Tag Archives: FAI

26 March 1966

Allison Engine Co. test pilot Jack l. Schweibold with teh record-setting prototype Hughes YOH-6A, 62-4213, at Edwards Air Force Base, California, 1966. (FAI)
Allison Engine Co. test pilot Jack Schweibold with the record-setting number three prototype Hughes YOH-6A Light Observation Helicopter, 62-4213, at Edwards Air Force Base, California, 1966. (FAI)

26 March 1926: Allison Engine Company test pilot Jack Schweibold flew the third prototype Hughes Aircraft Company YOH-6A Light Observation Helicopter, 62-4213, 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), including an Absolute Record for Class E (Rotorcraft).¹ These records still stand.

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

One week earlier, 20 March 1966, Hughes Aircraft Company test pilot Jack L. Zimmerman flew the same helicopter to set another distance record of of 1,700.12 kilometers (1,056.41 miles).² One 27 March, Zimmerman would set six more world records with 62-4213.³

Jack Schweibold wrote about the record flight in his autobiography, In the Safety of His Wings (Holy Fire Publishing, DeLand, Florida, 2005). He was one of a group of military and civilian test pilots selected to attempt a series of world record flights, using the number three prototype Hughes YOH-6A, 62-4213, from 20 March to 7 April 1966.

The record attempt began at midnight to take advantage of the cold desert air. The cold-soaked YOH-6A had been fueled with pre-cooled JP-5 in order to get the maximum amount of fuel on board. In addition to the standard fuel tank, two auxiliary tanks were placed in the cabin. The helicopter was so heavy from the overload that it could not hover. Jack made a running take-off, sliding the skids across the concrete until the increasing translational lift allowed the aircraft to break free. He began a very shallow climb.

Schweibold was flying a 60 kilometer (37.28 miles) closed course, but because of the near total darkness, he flew on instruments and was guided from the ground by Air Force test range radar controllers (Spatial Positioning and Orientation Radar Tracking, call sign SPORT). Accuracy was critical. The attempt would be disqualified if the helicopter cut inside of a pylon—which Jack could not see—but if he flew too far outside, the extra distance flown would not be counted and time would be lost. The maximum range would be controlled by the amount of fuel carried in the three tanks, and by the endurance of the pilot.

Throughout the flight, Jack gradually increased the altitude, as the T-63-A-5 turboshaft would be more efficient in thinner, colder air. He was flying a precisely calculated profile, taking into consideration aerodynamic drag, the efficiency of the helicopter’s rotor system, and the performance characteristics of the engine. He had been airborne for four hours before he climbed through 10,000 feet (3,048 meters).

At 14,000 feet (4,267 meters), Schweibold was on oxygen. He continued through 20,000 feet (6,096 meters) but was having trouble staying alert. (It would later be discovered that there was a malfunction in his oxygen mask.)

On the final lap, at 22,000 feet (6,706 meters) Jack had to fly around a towering cumulus cloud and radar contact was lost. He dived to lose altitude and popped out from under the cloud about a half-mile short of the runway.

When he shut down the engine, Jack Schweibold had flown the prototype YOH-6A 2800.20 kilometers (1,739.96 statute miles), non-stop. His record still stands.

Jack set 30 FAI World Records between 1966 and 1986. 26 of these remain current.

Frederick Jack Schweibold was born at Toledo, Ohio, 8 November 1935, the son of Henry E. and Jeanette Schweibold. He attended Ohio State University and majored engineering. He had enlisted in the United States Navy Reserve in 1952 and the joined the United States Air Force in 1954 as an Aviation Cadet. Schweibold went through pilot training at Randolph Air Force Base, San Antonio, Texas, flying the T-34 and T-28. He went on to train in the B-25 at Reese Air Force Base, Lubbock, Texas. Schweibold was commissioned as a second lieutenant and received his pilot’s wings in July 1957. In  momentary decision, he selected helicopter training.

Lieutenant Schweibold flew the Sikorsky H-19B for the Air Rescue Service, assigned to Oxnard Air Force Base, California. (The airfield is now Camarillo Airport, CMA, where I first soloed, and is about ten miles away from my desk.)

