Tag Archives: Helicopter

10 November 1949

Sikorsky YH-19 49-2012 first flight, Bloomfield, Connecticut, 10 November 1949. (Sikorsky, a Lockheed Martin Company)

10 November 1949: At Bloomfield, Connecticut, Dimitry D. (“Jimmy”) Viner, a nephew of Igor Sikorsky and chief test pilot for the Sikorsky Aircraft Corporation, made the first flight of the prototype Sikorsky S-55 helicopter, serial number 55-001, which the U.S. Air Force had designated YH-19 and assigned serial number 49-2012.

Five YH-19 service test aircraft were built. Two were sent to Korea for evaluation in combat. As a result, the United States Air Force placed an initial order for 50 H-19A Chickasaw helicopters. (It is customary for U.S. Air Force and U.S. Army helicopters to be named after Native American individuals or tribes, though there are exceptions.) This was quickly followed by orders for 264 H-19B helicopters.

Sikorsky YH-19 49-2014 in Korea, circa 1951. (U.S. Air Force)

The United States Navy ordered 118 S-55s which were designated HO4S-1 and HO4S-3. The U.S. Coast Guard bought 30 HO4S-1G and HO4S-3Gs configured for rescue operations. The U.S. Marine Corps purchased 244 HRS-1, HRS-2 and HRS-3 helicopters. The U.S. Army ordered 353 H-19C and H-19D Chickasaw utility transports. The remaining 216 Sikorsky-built helicopters were S-55, S-55C and S-55D commercial models.

Cutaway drawing of the Sikorsky S-55/H-19/HO4S/HRS. Note the rearward-facing, angled placement of the radial engine.(Sikorsky Historical Archives)
Cutaway illustration of the Sikorsky S-55/H-19/HO4S/HRS. Note the rearward-facing, angled placement of the radial engine. (Sikorsky Historical Archives)

The S-55 was flown by two pilots in a cockpit placed above the passenger/cargo compartment. The most significant design feature was moving the engine from directly under the main rotor mast to a position at the front of the helicopter. Installed at an angle, the engine turned a drive shaft to the main transmission. The engine placement provided space for a large passenger/cargo compartment. The aircraft was constructed primarily of aluminum and magnesium, with all-metal main and tail rotor blades.

The main rotor consisted of three fully-articulated blades built of hollow aluminum spars, with aluminum ribs. Spaces within the blade were filled with an aluminum honeycomb. The blades were covered with aluminum sheet. The hollow spars were filled with nitrogen pressurized to 10 p.s.i.  An indicator at the blade root would change color if nitrogen was released, giving pilots and mechanics an indication that the spar had developed a crack or was otherwise compromised. The main rotor turned counter-clockwise as seen from above. (The advancing blade is on the helicopter’s right.) Flapping hinges were offset from the main rotor axis, giving greater control response and effectiveness. The tail rotor was mounted on the helicopter’s left side in a pusher configuration. It turned clockwise as seen from the helicopter’s left.

The helicopter’s fuselage was 42 feet, 2 inches (12.852 meters). The main rotor had a diameter of 53 feet, 0 inches (16.154 meters) and tail rotor diameter was 8 feet, 8 inches (2.642 meters), giving the helicopter an overall length with all blades turning of 62 feet, 2 inches (18.948 meters). It was 13 feet, 4 inches (4.064 meters) high. The landing gear tread was 11 feet (3.353 meters). The S-55 had an empty weight of 4,785 pounds (2,173 kilograms) and maximum takeoff weight of 7,200 pounds (3,271 kilograms). Fuel capacity was 185 gallons (698 liters).

The YH-19 was powered by an air-cooled, supercharged 1,343.804-cubic-inch-displacement (22.021 liter) Pratt & Whitney R-1340-57 (Wasp S1H2) 9-cylinder radial engine mounted at a 35° angle in the fuselage forward of the crew compartment. This was a direct-drive engine which had a Normal Power rating of 550 horsepower at 2,200 r.p.m. to 8,000 feet (2,438 meters), and 600 horsepower at 2,250 r.p.m. for Take Off.

