Tag Archives: Allison Division of General Motors

19 June 1947

P-80R speed run
Colonel Boyd flies the Lockheed XP-80R over the 3 kilometer course at Muroc Army Air Field, 19 June 1947. (U.S. Air Force)

19 June 1947: At Muroc Army Airfield (now, Edwards Air Force Base) Colonel Albert Boyd, United States Army Air Forces, set a Fédération Aéronautique Internationale (FAI) World Record for Speed Over a 3 Kilometer Course, with an average speed of 1,003.81 kilometers per hour (623.74 miles per hour).¹ This was not just a class record, but an absolute world speed record.

Col. Boyd flew the Lockheed P-80R Shooting Star, serial number 44-85200, four times over the course, twice in each direction. The record speed was the average of the two fastest consecutive runs. As can be seen in the above photograph, these runs were flown at an altitude of approximately 70 feet (21 meters).

Originally a production P-80A-1-LO Shooting Star, 44-85200 had been converted to the XP-80B, a single prototype for the improved P-80B fighter.

Lockheed P-80A-1-LO shooting Star 44-85004, similar to the fighter being test flown by Richard I. Bong, 6 August 1945. (U.S. Air Force)
A very early production Lockheed P-80A-1-LO Shooting Star, 44-85004. (U.S. Air Force)

The P-80A-1-LO was a single-place, single-engine, low-wing monoplane powered by a turbojet engine. It was a day fighter, not equipped for night or all-weather combat operations. The P-80A was 34 feet, 6 inches (10.516 meters) long with a wingspan of 38 feet, 10.5037 inches (11.8492 meters) and overall height of 11 feet, 4 inches (3.454 meters). The wing had an angle of incidence of 1°, with 1° 30′ negative twist, and 3° 50′ dihedral. The leading edge was swept aft 9° 18′ 33″. The fighter had an empty weight of 7,920 pounds (3,592 kilograms) and a gross weight of 11,700 pounds (5,307 kilograms).

Lockheed P-80A Shooting Star, three-view illustration with dimensions. (U.S. Air Force)

Early production P-80As were powered by either an Allison J33-A-9 or a General Electric J33-GE-11 turbojet engine. The J33 was a licensed version of the Rolls-Royce Derwent. It was a single-shaft turbojet with a 1-stage centrifugal compressor section and a 1-stage axial-flow turbine. The -9 and -11 engines were rated at 3,825 pounds of thrust (17.014 kilonewtons) at 11,500 r.p.m. They were 8 feet, 6.9 inches (2.614 meters) long, 4 feet, 2.5 inches (1.283 meters) in diameter and weighed 1,775 pounds (805 kilograms).

The P-80A-1 had a maximum speed of 510 miles per hour (821 kilometers per hour) at Sea Level, 520 miles per hour (837 kilometers per hour) at 20,000 feet (6,096 meters), and 495 miles per hour (797 kilometers per hour) at 40,000 feet (12,192 meters). The service ceiling was 45,000 feet (13,716 meters).

The P-80A Shooting Star was armed with six Browning AN-M3 .50-caliber  aircraft machine guns mounted in the nose, with 300 rounds of ammunition per gun.

Lockheed P-80B-1-LO Shooting Star 45-8554, 1948. (U.S. Air Force)
Lockheed P-80B-1-LO Shooting Star 45-8554, 1948. (U.S. Air Force)

After modification to the XP-80B configuration, 44-85200 was powered by an Allison J33-A-17 with water/alcohol injection. Retaining the previous engine’s rating of 3,825 pounds of thrust, when augmented with water/alcohol injection, this increased to   4,500 pounds of thrust (20.017 kilonewtons). Fuel capacity was reduced by 45 gallons (170 liters) to allow for the water/alcohol tank.

The XP-80B was the first American-built fighter to be equipped with an ejection seat.

The P-80B was heavier than the P-80A, with an empty weight of 8,176 pounds (3,709 kilograms) and gross weight of 12,200 pounds (5,534 kilograms). Visually, the two variants are almost identical.

The XP-80B had a maximum speed of 577 miles per hour (929 kilometers) per hour at 6,000 feet (1,829 meters), a 19 mile per hour (31 kilometers per hour) increase. The service ceiling increased to 45,500 feet (13,868 meters).

