Tag Archives: Helicopter

20 October 1956

October 20, 2019Aviation55-4459, Bell Aircraft Corporation, Bell Helicopter Company, Bell Model 204, Bell XH-40, Elton J. Smith, First Flight, Floyd W. Carlson, Helicopter, Huey, Lycoming LTC1B-1, Lycoming Turbine Engine Division, Lycoming XT53-L-1, Prototype, Test PilotBryan Swopes

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).

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).

Lycoming XT53-L-1 turboshaft engine installed on the first Bell XH-40 prototype, 10 August 1956. (University of North Texas Libraries, Special Collections texashistoty.unt.edu/ark:/67531/metasc9950041/ ) — 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)

The Bell XH-40 at the United States Army Aviation Museum.

17 October 1974

October 17, 2019Aviation73-21650, First Flight, GE Aircraft Engines, General Electric T700-GE-700, Helicopter, James R. Wright, John Dixson, Prototype, s/n 70-001, Sikorsky Aircraft Corporation, Sikorsky S-70, Sikorsky UH-60A Black Hawk, Utility Tactical Transport Aircraft System, UTTASBryan Swopes

17 October 1974: Sikorsky Chief Pilot James R. (Dick) Wright and project chief test pilot John Dixson made the first flight of the prototype YUH-60A, 73-21650, at the company’s Stratford, Connecticut, facility. This helicopter was the first of three prototypes.

Early flight testing revealed excessive vertical vibrations associated with the main rotor. Extensive engineering and flight testing determined that this was caused by air flow upward through the rotor system and around the transmission and engine cowlings. The purpose of the low-mounted main rotor was to aid in fitting inside transport aircraft with minimal disassembly. It was necessary to increase the height of the mast and reshape the cowlings to achieve an acceptable level of vibration.

After eight months of testing, the U.S. Army selected the YUH-60A for production over its competitor, the Boeing Vertol YUH-61A. In keeping with the Army’s tradition of naming helicopters after Native Americans, the new helicopter was named Black Hawk, who was a 17th Century leader of the Sauk (or Sac) people.

Sikorsky YUH-60A Black Hawk 73-21650 in its original configuration, 28 June 1974. (Sikorsky, a Lockheed Martin Company) — Sikorsky YUH-60A 73-21650 at roll-out, 28 June 1974, with low main rotor, large-area tail rotor pylon and swept stabilator. (Sikorsky, a Lockheed Martin Company)

The Sikorsky Model S-70 (YUH-60A) was designed to meet the requirements of the U.S. Army Utility Tactical Transport Aircraft System (UTTAS). It had a 3-man crew and could carry an 11-man rifle squad. The helicopter could be transported by a Lockheed C-130 Hercules.

The three UTTAS prototypes were 63 feet, 6 inches (19.355 meters) long, with rotors turning. The span of the horizontal stabilizer was 15 feet, 0 inches (4.572 meters). The prototypes’ overall height was 16 feet, 10 inches (5.131 meters).

The three Sikorsky YUH-60A UTTAS prototypes. A fourth prototype, an S-70, was built and retained by Sikorsky for internal research and development and demonstrations. (Vertical Flight Society)

The YUH-60A had an empty weight of 11,182 pounds (5,072 kilograms) and gross weight of 16,750 pounds (7,598 kilograms). The helicopter had a structural load factor of 3.5 Gs. With 1,829 pounds (830 kilograms) of fuel, it had an endurance of 2 hours, 18 minutes.

The YUH-60A had a four-blade fully-articulated main rotor with elastomeric bearings. It had a diameter of 52 feet, 0 inches (15.850 meters). During flight testing, the diameter was increased to 52 feet, 4 inches (15.951 meters), and finally to 52 feet, 8 inches (16.053 meters). The blades were built with titanium spars and used two different airfoils and a non-linear twist (resulting in a net -16.4°). The outer 20 inches (0.508 meters) were swept aft 20°. These characteristics improved the helicopter’s maximum speed and hover performance. The main rotor turned counterclockwise, as seen from above (the advancing blade is on the right) at 258 r.p.m. The blade tip speed was 728 feet per second (222 meters per second). During flight testing it was decided to change the main transmission gear reduction ratio in order to operate the engines at a slightly increased r.p.m. At the higher r.p.m., the engines produced an additional 50 horsepower, each.

Sikorsky YUH-60A 73-21650 (c/n 70-001), right profile. In this photograph, the prototype has been modified closer to the production variant. The rotor mast is taller, the vertical fin has been decreased in size, a variable-pitch stabilator has replaced the fixed horizontal stabilizer, the engine cowlings have been redesigned, and the crew side window is the two-piece version. (U.S. Army Aviation Museum)

The four-bladed bearingless tail rotor was positioned on the right side of the tail rotor pylon in a tractor configuration. The tail rotor diameter was 11 feet (3.353 meters), and turned 1,214 r.p.m., rotating clockwise as seen from the helicopter’s left (the advancing was blade below the axis of rotation). The blade tip speed was 699 feet per second (213 meters per second). The tail rotor blades had -18° of twist. Because the Black Hawk’s engines are behind the transmission, the aircraft’s center of gravity (c.g.) is also aft. The tail rotor plane is inclined 20° to the left to provide approximately 400 pounds of lift (1.78 kilonewtons) to offset the rearward c.g.

