Bell RAH-71 Algonquin Scout Attack Helicopter

AH-71 Viper

Bell RAH-71 Algonquin Scout Attack Helicopter

by Tim Wing

The Algonquian was a scout attack helicopter fielded by the United States Army in the late 2000’s to replace the AH-1 Cobra and OH-56 Kiowa Warrior. About the same size as the Cobra it replaced, it featured internal weapons carrying, folding landing gear and NOTAR (No Tail Rotor) system. It was also purchased by the United States Marine Corps and various other militaries throughout the world.

  • Role: Reconnaissance and Attack helicopter
  • National origin: United States
  • Manufacturer: Bell Helicopter (Textron)
  • First flight: 2 December 1996
  • Introduction: September 2002
  • Status: Retired
  • Primary user: US Army (RAH-71), US Marine Corps (AH-71)
  • Number built: 3,228
  • Unit cost: $38 million (in adjusted 2070 International Credits)

Development

Background

The Bell RAH-71 Algonquin was a twin-engine attack helicopter developed from the AH-1W Super Cobra. It was developed for the United States Army to replace its OH-58 Kiowa Warrior and the AH-1 Cobras in National Guard service. The US Marine Corps version, the AH-71 Sea Viper, was further developed to replace the AH-1 Sea Cobra. The RAH-71 features retractable landing gear, internal weapons carriage, a no tail rotor (NOTAR) directional yaw control, a four-blade, bearingless, composite main rotor system, uprated transmission, and a new target sighting system.

In 1994, the US Army launched the Future Scout program by signing a contract with Bell Helicopter for upgrading the AH-1 into what would eventually become the RAH-71. Initially meant to an avionics and rotor upgrade program, what emerged was a very different and much more capable helicopter. Originally the RAH-71 was to be built from existing AH-1 airframes, but due to the extensive changes, it was found to be more cost effective to build all aircraft from new.

Rotors

The two-blade semi-rigid, teetering rotor system on the AH-1W was replaced by a four-blade, hingeless, bearingless rotor system. The four-blade configuration provided improvements in flight characteristics including increased flight envelope, maximum speed, vertical rate-of-climb, payload and reduced rotor vibration level. The new bearingless, hingeless rotor system had 75% fewer parts than that of four-bladed articulated systems. The blades were made of composites, which had an increased ballistic survivability, and for the Marine Corps AH-71 there was a semiautomatic folding system for storage aboard amphibious assault ships.

The tail rotor of the AH-1 series was replaced by a NOTAR system. The NOTAR was developed by Hughes Helicopters. The name was an acronym derived from the phrase no tail rotor. The system used a fan inside the tailboom to build a high volume of low-pressure air, which exited through two slots and created a boundary layer flow of air along the tailboom utilizing the Coandă effect. The boundary layer would change the direction of airflow around the tailboom, creating thrust opposite the motion imparted to the fuselage by the torque effect of the main rotor. Directional yaw control was gained through a vented, rotating drum at the end of the tailboom, called the direct jet thruster.

Armament

The RAH-71 was armed with a 20mm M197 3-barreled Gatling cannon in an A/A49E-10 turret with 1100 rounds of ammo capacity. In late 2006 Meggitt Defense Systems developed a new linkless 20mm ammunition handling system to improve the gun feed reliability of the existing linked feed system.

The internal weapons bay could carry nine Brimstone short range variable warhead, combined infra-red imager and active radar homing guided anti-armor missiles per side. The bays were also capable of holding four AGM-114 Hellfire missiles or box launcher containing 38 unguided 70 mm Hydra 70 rockets, per side.

Both the RAH-71 and the AH-71 could also mount wing stubs. These wings had a wing-tip station for a missile such as the AIM-9 Sidewinder. Each wing had two underwing stations for pods containing 10 Brimstone missiles, 36 70 mm Hydra 70 rocket pods, or AGM-114 Hellfire quad missile launchers. When these wing stubs were mounted, the internal weapons bay had to be deleted. This would be replaced with a low profile internal fuel tank. Though it was possible to configure the RAH-71 in such a manner, the US Army rarely did. The US Marine Corps, who operated the AH-71 Sea Viper, used this configuration almost exclusively.

AH-71 Algonquian

Avionics

The RAH-71’s integrated avionics system (IAS) was developed by Northrop Grumman. The system included two mission computers and an automatic flight control system. Each crew station had two multifunction liquid crystal displays (LCD) and one dual function LCD display. The communications suite combined an RT-1824 integrated radio, UHF/VHF, COMSEC and modem in a single unit. The navigation suite included an embedded GPS inertial navigation system (EGI), a digital map system and Meggitt’s low-airspeed air data subsystem, which allowed weapons delivery when hovering.

The crew was equipped with the Thales “Top Owl” helmet-mounted sight and display system. The Top Owl had a 24-hour day/night capability and a binocular display with a 40° field of view. Its visor projection provided forward looking infrared (FLIR) or video imagery. The RAH-71 had survivability equipment including the Hover Infrared Suppression System (HIRSS) to cover engine exhausts, countermeasure dispensers, radar warning, incoming/on-way missile warning and on-fuselage laser spot warning systems.

