Bell UH-1N Twin Huey

The Bell UH-1N Twin Huey is a medium military helicopter. The UH-1N has a fifteen seat configuration, with one pilot and fourteen passengers. In cargo configuration the UH-1N has an internal capacity of 220 ft³ (6.23 m³). An external load of 5,000 lb (2,268 kg) can be carried by the UH-1N. It is currently being replaced in USMC service by the UH-1Y.

History
Based on the stretched fuselage Bell 205, the Bell 212 was originally developed for the Canadian Forces (CF) under the designation CUH-1N Twin Huey. Later the CF adopted a new designation system and the aircraft was re-designated as the CH-135 Twin Huey. The CF approved the development of the aircraft on 1 May 1968 and purchased 50 aircraft, with deliveries commencing in May 1971.

The US military came very close to not procuring the Twin Huey. The purchase of the aircraft for US military use was opposed by the Chairman of the House Armed Services Committee at the time, L. Mendel Rivers. Rivers took this position because the aircraft powerplant, the Pratt & Whitney Canada PT6T was produced in Canada. The Canadian government had not supported US involvement in Vietnam and had opposed US policies in southeast Asia, as well as accepting US draft dodgers. Rivers was also concerned that procurement of the engines would result in a negative trade deficit situation with Canada. Congress only approved the purchase when it was assured that a US source would be found for the PT6T/T400 engines. As a result the United States military services ordered 294 Bell 212s under the designation UH-1N, with deliveries commencing in 1970.

Unlike in the Canadian Forces, in US service, the UH-1N retained the official name "Iroquois" from the single engined UH-1 variants, although US service personnel refer to the aircraft as a "Huey" or "Twin Huey". The Bell 412 is a further development of the Bell 212, the major difference being the composite four-blade main rotor. The UH-1N has also been developed into the upgraded, four-blade UH-1Y.

Design
The UH-1N's main rotor is powered by a PT6T-3/T400 Turbo Twin Pac made up of two Pratt & Whitney Canada PT6 turboshaft power turbines driving a single output shaft. They are capable of producing up to 1,342 kW (1,800 shp). Should one engine fail the remaining engine can deliver 671 kW (900 shp) for 30 minutes or 571 kW (765 shp) enabling the UH-1N to maintain cruise performance at maximum weight.

The United States Marine Corps (USMC) modified a large number of their UH-1Ns with a Stability Control Augmentation System (SCAS) which provides servo inputs to the rotor head to help stabilize the aircraft during flight. This modification removed the gyroscopic "Stabilization Bar" on top of the main rotor head, instead relying on the computer system for stability.

Operational history
The United States Air Force employs UH-1Ns to fulfill its ICBM mission, providing a utility helicopter for transport between bases such as Minot AFB, Francis E. Warren AFB and Malmstrom AFB to missile launch sites in North Dakota, Montana, Wyoming, Nebraska, and Colorado. The UH-1N is also used by the 36th Rescue Flight (36 RQF) at Fairchild AFB, WA for conducting Search-and-Rescue (SAR) and medical evacuation missions.

On 6 March 1972, Hendrick V. Gorick of the United States Navy Antarctic Development Squadron Six (VXE-6) jumped at an altitude of 20,500 ft (6,248 m) from a UH-1N helicopter. In doing so he set a record for parachute jumping over the Antarctic continent.

During the 1982 Falklands War, the Argentine Air Force deployed two Bell 212 to Goose Green grass airstrip from where they performed general support duties including the recovery of many downed pilots. By the end of the hostilities both aircraft were still intact and both captured by the British.

USMC UH-1Ns were used by the USMC during its 2003 invasion of Iraq. UH-1Ns provided reconnaissance, and communications support to Marine ground troops. They were also called upon to provide close air support during heavy fighting in Nasiriyah.

