Tag Archives: Helicopter

9 October 1987

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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

6 October 1983

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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

2 October 1970

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The very first UH-1N, 68-10772, photographed in March 2012. (© Ralph Duenas. Photograph used with permission.)
The very first U.S. Air Force UH-1N Iroquois, 68-10772, photographed March 2012. (© Ralph Duenas. Photograph used with permission.)

2 October 1970: The U.S. Air Force 1st Special Operations Wing at Hurlburt Field, Florida (Eglin AFB Auxiliary Field #9), took possession of the very first Bell UH-IN Iroquois, UH-1N-BF 68-10772 (Bell Helicopter Co. serial number 31001).

Also known as the “Twin Huey,” the medium-lift helicopter is a two-engine version of the Bell Model 205 (UH-1H). Originally developed for the Canadian Forces as the Bell Model 212, the UH-1N is powered by a Pratt & Whitney T400-CP-400 (the military designation for the commercial PT6T-3 “Twin-Pac”) which consists of two PT6 turboshaft engines mated to a combining gearbox to drive a single output shaft to the helicopter’s main transmission. The combined unit can produce a maximum 1,800 shaft horsepower. If one engine fails, the remaining engine can operate at 900 shaft horsepower for 30 minutes. The T400 is de-rated to the main transmission limit of 1,290 shaft horsepower.

Bell UH-1N 69-6607

The helicopter has other improvements over the Model 205/UH-1D/H Huey. The main rotor blades have a wider chord, producing greater lift. The main transmission is rated for greater power input. The tail boom and tail rotor pylon are strengthened, and the tail rotor has been moved to the opposite side of the pylon, in a tractor configuration instead of the previous pusher configuration. The tail rotor blade rotation is reversed with the advancing blade moving upward into the down flow of the main rotor, making it more efficient. Visual differences are the streamlined nose and the reshaped “dog house” covering the twin engine installation.

Cockpit of a U.S. Air Force/Bell UH-1N Iroquois during a 60° bank. (A1C Nigel Sandridge, U.S. Air Force)
Cockpit of a U.S. Air Force/Bell UH-1N Iroquois during a 60° right bank. (A1C Nigel Sandridge, U.S. Air Force)

The U.S. Air Force normally operates the UH-1N with two pilots and a flight engineer, but it can be flown by a single pilot under visual weather conditions, if necessary. It is capable of transporting up to 12 passengers in addition to the three-man crew.

The Bell Helicopter Co. UH-1N Iroquois (Model 212) is 57 feet, 3 inches (17.450 meters) long, with a main rotor diameter of 48 feet, 0 inches (14.630 meters) and tail rotor diameter of 8 feet, 6 inches (2.591 meters). The overall height of the helicopter is 12 feet, 10 inches (3.912 meters) and the fuselage has a maximum width of 9 feet, 5 inches (2.870 meters). The helicopter’s empty weight is 6,032 pounds (2,736 kilograms), depending on installed equipment. The maximum takeoff weight is 10,500 pounds (4,763 kilograms).

The Pratt & Whitney Canada T400-CP-400 has a maximum continuous power rating of 1,530 shaft horsepower at 6,600 r.p.m. at Sea Level.

The helicopter’s cruise speed is 110 knots (127 miles per hour/204 kilometers per hour) and the maximum speed is 128 knots (147 miles per hour/237 kilometers per hour) at Sea Level. The UH-1N has an out-of-ground-effect hover ceiling (HOGE) of 13,000 feet (3,962 meters). The service ceiling is 21,600 feet (6,584 meters). The combat radius is 105 nautical miles (121 statute miles/194 kilometers) maximum ferry range is 565 nautical miles (650 statute miles/1,046 kilometers).

U.S. Air Force Bell UH-1N Iroquois helicopters deploy security personnel. (U.S. Air Force)
U.S. Air Force Bell UH-1N Iroquois helicopters deploy security personnel. (U.S. Air Force)

The UH-1N can be armed with GAU-16 .50-caliber machine guns or GAU-17 7.62mm “miniguns.”

The UH-1N is operated by the Air Force, the U.S. Navy and Marine Corps, as well as many foreign military services. In civil use, the Bell 212 is the most common medium lift helicopter worldwide and has been for 54 years.

Of the 79 UH-1N helicopters ordered by the U.S. Air Force in 1968, 59 remain in active service (as of September 2015). On 18 March 2024, a UH-1N assigned to the 58th Operations Group, Det 2, at Kirtland Air Force Base, New Mexico, the Air Force’s UH-1N training unit, 69-6650 logged its 20,000th flight hour.

On 24 September 2018, the U.S. Air Force announced that it would replace the UH-1N fleet with 84 Boeing/Leonardo MH-139A Grey Wolfs, with the first aircraft being delivered in 2021. In actuality, the first field-read MH-139A arrived at Malmstrom Air Force Base in Montana in March 2024.