Later production S-55 commercial and H-19/HO4S and HRS military helicopters used an air-cooled, supercharged 1,301.868-cubic-inch (21.334 liter) Wright Aeronautical Division 871C7BA1 Cyclone 7 (R-1300-3) 7-cylinder radial engine with a compression ratio of 6.2:1. The R-1300-3 was also a direct-drive engine, but was rated at 700 horsepower at 2,400 r.p.m., Normal Power, and 800 horsepower at 2,600 r.p.m. for Take-Off. Both engines incorporated a large cooling fan to circulate air around the cylinders. The R-1300-3 was 49.68 inches (1.261 meters) long, 50.45 inches (1.281 meters) in diameter, and weighed 1,080 pounds (490 kilograms).

Sikorsky Aircraft Corps. YH-19 49-2012 (c/n 55-001) shown with engine "clam shell" doors open. This allowed excellent access to the engine for maintenance.
Sikorsky Aircraft Corps. YH-19 49-2012 (c/n 55-001) shown with engine “clam shell” doors open. This allowed excellent access to the engine for maintenance. (Sikorsky Historical Archives)

The S-55 had a maximum speed of 95 knots (109 miles per hour, 176 kilometers per hour) at Sea Level. The helicopter’s hover ceiling in ground effect (HIGE) was 7,875 feet (2,400 meters) and out of ground effect (HOGE) is 4,430 feet (1,350 meters). The service ceiling was 11,400 feet (3,475 meters) and range was 405 miles (652 kilometers).

Sikorsky Aircraft Corporation built 1,281 S-55-series helicopters. Another 477 were built under license by Westland Aircraft Ltd., Société Nationale des Constructions Aéronautiques du Sud-Est (SNCASE) and Mitsubishi Heavy Industries.

49-1012 is in the collection of the Smithsonian Institution National Air and Space Museum.

The first of five YH-19 service test helicopters, 49-2012 is on display at the Smithsonian Institution National Air and Space Museum. (NASM)
The first of five YH-19 service test helicopters, 49-2012, is on display at the Smithsonian Institution National Air and Space Museum. (NASM)
Dimitry D. Viner, circa 1931

Дмитро Дмитрович Вінер (Dimitry Dimitry Viner) was born in Kiev, Ukraine, Imperial Russia, 2 October 1908. He was the son of Dimitry Nicholas Weiner and Helen Ivan Sikorsky Weiner, a teacher, and the sister of Igor Ivanovich Sikorsky.

At the age of 15 years, Viner, along with his mother and younger sister, Galina, sailed from Libau, Latvia, aboard the Baltic-American Line passenger steamer S.S. Latvia, arriving at New York City, 23 February 1923.

“Jimmy” Viner quickly went to work for the Sikorsky Aero Engineering Company, founded by his uncle, Igor Sikorsky.

Dimitry Viner became a naturalized United States citizen  on 27 March 1931.

Viner married Miss Irene Regina Burnett. The had a son, Nicholas A. Viner.

A Sikorsky YR-5A flown by Jimmy Viner with Captain Jack Beighle, hoists a crewman from Texaco Barge No. 397, aground on Penfield Reef, 29 November 1945. (Sikorsky Historical Archive)

On 29 November 1945, Jimmy Viner and Captain Jackson E. Beighle, U.S. Army, flew a Sikorsky YR-5A to rescue two seamen from an oil barge which was breaking up in a storm off of Fairfield, Connecticut. This was the first time that a hoist had been used in an actual rescue at sea.

Jimmy Viner made the first flight of the Sikorsky S-51 prototype on 16 February 1946, and in 1947, he became the first pilot to log more than 1,000 flight hours in helicopters.

Dimitry Dimitry Viner died at Stratford, Connecticut, 14 June 1998, at the age of 89 years.

