Tag Archives: World Record for Altitude Without Payload

13 June 1962

Aviation, , , , , , , , , , , , , , , ,
Captain Richard H. Coan, USAF, at Mono Lake, California, 13 June 1962. (FAI)
Captain Richard H. Coan, USAF, at Mono Lake, California, 13 June 1962. (FAI)

13 June 1962: At Mono Lake, California, Captain Richard H. Coan, United States Air Force, set a  Fédération Aéronautique Internationale (FAI) World Record for Distance Over a Closed Circuit Without Landing with a specially prepared Kaman HH-43B Huskie, serial number 60-0263. With cowlings, doors and unneeded internal equipment removed—including brake lines to the rear wheels—the helicopter had an empty weight of just 5,300 pounds (2,404 kilograms).

Captain Richard H. Coan prepares to lift off aboard the HH-43B Huskie, 13 June 1962. (U.S. Air Force)
Near Mono Lake, California, Captain Richard H. Coan prepares to lift off aboard HH-43B-KA Huskie 60-0263, at dawn, 13 June 1962. (U.S. Air Force)

Flying along a 12-mile (19.3 kilometer) section of California Highway 167 (Pole Line Road) on the north shore of the lake, Captain Coan flew 27 laps in just over seven hours, until the Huskie ran out of fuel and settled to the pavement in a low-altitude autorotation. Without brakes and with the rear wheels locked, the helicopter rolled off the side of the roadway, but came to a stop before ending up in a ditch. The total distance flown was 1,055.16 kilometers (655.65 miles), a new Fédération Aéronautique Internationale (FAI) World Record for Distance Over a Closed Circuit Without Landing.¹

Kaman HH-43B Huskie 60-0263 parked at the edge of the roadway after it’s record-setting flight, at Mono Lake, California, 13 June 1962. (FAI)
Kaman HH-43B Huskie 60-0263 parked at the edge of Pole Line Road after its record-setting flight near Mono Lake, California, 13 June 1962. (FAI)

This same helicopter, flown by Captain Walter C. McMeen, set an FAI World Record for Altitude with a 1000 kilogram Payload to an altitude of 8,037 meters (26,368 feet) over Luke Air Force Base, Arizona, 25 May 1961.² On 18 October 1961, again at Bloomfield, Lieutenant Colonel Francis M. Carney set a World Record for Altitude Without Payload when he flew 60-0263 to 10,010 meters (32,841 feet).³ The following week, on 24 October 1961, Colonel Carney set six more world records, flying the HH-43B to 3,000 meters (9,853 feet) in 2 minutes, 41.5 seconds;⁴ 6,000 meters (19,685 feet) in 6 minutes 49.3 seconds;⁵ and to 9,000 meters (29,528 feet) in 14 minutes, 31 seconds.⁶ The following summer, Captain Chester R. Radcliffe, Jr., set an FAI World Record for Distance Without Landing when he flew it from Hill Air Force Base, Utah, to Springfield, Minnesota, a distance of 1,429.80 kilometers (888.44 miles), 5 July 1962.⁷

California Highway 167 (Pole Line Road) runs WSW–ENE, just to the north of Mono Lake. (Google Maps)

The Kaman Aircraft Corporation Huskie was used by the U.S. Air Force, U.S. Navy and Marine Corps, primarily for short range rescue operations. It was operated by two pilots and two rescue crewmen.

A turboshaft engine drove a unique system of counter-rotating and intermeshing rotors to provide lift, thrust and directional control. The counter-rotation cancelled the torque effect so no anti-torque, or tail, rotor was necessary. This allowed all of the engine’s power to drive the main rotor system.