This photograph of XP-80R shows the cut-down windscreen an canopy, recontoured leading edges and the NACA-designed engine intakes. (U.S. Air Force)
This photograph of XP-80R shows the cut-down windscreen and canopy, re-contoured wing leading edges and the low-drag, NACA-designed engine intakes. (U.S. Air Force)

44-85200 was next modified to the XP-80R high-speed configuration. The canopy was smaller, the wings were shortened and their leading edges were re-contoured. In its initial configuration, the XP-80R retained the J33-A-17 engine, and incorporated new intakes designed by the National Advisory Committee for Aeronautics (NACA).

The initial performance of the XP-80R was disappointing. The intakes were returned to the standard shape and the J33-A-17 was replaced by a J33-A-35 engine. This improved J33 would be the first turbojet engine to be certified for commercial transport use (Allison Model 400). It was rated at 5,200 pounds of thrust (23.131 kilonewtons) at 11,750 r.p.m. at Sea Level, and 5,400 pounds of thrust (24.020 kilonewtons) with water/methanol injection.

The J33 was a single-spool turbojet with a single-stage centrifugal-flow compressor, 14 combustion chambers, and a single-stage axial-flow turbine. The J33-A-35 had a maximum diameter of 4 feet, 1.2 inches (1.250 meters) and was 8 feet, 8.5 inches (2.654 meters) long. It weighed 1,795 pounds (814 kilograms).

Lockheed P-80R 44-85200 at the National Museum of the United States Air Force
Lockheed P-80R 44-85200 at the National Museum of the United States Air Force

Technicians who modified the XP-80R at Lockheed Plant B-9 Production Flight Test Center, Metropolitan Airport, Van Nuys (just a few miles west of the main plant in Burbank). They nicknamed the modified Shooting Star “Racey.”

Lockheed XP-80R 44-85200 is in the collection of the National Museum of the United States Air Force at Wright-Patterson Air Force Base, Ohio.

DAYTON, Ohio -- Lockheed P-80R at the National Museum of the United States Air Force. (U.S. Air Force photo)
Lockheed P-80R 44-85200 at the National Museum of the United States Air Force.

At the time of the speed record flight, Colonel Boyd was chief of the Flight Test Division at Wright Field, Dayton, Ohio.

Albert Boyd was born 22 November 1906 at Rankin, Tennessee, the first of three sons of Kester S. Boyd, a school night watchman, and Mary Eliza Beaver Boyd. In 1924, Boyd graduated from high school in Asheville, North Carolina, then attended Buncombe Junior College in Asheville.

Boyd was one of the most influential officers to have served in the United States Air Force. He entered the U.S. Army Air Corps as an aviation cadet 27 October 1927. After completion of flight training at Maxwell Field, Alabama, Boyd was commissioned as a second lieutenant, Air Corps Reserve, 28 February 1929, and as a second lieutenant, Air Corps, United States Army, 2 May 1929.

Lieutenant Boyd married Miss Anna Lu Oheim at San Antonio, Texas, 8 September 1933. She was the daughter of Mr. and Mrs. G.F. Oheim of New Braunfels, Texas, (1907–1981).

He was promoted to 1st lieutenant 1 October 1934. Lieutenant Boyd served as a flight instructor at Maxwell Field, Alabama, and then Brooks, Kelly and Randolph Fields in Texas.

In 1934, 1st Lieutenant Boyd was assigned as engineering and operations officer at Chanute Field, Rantoul, Illinois. He completed the Air Corps technical School and the Engineer Armament Course. On 24 July 1936, Boyd was promoted to the temporary rank of captain. This rank became permanent 2 May 1939. In 1939 he was assigned to the Hawaiian Air Depot as assistant engineering officer, and was promoted to major (temporary), 15 March 1941. He and Mrs. Boyd lived in Honolulu. His Army salary was $3,375 per year. In December 1941, he became the chief engineering officer.

On 10 October 1941, Major Boyd was given the parallel rank of major, Army of the United States (A.U.S.). On 5 January 1942, Major Boyd was promoted to lieutenant colonel (temporary) and rated a command pilot. (Lieutenant colonel, A.U.S., 21 October 1942.) He was advanced to the rank of colonel, A.U.S. (A.C.), 2 November 1942. Following the end of World War II, Colonel Boyd reverted to his permanent rank of major, 2 May 1946, though he continued to serve in the rank of colonel.

In October 1945, Colonel Boyd was appointed acting chief of the Flight Test Division at Wright Field. He became chief of the division, October 1945, and also flew as an experimental test pilot. Boyd believed that it was not enough for Air Force test pilots to be superior pilots. They needed to be trained engineers and scientists in order to properly evaluate new aircraft. He developed the Air Force Test Pilot School and recommended that flight testing operations be centered at Muroc Field in the high desert of southern California, where vast open spaces and excellent flying conditions were available. He was the first commander of the Air Force Flight Test Center.