Dimitry D. (“Jimmy”) Viner with a Sikorsky S-51, the civil version of the R-5. (Sikorsky Historical Archive)

© 2018, Bryan R. Swopes

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30 October 1991

Sikorsky HH-60G Pave Hawk 88-26118 of the 12th Rescue Wing—a sister ship of Jolly 110—recovers pararescue jumpers during a training mission outside of San Francisco's Golden Gate. (TSGT Lance Cheung, U.S. Air Force)
Sikorsky HH-60G Pave Hawk 88-26118 of the 129th Rescue Wing, California Air National Guard, recovers pararescue jumpers during a training mission outside of San Francisco’s Golden Gate. (Technical Sergeant Lance Cheung, U.S. Air Force)

30 October 1991: United States Air Force Sikorsky HH-60G Pave Hawk, 88-26110, call sign “Jolly 110,” assigned to the 106th Rescue Wing, New York Air National Guard, headed out into a hurricane that would become known as “The Perfect Storm.” Aboard were Major C. David Ruvola, pilot; Captain Graham Buschor, co-pilot; Staff Sergeant James R. Mioli, flight engineer; and pararescue jumpers Technical Sergeant John Spillane and Technical Sergeant Arden Rick Smith. Their mission was to attempt a rescue 250 miles (400 kilometers) out to sea.

Due to the severity of the storm—a weather buoy located 264 miles (425 kilometers) south of Halifax, Nova Scotia, reported a wave height of 100.7 feet (30.7 meters) on 30 October, the highest ever recorded in that part of the Atlantic Ocean—the Pave Hawk crew was unable to make the rescue and had to return to their base.

Having already refueled from the Lockheed HC-130 Hercules tanker three times during the mission, and with low fuel, a fourth refueling was needed for the helicopter to make it back to the mainland. Because of the the extreme turbulence and lack of visibility, Jolly 110 could not make contact with the refueling drogue trailing behind the airplane.

Major Ruvola made more than 30 attempts, but finally both drogues had been damaged by the severe conditions. With just twenty minutes of fuel remaining, Jolly 110 would have to ditch in the middle of “The Perfect Storm.”

Sikorsky HH-60G Pave Hawk 88-26109, sistership of "Jolly 110", ready for refueling from a C-130. (U.S. Air Force)
Sikorsky HH-60G Pave Hawk 88-26109, a sistership of “Jolly 110,” ready for refueling from a Lockheed MC-130P Combat Shadow, 69-5828. This helicopter was destroyed 7 January 2014, when it crashed off the coast of England following multiple bird strikes at 130 knots. The four-man crew was killed. (TSGT Justin D. Pyle, U.S. Air Force)
Technical Sergeant Arden R. Smith, Pararescue Jumper, 106th Rescue Wing, New York Air National Guard. (U.S. Air Force)
Technical Sergeant Arden R. Smith, Pararescue Jumper, 106th Rescue Wing, New York Air National Guard. (U.S. Air Force)

Unable to refuel, Major Ruvola made the decision to ditch the helicopter into the sea while the engines were still running. At 9:30 p.m., the Sikorsky’s number one engine flamed out from fuel starvation. With one engine still operating, Ruvola held the Pave Hawk in a hover over the raging ocean while Buschor, Mioli, Spillane and Smith jumped.

When the number two engine flamed out, Ruvola put the Pave Hawk into a hovering autorotation. Its blades came to a sudden stop when they hit the face of an oncoming wave. Ruvola was about 15 feet (4.6 meters) under water by the time he was able to escape from the sinking helicopter.

The Pave Hawk had gone down 90 miles (145 kilometers) south of Montauk Point in 100-knot (185 kilometers per hour) winds and 80-foot (25 meter) waves. After five hours in the water, four airmen were rescued by USCGC Tamaroa (WMEC-166), a 48-year-old former U.S. Navy fleet tug, operated by the Coast Guard since the end of World War II as a medium endurance cutter.

The search for Rick Smith continued for a week. He was never found.

