On November 2, 2022, Bell's last AH-1Z Viper delivery to the U.S. Marine Corps rolled off the assembly line, the company's last H-1 series helicopter delivered to the U.S. Marine Corps. The U.S. military and Bell collectively refer to the AH-1 and UH-1 Huey as the H-1 series because the AH-1 is an improvement from the UH-1, which is also the last model of the H-1 family. The helicopter family has been in development for 60 years and has built more than 16,000 units. Will traditional attack helicopters survive future conflicts, and how effective are helicopters in modern warfare? To answer the above questions, reviewing the development of the H-1 series of helicopters is undoubtedly very instructive and relevant.
The origin of "Huey"
The entire "Huey" family originated from Bell's XH-40 prototype, which learned from the experience and lessons of helicopter combat during the Korean War, and was developed to meet the needs of the U.S. Army for utility helicopters and first flew on October 20, 1956, and Bell built six YH-40 evaluation aircraft. In March 1960, the U.S. Army awarded Bell a contract to produce 100 helicopters, which were named HU-1A and named "Iroquois" after the Native American peoples. However, the "HU" in the number gave rise to a very popular unofficial nickname "Huey", and after September 1962, according to the unified naming rules of the US Department of Defense, the US military changed the above number to the now known UH-1 (company number Bell 204).
Due to the turboshaft engine, the performance of the "Huey" helicopter is much better than that of helicopters with piston engines. However, the U.S. Army's service test report on the YH-40 concluded that it was underpowered. When the first UH-1A was delivered, the Army indicated that it would improve subsequent models, and in response, Bell proposed the UH-1B, which was equipped with a 960-axle horsepower T53-L-5 engine and a longer cabin, and the first production version of the UH-1B was delivered in March 1961.
In 1960, Bell began developing the UH-1C, equipping it with the 1100-shaft horsepower Lycoming T53-L-11 engine, and the U.S. Army eventually modified all UH-1B helicopters with the same engine. Bell also developed a new rotor system for the UH-1C, introducing a dual hydraulic control system and an improved air intake filtration system. The fuel capacity of the UH-1C was increased to 920 liters, the gross weight was increased to 4309 kg, and the nominal payload was 2120 kg. Production of the UH-1C began in June 1966 with 766 built.
Although the early "short-bodied" "Huey" was successful, the US Army wanted to carry more personnel. Bell's solution was to lengthen the HU-1B fuselage by about 1 meter and use the added space to place four outward-facing seats next to the gearing, increasing the seating capacity to 15, and the enlarged cabin could also accommodate six stretchers and doctors. The aircraft is fitted with larger hatches and a small dumpling chain panel with optional windows to provide better access to the cabin.
The Bell 205 prototype, which first flew on August 16, 1961, was initially equipped with a main rotor with a diameter of about 13.4 meters and a T53-L-9 engine. The rotor diameter was lengthened to about 14.6 meters and the chord length was about 53 centimeters. The tail boom was also lengthened to accommodate longer rotor blades, and in all, the modifications resulted in a total weight of 4,309 kg. The U.S. Army ordered the production version of the Bell 205 in 1963, and the production helicopter was designated UH-1D. In 1966, Bell installed a 1400-shaft horsepower T53-L-13 engine to provide more power to the helicopter. The pitot tube was moved from the nose to the top of the cockpit to prevent damage during landing, and the production version of this configuration was designated UH-1H.
"Cobra" came out
In parallel with the development of general-purpose helicopters, Bell and the U.S. Army began to develop armed helicopters. Inspired by the French army's mounting of weapons to helicopters during the Algerian War to strike ground forces, Bell developed a conceptual model of the D-255 gunship, named the Iroquois Warrior, a dedicated attack helicopter based on UH-1B components with a new slender fuselage and tandem two-seat cockpit, a grenade launcher in the spherical turret in the nose, a belly pod for 20mm cannons, and short wings for mounting rockets or SS-10 anti-tank missiles.
In June 1962, Bell showed a model helicopter to the U.S. Army, which was interested and awarded Bell a proof-of-concept contract in December 1962. Bell developed the Type 207 Sioux Scout, which first flew in July 1963. "Sioux Scout" has all the main features of modern attack helicopters: a tandem cockpit, short wings with weapons on board and a turret mounted on the "jaw". In early 1964, after evaluating the Sioux Scout, the U.S. Army decided that it was small in size and underpowered.
