Captain Walter J. Hodgson (1924–1978) and Major William J. Davis, U.S. Air Force, with the world record-setting Kaman H-43B Huskie, 58-1848. (FAI)
9 December 1959: At Bloomfield, Connecticut, U.S. Air Force Captain Walter J. Hodgson test pilot and Major William J. Davis flew a Kaman H-43B-KA Huskie, 58-1848, to an altitude of 9,097 meters (29,845.8 feet), setting a Fédération Aéronautique Internationale (FAI) World Record for Altitude Without Payload.¹
The helicopter lifted off at 9:12 a.m., after a 1 hour, 12 minute weather delay, and reached its peak altitude at 10:30½. It landed back at Bloomfield after a flight of 1 hour, 53 minutes. 58-1848 was described as being in “mission configuration,” carrying all equipment for a normal operational flight. 58-1848 weighed 5,443 pounds (2,469 kilograms) at takeoff.
It was reported that this was the first altitude record for helicopters accomplished with two pilots on board.
Davis and Hodgson were presented with the Frederick L. Feinberg Award in 1960, for “demonstrating outstanding skills or achievement,” by the American Helicopter Society.
The Kaman Aircraft Corporation H-43 Huskie was a single-engine helicopter using a unique arrangement of counter-rotating and intermeshing rotors. The two rotors turning in opposite directions counteracted the torque effect, eliminating the need for a anti-torque tail rotor. In helicopters using a tail rotor, as much as 30% of the total engine power is used to drive the tail rotor. By eliminating that requirement, the total engine power could be used to produce lift. The Huskie could lift more weight and climb higher than a similar size helicopter with the same engine. Also, retreating blade stall was significantly reduced.
Anton Flettner, 1885–1961. (Library of Congress)
The Kaman Huskie was designed by German inventor Anton Flettner. He had designed and built the Flettner Fl 282 Kolibri. He was brought to the United States at the end of World War II under Operation Paperclip, and went to work at Kaman Aircraft Corporation, Bloomfield, Connecticut.
The 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.
The fuselage of the H-43 was 25.0 feet (7.62 meters) long. Each rotor had a diameter of 47.0 feet (14.33 meters). The overall height was 15 feet, 6 inches (4.724 meters).
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 maximum speed was 107 miles per hour (172 kilometers per hour). Its hover ceiling in ground effect (HIGE) was 20,000 feet (6,096 meters) and it had a range of 250 miles (402 kilometers).
Kaman H-43B-KA Huskie 58-1848 was reclassified as HH-43B in 1962. It was retired to The Boneyard at Davis-Monthan Air Force Base, Tucson, Arizona, in 1972, and was scrapped in 1977.
Kaman H-43B-KA Huskie 58-1848 at Bloomfield, Connecticut, 9 December 1959. (FAI)
21 June 1972: Aérospatiale Chief Test Pilot Jean Boulet set a Fédération Aéronautique Internationale (FAI) Absolute World Record for helicopters by flying the first Aérospatiale SA 315 Lama, serial number 315-001, to an altitude of 12,442 meters (40,820 feet) from Aérodrome d’Istres, northwest of Marseille, France.¹ He also set two class and sub-class world records.² These records remain current.
The SA 315B Lama was designed to perform at the very high altitudes and temperatures necessary for service with the Indian Army. It combined an SE.3130 Alouette II airframe with a much more powerful Turboméca Astazou IIIB turboshaft engine—derated to 550 shaft horsepower—and the rotor system, transmission and gearboxes from the larger 7-place Alouette III.
Jean Boulet in the cockpit of his SA 315 Lama, just prior to his record flight. (Airbus)
The record-setting helicopter was modified by removing all equipment that was not needed for the record flight attempt. Various instruments and the co-pilot and passengers seats were taken out of the cockpit, as well as the helicopter’s synchronized horizontal stabilizer and tail rotor guard. The standard fuel tank was replaced with a very small tank holding just 70 kilograms (approximately 22.7 gallons) of jet fuel. Turboméca modified the engine to increase the output shaft r.p.m. by 6%. After Jean Boulet started the turbine engine, mechanics removed the battery and starter motor to decrease the weight even further.
Final preparations for the altitude record attempt. Jean Boulet sits in the cockpit, wearing an oxygen mask. (Helico-Fascination)
In just 12 minutes, the Lama had climbed to 11,000 meters (36,089 feet). As he approached the peak altitude, the forward indicated airspeed had to be reduced to 30 knots (34.5 miles per hour, 55.6 kilometers per hour) to prevent the advancing main rotor blade tip from reaching its Critical Mach Number in the thin air, which would have resulted in the blade stalling. At the same time, the helicopter was approaching Retreating Blade Stall.