USCGC Tamaroa (WMEC-166). (U.S. Coast Guard)
USCGC Tamaroa (WMEC-166). (U.S. Coast Guard)
USCGC Tamaroa (WHEC-166) pitches and rolls in heavy seas during the rescue of Satori, during "The Perfect Storm". (U.S. Coast Guard)
USCGC Tamaroa (WMEC-166) pitches and rolls in heavy seas during the rescue of Satori, a 32-foot sail boat, 29 October 1991. (U.S. Coast Guard) 

The U.S. Air Force HH-60G Pave Hawk is medium-sized twin-engine combat search-and-rescue (CSAR) helicopter, developed from the Army UH-60A Black Hawk transport. These helicopters were upgraded with an extendable probe for air-to-air refueling and additional fuel tanks in the cabin. They were given the project name Credible Hawk.

The Credible Hawks were further upgraded to the MH-60G Pave Hawk standard, which incorporated an sinertial navigation system, GPS, and Doppler radar for precision navigation. Low-light television, infrared cameras and night vision systems allowed the MH-60G to operate at night and very low altitude. The Pave Hawk is equipped with an Automatic Flight Control System (AFCS), a very sophisticated autopilot which incorporates automatic hover capability.

Some of the MH-60G Pave Hawks received further upgrades for the special operations mission. Helicopters dedicated to CSAR were redesignated HH-60G. A rescue hoist capable of lifting 600 pounds (272 kilograms) from a 200-foot (60.7 meter) hover is incorporated on the upper right side of the fuselage.

Sikorsky HH-60G Pave Hawk, 88-26107, sister ship of 88-26110, which was lost in "The Perfect Storm".
Sikorsky HH-60G Pave Hawk, 88-26107, sister ship of 88-26110, which was lost in “The Perfect Storm.” (U.S. Air Force)

The HH-60G is operated by a crew of two pilots, a flight engineer and gunner. For rescue operations, pararescue jumpers, the famous “P.J.s,” are added to the crew. The helicopter has an overall length of 64 feet, 11 inches (19.787 meters) with rotors turning. The fuselage is 49 feet, 10 inches (15.189 meters) long and 7 feet, 9 inches (2.362 meters) wide. Overall height (rotors turning) is 16 feet, 11 inches (5.156 meters).

The fully-articulated main rotor has a diameter of  53 feet, 8 inches (16.358 meters) and turns counterclockwise as seen from above. (The advancing blade is on the helicopter’s right.) The main rotor turns 258 r.p.m., resulting in a blade tip speed of 725 feet per second (221 meters per second). The four blades have a chord of 1.73 feet (0.527 meters) and 18° negative twist. The blade tips are swept back at a 20° angle. The four-blade tail rotor assembly is mounted on the right side of a pylon in a tractor configuration. The tail rotor plane is inclined 20° to the left to provide approximately 400 pounds of additional lift. The tail rotor turns clockwise as seen from the helicopter’s left side. (The advancing blade is below the axis of rotation.) The tail rotor has a diameter of 11 feet (3.353 meters) and each blade has a chord of 0.81 feet (0.247 meters). The tail rotor has a tip speed of 699 feet per second (213 meters per second).

Sikorsky HH-60G Pave Hawk 88-26106, sister ship of Jolly 110, at William J. Fox Field, Lancaster, California. (Alan Radecki)
Sikorsky HH-60G Pave Hawk 88-26106 at William J. Fox Field, Lancaster, California. (Alan Radecki)

Power is supplied by two General Electric T700-GE-701C turboshaft engines which are mounted on top of the fuselage on either side of the transmission and main rotor mast. They have a Maximum Continuous Power rating of 1,662 shaft horsepower, each, at Sea Level on a Standard Day. Maximum Power (10 minute limit) is 1,890 shaft horsepower, and the One Engine Inoperative (OEI) rating is 1,940 shaft horsepower (2½ minute limit.) The -701C is 3 feet, 10 inches (1.684 meters) long), 1 foot,3.6 inches (0.396 meters) in diameter and weighs 458 pounds (208 kilograms). The helicopter’s main transmission is rated for a maximum 3,400 horsepower.