Since then, the U.S. Army has proposed the Advanced Air Fire Support System (AAFSS), which aims to develop a fully armed helicopter with a speed of at least 322 km/h. Despite the Army's preference for the AAFSS program, Bell stuck to the idea of smaller and lighter helicopter gunships. In January 1965, Bell decided to proceed with the detailed design. The researchers combined the mature retarder, the UH-1C's 540 rotor system and stability control enhancement system, and the UH-1's T53 turboshaft engine with the previous Sioux Scout design concept to introduce the Bell 209, which is largely similar to the Iroquois Warrior, especially its cockpit and tail. From the outside, the new design does not bear much resemblance to the UH-1, but the rear wing and most of the powertrain of the Type 209 are identical to the UH-1, with about 80% of the components using UH-1 parts.
On September 7, 1965, the Bell 209 prototype made its first flight, which quickly attracted the attention of the military. As the Vietnam War progressed, pressure on the U.S. military increased, and by the end of June 1965, 50,000 U.S. ground troops had been deployed to Vietnam, and the U.S. Army needed a type of temporary helicopter gunship for the Vietnam War. In April 1966, Bell's products won the competition with other competitors, and the U.S. Army initially ordered 110 helicopters, and by the end of the year, subsequent orders had reached 500. Bell nicknamed the Model 209 "Huey Cobra", and the U.S. Army named the helicopter "Cobra".
In June 1967, the first AH-1G "Huey Cobra" entered service, initially designated UH-1H, and soon received the special designation "A" for attack helicopters. Between 1967 and 1973, Bell built 1,116 AH-1G helicopters for the U.S. Army. During the Vietnam War, the U.S. Army Air Cavalry and other units used UH-1s so heavily that the war became known as the "helicopter war."
Constantly improving
The Cobra and Iroquois are single-engine, skid landing gear, seesaw-type rotors. However, the Cobra's exterior design looks streamlined, similar to a jet fighter. Aviation writer Stanley McGowan observed that its appearance was different from any rotorcraft previously designed by Bell, with a relatively narrow fuselage, a tandem cockpit in the cockpit, and a large canopy covering the crew, protected by armor.
The Cobra helicopter is operated by the pilot and the gunner, the pilot sits in the back seat, the gunner sits in the front row, and the front weapon operator is more conducive to controlling the weapons and various sensors located in the nose. Most of the Cobra's weapons can be mounted on pylons under short wings, and the Cobra typically carries twice as much ammunition as the UH-1 and arrives at the station in half the time, leaving it empty three times as long as the UH-1. This allows the helicopter to reach the landing zone in front of the transport helicopter at the designated time, provide fire support when they appear, and continue fighting while they are withdrawn.
"Cobra" is a light armed helicopter, its empty weight is 2635 kg, the maximum take-off weight is 4309 kg, the power plant is a T53-L-13 turboshaft engine, the output is 1400 horsepower, the diameter of the main rotor is 13.4 meters, the maximum speed is 276 km / h, the range is 570 km, and the ceiling is 3500 m.
Typically, the Cobra avoids circling during engagement, focusing on maintaining speed and maneuverability. Cobras usually do not act alone, but in two or in groups, usually using hunting tactics to eliminate ground targets. It is also often used in conjunction with other helicopters, such as the OH-58 reconnaissance helicopter.
After the Cobra entered service, a number of changes were made to the design, the main of which was the movement of the tail rotor from the left to the right, which helped to improve the efficiency of the tail rotor. In 1972, the U.S. Army sought to improve anti-armor capabilities. Under the Improved Cobra Weapons Program, the AH-1 with the Tao missile was tested in October 1973. After passing the test the following year, Bell signed an AH-1Q to upgrade 101 AH-1Gs to launch Tao anti-tank missiles.
After that, more modifications of the "Cobra" appeared. In March 1978, the U.S. Army purchased 100 new Cobra AH-1S. These "Cobras" are based on the AH-10 with a new T-shaped dashboard, improved composite rotor blades, an improved gearbox, an M128 helmet-mounted sight and an M28A3 weapon system. At the same time, a more powerful T53-L-703 engine was adopted, with an output of 1800 shaft horsepower. As the AH-1S continued to be upgraded, the Cobra had the AH-1P, AH-1E, and AH-1F. Before 1988, the AH-1F was known as the "modernized AH-1S."