After leaving the Air Force, Jack flew Sikorsky S-55s for Chicago Helicopter Service, then Bell 47s for Butler Aviation. In 1960, he was hired by the Allison Division of General Motors as a test pilot and engineer for the new 250-series turboshaft engine.

I had the good fortune to have known Jack Schweibold. I first met him through his involvement in the Helicopter Association International biennial flight instructor recertification seminars, held during the HAI’s annual convention. He kept the seminar classes on track, and in between, was always available for questions. He was the authority on Allison’s 250-series turboshaft engines, and over the years I often called him for technical information and operational advice. On top of that, Jack Schweibold was just an all-around nice guy.

U.S. Army Hughes YOH-6A prototype 62-4213 at Le Bourget, circa 1965.
U.S. Army Hughes YOH-6A prototype 62-4213 at Le Bourget, circa 1965. (R.A. Scholefield Collection)

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 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 mast and also allowed 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 on top.)

Overhead photograph of a Hughes YOH-6. Note the blade cuffs. (U.S. Army)
Overhead photograph of a Hughes YOH-6A. Note the blade cuffs. (U.S. Army)

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.

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

¹ FAI Record File Numbers 786, 787 and 11656

² FAI Record File Number 762

³ FAI Record File Numbers 771, 772, 9920, 9921, 9922, and 9923

© 2017, Bryan R. Swopes

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24 March 1960

The prototype Tupolev Tu-114, CCCP-L5611, a long-range turboprop airliner, on display at the Monino Central Air Force Museum, Moscow. (Aldo Bidini)

24 March 1960: Over a 1,000-kilometer course at Sternberg Point Observatory,¹ a Tupolev Tu-114 Rossiya four-engine turboprop airliner, serial number 88402, registered  CCCP-76459, set eight Fédération Aéronautique Internationale flight records, including a world speed record of 871.38 kilometers per hour (541.45 miles per hour) while carrying a load of 25,000 kilograms (55,115.6 pounds).

Colonel Ivan Moiseevich Sukhomlin, Honored Test Pilot of the Soviet Union

The flight crew for these records were Tupolev Design Bureau senior test pilot Ivan Moiseevich Sukhomlin, Pilot, and Boris Mikhailovich Timoshok, Co-Pilot, and four others.

This is the fastest speed record ever established for any propeller-driven airplane, a record that has stood for 56 years.

FAI Record File Num #8125 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km without payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B. TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

FAI Record File Num #8126 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km with 1 000 kg payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B. TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

FAI Record File Num #8127 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km with 2 000 kg payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B. TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

FAI Record File Num #8128 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km with 5 000 kg payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B. TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

FAI Record File Num #8129 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km with 10 000 kg payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B. TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

FAI Record File Num #8130 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km with 15 000 kg payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B. TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

FAI Record File Num #8131 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km with 20 000 kg payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B.TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

FAI Record File Num #8880 [Direct Link]
Status: ratified – retired by changes of the sporting code
Region: World
Class: C (Powered Aeroplanes)
Sub-Class: C-1 (Landplanes)
Category: Not applicable
Group: 2 : turboprop
Type of record: Speed over a closed circuit of 1 000 km with 25 000 kg payload
Performance: 871.38 km/h
Date: 1960-03-24
Course/Location: Sternberg-Point, Observatoire (USSR)
Claimant Ivan Soukhomline (URS)
Crew B. TIMOCHOK + équipage de 4
Aeroplane: Tupolev TU-114
Engines: 4 Kuznetsov NK- 12

Colonel Alexei Petrovich Yakimov, Honored Test Pilot of the Soviet Union.

The Tupolev Tu-114 Rossiya was a four-engine, turboprop-powered airliner developed from the Tu-95 Bear nuclear-capable long-range heavy bomber. It had a flight crew of five and could be configured to carry from 120 to 220 passengers. The airliner made its first flight 15 November 1957 under the command of Colonel Alexei Petrovich Yakimov,  and began regular service with Aeroflot 24 April 1961.

The Tu-114 is 54.10 meters (177 feet, 6 inches) long, with a wingspan of 51.10 meters (167 feet, 8 inches) and overall height of 15.50 meters (50 feet, 10 inches). The wings are swept to a 35° angle and have significant anhedral. The airliner’s empty weight is 91,000 kilograms (200,621 pounds) and maximum takeoff weight is 171,000 kilograms (376,990 pounds).