Cutaway illustration of the T700-GE-700 turboshaft engine. (Global Security)

Power was supplied by two General Electric T700-GE-700 modular turboshaft engines, rated at 1,622 shaft horsepower at 20,900 r.p.m. Np, at Sea Level under standard atmospheric conditions. The T700 has a 5-stage axial-flow, 1-stage centrifugal-flow compressor, with a 2-stage axial-flow gas producer and 2-stage axial-flow power turbine. The T700 is 3 feet, 11 inches (1.194 meters) long, 2 feet, 1 inch (0.635 meters) in diameter and weighs 437 pounds (198 kilograms). The helicopter’s main transmission was designed for 2,828 horsepower. The engines are derated to the transmission limit.

The YUH-60A had a cruise speed of 147 knots (169 miles per hour/272 kilometers per hour) at 4,000 feet (1,219 meters) and 95 °F. (35 °C.). It could climb at 450 feet per minute (2.29 meters per second) at the same altitude and air temperature.

Sikorsky YUH-60A prototype, 73-21650, late configuration. (Vertical Flight Society)

While operating with an Army crew on the night of 9 August 1976, YUH-60A 73-21650 developed a significant vibration. An emergency landing was made. Because of darkness and mist, the pilots thought they were landing in a corn field, but it was actually a pine tree plantation. The helicopter’s rotors cut down more than 40 trees with trunk diameters up to 5 inches (12.7 centimeters).

Close inspection by Army and Sikorsky personnel found that the only visible damage was to the four main and four tail-rotor blades other than nicks and dents to the airframe that were of no structural concern. All gearboxes and engines turned freely, and all flight controls responded properly. ¹ The blades were replaced on-site and the helicopter was flown out the following day.

73-21650 crashed into the Housatonic River near the Stratford plant at 9:10 a.m., Friday, 19 May 1978, killing all three Sikorsky employees on board, pilots Albert M. King, Jr., John J. Pasquarello, and flight engineer John Marshall.

During routine maintenance an airspeed sensor for the all-flying tailplane had been disconnected. As the Black Hawk transitioned from hover to forward flight, the all-flying tailplane remained in the hover position and forced the helicopter’s nose to pitch down to the point that recovery was impossible.

A Sikorsky YUH-60A and Boeing Vertol YUH-61A hover for the camera. (U.S. Army)

The Black Hawk has been in production since 1978. More than 4,000 of the helicopters have been built and the type has been continuously improved. The current production model is the UH-60M.

Sikorsky is a Lockheed Martin Company.

A Sikorsky UH-60M Black Hawk in flight. (Sikorsky, a Lockheed Martin Company)

Sikorsky's UH-60M Black Hawk for the U.S. Army, seen here in the Military Hangar at Sikorsky Aircraft in Stratford, Conn. Feb. 20, 2008. — Sikorsky’s UH-60M Black Hawk for the U.S. Army, seen here in the Military Hangar at Sikorsky Aircraft in Stratford, Connecticut, 20 February 2008. (Sikorsky, a Lockheed Martin Company)

¹ Black Hawk: The Story of a World Class Helicopter, by Ray D. Leoni, American Institute of Aeronautics and Astronautics, Reston, Virginia, 2007, Chapter 8 at Page 173.

9 October 1987

October 9, 2019AviationAgustaWestland, AgustaWestland NV, BERP, Colin W. Hague OBE, Costruzioni Aeronautiche Giovanni Agusta S.p.A., EH 101, European Helicopter Industries EHI 01, First Flight, Helicopter, John Trevor Eggington, Merlin, OBE, Officer of the Most Excellent Order of the British Empire, PP1, Prototype, Rolls-Royce/Turboméca RTM322, Safran Helicopter Engines, Safran RTM322 02/8, Test Pilot, Trevor Eggington, Yeovil, ZF 641Bryan Swopes

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)

6 October 1983

October 6, 2019AviationAGM-114 Hellfire, Allison 250-C30R3, Bell Helicopter Company, Bell OH-58D Kiowa Warrior, Helicopter, M3P, M70 Hydra, Rolls-Royce T703-AD-700ABryan Swopes

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)

2 October 1970

October 2, 2019Aviation1st Special Operations Wing, 31001, 40th Helicopter Squadron, 68-10772, Bell 212, Bell Helicopter Company, Bell Model 212, Bell UH-1N Iroquois, Helicopter, Hurlburt Field, Pratt & Whitney Canada PT6T-3 Twin-Pac, Pratt & Whitney Canada T400-CP-400, Twin Huey, Twin Pac, Two-Twelve Twin, UH-1N-BFBryan Swopes

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.

This Bell UH-1N, 69-6650, assigned to Kirtland AFB, has been in service for more than 40 years. It just passed 15,000 total flight hours. (U.S. Air Force) — This Bell UH-1N, 69-6650, assigned to Kirtland AFB, has been in service for more than 45 years. It passed 15,000 total flight hours in March 2011. (U.S. Air Force)

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)

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 45 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 24 September 2018, the U.S. Air Force announced that it would replace the UH-1N fleet with 84 Boeing/Leonardo MH-139s, with the first aircraft being delivered in 2021.

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