"Cobra" "Into the Sea"
The success of the AH-1G got the U.S. Marine Corps interested in the Cobra, but they preferred a twin-engine configuration to improve safety on the water. The Marine Corps also requested that the turret be equipped with more powerful weapons.
In May 1968, Bell was awarded a contract for 49 twin-engine AH-1J Sea Cobras. The AH-1J is equipped with a three-barreled 20mm M197 cannon with a rotor diameter of 13.4 meters, an empty weight of 2998 kg, a maximum take-off weight of 4500 kg, and a power plant of two Pratt & Whitney T400-CP engines.
Entering the 70s of the 20th century, the Marine Corps put forward higher requirements for the "Cobra" - a greater carrying capacity at high temperatures. Based on the Bell 309 "King Cobra", Bell developed the AH-1T "Improved Sea Cobra", which is equipped with an extended tail boom and fuselage and Bell 309 upgraded transmission and engine. The AH-1T is more reliable and easier to maintain in the field. It is capable of launching Tao anti-tank missiles, with a dedicated sighting system and other sensors. An advanced version, known as the AH-1T+, is equipped with more powerful T700-GE-700 engines and advanced avionics.
In the early 80s of the 20th century, the US Marine Corps sought new helicopters. Because Congress did not approve the purchase, the Marine Corps chose to continue improving the AH-1T, including modifying the fire control system to carry and launch the AIM-9 and AGM-114 missiles, a new version of the AH-1W Super Cobra. In March 1986, deliveries of the AH-1W began, eventually delivering 179 aircraft. The empty weight of the AH-1W was increased to 4627 kg, the maximum take-off weight was increased to 6690 kg, and the engines were 2 General Electric T700-GE-401 turboshaft engines of 1690 hp each.
Sea Cobra participated in a number of major operations in the second half of the 20th century, such as the US invasion of Grenada in 1983, the extensive use of Sea Cobra by Iran during the Iran-Iraq War, and the destruction of more than 200 tanks and armored personnel carriers during Operation Desert Storm in 1991. In the 21st century, the helicopter also participated in the wars in Afghanistan and Iraq. In October 2020, the U.S. Marine Corps retired the last AH-1W.
"Mutation" of "Viper"
Bell used the AH-1T+ demonstrator and AH-1W prototype to test a new experimental composite four-blade main rotor system. The new configuration provides better flight performance, lower noise and higher protection. Bell developed this new design into the AH-1Z, nicknamed "Viper".
In 1996, the Marine Corps signed a contract with Bell to launch the AH-1W upgrade program, upgrading 180 AH-1Ws to AH-1Z and 100 UH-1N to UH-1Y "Venom" Although the original contract called for upgrading the existing helicopter airframe, the contract was amended in 2008 to require the creation of an entirely new airframe.
The AH-1Z first flew on December 8, 2000, and completed its sea test flight in May 2005. On October 15, 2005, the U.S. Marine Corps took delivery of the first AH-1Z production helicopter. In the first quarter of 2006, the first production UH-1Y made its maiden flight and was transferred to Paterson River Naval Air Station to begin operational evaluation testing.
In February 2008, Bell converted 40 of the 180 AH-1Z aircraft to build new airframes. In September of that year, the Naval Aviation Department proposed to add 46 AH-1Zs to order a total of 226 aircraft, and UH-1Y purchases became 123. The AH-1Z reached initial operational capability in September 2010 and production began at full speed on December 10, 2010.
The AH-1Z and UH-1Y share the same tail boom, engine, rotor system, drivetrain, avionics architecture, software, controls, and displays, with about 85% of the same components. Both helicopters use two General Electric T700-GE-401C turboshaft engines, each with a maximum power output of 1800 shaft horsepower, and the skid landing gear has also been upgraded. The aircraft can be armed with 8 Hellfire, 14 70mm rockets (unguided or laser-guided), 650 rounds of 20mm ammunition, 120 jamming shells and a 20-minute fuel reserve. Its maximum take-off weight is about 8390 kg, making it the heaviest model of the AH-1 series.