The Tu-114 was powered by four Kuznetsov NK-12MV turboprop engines, each driving two counter-rotating four-bladed propellers. The NK-12 was rated at 14,795 shaft horsepower (10.89 megawwatts). The NK-12 is a single-shaft axial-flow turbpprop engine with a 14-stage compressor section and 5-stage turbine. The engine is 19 feet, 8.2 inches (6.000 meters) long, 3 feet, 11.3 inches (1.151 meters) in diameter, and weighs 5,181 pounds (2,350 kilograms).

The Tu-114 had a cruise speed of 770 kilometers per hour (478 miles per hour) at 9,000 meters (29,528 feet) (0.70 Mach), and a maximum speed of 870 kilometers per hour (541 miles per hour) at 8,000 meters (26,247 feet) (0.78 Mach).

The Tupolev Tu-114 was produced from 1958 to 1963, with 32 built. They were in service until 1976.

CCCP-76459, the world-record-setting airliner, was displayed at Novogorod Airport, Veliky Novogorod, Russia, in 1977. It was destroyed by fire in 1990.

¹ The Sternberg Point Observatory, also known as the Sternberg Astronomical Institute (Государственный астрономический институт имени Штернберга), is located in Moscow, Russia.

Sternberg Astronomical Institute

© 2017, Bryan R. Swopes

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23 March 1948

John Cunningham with the record-setting de Havilland DH.110 Vampire (BNPS).
John Cunningham with the record-setting de Havilland DH.100 Vampire F.1, TG/278. Note the metal canopy with porthole. (BNPS).

23 March 1948: During a 45-minute flight over Hatfield, Hertfordshire, England, the de Havilland Aircraft Company chief test pilot, Group Captain John Cunningham, DSO, flew a modified DH.100 Vampire F.1 fighter to a Fédération Aéronautique Internationale (FAI) World Record for Altitude of 18,119 meters (59,446 feet).¹ Cunningham broke the record set nearly ten years earlier by Colonel Mario Pezzi in a Caproni Ca.161 biplane.² (See This Day in Aviation, 22 October 1938)

DH.100 Vampire F.1 TG/278 prior to high-altitude modifications. (de Havilland)
DH.100 Vampire F.1 TG/278 prior to high-altitude modifications. (de Havilland)

The de Havilland DH.100 Vampire F.1 flown by Cunningham was the fifth production aircraft, TG/278. It was built by the English Electric Company at Preston, Lancashire, with final assembly at Samlesbury Aerodrome, and made its first flight in August 1945. It was intended as a prototype photo reconnaissance airplane. The cockpit was heated and pressurized for high altitude, and a metal canopy installed.

The photo reconnaissance project was dropped and TG/278 became a test bed for the de Havilland Engine Company Ghost 2 turbojet (Halford H.2), which produced 4,400 pounds of thrust (19.57 kilonewtons) at 10,000 r.p.m. The Vampire could take the Ghost engine to altitudes beyond the reach of the Avro Lancaster/Ghost test bed already in use. The airplane’s wing tips were each extended 4 feet (1.219 meters) to increase lift.

De Havilland DH.100 Vampire F.1 TG/278 before the record flight. (De Havilland)
De Havilland DH.100 Vampire F.1 TG/278 after modifications. (De Havilland)

The aircraft was stripped of paint to reduce weight. Smaller batteries were used and placed in normal ballast locations. Special instrumentation and recording cine cameras were installed in the gun compartment, and ten cylinders of compressed air for breathing replaced the Vampire’s radio equipment. At takeoff, the Vampire carried 202 gallons (765 liters) of fuel, 40 gallons less than maximum, sufficient for only one hour of flight. The takeoff weight of TG/278 was 8,400 pounds (3,810 kilograms).

John Cunningham had previously flown TG/278 to a world record 496.876 miles per hour (799.644 kilometers per hour) over a 100 kilometer course at Lympne Airport, 31 August 1947.³

TG/278 continued as a test aircraft until it was damaged by an engine fire in October 1950. It was used as an instructional airframe at RAF Halton.