Still in service, UH-1N 68-10772 was photographed in flight 4 May 2022 at Gowen Field, Boise, Idaho. The helicopter was painted in the Southeast Asia camouflage scheme of the 20th Special Operations Squadron, “Green Hornets.”

This rear quarter view of UH-1N-BF 68-10776 of the 40th Helicopter Squadron, flying across Montana, shows the two exhaust ducts of the PT6T-3 Twin Pac. This helicopter, Bell serial number 31005, was the fifth UH-1N built. (U.S. Air Force)
Bell UH-1N-BF 69-6615, 40th Helicopter Squadron, in the Front Range of the Rocky Mountains. (Senior Airman Eydie Sakura, U.S. Air Force)
The very first Bell UH-1N, 68-10772, was photographed at Gowen Field, Boise, Idaho, on 4 May 2022, by Sean Asay. The helicopter is shown in the Southeast Asia camouflage scheme of the 20th Special Operations Squadron, “Green Hornets.” (Photograph © Sean Asay. Used with permission.)

© 2024, Bryan R. Swopes

1 October 1947

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A Los Angeles Airways Sikorsky S-51 helicopter takes off from the roof of the Terminal Annex Post Office, 1 October 1947. The Los Angeles Times published this photograph 2 October 1947 with the following caption: “NEW MAIL SERVICE — Los Angeles Airways helicopter shown landing on the roof of Terminal Annex Post office yesterday to inaugurate helicopter air-mail service, the first of its kind in the United States. Two flights daily are planned on this run with another to start Oct. 16.” (Los Angeles Times Photographic Archive/UCLA Library)

1 October 1947: Los Angeles Airways began regularly scheduled air mail service in Los Angeles, using the Sikorsky S-51 helicopter.

“. . . the U.S. Civil Aeronautics Board awarded LAA the route authorities to operate local air mail services in Southern California using the Sikorsky S-51. Before long, LAA was operating a twice-a-day mail service between the main downtown post office and Los Angeles International Airport along with a small package air express service.

“With a fleet of five S-51s, LAA’s first year of operations resulted in 700 tons of mail being carried with approximately 40,000 landings throughout the Los Angeles metropolitan area. The small operation maintained a 95% reliability rate and by the time it began its small package air express service in 1953, it was annually moving nearly 4,000 tons of mail a year.

“In July 1951 the CAB awarded LAA’s reliable helicopter operation the rights for passenger services which started in November 1954 with larger Sikorsky S-55 helicopters while the smaller S-51s continued the mail and small package services. . . .”

— Tails Through Time, http://aviationtrivia.blogspot.com/2010/06/on-1-october-1947-los-angeles-airways.html

The S-51 was a commercial version of the Sikorsky R-5 series of military helicopters. It was a four-place, single-engine helicopter, operated by one pilot. The cabin was built of aluminum with Plexiglas windows. The fuselage was built of plastic-impregnated plywood, and the tail boom was wood monocoque construction. The main rotor consisted of three fully-articulated blades built of metal spars and plywood ribs and covered with two layers of fabric. (All metal blades soon became available.) The three bladed semi-articulated tail rotor was built of laminated wood. The main rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right.) 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 41 feet, 7.5 inches (12.687 meters) long. The main rotor had a diameter of 48 feet (14.630 meters) and tail rotor diameter was 8 feet, 5 inches (2.565 meters), giving the helicopter an overall length of 57 feet, 1 inch (17.399 meters). It was 13 feet, 1.5 inches (4.001 meters) high. The landing gear tread was 12 feet (3.7 meters). The S-51 had an empty weight of 4,050 pounds (1,837 kilograms) and maximum takeoff weight of 5,500 pounds (2,495 kilograms). Fuel capacity was 100 gallons (378.5 liters).

The helicopter was powered by an air-cooled, supercharged, 986.749-cubic-inch-displacement (16.170 liter) Pratt & Whitney Wasp Jr. T1B4 (R-985 AN-5) direct-drive, nine-cylinder radial engine which was placed vertically in the fuselage behind the crew compartment. This engine was rated at 450 horsepower at 2,300 r.p.m., Standard Day at Sea Level. The R-985 AN-5 was 48.00 inches (1.219 meters) long, 46.25 inches (1.175 meters) in diameter and weighed 684 pounds (310.3 kilograms) with a magnesium crankcase.

The S-51 had a maximum speed (Vne) of 107 knots (123.1 miles per hour/198.2 kilometers per hour). Range was 275 miles (442.6 kilometers). The service ceiling was 14,800 feet (4,511 meters). The absolute hover ceiling was 3,000 feet (914.4 meters).

Of 220 helicopters in the S-51 series built by Sikorsky, 55 were commercial models.