The semi-rigid, seesaw-type twin-blade rotor system used in previous models was replaced by a four-blade, hingeless, bearingless composite rotor system. The four-blade design improves flight performance, with increased flight envelope, maximum speed, vertical climb rate, payload, and reduced rotor vibration. This design has 75% fewer parts than the articulated system, eliminating all bearings, hinges and shock absorbers in the paddle hub, reducing weight. The paddles are made of carbon fiber composite for greater ballistic resistance and have a semi-automatic folding system for loading on amphibious assault ships.
The new integrated avionics system includes two mission computers, an automated flight control system and a glass cockpit with two multifunction LCD displays and one dual-function LCD display for each crew. The communications suite combines the Navy's RT-1824 integrated radio, UHF/VHF communications, satellite communications, and modems in a single unit. The navigation kit includes an embedded GPS inertial navigation system, a digital map system, and a low-airspeed air data subsystem to deliver weapons while hovering. The new cockpit system increases interoperability and can transmit and receive data from ground and air systems in other branches.
The AH-1Z's "Target Aiming System," which uses a third-generation infrared imaging sensor to provide target aiming during the day, night, or adverse weather conditions, has multiple viewing modes and can be tracked using FLIR or TV, and this system is also used on the KC-130J. Both the pilot and co-pilot are equipped with Thales' "TopOwl" helmet-mounted sighting and display system, which has a 24-hour day/night function and a binocular display with a 40° field of view, and its visor projection provides forward-looking infrared or video images.
The AH-1Z's two redesigned short wings are longer, with each wingtip added to a wingtip pylon, which can carry AIM-9 missiles There are also two hardpoints under each wing that can be used to hang 70mm rocket pods or AGM-114 quad missile launchers, and the Longbow radar can also be mounted on wing tip pylons. The AH-1Z can cruise at speeds of 250 to 259 kilometers per hour and sprint at speeds of 330 kilometers per hour. The AH-1Z improves its survivability through a variety of means, including an infrared suppression system for engine exhaust, an infrared jamming bomb and chaff jamming bomb delivery device, radar warning, missile approach warning and laser warning system.
H-1 series still "rampant"
Although the US Marine Corps received the last AH-1Z attack helicopter, the production of the H-1 series will not end there. Bell is also producing the helicopter for foreign customers, such as 12 A1H-1Zs for Bahrain and 8 UH-IYs and 4 AH-1Zs for the Czech Republic starting in 2023.
The AH-1Z in service has about 20 years to live, and to make these helicopters fit for the battlefield of the future, the Marine Corps intends to take a three-pronged approach: improving survivability, lethality and interoperability. The planned "Survivability Enhancement" project includes the installation of a distributed aperture infrared countermeasure system and an AN/APR-39 digital radar warning receiver to prevent missile attacks. To upgrade the potential, Bell and the Marine Corps plan to increase the helicopter's onboard power by about 200 percent through the Structural Improvements and Power Upgrades program, supporting a range of future airborne weapons and sensors. The H-1Z has been upgraded with the AGM-179 Joint Air-to-Surface Missile, which has radar and laser guidance modes. The Marine Corps also plans to integrate the AIM-9X missile into the AH-1Z, a major upgrade from the AIM-9M currently used in the JAH-17. There is even news that the US Marine Corps intends to upgrade the AIM-120 medium-range air-to-air missile for it. The AH-1Z itself does not carry a radar, and the AIM-120 is guided primarily by a network sight. However, the author believes that this improvement is of little value. The AH-1Z carries the AIM-120, because of its own slow flight speed and low altitude, resulting in the AIM-120's launch distance is very close, unable to fight with fighters, and the use is very limited. In fact, the current AIM-9 missile has few opportunities to be used in real combat.
The U.S. Marine Corps plans to replace its fleet of light and medium attack aircraft and utility helicopters starting in the 2030s. It is tracking plans for the Army's Future VTOL to develop a range of advanced rotorcraft that are faster and more maneuverable than conventional helicopters. While the Marine Corps has no official plan to replace the H-1, the Navy has replaced the MH-60R/S Seahawk with a Sea Strike Vehicle in response to the Army's plan.