The fuselage of the H-43B was 25 feet, 2 inches (7.671 meters) long. Each rotor had a diameter of 47 feet, 0 inches (14.326 meters). It’s height was 15 feet, 6½ inches (4.737 meters). The helicopter’s empty weight was 4,470 pounds (2,028 kilograms) and its maximum gross weight was 8,800 pounds (3,992 kilograms).****

The H-43B was powered by one Lycoming T53-L-1B turboshaft engine, rated at 860 shaft horsepower at 21,510 r.p.m. The engine uses a 5-stage axial-flow, 1 stage centrifugal-flow, compressor with a single stage gas producer turbine and single-stage power turbine. A reverse-flow combustion section allows significant reduction in the the engine’s total length. The power turbine drives the output shaft through a 3.22:1 gear reduction. The T53-L-1 is 3 feet, 11.8 inches (1.214 meters) long and 1 foot, 11.0 inches (0.584 meters) in diameter. It weighs 460 pounds (209 kilograms).

The Huskie’s economical cruise speed was 98 miles per hour (158 kilometers per hour), and the maximum speed was 120 miles per hour (193 kilometers per hour). Its hover ceiling out of ground effect (HOGE) was 18,000 feet (5,486 meters), and in ground effect (HIGE) was 20,000 feet (6,096 meters) and it had a range of 235 miles (378 kilometers). Normal rotor speed in flight was 255–260 r.p.m., with a minimum 238 r.p.m. in autorotation.

Captain Coan was awarded the Distinguished Flying Cross for the record flight. Later as a major, he commanded Detachment 8, 38th Aerospace Rescue and Recovery Squadron, at Cam Ranh Bay Air Base during the Vietnam War. He retired from the Air Force at the rank of lieutenant colonel.

With the call sign Pedro, the HH-43 was a rescue helicopter that served in combat during the Vietnam War.

The record-setting Kaman HH-43B Huskie 60-0263 was last assigned to Detachment 3, 42nd Aerospace Rescue and Recovery Squadron, Kirtland Air Force Base, New Mexico. It is in the collection of the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio. Its distance record still stands.

Kaman HH-43B-KA Huskie 60-0263 at the National Museum of the United States Air Force. (U.S. Air Force)
Kaman HH-43B-KA Huskie 60-0263 at the National Museum of the United States Air Force. (U.S. Air Force)

¹ FAI Record File Number 1258

² FAI Record File Number 13154

³ FAI Record File Number 1870

⁴ FAI Record File Numbers 13057 and 13135

⁵ FAI Record File Numbers 13056 and 13136

⁶ FAI Record File Number 13137

⁷ FAI Record File Number 13208

**** Maximum overload gross weight is 9,150 pounds (4,150 kilograms) at a load factor of 2.0

© 2020, Bryan R. Swopes

6 June 1955

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Jean Boulet (1920–2011)
Jean Boulet (1920–2011) (Musée de l’Air et de l’Espace)

6 June 1955: Société nationale des constructions aéronautiques du Sud-Est  (SNCASE) Chief Test Pilot Jean Boulet set two Fédération Aéronautique Internationale (FAI) World Records for Altitude Without Payload when he flew the number two prototype SE.3130 Alouette II to an altitude of 8,209 meters (26,932 feet) near Buc, France.¹

SNCASE SE.3130-02
SNCASE SE.3130-02, F-WHHF. An Aérospatiale AS350 Écureuil (A-Star) is approaching. (Airbus Helicopters)

FLIGHT and Aircraft Engineer briefly mentioned the flight:

“. . . On the same day S.N.C.A.S.E. claimed the world’s helicopter height record when the Alouette II, powered by a Turboméca Artouste, reached 27,100ft. The machine took off from Buc, near Paris, climbed for 42 min and landed at Montesson. The pilot was M. Jean Boulet.”

—FLIGHT and AIRCRAFT ENGINEER, No. 2420 Vol. 67. Friday, 10 June 1955, at Page 784

Powered by a Turboméca Artouste IIB1 turboshaft engine, the Alouette II was the first gas turbine helicopter to enter series production. SNCASE would become Aérospatiale, later, Eurocopter, and is now Airbus Helicopters.