When the helicopter could climb no higher, Boulet reduced power and decreased collective pitch. The Turboméca engine, not calibrated for the very high altitude and cold temperature, -62 °C. (-80 °F.), flamed out. With no battery and starter, a re-start was impossible. Boulet put the Lama into autorotation for his nearly eight mile descent. Entering multiple cloud layers, the Plexiglas bubble iced over. Because of the ice and clouds, the test pilot had no outside visibility. Attitude instruments had been removed to lighten the helicopter. Boulet looked up through the canopy at the light spot in the clouds created by the sun, and used that for his only visual reference until he broke out of the clouds.
Still in autorotation, the SA 315 missed touching down exactly on its takeoff point, but was close enough that FAI requirements were met.
Aérospatiale SA 315 Lama, FAI World Record Holder, 12,442 meters, in autorotation, just before touching down at at Istres, 21 June 1972. (Helico-Fascination)
Two days earlier, 19 June 1972, Boulet and fellow test pilot Gérard Boutin had set another FAI World Record for Altitude Without Payload, when they flew the Lama to 10,856 meters (35,617 feet).³ This record also still stands.
Jean Boulet and Gérard Boutin in the cockpit of SA 315B s/n 315-001. (Airbus)
The SA 315B Lama is a 5-place light turboshaft-powered helicopter which is operated by a single pilot. The helicopter was built to meet the specific needs of the Indian Air Force for operations in the Himalayan Mountains. It was required to take off an land at an altitude of 6,000 meters (19,685 feet) while carrying a pilot, one passenger and 200 kilograms (441 pounds) of cargo.
The fuselage is 10.26 meters (33 feet, 7.9 inches) long. With all rotors turning, the helicopter has an overall length of 12.92 meters (42 feet, 4.7 inches) and height of 3.09 meters (10 feet, 1.7 inches). The SA 315B has an empty weight of 1,021 kilograms (2,251 pounds) and a maximum gross weight of 1,950 kilograms (4,299 pounds). With an external load carried on its cargo hook, the maximum gross weight is 5,070 pounds (2,300 kilograms).
The three-bladed, fully-articulated main rotor has a diameter of 11.02 meters (36 feet, 1.9 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 three-bladed anti-torque tail rotor is 1.91 meters (6 feet, 3.2 inches) in diameter and turns clockwise, as seen from the helicopter’s left side. (The advancing blade is below the axis of rotation.) It turns at 2,020 r.p.m.
The Lama was initially powered by a Turboméca Artouste IIIB (later aircraft, Artouste IIIB1) turbo-moteur. This is a turboshaft engine with a two-stage compressor section (1 axial-flow, 1 centrifugal-flow stages), and a three-stage axial-flow turbine. The engine turns 33,500 r.p.m. and the output drive shaft turns 5,773 r.p.m. The Artouste IIIB1 produces a maximum 870 horsepower, but is derated to 570 horsepower for installation in the Lama. The engine is 1.815 meters (5 feet, 11.5 inches) long, 0.667 meters (2 feet, 2.3 inches) high and 0.520 meters (1 foot, 8.5 inches) wide. It weighs 178 kilograms (392 pounds).
The helicopter has a cruise speed 103 knots (191 kilometers per hour, 119 miles per hour) and a maximum speed of 113 knots (209 kilometers per hour, 130 miles per hour) at Sea Level. The service ceiling is 5,400 meters (17,717 feet). At 1,950 kilograms (4,299 pounds), the Lama has a hover ceiling in ground effect (HIGE) of 5,050 meters (16,568 feet), and out of ground effect (HOGE), 4,600 meters (15,092 feet).
Société nationale des constructions aéronautiques du Sud-Est became Aérospatiale in 1970. The company produced the SA 315B Lama beginning in 1971. It was also built under license by Hundustan Aeronautics in India and Helibras in Brazil.
The total number of SA 315Bs and its variants built is uncertain. In 2010, Eurocopter, the successor to Aérospatiale, announced that it will withdraw the Lama’s Type Certificate in 2020.
The world-record-setting Aérospatiale SA 315B Lama, F-BPXS, serial number 315-001, lifting an external load on its cargo hook, 18 May 1980. (Kenneth Swartz)
After setting the world altitude record, 315-001 was returned to the standard configuration and assigned registration F-BPXS. It crashed at Flaine, a ski resort in the French Alps, 23 February 1985.
