 47D) H-13G was the now familiar "Goldfish bowl" plexiglass canopy, featured in the TV-series MASH (Mobile Army Surgical Hospital). The H-13 earned the nickname "Angel of Mercy" for evacuating some 18,000 United Nation's casualties during the war. The OH-13H/OH-13S Sioux also saw service during the early days of the Vietnam war before the fielding of the OH-6A Cayuse in early 1968. The Sioux had a single two-bladed main rotor and a metal two-bladed tail rotor. The Sioux could be armed with twin M37C .30 Cal. machine guns on the XM1 armament subsystem or twin M60C 7.62mm machine guns on the M2 armament subsystem.
H-13 Sioux armed with twin M37C .30 Cal. machine guns on XM1 armament subsystem line drawing
OH-13 Sioux armed with twin M60C 7.62mm machine guns on M2 armament subsystem line drawing

The Bell (model 201) XH-13F, powered by a Continental-Turbomeca XT51-T-3 Artouste I 220 hp turboshaft engine, was Bell Helicopter's first turbine powered aircraft.
XH-13F experimental turbine powered Sioux (1955)

Bell (model 47) H-13 series powerplants were:

Bell Model No.	Army Model	Powerplant
47, 47A	H-13B/H-13C	Franklin 157hp O-335-1
47B, 47B-3	H-13D/H-13E	Franklin 178hp O-335-5
47D, 47D-1, 47G, 47H	H-13G	Franklin 200hp
47G-2, 47J, 47K	H-13H	Lycoming 250hp VO-435
47G-2A	unknown	Lycoming 240hp TVO-435
47G-3	H-13K	Franklin 225hp 6VS-335-A
47G-3B	unknown	Lycoming 280hp TVO-435
47G-4	unknown	Lycoming VO-540
47G-5	unknown	Lycoming VO-435
47G-5A	unknown	Lycoming 265hp VO-435-B1A
47J-2	unknown	Lycoming 305hp

An experimental armed Bell (model 207) Sioux Scout (1963), based on the a Bell (model 47G-3B1) body and engine, with a newly developed gun ship front end, aided in the development of the AH-1G Huey Cobra attack helicopter. The Sioux Scout featured revised seating for two in tandem, small stub wings containing additional fuel, and a remotely-controlled chin barbette with two M60C 7.62mm machine guns. The Bell (207) was powered by a Lycoming 260hp TVO-435-A1A turbocharged piston engine.
Bell (model 207) Sioux Scout

H-23/OH-23 Series Raven light observation helicopter (1948). The 3-place Hiller (model 360) H-23 was based on the U.S. Navy UH-12, which was first flown in 1948. The H-23 Raven performed as a utility, observation, and MedEvac helicopter during the Korean war. Model numbers ranged A through D, F and G. The H-23A had a sloping front windshield. The H-23B was used as a primary helicopter trainer. Beginning with the UH-23C, all later models featured the "Goldfish bowl" canopy similar to the Bell model 47, and also featured the Bell-designed short weighted gyro-stabilizer bar. The OH-23 had a speed of 97 mph (84 knots). The Raven had a two-bladed main rotor, a metal two-bladed tail rotor. Both the OH-23B and the OH-23C were powered one O-335-5D engine. The OH-23B trainer was replaced by the Hughes TH-55A Osage trainer.
Two early model H-23A Ravens in flight (Source US Army AMCOM)
H-23D Raven in flight
H-23D/OH-23D, the personal aircraft of Bruce Briggs, Denton, Texas
OH-23G Raven at Ft. Wolters, TX in 1966 (Copyright Jerry Barnes, baron67@airmail.net )