The Alouette II is a 5-place light helicopter operated by a single pilot. The fuselage is 9.66 meters (31 feet, 9 inches) long. The three-bladed fully-articulated main rotor has a diameter of 10.20 meters (33 feet, 6 inches). It turns clockwise, as seen from above. (The advancing blade is on the left side of the helicopter.) Normal main rotor speed, NR, is 350–360 r.p.m. The two-blade anti-torque rotor is 1.81 meters (9 feet, 11.25 inches) in diameter and turns clockwise, as seen from the helicopter’s left side. (The advancing blade is below the helicopter.) It turns at 2,020 r.p.m.

Jean Boulet hovers the prototype SE.3130 Alouette II, F-WHHF, 12 March 1955. (Eurocopter)
Jean Boulet hovers the prototype SE.3130-01 Alouette II, F-WHHE, 12 March 1955. (Airbus Helicopters)

The SE.3130 has an empty weight of 895 kilograms (1,973 pounds) and a maximum takeoff weight (MTOW) of 1,600 kilograms (3,527 pounds). The prototype was powered by one Turboméca Artouste IIB1 turboshaft engine which produced 400 horsepower, but was derated to 360 horsepower for installation in the Alouette II.

The helicopter has a cruise speed 175 kilometers per hour (109 miles per hour) at Sea Level, and a maximum speed of 185 kilometers per hour (115 miles per hour) at Sea Level. VNE is 195 kilometers per hour (121 miles per hour.)

The service ceiling is 4,000 meters (13,123 feet) at 1,500 kilograms (3,307 pounds) gross weight. The absolute ceiling is 4,500 meters (14,764 feet). At 1,350 kilograms (2,976 pounds) the Alouette II has a hover ceiling in ground effect, HIGE, of 3,400 meters (11,155 feet) and hover ceiling out of ground effect of 1,900 meters (6,234 feet). At 1,500 kilograms the Alouette II’s HIGE is 2,000 meters (6,560 feet) and HOGE is 600 meters (1,968 feet).

The SE.3130 Alouette was in production from 1956 until 1975. More than 1,300 of these helicopters were built.

SNCASE SE 3130 Alouette II F-WHHF prototype with test pilot jean Boulet, 12 March 1955. (Eurocopter)
SNCASE SE.3130-01 Alouette II F-WHHE prototype with test pilot Jean Boulet, 12 March 1955. (Airbus Helicopters)

Jean Boulet was born 16 November 1920, in Brunoy, southeast of Paris, France. He graduated from Ecole Polytechnique in 1940 and the Ecole Nationale Supérieure de l’aéronautique In 1942. As an officer of the Armée de l’Air (French Air Force) he was sent to the United States for training as a fighter pilot, and later as a helicopter pilot. In 1947 he  joined Société nationale des constructions aéronautiques du Sud-Est (SNCASE) as an engineer and test pilot. As a test pilot he made the first flight in every helicopter produced by SNCASE, which would become Sud-Aviation and later Aérospatiale (then, Eurocopter, and now, Airbus Helicopters). He set 24 Fédération Aéronautique Internationale world records for speed, distance and altitude. While flying a SE 530 Mistral fighter, 23 January 1953, he entered an unrecoverable spin and became the first French pilot to escape from an aircraft by ejection seat during an actual emergency. Médaille de l’Aéronautique. In 1972 he was appointed Officier de la Légion d’honneur. He had more than 9,000 flight hours with over 8,000 hours in helicopters.

Jean Boulet died at Aix-en-Provence, 15 February 2011, at the age of 90.

¹ FAI Record File Numbers 9876, 9877

© 2018, Bryan R. Swopes

21 May 1949

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Captain Hubert D. Gaddis, USAAF with teh Sikorsky S-51-1. NAA representatives check baraographs. (Sikorsky Archives)
Captain Hubert D. Gaddis, United States Army, with the Sikorsky S-52-1 NX92824. NAA representatives Walter Goddard and Charles Logsdon check the barographs. (Sikorsky Archives)

21 May 1949: Captain Hubert Dale Gaddis, Field Artillery, United States Army, flew a prototype Sikorsky S-52-1 helicopter, serial number 52003, registration NX92824, to a Fédération Aéronautique Internationale (FAI) World Record for Altitude Without Payload of 6,468 meters (21,220 feet) over Bridgeport, Connecticut. ¹ The flight was observed by National Aeronautic Association representatives Walter Goddard and Charles Logsdon.