Jean Boulet with a SNCASE SE.3130 Alouette II.Médaille de l’Aéronautique
Jean Ernest Boulet was born 16 November 1920, in Brunoy, southeast of Paris, France. He was the son of Charles-Aimé Boulet, an electrical engineer, and Marie-Renée Berruel Boulet.
He graduated from Ecole Polytechnique in 1940 and the Ecole Nationale Supérieure de l’aéronautique In 1942. (One of his classmates was André Edouard Turcat, who would also become one of France’s greatest test pilots.)
Following his graduation, Boulet joined the Armée de l’Air (French Air Force)and was commissioned a sous-lieutenant. He took his first flight lesson in October. After the surrender of France in the Nazi invaders, Boulet’s military career slowed. He applied to l’Ecole Nationale Supérieure de l’Aéronautique in Toulouse for post-graduate aeronautical engineering. He completed a master’s degree in 1943.
During this time, Boulet joined two brothers with LaResistance savoyarde, fighting against the German invaders as well as French collaborators.
In 1943, Jean Boulet married Mlle. Josette Rouquet. They had two sons, Jean-Pierre and Olivier.
In February 1945, Sous-lieutenant Boulet was sent to the United States for training as a pilot. After basic and advanced flight training, Bouelt began training as a fighter pilot, completing the course in a Republic P-47D Thunderbolt. He was then sent back to France along with the other successful students.
On 1 February 1947 Jen Boulet joined Société nationale des constructions aéronautiques du Sud-Est (SNCASE) as an engineer and test pilot. He returned to the United States to transition to helicopters. Initially, Boulet and another SNCASE pilot were sent to Helicopter Air Transport at Camden Central Airport, Camden, New Jersey, for transition training in the Sikorsky S-51. An over-enthusiastic instructor attempted to demonstrate the Sikorsky to Boulet, but lost control and crashed. Fortunately, neither pilot was injured. Boulet decided to go to Bell Aircraft at Niagara Falls, New York, where he trained on the Bell Model 47. He was awarded a helicopter pilot certificate by the U.S. Federal Aviation Administration, 23 February 1948.
Test pilot Jean Boulet (center), with Mme. Boulet and the world-record-setting SE.3130 Alouette II, 1955. (HELIMAT)Officier de l’Legion de Honneur
As a test pilot Boulet made the first flight in every helicopter produced by SNCASE, which would become Sud-Aviation and later, Aérospatiale (then, Eurocopter, and now, Airbus Helicopters).
While flying a SE 530 Mistral fighter, 23 January 1953, Boulet entered an unrecoverable spin and became the first French pilot to escape from an aircraft by ejection seat during an actual emergency. He was awarded the Médaille de l’Aéronautique.
Jean Boulet was appointed Chevalier de la légion d’honneur in 1956, and in 1973, promoted to Officier de la Légion d’honneur.
Jean Boulet had more than 9,000 flight hours, with over 8,000 hours in helicopters. He set 24 Fédération Aéronautique Internationale world records for speed, distance and altitude. Four of these are current.
Jean Boulet wrote L’Histoire de l’Helicoptere: Racontée par ses Pionniers 1907–1956, published in 1982 by Éditions France-Empire, 13, Rue Le Sueuer, 75116 Paris.
Jean Ernest Boulet died at Aix-en-Provence, in southern France, 15 February 2011, at the age of 90 years.
¹ FAI Record File Number 11657: Class: E (Rotorcraft): Sub-Class: E-Absolute (Absolute Record of class E)
² FAI Record File Number 753: Altitude Without Payload: Sub-Class: E-1b (Helicopters: take off weight 500 to 1000 kg). FAI Record File Number 754: Altitude Without Payload: Sub-Class: E-1 (Helicopters).
³ FAI Record File Number 788: Altitude Without Payload: Sub-Class E-1c.
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, 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.3130-01 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.3130-01 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.
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)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 trelocated 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.
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-three 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-three 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.
The Kaman Aircraft Corporation H-43 Huskie was a single-engine helicopter using a unique arrangement of counter-rotating and intermeshing rotors. The two rotors turning in opposite directions counteracted the torque effect, eliminating the need for a anti-torque tail rotor. In helicopters using a tail rotor, as much as 30% of the total engine power is used to drive the tail rotor. By eliminating that requirement, the total engine power could be used to produce lift. The Huskie could lift more weight and climb higher than a similar size helicopter with the same engine. Also, retreating blade stall was significantly reduced.
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).
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