Colonel Albert G. Boyd with XP-80R 44-85200 (U.S. Air Force)
Colonel Albert G. Boyd with the Lockheed XP-80R, 44-85200. (U.S. Air Force)

Major Boyd was promoted to colonel, United States Air Force, 2 April 1948, and to brigadier general (temporary), 12 January 1950. When Colonel Boyd took command of Muroc Air Force Base in September 1949, he recommended that its name be changed to honor the late test pilot, Captain Glen Edwards, who had been killed while testing a Northrop YB-49 near there, 5 June 1948. Since that time the airfield has been known as Edwards Air Force Base.

Brigadier General Albert Boyd, USAF, commanding the Air Force Flight Test Center at Edwards Air Force Base, with Walter Charles Williams, Director of the National Advisory Committee on Aeronautics High-Speed Flight Research Center, also at Edwards, circa 1950. The model aircraft is of the Northrop X-4 Bantam. (NASA E95-43116-7)

Brigadier General Boyd’s temporary rank was made permanent 9 October 1951, with his date of rank retroactive to 12 January 1950. He was promoted to major general (temporary), 8 March 1952.

In February 1952, General Boyd was assigned as vice commander of the Wright Air Development Center, and commander, 8 June 1952. His final assignment on active duty was as deputy commander of the Air Research and Development Command at Baltimore, Maryland, from 1 August 1955.

From 1947 until he retired in 1957 as a major general, Albert Boyd flew and approved every aircraft in use by the U.S. Air Force. By the time he retired, he had logged over 21,120 flight hours in more than 700 different aircraft. He had been awarded the Legion of Merit, the Distinguished Flying Cross and the Distinguished Service Medal.

Major General Albert Boyd retired from the Air Force 30 October 1957 following 30 years of service.

Major General Albert Boyd, United States Air Force (U.S.. Air Force 200o416-F-AF999-1007)

General Boyd died at Saint Augustine, Florida, 18 September 1976, at the age of 69 years. He is buried at the Arlington National Cemetery.

¹ FAI Record File Number 9863

© 2018, Bryan R. Swopes

20–21 April 1964

Lockheed L-100 Hercules N1130E, in flight. Both outboard engines are shut down and the propellers feathered. (Lockheed Martin)

20–21 April 1964: Nearly ten years after the first flight of the Lockheed YC-130 Hercules prototype, the Lockheed Model 382, serial number 3946, the commercial version of the military C-130E, made the longest first flight in history when it flew for 25 hours, 1 minute, after taking off from Marietta, Georgia.

The flight crew, led by Chief Production Pilot Joe Garrett, flew the Hercules in a racetrack pattern over Georgia and Alabama, and for all but 36 minutes of the flight, the outboard engines were shut down and their propellers feathered.

The Lockheed Model 382 was certified by the Federal Aviation Administration 16 February 1965.

Lockheed personnel celbrate the 25 hour, 1 minute first flight of the commercial L100 Hercules. (Lockheed Martin)
Lockheed personnel celebrate the 25 hour, 1 minute first flight of the commercial L-100 Hercules. (Lockheed Martin)

The L-382 was powered by four Allison 501-D22 turboprop engines, rated at 3,755 shaft horsepower at 13,820 r.p.m., and driving four-bladed Hamilton Standard Hydromatic constant-speed, reversible-pitch propellers with a diameter of 13 feet, 6 inches (4.115 meters). at 1,020 r.p.m.

Maximum operating altitude 32,600 feet (9.936 meters)

N1130E at Fairbanks, leased to Alaska Airlines. (Lockheed Martin)
N1130E at Fairbanks, leased to Alaska Airlines, 1965. (Lockheed Martin)

N1130E was retained by Lockheed as a demonstrator, however it was briefly leased to Alaska Airlines in March 1965, and returned the following month.

The L-382 was converted to the L382E-44K-20 standard in April 1968, with a 5 foot, 0 inch (1.524 meters) segment added to the fuselage behind the cockpit, and a 3 foot, 4 inch (1.016 meter) section behind the wing.