The OH-23D was a purely military version with a 0-435-23C engine and a more reliable transmission. Most OH-23Ds were replaced by the OH-23G, the most common version of the Raven, with a more powerful Lycoming O-540-9A six-cylinder, horizontally opposed, air cooled 305 hp engine. The OH-23G could seat four. The MedEvac version carried two external skid-mounted litters or pods. The Raven saw service as a scout during the early part of the Vietnam war before being replaced by the OH-6A Cayuse in early 1968. The Raven could be armed with twin M37C .30 Cal. machine guns on the XM1 armament subsystem or twin M60C 7.62mm machine guns on the M2 armament subsystem. The XM76 sighting system was used for sighting the guns.
H-23D Raven armed with twin M37C .30 Cal. machine guns on XM1 armament subsystem
H-23 armed with twin M60C 7.62mm machine guns on M2 armament subsystem

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H-19/UH-19 Series Chickasaw utility and light tactical helicopter (1949). The Sikorsky (model S-55), initially procured in November 1949, was the World's first transport helicopter. The 12-place H-19 (redesignated UH-19 in 1962), with a crew of two, served as a utility, troop carrier, and rescue helicopter with winch. Air Force model numbers were H-19A and H-19B; Army model numbers were H-19C and H-19D. In the MedEvac role it could carry six litters and one medical attendant. For the first time casualties could be carried and attended to under cover, within the aircraft. Two companies of H-19 Chickasaw helicopters proved the value of helicopter transport by moving cargo and personnel during the final months of the Korean war and then by participating in prisoner exchanges and other functions after the armistice. The Sikorsky (model S-55) was licensed and built in Great Britain as the Whirlwind. The UH-19 had a three-bladed main rotor and a metal two-bladed tail rotor. The H-19C was powered by a single Pratt & Whitney R-1340-57 550 hp engine; H-19D by a Curtis-Wright R-1300-3D 700 hp piston engine. The Chickasaw had a speed of 113 mph (98 knots). The UH-19D had a cruising speed of 75 mph (65 knots).
H-19 Chickasaw utility helicopter supporting UN Troops in Korea

H-21/CH-21 Series Shawnee assault helicopter (1949). The Beoing-Vertol (formerly Piasacki) H-21 Shawnee was the fourth of a line of tandem rotor helicopters designed by Piasecki. The Boeing Vertol (model 43) H-21, commonly called the "flying banana", was a multi-mission helicopter, utilizing wheels, skis, or floats, and an under-fuselage sling hook. It was used by the USAF for Artic rescue because it performed so well at low temperatures. The CH-21A/CH-21B served with the U.S. Air Force (as the Workhorse), the French Navy, the Royal Canadian Air Force and the West German Air Force. The French used an armed version of the CH-21 in Algeria, mounting guns in the door ways and on the skids. The Army CH-21C assault helicopter could carry 20 fully-equipped troops, or 12 stretchers, plus space for two medical attendants, in the MedEvac role. The CH-21C was first deployed to Vietnam in December 1961 with the Army's 8th and 57th Transportation Companies, in support of ARVN (Army Vietnam) troops. The CH-21B/CH-21C Shawnee could be armed with 7.62mm or 12.7mm door guns. The CH-21C was relatively slow. It's cables and fuel lines were so vulnerable to small arms fire it was even rumored that a CH-21C had been downed by a Viet Cong spear. The Shawnee was the "Workhorse" of Vietnam until 1964 when it was replaced with the fielding of the UH-1 Huey in 1963, and the fielding of the CH-47A Chinook in the early 1960s. Some Shawnees were armed with flex guns under the nose. An interesting experimental version was tested stateside with a Boeing B-29 Superfortress ball-turret mounted beneath the nose. The Shawnee had two tandem fully-articulated three-bladed counter-rotating rotors. The CH-21C was powered by one Curtis-Wright R1820-103 Cyclone supercharged 1250 hp piston engine. The CH-21 had a speed of 128 mph (110 knots).
Initial fielding of 32 CH-21Cs in Vietnam, December 12, 1961
CH-21C Shawnee transporting M101 105mm howitzer (Source US Army AMCOM)
Experimental Cal. .50 twin gun mounts on CH-21 Shawnee (Cancelled December 1962)