Sikorsky HH-60G Pave Hawk 91-26403, 33rd Rescue Squadron, Kadena Air Base, Japan, 2001. (MSgt Val Gempis, United States Air Force)

The HH-60G has a cruise speed of 184 miles per hour (296 kilometers per hour) and its maximum speed is 224 miles per hour (361 kilometers per hour). The service ceiling is 14,000 feet (4,267 meters) and maximum range is 373 miles (600 kilometers). The hover ceiling, in ground effect (HIGE) is approximately 10,000 feet (3,048 meters), and out of ground effect (HOGE) is about 6,000 feet (1,830 meters).

Defensive armament consists of two GAU-18A .50-caliber machine guns.

Sikorsky HH-60G Pave Hawk 89-26212. (U.S. Air Force)
Captain Marisa Catlin, 83rd Expeditionary Rescue Squadron, flies a Sikorsky HH-60G Pave Hawk, 89-26212, over the Kunar Province, Afghanistan, 9 February 2011. (Captain Erick Saks, U.S. Air Force)

The U.S. Air Force initially purchased 112 HH-60G Pave Hawk helicopters, though as of May 2016, 96 remain in service. Most of these are approaching their design airframe lifetime limit of 7,000 flight hours. Several have passed 10,000 hours. The Air Force will replace them with a new HH-60W, a combat rescue helicopter based on the Sikorsky UH-60M Black Hawk. Currently, 21 U.S. Army UH-60Ls are being modified to replace HH-60G losses. The next CSAR helicopter, the HH-60W, based on the Sikorsky UH-60M, is expected to make its first flight in late 2018.

The first Sikorsky HH-60W airframe ready for final assembly at Stratford, Connecticut, February 2018. (Sikorsky, a Lockheed Martin Company)

© 2018, Bryan R. Swopes

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20 October 1956

Bell XH-40 55-4459 with cowlings and rear doors installed. (U.S. Army)
Bell XH-40 55-4459 with stabilizer bar, cowlings and rear doors installed. (U.S. Army)

20 October 1956: Bell Aircraft Corporation Chief Pilot Floyd W. Carlson and Chief Experimental Test Pilot Elton J. Smith made the first flight of the Bell Model 204 (designated XH-40-BF serial number 55-4459 by the United States Army) at Bell’s helicopter factory in Hurst, Texas.

The XH-40 is a six-place, turboshaft-powered light helicopter, designed with a primary mission of battlefield medical evacuation. Operated by one or two pilots, it could carry four passengers, or two litter patients with an attendant. The prototype’s fuselage was 39 feet, 3.85 inches (12.294 meters) long. The overall length of the helicopter with rotors turning was 53 feet, 4.00 inches (16.256 meters). The height (to the top of the tail rotor arc) is 14 feet, 7.00 inches (4.445 meters). The empty weight of the XH-40 was 3,693 pounds (1,675 kilograms), with a maximum gross weight of 5,650 pounds (2,563 kilograms).

Bell XH-40 first flight. (U.S. Army)
Bell XH-40 first flight. (U.S. Army)

The two blade semi-rigid, under-slung main rotor had a diameter of 44 feet, 0.00 inches (12.294 meters), and turned counter clockwise when viewed from above. (The advancing blade is on the helicopter’s right.) The blades used a symmetrical airfoil. They had a chord of 1 foot, 3.00 inches (0.381 meters) and 10° negative twist. The main rotor hub incorporated pre-coning. At 100% NR, the main rotor turned 324 r.p.m. The two blade tail rotor assembly had a diameter of 8 feet, 6.00 inches (2.591 meters). It was mounted on the left side of the pylon in a pusher configuration and turned counter-clockwise as seen from the helicopter’s left. (The advancing blade is above the axis of rotation.)

The first prototype Bell XH-40, 55-4459, hovers in ground effect. (U.S. Army)

The prototype XH-40 was powered by a Lycoming LTC1B-1 (XT53-L-1) free-turbine (turboshaft). 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 with 12 burners allows a significant reduction in the the engine’s total length. The XT53L-1 had a Maximum Continuous Power rating of 770 shaft horsepower, and Military Power rating of 825 shaft horsepower. It could produce 860 shaft horsepower at 21,510 r.p.m. At Military Power, the XT53-L-1 produced 102 pounds of jet thrust (0.454 kilonewtons). 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, 11.25 inches (0.591 meters) in diameter, and weighs 460 pounds (209 kilograms).