N1130E's fuselage was cut in two places to accommodate an 8 foot, 4 inch ( meter) stretch. (Lockheed Martin)
N1130E’s fuselage was cut in two places to accommodate an 8 foot, 4 inch (2.540 meter) stretch. (c-130hercules.net)
N1130E after conversion to the L100-20 configuration, at Lockheed-Burbank Airport, 1968. (Unattributed)
N1130E after conversion to the L100-20 configuration, at Lockheed-Burbank Airport, 1968. (c-130hercules.net)

N1130E was leased to Delta Air Lines in October 1968, and returned after six months.

Lockheed sold N1130E to Pepsico Airlease Corporation, who leased the freighter to Flying W Airways. It was reregistered as N50FW. In March 1973 Pepsico sold it to Philippine Aerotransport and it was operated for the Philippine government, first as PI-97, then RP-97, and finally, RP-C97. The Hercules was placed in storage in March 1981. With a total flight time of 13,144.8 hours, it was scrapped 18 February 2014.

The first commercial Lockheed L-100, s/n 3946, in service with the Republic of the Philippines. (Ken Fielding via flickr)
The first commercial Lockheed L-100, s/n 3946, in service with the Republic of the Philippines. (Ken Fielding via flickr)

After 71 years, the Lockheed Hercules remains in production, and both military and civil versions are in service worldwide.

Lockheed Martin Model 382J Super Hercules (Lockheed Martin)
Lockheed Martin Model 382J Super Hercules, N100J. (Lockheed Martin)

© 2018, Bryan R. Swopes

16 April 1949

Tony Levier and  Glenn Fulkerson in the prototype Lockheed YF-94. (Lockheed Martin)

16 April 1949: At Van Nuys Airport, California, test pilot Tony LeVier and flight test engineer Glenn Fulkerson made the first flight of the Lockheed YF-94 prototype, serial number 48-356. The aircraft was the first jet-powered all-weather interceptor in service with the United States Air Force and was the first production aircraft powered by an afterburning engine.

Prototype Lockheed YF-94 48-356, first flight, 16 April 1949. (U.S. Air Force)

Two prototypes were built at Lockheed Plant B-9, located on the east side of Van Nuys Airport. Two TF-80C-1-LO (later redesignated T-33A) Shooting Star two-place trainers, 48-356 and 48-373, were modified with the installation of air intercept radar, an electronic fire control system, radar gun sight, four Browning AN-M3 .50-caliber (12.7 × 99 NATO) aircraft machine guns and a more powerful Allison J33-A-33 turbojet engine with water-alcohol injection and afterburner. The rear cockpit was equipped as a radar intercept officer’s station.

The prototype Lockheed YF-94 test fires its four .50-caliber guns at Van Nuys, California. (Lockheed Martin)

It was initially thought that the project would be a very simple, straightforward modification. However, the increased weight of guns and electronics required the installation of a more powerful engine than used in the T-33A. The new engine required that the aft fuselage be lengthened and deepened. Still, early models used approximately 80% of the parts for the F-80C fighter and T-33A trainer. The Air Force ordered the aircraft as the F-94A. Improvements resulted in an F-94B version, but the definitive model was the all-rocket-armed F-94C Starfire.

The prototype Lockheed YF-94, 48-356. (U.S. Air Force)

The Allison J33-A-33 was a single-shaft turbojet engine with a single-stage centrifugal-flow compressor, 14 combustion chambers and, a single-stage axial flow turbine. The engine was rated at 4,600 pounds of thrust (20.46 kilonewtons) and 6,000 pounds (26.69 kilonewtons) with afterburner. The J33-A-33 was 17 feet, 11.0 inches (5.461 meters) long, 4 feet, 1.3 inches (1.252 meters) in diameter and weighed 2,390 pounds (1,084 kilograms).

Originally a P-80C Shooting Star single-place fighter, 48-356 had been modified at Lockheed Plant B-9 in Van Nuys to become the prototype TF-80C two-place jet trainer (the designation was soon changed to T-33A), which first flew 22 March 1948. It was then modified as the prototype YF-94. 48-356 was later modified as the prototype F-94B. It is in the collection of the Air Force Flight Test Museum, Edwards Air Force Base, and is in storage awaiting restoration.

Probably the best-known Lockheed F-94 variant is the all-rocket-armed F-94C Starfire. (Lockheed Martin)

© 2019, Bryan R. Swopes

14 April 1947

Douglas test pilot Gene May with a D-558-I Skystreak research airplane. (Douglas Aircraft Company)

14 April 1947:¹ Douglas Aircraft Company test pilot Eugene Francis (“Gene”) May took the Number 1  U.S. Navy/NACA/Douglas D-558-I Skystreak high-speed research aircraft, Bu. No. 37970, for its first flight at at Muroc Army Airfield. The aircraft had been transported from the Los Angeles factory to Muroc by truck.