The Sikorsky S-52-1 was a completely new design based on the company’s experience with the earlier R-4 and R-5/S-51 models. It was a two-place light helicopter of all metal monocoque construction, using primarily aluminum and magnesium. With Sikorsky test pilot Harold Eugene (“Tommy”) Thompson at the controls, the prototype made its first flight 4 May 1948.

The three-bladed fully-articulated articulated main and two-bladed tail rotor were also of all metal construction. The main rotor had a diameter of 33 feet (10.058 meters) and rotated counter-clockwise as seen from above. (The advancing blade is on the right side of the helicopter.) It had an extruded aluminum spar, covered with sheet duralumin, riveted and glued in place. The blade used a NACA 0012 airfoil with -6° twist. The two-bladed semi-rigid tail rotor was mounted on the left side of the tail boom in a pusher configuration. It had a diameter of 6 feet, 4 inches (1.930 meters) and rotated counter clockwise, as seen from the helicopter’s left. (The advancing blade is at the top of the tail rotor arc.)

The S-52-1 was powered by an air-cooled, normally-aspirated, 425.29-cubic-inch-displacement (6.97 liter) Franklin Engine Company 6V6-245-B16F (O-425-1) vertically-opposed 6-cylinder overhead valve engine. The engine was rated at 245 horsepower at 3,275 r.p.m.

On 27 April 1949 Tommy Thompson flew the same helicopter to an FAI speed record of 208.49 kilometers per hour (129.55 miles per hour) over a 3 kilometer straight course at Cleveland, Ohio, ² and on 6 May, to 197.54 kilometers per hour (122.75 miles per hour) over a 100-kilometer course between Milford and Westbrook, Connecticut. ³

Sikorsky S-52-1 NX92824 (FAI)
Sikorsky S-52-1 NX92824 (FAI)
Hubert Gaddis. (Tom Tom 1938)

Hubert Dale Gaddis was born in Jasper County, Missouri, 9 September 1920, the first of two children of Hubert E. Gaddis, a utility company purchasing agent, and Beatrice Mae Cook Gaddis.

The family relocated to Tulsa, Oklahoma, where Hubert attended Central High School. While there, he developed an interest in radio. Gaddis graduated in 1938.

Gaddis married Martha Tucker in 1950. They would have three children, Cheryl, Sandra and Dale.

Captain Hubert D. Gaddis, Artillery, United States Army. (FAI)

Gaddis enlisted in the United States Army in Oklahoma, 24 September 1942. He had brown hair and hazel eyes, was 5 feet, 6 inches (1.68 meters) tall and weighed 133 pounds (60.3 kilograms).

Gaddis was commissioned a second lieutenant, Army of the United States (AUS), 18 February 1944. He remained in the Army following World War II as an officer in the Field Artillery (Regular Army). In 1956, he graduated of the Army Command and General Staff College.

On September 8 1966, Gaddis was promoted to the rank of colonel (temporary). The rank became permanent 1 July 1971. He was released from military service 28 February 1974. During his career, Colonel Gaddis had been awarded the Distinguished Flying Cross, the Bronze Star Medal, and the Air Medal with 14 oak leaf clusters (15 awards).

Colonel Hubert Dale Gaddis, United States Army (Retired) died 24 February 1976 at the age of 55 years. He was buried at Woodlawn Memorial Gardens, Ozark, Alabama.

¹ FAI Record File Number 2181

² FAI Record File Number 13097

³ FAI Record File Number 13146

© 2019, Bryan R. Swopes

29 April 1975

Aviation, , , , , , , , , , ,
Major General Manucheher Khosrowdad ( منوچهر خسروداد ), Imperial Iranian Army Aviation, in the cockpit of a Bell 214A Isfahan.