A Lycoming XT53-L-1 turboshaft engine installed on the first Bell XH-40 prototype, at Hurst, Texas, 10 August 1956. (University of North Texas Libraries, Special Collections)

The XH-40 had a maximum speed of 133 knots (153 miles per hour/246 kilometers per hour) at 2,400 feet (732 meters), and 125 knots (144 miles per hour/232 kilometers per hour) at 5,000 feet (1,524 meters). The in-ground-effect hover ceiling (HIGE) was 17,300 feet (5,273 meters) and the service ceiling was 21,600 feet (6,584 meters). The helicopter’s fuel capacity was 165 gallons (625 liters), giving it a maximum range of 212 miles (341 kilometers).

The Bell XH-40 prototype hovering in ground effect at the Bell Aircraft Company plant at Hurst, Texas. The helicopter's cowlings are not installed in this photograph. (U.S. Army)
The Bell XH-40 prototype hovering in ground effect at the Bell Aircraft Corporation helicopter plant at Hurst, Texas. The helicopter’s cowlings and doors are not installed in this photograph. (U.S. Army)

Three XH-40 prototypes were built, followed by six YH-40 service test aircraft. The designation of the XH-40 was soon changed to XHU-1.

This helicopter was the prototype of what would be known world-wide as the “Huey.” The helicopter was designated by the U.S. Army as HU-1, but a service-wide reorganization of aircraft designations resulted in that being changed to UH-1. Produced for both civil and military customers, it evolved to the Model 205 (UH-1D—UH-1H), the twin-engine Model 212 (UH-1N), the heavy-lift Model 214, and is still in production 62 years later as the twin-engine, four-bladed, glass-cockpit Model 412EPI and the UH-1Y.

Left rear quarter view of the Bell XH-40 hovering in ground effect at the Bell Helicopter Company plant at Hurst, Texas. (U.S. Army)
Left rear quarter view of the Bell XH-40 hovering in ground effect at the Bell Aircraft Corporation helicopter plant at Hurst, Texas. (U.S. Army)

Sources differ as to the date of the first flight, with some saying 20 October, and at least one saying 26 October, but most cite 22 October 1956. This individual aircraft is at the U.S. Army Aviation Museum, Fort Rucker, Alabama. The museum’s director, Robert S. Maxham, informed TDiA that, “The earliest and only historical record cards that we have on 4459 are dated 2 MAY 1958, and at that time the aircraft had 225.8 hours on it.” The Smithsonian Institution National Air and Space Museum, a generally reliable source, states the first flight was 22 October 1956.

Many sources also state the the XH-40 first flew on the same day on which Lawrence D. Bell died, which was 20 October.

The earliest contemporary news report yet discovered by TDiA, states,

On October 20, after several hours of ground running, the new Bell XH-40 helicopter was flown for the first time.

FLIGHT and AIRCRAFT ENGINEER, No. 2506, Vol. 71, Friday, 1 February 1957, Page 136, at Column 1

A rare color photograph of of a prototype Bell XH-40, hovering in ground effect. In this photo, a stabilizer bar is installed, and the synchronized elevator has end plates similar to those on Bell Model 47 helicopters. (Unattributed)

Beginning in 2015, XH-40 55-4459 was restored by Blast Off, Inc., at Atmore, Alabama. It was then returned to the Army Aviation Museum.

Bell XH-40 55-4459 ready for transport to Blast Off, Inc., 16 June 2015. (The Atmore Advance)

© 2018, Bryan R. Swopes

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9 October 1987

PP1, the first prototype of the EH101, ZF 641. (Paul Thallon)
PP1, the first prototype of the EH101, ZF 641. (Paul Thallon)

9 October 1987: Westland Helicopters Ltd. Chief Test Pilot John Trevor Eggington and Deputy Chief Test Pilot Colin W. Hague take PP1, the first EH 101 prototype, for its first flight at Yeovil, Somerset, United Kingdom. The helicopter had been completed 7 April 1987 and underwent months of ground testing.