H-25A Army Mule light cargo helicopter (1951). The Piasekci H-25 was an eight-place tandem rotor helicopter developed for the U.S. Navy for naval rescue operations. With minor modification, it met Army needs for a light cargo and utility helicopter. The maximum Army inventory reached 63 in 1955. All inventory aircraft were later turned over to the U.S. Navy. The H-25 had two three-bladed counterrotating rotors. The H-25 was powered by a single Continental Motors nine-cylinder radial R-975-46A 550 hp engine and had a cruising speed of 92 mph (80 knots).
H-25A Army Mule light cargo helicopter (Source US Army AMCOM)
H-25A helicopter in flight

CH-34 Choctaw cargo and light tactical transport helicopter (1954). The Sikorsky (model S-58) CH-34A/CH-34B/CH-34C, essentially a lengthened and more powerful version of the Sikorsky (model S-55) H-19 Chickasaw cargo helicopter, could carry up to 16 troops. It could carry eight litters in the MedEvac role. The U.S. Marine Corps version, UH-34D, was the primary Marine utility/assault helicopter used in Vietnam. The Sikorsky (model S-58) was licensed and built in Great Britain as the Wessex. The Choctaw had a single four-bladed main rotor and a four-bladed metal tail rotor. The CH-34C was powered by a single Curtis-Wright R-1820-84C 1425 hp piston engine and had a speed of 123 mph (107 knots).
U.S. Army CH-34 Choctaw cargo helicopter (Source US Army AMCOM)
CH-34 Choctaw armed with XM3 24-tube 2.75 inch rocket launcher (Source US Army AMCOM)
U.S. Marine Corps UH-34D utility helicopter in Vietnam

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CH-37 Series Mojave medium cargo helicopter (1953). Initially procured in 1956, the Sikorsky (model S-56) CH-37A/CH-37B, with a crew of three, was a large medium lift transport helicopter. Clam shell doors in the nose provided access to a cargo compartment that could accommodate two jeeps or a 105mm howitzer. The Mojave could carry 26 troops or 24 litters in the MedEvac role. The CH-37 had a single five-bladed main rotor and a metal four-bladed tail rotor. The CH-37A was powered by two Pratt & Whitney R-2800-50 1900 hp pistons engines; CH-37B was powered by two Pratt & Whitney R-2800-54 2100 hp pistons engines and had a speed of 131 mph (114 knots). It was used for aircraft recovery in Vietnam. The CH-37 was replaced by the CH-47D Chinook, but of course the CH-47 did not have CH-37's heavy-lift capability.
CH-37 Mojave attempting to lift downed CH-21 Shawnee from paddy

CH-47 Series Chinook cargo helicopter (1961). The Boeing Vertol (model 114) YCH-1B/YCH-47A made it's initial hovering flight on 21 September 1961. The all-weather medium lift CH-47A Chinook first entered service in Vietnam about 1966. The CH-47A was powered by either AlliedSignal Engines T55-L-5 2200 shp or T55-L-7 2650 shp engines. CH-47B was powered by two AlliedSignal Engines T55-L-7C 2850 shp engines. Models CH-47A, CH-47B, and CH-47C, all utilized the same airframe, but later models featured upgraded engines. The CH-47B featured a blunted rear rotor pylon, redesigned rotor blades, and strakes along the rear ramp and fuselage to improve flying characteristics. The Boeing Vertol (model 234) CH-47C had a strengthened transmission, AlliedSignal Engines T55-L-11C 3750 shp engines, and increased range. The CH-47C could carry from 33 to 44 troops or 24 litters plus two medical attendants. All three models saw wide use during the Vietnan war. They replaced the H-21 Shawnee in the combat assault role. The Chinook has two three-bladed main rotors, two engines, and a speed of 173 mph (150 knots).
CH-47A SN 64-13140 (with M60D window and door guns) lifting M102 105mm howitzer (Copyright Arnold Da Foot Christensen)
CH-47C Super C with the 242nd ASHC in Alaska (late 1970s) (Copyright Fred Lohr )
Closeup of 242nd ASHC CH-47C Super C equipped with skis (Copyright Fred Lohr )