29 April 1975: 3 days after delivery of first production Bell 214A “Isfahan,” (IIAF serial number 6-4651, Bell serial number 27004), Major General Manucheher Khorowdad, Imperial Iranian Army Aviation, with Clem A. Bailey, Bell assistant chief production test pilot, as co-pilot, took off from Ahwaz Commercial Airport (AWZ) in southwestern Iran to set five Fédération Aéronautique Internationale (FAI) world records. The airport’s elevation is 66 feet (20 meters) above Sea Level. The air temperature at the time was reported to be 35–38 °C. (95–100 °F.).

The Bell 214A climbed to a height of 3,000 meters (9,842.52 feet) in 1 minute, 58 seconds; ¹ 6,000 meters (19,685.04 feet) in 5 minutes, 14 seconds; ² and 9,000 meters (29,527.56 feet) in 15 minutes, 5 seconds; ³ The helicopter reached a peak altitude of 9,071 meters (29,760.5 feet), setting a record for altitude without payload.⁴ It was able to maintain an altitude of 9,010 meters (29,560.4 feet) in horizontal flight.⁵

All five of these records remain current.

Major General Manucheher Khosrowdad was murdered by Islamic revolutionaries at 23:30, 15 February 1979. He and three other Iranian military officers were the first to be killed following the revolution. A “tribunal” found him guilty of “corruption on Earth.” His prized German Shepherd Dogs were also slaughtered. His remains were then displayed in public. Eventually, his body was interred at Behesht-e Zahra Cemetery, Tehran.

Bell 214A Isfhahan 6-4656. This is the fifth production BH 214A, manufacturer’s serial number 27009. It was photographed at Tabriz International Airport (TBZ) on 7 March 2023. (© Mehdi Piltan. Image used with permission.)

The Bell 214A was developed from the prototype Bell 214 Huey Plus (which first flew in October 1970 and was powered by a 1,900-shaft horsepower Lycoming T53-L-702 turboshaft engine) for Imperial Iranian Army Aviation. Bell built three prototype 214As, powered by the Lycoming T55-L7C (2,050 shaft horsepower). One of these was shipped to Iran in August 1972 for evaluation.

The helicopter is flown by a pilot and co-pilot. It can carry 15 combat troops.

The production 214A was powered by the Lycoming LTC4B-8D turboshaft, rated at 2,930 shaft horsepower.

Iran ordered 287 Bell 214As. Iran named the Bell 214, “Isfahan,” after a city in Iran where it was planned to build a Bell helicopter production facility to produce additional 214A/Cs, and as many as 350 of the stretched, twin-engine Bell 214STs.

The first production BH 214A, 6-4561 (Bell serial number 27004), was built in Texas and delivered in Iran on 26 April 1975.

Because of the Iranian revolution of 1978–1979, the Isfahan facility was never built. All of the BH 214A/Cs and BH 214STs for Iran were built in Texas: 287 214As, 39 214C search and rescue variants, and 48 214STs. Sanctions against the Iran regime have prevented any spare parts for these helicopters being delivered to Iran, but it is believed that that country has produced counterfeit parts. It is not known how many of these helicopters remain in service, but a 2018 estimate suggested just 22.

The Bell 214A was built using a strengthened UH-1H airframe. It had a semi-rigid rotor system without the stabilizer bar of previous UH-1 models. The 214A’s rotor system included elastomeric bearings.

The fuselage is 44 feet, 1.09 inches (13.4389 meters) long. The helicopter has a maximum height of 12 feet, 10 inches (3.9116 meters). With blades turning, its maximum length is 60 feet, 2.27 inches (18.3457 meters). The 214A’s main rotor diameter is 50 feet, 0 inches (15.24 meters). The main rotor blades have a chord of approximately 3 feet (0.9 meters). As with all American helicopters, the main rotor turns counter-clockwise when viewed from above. (The advancing blade is on the right.) The tail rotor is mounted on the right side of the vertical pylon, and turns clockwise as viewed from the left side of the helicopter. (The advancing blade is below the axis of rotation.) It has a diameter of 9 feet, 8.00 inches (2.9464 meters). The tail rotor blades have a chord of 12.00 inches (0.3048 meters).