A medium-lift helicopter, the EH 101 was a joint venture of Westland and Costruzioni Aeronautiche Giovanni Agusta S.p.A. of Italy, known then as European Helicopter Industries, or EHI, to produce a replacement for the Sikorsky S-61 Sea King, which both companies built under license. The Italian and British companies merged in July 2000 and are now known as AgustaWestland NV, with corporate headquarters in the Netherlands. After the merger of the two helicopter manufacturers, the EH 101 was redesignated AW101. It is also known as the Merlin.

Canadian Forces CH-149 Cormorant, a search and rescue variant of the AgustaWestland AW101. (Korona4Reaal via Wikipedia)
Canadian Forces CH-149 Cormorant 149902, a search and rescue variant of the AgustaWestland AW101. (Korona4Reel via Wikipedia)

Nine prototypes were built, four by Agusta at Vergiate, Italy, and five by Westland at Yeovil. During testing, Agusta-built PP2 and Westland’s PP4 were destroyed.

PP1, the first prototype, was powered by three General Electric CT7-2A turboshaft engines which were rated at 1,625 shaft horsepower, each. In production, Rolls-Royce/Turbomeca RTM322 engines are optional, as are the more powerful CT7-8s. Produced in both military and civil variants, the Merlin is used in search-and-rescue, anti-submarine warfare, mine countermeasures, airborne early warning and utility configurations. Production began in 1995 and continues today.

The AgustaWestland AW101 Merlin is a single main rotor/tail rotor medium helicopter powered by three turboshaft engines. It is equipped with retractable tricycle landing gear. The helicopter may be flown by a single pilot and uses a digital flight control system. The actual flight crew is dependent on aircraft configuration and mission.

The five blade composite main rotor has a diameter of 61 feet, 0 inches (18.593 meters) and turns counterclockwise as seen from above. (The advancing blade is on the helicopter’s right side.) The blades use a BERP feature that was pioneered on the Westland Lynx AH.1 Lynx, G-LYNX, which Trevor Eddington flew to a world speed record, 11 August 1986. This allows higher speeds, greater gross weight and is quieter than a standard blade. A four blade tail rotor with a diameter of 13 feet, 1 inch (3.962 meters) is positioned on the left side of the tail boom in pusher configuration. It rotates clockwise as seen from the helicopter’s left. The tail rotor pylon is inclined to the left.

PP.5 parked aboard HMS iron Duke. (Royal Navy)
PP5, the prototype  ASW variant parked aboard HMS Iron Duke (F234). (Royal Navy)

Overall length of the AW101 is 74 feet, 10 inches (22.809 meters) with rotors turning. The fuselage is 64 feet, 1 inch (19.533 meters) long. Overall height of the helicopter is 18 feet, 7 inches (5.664 meters). Its empty weight is 20,018 pounds (9,080 kilograms) and the maximum takeoff weight (MTOW) is 34,392 pounds (15,600 kilograms).

The RTM322 engine was developed as a joint venture between Rolls-Royce and Turboméca, but is now a Safran Helicopter Engines product. The RTM322 02/8 is a modular reverse-flow turboshaft engine with a 3-stage axial-flow, 1 stage centrifugal-flow compressor and 2-stage high-pressure, 2-stage power turbine. The output drive shaft turns 20,900 r.p.m. The RTM322 02/08 is rated at 2,000 shaft horsepower, and 2,270 shaft horsepower for takeoff. It has a One Engine Inoperative (OEI) rating of 2,472 shaft horsepower (30 minute limit). The engine is 3 feet, 10.1 inches (1.171 meters) long, 2 feet, 1.5 inches (0.648 meters) in diameter and weighs 503 pounds (228.2 kilograms).

The AW101’s cruise speed is 278 kilometers per hour (150 knots). The hover ceiling in ground effect (HIGE) is 3,307 meters (10,850 feet). In utility configuration, the Merlin carries fuel for 6 hours, 30 minutes of flight and has a maximum range of 1,363 kilometers (735 nautical miles).