The Lockheed Martin target sight system (TSS) incorporated a third-generation FLIR sensor. The TSS provided target sighting in day, night or adverse weather conditions. The system had various view modes and could track with FLIR or by TV.

The RAH-71 was also equipped with the AN/APG-78 Longbow millimeter-wave fire-control radar also used on the AH-64D Longbow Apache. The AN/APG-78 fire-control radar (FCR) target acquisition system and the Radar Frequency Interferometer (RFI), was housed in a dome located above the main rotor. The radome’s raised position enabled target detection while the helicopter is behind obstacles such as terrain, trees or buildings. The AN/APG-78 was capable of simultaneously tracking up to 128 targets and engaging up to 16 at once, an attack could be initiated within 30 seconds. A radio modem integrated with the sensor suite allowed data to be shared with ground units and other helicopters; allowing them to fire on targets detected by a single helicopter.

Armor

The skin of the RAH-71 was composed of treated steel plate. The armored skin stopped all small arms fire, provided good protection against heavier infantry weapons, such as a 12.7mm machinegun round, and fair resistance to light mecha-mounted weaponry, such as the Zentraedi 22.3mm HE autocannon round.

Operational history

The RAH-71 Algonquin first entered service with the US Army in September of 2002. By late 2008, the RAH-71 had replaced all OH-58s and AH-1s in both the active duty and National Guard inventories. Though the RAH-71 was never meant to replace the AH-64 Apache (which at the time was in the process of being phased out in favor of the Sikorsky AH-68 Comanchero) it did find itself being acquired in greater numbers than both of the aircraft which it was meant to replace. This was due to the fact that it was less expensive than the AH-68, but offered similar performance. The primary advantage of both the AH-64 and AH-68 was increased operational range and payload. This was to be expected, as the RAH-71 was a lighter aircraft with a max take-off weight of 8,400 kg compared to the AH-68’s 12,600 kg max take-off weight.

In 2002 the US Marine Corps was in the process of developing an upgrade program for its aging fleet of AH-1W Sea Cobras and UH-1 utility helicopters. Being that the RAH-71 satisfied almost all of the program requirements for the AH-1W replacement, a navalised version was soon accepted into service as the AH-71 Sea Viper. This primary difference between the two was the addition of folding main rotors and increased corrosion protection to help the helicopter deal with life at sea.

The UN Spacy never operated the RAH-71, having decided in favor of the AH-68. The UEDF Tactical Corps did fly Algonquins for several years after the signing of the Treaty of the Southern Cross. However, these helicopters were quickly phased out. The RAH-71 did see extensive use in other militaries prior to the Southern Cross treaty and continued to be used by the Israeli Defense Force (at least up till its absorption into the UEG) and the Merchant Republic up till the Invid Invasion.

Operators:

United States – United States Marine Corps (2004-2018), United States Army (2002-2018); Bahrain – Bahrain Air Force (2005-2011); Israel – Israeli Defense Force (2005-2027); Japan – Japan Ground Self-Defense Force (AH-71J, 2006-2018); Jordan – Jordanian Air Force (2008-2018); Pakistan – Pakistan Army (2008-2011); South Korea – Republic of Korea Army (2010-2018); Merchant Republic – Argentine Army Airforce (2015-2033)

Specifications (RAH-71)

  • General characteristics
  • Crew: 2 (pilot, co-pilot/gunner)
  • Length: 19.6 m
  • Rotor diameter: 14.6 m
  • Height: 4.37 m (5.39 m with radar)
  • Disc area: 168.0 m²
  • Empty weight: 5,200 kg
  • Useful load: 2,450 kg
  • Max. takeoff weight: 8,400 kg
  • Powerplant: 2 × General Electric T700-GE-401C turboshafts, 1,340 kW (1,800 shp) each
  • Rotor systems: 4 blades on main rotor, NOTAR yaw control

Performance

  • Never exceed speed: 450 kph in a dive
  • Cruise speed: 320 kph
  • Range: 790 km
  • Combat radius: 250 km with full internal weapons carriage, 340 km with wing stubs and fuel fast pack
  • Service ceiling: 6,000+ m
  • Rate of climb: 14.2 m/s

Armament

  • 1x 20mm M197 3-barreled Gatling cannon with 1100 rounds of ammo

Internal weapons bay

  • 18x Brimstone short range variable warhead, combined infra-red imager and active radar homing guided anti-armor missiles or,
  • 8x AGM-114 Hellfire missiles or,
  • 76x unguided 70 mm Hydra 70 rockets

Wing stubs

  • 40x Brimstone short range variable warhead, combined infra-red imager and active radar homing guided anti-armor missiles or,
  • 16x AGM-114 Hellfire missiles or,
  • 144x unguided 70 mm Hydra 70 rockets and,
  • 2x AIM-9 Sidewinder air to air missiles

 


 

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Original artwork by: Tim Wing

Content by Tim Wing

Copyright © 2015 Tim Wing

 

 

 

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