Los Angeles Airways Sikorsky S-51 (Viewliner)
A Los Angeles Airways Sikorsky S-51. The main rotor hub is covered. (Viewliner)

© 2016, Bryan R. Swopes

30 September 1982

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H. Ross Perot, Jr. and Jay W. Coburn with Bell 206L-1 LongRanger II, N3911Z, after their 29-day around-the-world flight. (© Bettman/Corbis)

30 September 1982: H. Ross Perot, Jr. and Jay W. Coburn completed their around-the-world helicopter flight when they landed Spirit of Texas at their starting point at Dallas, Texas. They had flown the single-engine Bell 206L-1 LongRanger II, serial number 45658, civil registration N3911Z, more than 26,000 miles (41,843 kilometers) in 246.5 flight hours over 29 days, 3 hours and 8 minutes.

They had begun their journey 1 September 1982. Perot and Coburn traveled across twenty-six countries. They established a Fédération Aéronautique Internationale (FAI) record for helicopter speed around the world, eastbound, having averaged 56.97 kilometers per hour (35.399 miles per hour). (Class E-1d, FAI Record File Number 1254). They also established a series of point-to-point records while enroute, with the highest speed, an average of 179.39 kilometers per hour (111.47 miles per hour), taking place on 7 September 1982, while flying Spirit of Texas from London to Marseilles (FAI Record File Number 10018).

The Bell Helicopter Company Model 206L-1 LongRanger II is a 7-place light helicopter developed from the earlier 5-place Model 206B JetRanger series. It is designed to be flown by a single pilot in the right front seat, and is certified for Visual Flight Rules.

The 206L-1 is 42 feet, 8 inches (13.005 meters) long, overall, and the two-bladed main rotor is semi-rigid and under-slung, a common feature of Bell’s main rotor design. It has a diameter of 37 feet (11.278 meters) and turns counter-clockwise (seen from above) at 394 r.p.m. (100% NR). (The advancing blade is on the helicopter’s right side.) The rotor blade has a chord of 1 foot, 1.0 inches (0.330 meter) and 11° negative twist. The blade tips are swept.

The two-bladed tail rotor assembly is also semi-rigid and is positioned on the left side of the tail boom in a pusher configuration. It turns clockwise, as seen from the helicopter’s left. (The advancing blade is below the axis of rotation.) The tail rotor diameter is 5 feet, 6.0 inches (1.676 meters).

The LongRanger II is powered by an Allison 250-C28B turboshaft engine. This engine produces 500 shaft horsepower but is de-rated to 435 horsepower, the limit of the main transmission. The engine is mounted above the roof of the fuselage, to the rear of the main transmission. Output shafts lead forward to the transmission and the tail rotor drive shaft aft to the tail rotor 90° gear box. The transmission and rotor mast are mounted angled slightly forward and to the right. This assists in the helicopter’s lift off to a hover, helps to offset its translating tendency, and keeps the passenger cabin in a near-level attitude during cruise flight.

A vertical fin is attached at the aft end of the tail boom. The fin is offset 4° to the right to unload the tail rotor in cruise flight. Fixed horizontal stabilizers with an inverted asymmetric airfoil are attached to the tail boom. In cruise flight, these provide a downward force that keeps the passenger cabin in a near-level attitude. Vertical fins are attached to the outboard ends of the horizontal stabilizers and above the tailboom centerline. The fins are slightly offset to the left and counteract the helicopter’s Dutch roll tendency.

The helicopter has an empty weight of approximately 2,160 pounds (979 kilograms), depending on installed equipment, and the maximum gross weight is 4,050 pounds (1,836 kilograms).

The Model 206L LongRanger first flew in 1974 and the 206L-1 LongRanger II variant entered production in 1978. It was replaced several years later by the 206L-3. The LongRanger remains in production as the Model 206L-4.

Screen Shot 2015-09-30 at 09.44.55Perot had purchased the LongRanger II for $750,000, specifically for this flight. Modifications started immediately and over the next three weeks an additional 151-gallon fuel tank was added giving the helicopter approximately 8 hours’ endurance. “Pop-out floats”—inflatable pontoons that can be deployed for emergency landings on water—were installed. The helicopter also carried a life raft and other emergency equipment and supplies. Additional communication, navigation equipment and radar was installed.

Spirit of Texas aboard a container ship.
N3911Z aboard a container ship.

During the circumnavigation, the helicopter burned 56,000 pounds (25,400 kilograms) of jet fuel and made 56 fueling stops, including aboard a pre-positioned container ship in the North Pacific Ocean.

The helicopter was donated to the Smithsonian Institution and is on display at the Steven V. Udvar-Hazy Center of the National Air and Space Museum.

Bell 206L-1 LongRanger II s/n 45658, N3911Z, “Spirit of Texas,” on display at the Steven F. Udvar-Hazy Center of the Smithsonian Institution National Air and Space Museum. (NASM)

© 2016, Bryan R. Swopes