John Trevor Egginton, Chief Test Pilot, Westland Helicopters. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
John Trevor Eggington, Chief Test Pilot, Westland Helicopters. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

Trevor Eggington retired from Westland in 1988 and Colin Hague became the company’s chief test pilot. In 2003, Hague was appointed an Officer of the Most Excellent (OBE) Order of the British Empire for his contributions to aviation.

Deputy Chief Test Pilot Colin W.Hague, with the first prototype EH101, PP1. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
Deputy Chief Test Pilot Colin W. Hague, with the first prototype EH101, PP1. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

Since 2010, PP1 has been used as an instructional airframe for maintenance personnel at RNAS Culdrose, Cornwall, UK.

ZF641, the first prototype of the EH101 (AW101) Merlin, at RNAS Culdrose, 2010. (dyvroeth)
ZF 641, the first prototype of the EH 101 (AW101) Merlin, at RNAS Culdrose, 2010. (dyvroeth)

© 2016, Bryan R. Swopes

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6 October 1983

A flight of two U.S. Army OH-58D Kiowa Warrior scout helicopters. (Bell Helicopter)
A flight of two U.S. Army OH-58D Kiowa Warrior scout helicopters. (Bell Helicopter)

6 October 1983: First flight of the Bell Helicopter Company Model 406/OH-58D Kiowa reconnaissance helicopter. Developed from the earlier Model 206/OH-58A and OH-58C Kiowa, the D model features a four-blade composite main rotor, an upgraded engine and transmission, and improved avionics. The most visible features are the spherical mast-mounted sighting system above the main rotor and much larger engine/transmission cowling, or “dog house.”

The helicopter was designed with very low level, “nap-of-the-Earth,” (NOE) flight, using terrain and trees for cover. The four-bladed rotor provides more lift and increased responsiveness over the two-bladed semi-rigid rotor of the OH-58A and C.

The mast-mounted sight allows the helicopter to hover behind terrain or trees with just the sight exposed. The sight contains television, thermal imaging and laser range-finding and target designation equipment.

The instrument panel of a Bell OH-58D Kiowa. (Bell helicopter)
The instrument panel of a Bell OH-58D Kiowa. (Bell Helicopter)

Operated by two pilots, the Bell OH-58D Kiowa is 42 feet, 2 inches (12.852 meters) long, with rotors turning. The four-bladed composite main rotor has a diameter of 35 feet (10.668 meters). As is customary with American-designed helicopters, the main rotor turn counter-clockwise as seen from above. (The advancing blade is on the right side of the aircraft.) The two-blade semi-rigid tail rotor is mounted on the left side of the tail boom and turns clockwise when seen from the left. (The advancing blade is below the tail boom.) The overall height of the OH-58D is 12 feet, 10–5/8 inches (3.928 meters). Empty weight of the helicopter is about 3,500 pounds (1,588 kilograms), depending on installed equipment. This is approximately 15% greater than the maximum gross weight of the OH-58A. The OH-58D has a maximum gross weight of 5,500 pounds (2,495 kilograms).

Power for the Kiowa is supplied by a Rolls-Royce T703-AD-700A (Allison 250-C30R3) turboshaft engine which produces 750 shaft horsepower. The main transmission is limited to transient input of 637 shaft horsepower.

The helicopter can be armed with a fixed, remotely-fired, M3P .50-caliber (12.7 mm) machine gun, a pod carrying seven 2.75-inch (70 mm) rockets, or two AGM-114 Hellfire antitank guided missiles.

The OH-58D has a cruise speed of 95 knots (109 miles per hour/176 kilometers per hour) when armed. Its range is 140 nautical miles (161 miles/259 kilometers). The hover ceiling in ground effect (HOGE) at +15 °C. is 7,500 feet MSL (2,286 meters).

An OH-58D Kiowa decelerates as it approaches trees at Fort Lewis, Washington.( U.S. Army)
An OH-58D Kiowa decelerates as it approaches trees during gunnery exercises at Fort Lewis, Washington. A .50-caliber machine gun is mounted on the left side of the helicopter. (U.S. Army)

© 2015, Bryan R. Swopes

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