Bell 214 two-view illustration

The Lycoming LTC4B-8D (an uprated version of the T55-L-7) is a turboshaft engine with a 7-stage axial-flow, single-stage centrifugal-flow compressor section, a reverse-flow combustor, two-stage high-pressure gas producer and two-stage free power turbine. It can produce 2,930 shaft horsepower, but is derated to 2,250 shaft horsepower. The engine is 3 feet, 9.5 inches (1.557 meters) long, 2 feet, 1.1 inches (0.63754 meters) in diameter, and weighs 618 pounds (280 kilograms).

The Bell 214A has an empty weight of 7,588 pounds (3,441.9 kilograms) and gross weight of 13,800 pounds (6,259.6 kilograms). It can carry up to 7,500 pounds of cargo suspended from its cargo hook, in which case its maximum gross weight is 16,000 pounds (7,257.5 kilograms).

The Bell 214A has a maximum speed of 140 knots (161.1 miles per hour/259.3 kilometers per hour). Its range is 222 nautical miles (255 statute miles/411 kilometers). Its service ceiling of 16,400 feet (4,998.7 meters).

First flight, Bell 214A, Fort Worth, Texas. (Vertiflite May/June 1974)

Bell went on to produce a commercial variant of the BH 214A, which it designated the Bell 214B BigLifter. This model received a FAA Type Certificate 27 January 1976. On 3 February 1976, a second model, the BH 214B-1, was also certified. The BH 214B-1 has a lower gross weight than the 214B, but the only actual difference between the two models is the aircraft data plate and the flight manual. This was done due to certification standards of various countries which would place the 214B in a “large helicopter” classification. Only 70 of these commercial models were built.

A commercial Bell 214B BigLifter with Canadian registration. (Aircraft.com)

Another commercial BH214 variant was also produced, the 214ST. Initially called the “Stretched Twin,” this helicopter featured two turboshaft engines, a 2 foot, 6 inch (0.762 meters) increase in length, and a larger diameter main rotor system. This helicopter was also intended to serve with Iranian Army Aviation, and 350 were to be built at the Isfahan facility.

A Bell 214ST Super Transport, G-BKFN, of British Caledonian Helicopters, photographed at Aberdeen Airport, 8 September 1982. (Gary Watt via Wikipedia).

Marketed as the 214ST SuperTransport, this helicopter could be ordered with either fixed skids or fixed tricycle landing gear. A total of just 96 were built, with 48 for Iran. The others were for commercial customers, or the militaries of several countries.

Bell Helicopter transferred FAA Type Certificates for the Model 214B, 214B-1, and 214ST helicopters to Erickson Incorporated, Central Point, Oregon, in 2020.

¹ FAI Record File Number 1850

² FAI Record File Number 1849

³ FAI Record File Number 1848

⁴ FAI Record File Number 1879

⁵ FAI Record File Number 9935

© 2024, Bryan R. Swopes

27 March 1966

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Test pilot Jack L. Zimmerman with the record-setting Hughes YOH-6A Light Observation Helicopter, 62-4213. (FAI)

27 March 1966: At Edwards Air Force Base in the high desert of southern California, Hughes Aircraft Company test pilot Jack Louis Zimmerman flew the third prototype YOH-6A Light Observation Helicopter, 62-4213, to set six Fédération Aéronautique Internationale (FAI) World Record for Altitude and Time-to-Climb. The records were set in two sub-classes, based on the helicopter’s take-off weight. Fifty-eight years later, one of these records still stands.

Hughes YOH-6A 62-4213 at Edwards Air Force Base, 1966. (FAI)

Zimmerman took the YOH-6A from the surface to a height of 3,000 meters (9,843 feet) in 4 minutes, 1.5 seconds ;¹ and to 6,000 meters (19,685 feet) in 7 minutes, 12 seconds.² The helicopter reached an altitude in level flight of 8,061 meters (26,447 feet).³  9921 remains the current record for helicopters in Sub-Class E-1b, with a takeoff weight of 500–1,000 kilograms (1,102–2,205pounds).