De Havilland DH.100 F Mk 1 Vampire TG/278 after high-altitude modifications (Vic Flintham)
De Havilland DH.100 Vampire F.1 TG/278 with high altitude modifications (De Havilland)

A standard Vampire F.1 was 9.370 meters (30 feet, 8.9 inches) long with a wingspan of 12.192 meters (40 feet, 0 inches) and overall height of 2.700 meters (8 feet, 10.3 inches). The fighter had an empty weight of 6,380 pounds (2,894 kilograms) and gross weight of 8,587 pounds (3,895 kilograms).

The basic Vampire F.1 was powered by a de Havilland-built Halford H.1B Goblin turbojet engine. This engine used a single-stage centrifugal-flow compressor and single-stage axial-flow turbine. It had a straight-through configuration rather than the reverse-flow of the Whittle turbojet from which it was derived. It produced 2,460 pounds of thrust (10.94 kilonewtons) at 9,500 r.p.m., and 3,000 pounds (13.34 kilonewtons) at 10,500 r.p.m. The Goblin weighed approximatley 1,300 pounds (590 kilograms).

It had a maximum speed of 540 miles per hour (869 kilometers per hour), a service ceiling of 41,000 feet (12,497 meters) and range of 730 miles (1,175 kilometers).

The Vampire F.1 was armed with four 20 mm Hispano autocannon in the nose, with 150 rounds of ammunition per gun.

Group Captain John Cunningham, Royal Air Force. (Daily Mail)
Group Captain John Cunningham, Royal Air Force. (BNPS)

Group Captain John Cunningham CBE, DSO and Two Bars, DFC and Bar, AE, DL, FRAeS, was born 1917 and educated at Croydon. In 1935 he became an apprentice at De Havilland’s and also joined the Auxiliary Air Force, where he trained as a pilot. He was commissioned as a Pilot Officer, 7 May 1936, and was promoted to Flying Officer, 5 December 1937. Cunningham was called to active duty in August 1939, just before World War II began, and promoted to Flight Lieutenant, 12 March 1940.

While flying with No. 604 Squadron, Cunningham was awarded the Distinguished Flying Cross, 28 January 1941. He was appointed Acting Squadron Leader, Auxiliary Air Force, and was decorated with the Distinguished Service Order, 29 April 1941. The Gazette reported,

“This officer has continued to display the highest devotion to duty in night fighting operations. One night in April, 1941, he destroyed two enemy bombers during a single patrol and a week later destroyed  three enemy raiders during three different patrols. Squadron Leader Cunningham has now destroyed at least ten enemy aircraft and damaged a number of others. His courage and skill are an inspiration to all.”The London Gazette, 29 April 1941, Page 2445 at Column 1.

King George VI greets Squadron Leader John Cunningham, DSO, DFC, 1941. (BNPS)

Acting Squadron Leader Cunningham’s promotion to Squadron Leader (Temporary) became official 10 June 1941. The King approved the award of a Bar to his Distinguished Flying Cross, 19 September 1941. Squadron Leader Cunningham took command of No. 604 Squadron 1 August 1946.

On 3 March 1944 Wing Commander Cunningham received a second Bar to his Distinguished Service Order. According to The Gazette,

“Within a recent period Wing Commander Cunningham has destroyed three more hostile aircraft and his last success on the night of 2nd January, 1944, brings his total victories to 20, all with the exception of one being obtained at night. He is a magnificent leader, whose exceptional ability and wide knowledge of every aspect of night flying has contributed in large measure to the high standard of operational efficiency of his squadron which has destroyed a very large number of enemy aircraft. His iron determination and unswerving devotion to duty have set an example beyond praise.The London Gazette, 3 March 1944, Page 1059 at Column 1.

Promoted to Group Captain 3 July 1944, Cunningham was the highest scoring Royal Air Force night fighter pilot of World War II, credited with shooting down 20 enemy airplanes. He was responsible for the myth that eating carrots would improve night vision.

In addition to the medals awarded by the United Kingdom, he also held the United States Silver Star, and the Union of Soviet Socialist Republics Order of the patriotic War (1st Class).

Following the War, John Cunningham returned to de Havilland as a test pilot. After the death of Geoffrey Raoul de Havilland, Jr., in 1946, Cunningham became the de Havilland’s chief test pilot. He remained with the firm through a series of mergers, finally retiring in 1980.