U.S. variants
UH-1N Iroquois


 * Initial production model, used by the USAF, USN, and USMC. Over the years the primary operators, the USMC has developed a number of upgrades for the aircraft including improved avionics, defenses, and a FLIR turret. The USAF plans to replace their UH-1Ns with the Common Vertical Lift Support Platform to support the service's ICBM activities.

VH-1N


 * VIP transport configuration

HH-1N


 * SAR variant.

UH-1Y Venom


 * A UH-1N replacement and upgrade as part of the H-1 upgrade program for the USMC, designed to coincide with a similar upgrade for the AH-1W attack helicopter to AH-1Z Viper standard, with common engines and other major systems.

Canadian variants
CUH-1N Twin Huey CH-135 Twin Huey Canada purchased 50 CH-135s with deliveries starting in 1971. The aircraft were retired from the Canadian Forces starting in 1996 and struck off strength in December 1999. 41 of the surviving CH-135s were acquired by the US government in December 1999 and transferred to the National Army of Colombia and Colombian National Police. At least one CH-135 was destroyed in combat. 135135 was transferred to the Colombian National Police and flown by the Dirección Antinarcóticos (DIRAN). It was destroyed on the ground by FARC rebels on 18 January 2002, following an incident in which it was forced down by gunfire. Two CH-135s are on display in museums, one at the Canada Aviation Museum in Ottawa and one at the National Air Force Museum of Canada at CFB Trenton.
 * Original Canadian Armed Forces designation for the UH-1N utility transport helicopter.
 * Canadian version of the UH-1N.

Italian-built variants
Agusta-Bell AB 212 Agusta-Bell AB 121EW Agusta-Bell AB 212ASW The AB-212ASW is a Model 212 Twin Huey with a prominent radome above the cockpit. Early production had a dome-shaped radome, while later production had a flatter "drum" radome. A left side winch is used for dipping the Bendix ASQ-18 sonar. Other changes include structural reinforcement for a gross weight of 11,197 lbs (5080 kg), ECM, shipboard deck tie-down attachments and corrosion protection. Armament is two Mk 44 or Mk 46 torpedoes or two depth charges in the ASW role and four AS.12 air-to-surface wire-guided missiles for the anti-shipping role.
 * Civil or military utility transport version. Built under license in Italy by Agusta.
 * Electronic warfare version for Turkey.
 * Anti-submarine warfare, anti-shipping version of the AB 212 helicopter, built under license in Italy by Agusta. Operated by the Italian Navy, Hellenic Navy and Islamic Republic of Iran Navy, Greece, Iran, Italy, Peru, Spain, Turkey, and Venezuela.

General characteristics

 * Crew: 4 (Pilot, copilot, crew chief, gunner)UH-1N_marines_repel.png
 * Capacity: 6-8 combat-equipped troops, or equivalent cargo
 * Length: 41 ft 8 in (12.69 m)
 * Rotor diameter: 48 ft 0 in (14.6 m)
 * Height: 14 ft 5 in (4.4 m)
 * Disc area: 1,808 ft² (168.0 m²)
 * Empty weight: 6,000 lb (2,721.5 kg)
 * Loaded weight: 10,500 lb (4,762.7 kg)
 * Useful load: 4500 lb (2038.0 kg)
 * Max takeoff weight: 10,500 lb (4,762.7 kg)
 * Powerplant: 2× Pratt & Whitney Canada T400-CP-400 turboshaft, 900 shp (671 kW), (total 1,250 shp) each

Performance

 * Maximum speed: 120 knots (135 mph, 220 km/h)
 * Cruise speed: 110 knots (126 mph, 207.3 km/h)
 * Range: 248 nmi (286 mi, 460 km)
 * Service ceiling: 17,300 ft (5,273 m)
 * Rate of climb: 1,755 ft/min (8.9 m/s)
 * Power/mass: hp/lb (W/kg)

Armament

 * 2.75-inch rocket pods,
 * GAU-16 .50 Cal. Machinegun,
 * GAU-17 7.62mm minigun or M240 7.62mm lightweight machinegun