Douglas Aircraft Company test pilot Eugene Francis May. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

The Skystreak was a joint United States Navy/National Advisory Committee for Aeronautics (NACA) research aircraft designed to explore flight at high subsonic speed. The Phase I Skystreak was designed by a team led by Douglas Chief Engineer Edward Henry Heinemann. Flight testing was conducted at the NACA High Speed Flight Station at Muroc Army Airfield (later known as Edwards Air Force Base). Three D-558-Is were built, followed by the Phase II, swept-wing Mach 2 D-558-II Skyrocket rocketplane.

The D-558-I carried extensive flight test instrumentation for its time. The wings had 400 orifices for air pressure sensors. During the test series, aircraft stability in the range of 0.82–0.99 Mach was investigated. One of the Skystreaks may have briefly exceeded Mach 1 as it came out of a dive.

Unlike some of the other experimental high speed aircraft of the time, the Skystreak took off from the ground under its own power rather than being carried aloft by a mother ship. While those other aircraft could briefly reach much higher speeds, the D-558-I was able to fly for extended periods in the high-subsonic range, providing scientists and engineers with a tremendous amount of data.

Cutaway illustration of the Douglas D-558-I Skystreak. (U.S. Navy)

The research airplane was a single-place, single-engine, low-wing monoplane with retractable tricycle landing gear. The fuselage of the D-558-I was constructed of an aluminum framework covered with sheet magnesium. It was designed for an ultimate load factor of 18 gs. The wings and tail surfaces were aluminum. The airplane was painted scarlet (not orange, like its contemporary, the Bell X-1) and was known as “the crimson test tube.”

The D-558-I was 35 feet, 1.5 inches (10.706 meters) long with a wingspan of 25 feet, 0 inches (7.620 meters) and overall height of 12 feet, 1.6 inches (3.698 meters). Gross weight 10,105 pounds (4,584 kilograms). It carried 230 gallons (871 liters) of kerosene in its wings.

A Douglas D-558-I Skystreak being inspected by U.S. Navy personnel at the Douglas Aircraft Company plant in Los Angeles, California. [Modelers: Note the GREEN anti-glare panel.] (Getty Images/Bettman)
The D-558-I was powered by a single Allison J35-A-11 turbojet engine. The J35 was a single-spool, axial-flow turbojet with an 11-stage compressor section, 8 combustion chambers and single-stage turbine. The J35-A-11 was rated at 5,000 pounds of thrust (22.24 kilonewtons). The engine was 12 feet, 1.0 inches (3.683 meters) long, 3 feet, 4.0 inches (1.016 meters) in diameter and weighed 2,455 pounds (1,114 kilograms).

Bu. No. 37970 made 101 of the 228 Phase I flights. It set a world speed record 1,031.178 kilometers per hour (640.744 miles per hour), flown by Commander Turner F. Caldwell Jr., U.S. Navy,  20 August 1947.² (Major Marion E. Carl, U.S. Marine Corps, flew the second Skystreak, Bu. No. 37971, to 1,047.356 kilometers per hour (650.797 miles per hour),³ breaking Caldwell’s record.)

After Douglas completed the contractor’s test series, the Number 1 Skystreak was turned over to the NACA High Speed Flight Station and designated NACA 140. It was not as highly instrumented as the Number 2 and Number 3 Skystreaks and was not flown, but was used as a source for spare parts for the other D-558-Is.

Douglas D-558-I Skystreak Bu. No. 37970 is on display at the National Naval Aviation Museum, NAS Pensacola, Florida.

Douglas D-558-I Skystreak, Bu. No. 37970, at the National Naval Aviation Museum, Naval Air Station Pensacola, Florida. (U.S. Navy)

¹ Determining the actual dates of historic events is sometimes difficult. In the case of the first flight of the Douglas D-558-I Skystreak, NASA sources cite 14 April 1947. The Naval History and Heritage Command National Naval Aviation Museum says it took place 15 April. Dozens of contemporary newspapers articles published on 15 April indicate that “flight testing will begin this week,” suggesting that the first flight had not yet taken place.

² FAI Record File Number 9864

³ FAI Record File Number 9865

© 2019, Bryan R. Swopes

27 March 1966

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