Cunningham was appointed an Officer of the Most Excellent Order of the British Empire (OBE) in 1951, and promoted to Commander of the Most Excellent Order of the British Empire (CBE) in 1963. He relinquished his  Auxiliary Air Force commission 1 August 1967.

Group Captain John Cunningham CBE, DSO and Two Bars, DFC and Bar, AE, DL,  died 21 July 2002 at the age of 84 years.

Wing Commander John Cunningham, DSO and two bars, DFC and Bar, AE, Auxiliary Air Force. (Test and Research Pilots, Flight Test Engineers)

¹ FAI Record File Number 9844

² FAI Record File Number 11713: 17,083 meters (56,047 feet)

³ FAI record file number 8884

© 2017, Bryan R. Swopes

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20 March 1966

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

20 March 1966: At Edwards Air Force Base in the high desert of southern California, Hughes Aircraft Company test pilot Jack L. Zimmerman flew the third prototype YOH-6A Light Observation Helicopter, 62-4213, to 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).¹ Fifty-one years later, this record still stands.

One week later, Zimmerman would set six more World Records ² with the “Loach.”

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

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 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 on top.)

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

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.
U.S. Army Hughes YOH-6A prototype 62-4213 at Aéroport de Paris – Le Bourget, 19 June 1965.(R.A. Scholefield via AVIAFORA)

Jack Louis Zimmerman was born 1 September 1921 at Chicago, Illinois, the second of three children of Bernard Zimmerman, an electrician, and Esther Rujawski Zimmerman. He studied engineering at the University of Chicago, but left to enlist in the U.S. Army Air Corps. He graduated from flight school in 1943 and was commissioned a second lieutenant.

Lieutenant Zimmerman was sent to Freeman Field, Indiana, as part of the Army’s first class of student helicopter pilots, training on the Sikorsky R-4. On completion of training he was assigned to a Liberty ship in the western Pacific as part of a Project Ivory Soap Aviation Repair Unit.

Taking off from the Army Transport Serviceship SS Maj. Gen. Robert Olds (formerly, the Liberty ship, SS Daniel E. Garrett), Lieutenant Zimmerman’s helicopter crashed into the sea. For his heroic actions in saving a passenger’s life, he was awarded the Soldier’s Medal:

“For heroism displayed in rescuing an enlisted man from drowning on 1 November 1944. While taking off from the flight deck of the SS Daniel E. Garrett, Lieutenant Zimmerman with Private William K. Troche as passenger was forced to land at sea. Lieutenant Zimmerman at the risk of his life made several dives into the plane when his passenger had difficulty in extricating himself from the craft. When Private Troche’s life preserver failed to operate properly, Lieutenant Zimmerman supported him in the water for approximately 30 minutes and afterwards pulled him to a life preserver, which had been thrown from the ship. The heroism displayed by Lieutenant Zimmerman on this occasion reflects great credit upon himself and the military service.” —http://collectair.org/zimmerman.html

Following World War II, Jack Zimmerman was employed as a commercial pilot, and then a test pilot for the Seibel Helicopter S-4 and YH-24 light helicopters, and when the company was bought by Cessna, he continued testing the improved Cessna CH-1 and UH-41 Seneca. In 1963, Zimmerman began working as a test pilot for the Hughes Tool Company’s Aircraft Division. He retired in 1982.

Jack Louis Zimmerman died at San Diego, California, on his 81st birthday, 1 September 2002.

¹ FAI Record File Number 762

² FAI Record File Numbers 771, 772, 9920, 9921, 9922, and 9923

© 2017, Bryan R. Swopes

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8 March 1910

Elise Raymonde Deroche
Elise Raymonde Deroche

8 March 1910: The Aéro-Club de France issued license # 36 of the Fédération Aéronautique Internationale to Elise Raymonde Deroche (also known as Raymonde de Laroche, and Baroness de Laroche) making her the first woman to become licensed as a airplane pilot.

Pilot Certificate number 36 of the FAI was issued to Mme. de LAROCHE. (Musee de l'Air at l'Espace
Pilot Certificate number 36 of the FAI was issued to Mme. de LAROCHE. (Musee de l’Air at l’Espace)

© 2015, Bryan R. Swopes

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