The CH-47B was the standard troop transport used by the 1st Cavalry Division in Vietnam. The Chinook could be equipped with two door mounting M60D 7.62mm machine guns on the M24 armament subsystem and a ramp mounted M60D using the M41 armament subsystem. A few CH-47A Go-Go Birds were also used experimentally in the gun ship role. Some CH-47 "Bombers" were equipped to roll-out riot control gas or napalm onto Viet Cong bunker complexes from the rear cargo ramp. The CH-47 could be equipped with a hoist and cargo hook. The Chinook proved especially valuable in "Pipe Smoke" aircraft recovery missions. The "Hook" recovered about 12,000 aircraft valued at over $3 billion during the war. Beoing-Vertol (models 114/234) were sold in 13 countries and built under license in Italy. The current versions of the Chinook are the CH-47D and CH-47F.
Royal Australian Air Force Maverick's Chinook picking-up an A-20 Boston twin-engined bomber in Papua New Guinea

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CH-54 Series Tarhe heavy lift helicopter (1962). The Sikorsky (model S-64A) CH-54A/CH-54B Skycrane, with a crew of three, was designed for heavy internal or external lift of heavy bulk loads. It had a rear-facing pilot's seat to provide a clear view of the cargo. A hoist was provided to allow pickups and deliveries without landing. A lightweight van (universal pod) could be attached to the fuselage for use as a mobile command post, maintenance and repair shop, or as a Mobile Army Surgical Hospital (MASH). The field hospital was equipped with X-Ray, lab equipment, and blood bank. It was well lighted and air conditioned so surgery could be performed where ever it was needed. A "people pod" was designed to carry 45 combat-ready troops. The Skycrane served with the 1st Cavalry Division in Vietnam. The CH-54 was used in aircraft recovery operations when loads were too heavy for the CH-47 Chinook. It was also useful for off-loading during ship-to-shore operations. The CH-54 could also be rigged to drop the large 10,000 lb. cratering bomb used to create landing zones ("LZs") in dense jungle. The T-54A Tahre had a six-bladed main rotor, four-bladed metal tail rotor, was powered by two Pratt & Whitney T73-P-1 4500 shp turbine engines, and had a speed of 128 mph (111 knots). The CH-54B was powered by two Pratt & Whitney T73-P-700 4800 sph turbine engines
CH-54 Skycrane recovering parachute stabilized Chinook in Vietnam

TH-55A Osage helicopter trainer (1964). The Hughes (model 269A-1) TH-55A was selected by the U.S. Army for use as it's primary helicopter trainer in mid-1964. It replaced the Hiller H-23B trainer. It was used to train pilots until about 1984. The TH-55A was powered by a Lycoming 180 hp HIO-360-B1A engine.
Hughes TH-55A helicopter trainer at Ft. Wolters, TX in 1966 (Copyright Jerry Barnes, baron67@airmail.net )

Source Material: The Complete Encyclopedia of World Aircraft, General Editor: David Donald, Barnes & Noble, Inc., 1997.

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	Bell Helicopter-Textron http://www.bellhelicopter.textron.com
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	Ft. Rucker, Home of Army Aviation http://www-rucker.army.mil/
	Helicopter's History Site http://www.helis.com
	Igor Sikorsky Historical Archives, Inc. http://www.iconn.net/igor/indexlnk.html
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	US Air Force Museum http://www.asc.wpafb.af.mil/museum/
	U.S. Army Aviation and Missile Command (AMCOM) http://www.redstone.army.mil/history/aviation/ AMCOM Army Aviation videos http://www.redstone.army.mil/history/multi/interact.html#Aviation

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