Beginning with a takeoff weight between 1,000–1,750 kilograms (2,205–3,858 pounds) (Sub-Class E-1c), Zimmerman took the “loach” to a height 3,000 meters (9,843 feet) in 5 minutes, 37 seconds.⁴ The helicopter reached an altitude of 5,503 meters (16,578 feet), without payload.⁵

[The field elevation of Edwards Air Force Base (EDW) is 2,210 feet (704 meters) above Sea Level. If the time-to-altitude flights had been made at nearby NAS Point Mugu (NTD) on the southern California coast, which has a field elevation 13 feet (4 meters), the times might have been significantly reduced. The air temperature at Edwards, though, was much colder.]

One day earlier, 26 March, Allison Engine Company test pilot Jack Schweibold flew the same YOH-6A  to set three Fédération Aéronautique Internationale (FAI) World Records for Distance Over a Closed Circuit Without Landing of 2,800.20 kilometers (1,739.96 miles).⁶ One week earlier, 20 March, Jack Zimmerman had set a Fédération Aéronautique Internationale (FAI) World Record for Distance Over a Closed Circuit Without Landing of 1,700.12 kilometers (1,056.41 miles).⁷ Fifty-eight years later, these four World Records still stand.

The Hughes Model 369 was built in response to a U.S. Army requirement for a Light Observation Helicopter (“L.O.H.”). It was designated YOH-6A, and the first aircraft received U.S. Army serial number 62-4211. It competed with prototypes from Bell Helicopter Company (YOH-4) and Fairchild-Hiller (YOH-5). All three aircraft were powered by a lightweight Allison Engine Company turboshaft engine. The YOH-6A won the three-way competition and was ordered into production as the OH-6A Cayuse. It was nicknamed “loach,” an acronym for L.O.H.

The third prototype YOH-6A, 62-4213, testing the XM-7 twin M60 7.62 weapons system. (U.S. Army)

The YOH-6A was a two-place light helicopter, flown by a single pilot. It had a four-bladed, articulated main rotor which turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right.) Stacks of thin stainless steel “straps” fastened the rotor blades to the hub and were flexible enough to allow for flapping and feathering. Hydraulic dampers controlled lead-lag. Originally, there were blade cuffs around the main rotor blade roots in an attempt to reduce aerodynamic drag, but these were soon discarded. A two-bladed semi-rigid tail rotor was mounted on the left side of the tail boom. Seen from the left, the tail-rotor rotates counter-clockwise. (The advancing blade is above the axis of rotation.)

The YOH-6A was powered by a T63-A-5 turboshaft engine (Allison Model 250-C10) mounted behind the cabin at a 45° angle. The engine was rated at 212 shaft horsepower at 52,142 r.p.m. (102% N1) and 693 °C. turbine outlet temperature for maximum continuous power, and 250 shaft horsepower at 738 °C., 5-minute limit, for takeoff. Production OH-6A helicopters used the slightly more powerful T63-A-5A (250-C10A) engine.

The Hughes Tool Company Aircraft Division built 1,420 OH-6A Cayuse helicopters for the U.S. Army. The helicopter remains in production as AH-6C and MH-6 military helicopters, and the MD500E and MD530F civil aircraft.

Hughes YOH-6A 62-4213 is in the collection of the United States Army Aviation Museum, Fort Rucker, Alabama.

U.S. Army Hughes YOH-6A prototype 62-4213 at Le Bourget, circa 1965.

¹ FAI Record File Number 9922

² FAI Record File Number 9923

³ FAI Record File Numbers 9920 and 9921

⁴ FAI Record File Number 771

⁵ FAI Record File Number 772

⁶ FAI Record File Numbers 786, 787 and 11656.

⁷ FAI Record File Number 762.

© 2017 Bryan R. Swopes