The Bell UH-1N Twin Huey is a medium military helicopter
that first flew in April, 1969. 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. The CUH-1N (later CH-135) Twin Huey was the
original version, first ordered by the Canadian Forces.
Development
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.
Variants
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
Original Canadian Armed Forces designation for the UH-1N utility
transport helicopter.
CH-135 Twin Huey
Canadian version of the UH-1N. 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.
Italian-built variants
Agusta-Bell AB 212
Civil or military utility transport version. Built under
license in Italy by Agusta.
Agusta-Bell AB 121EW
Electronic warfare version for Turkey.
Agusta-Bell AB 212ASW
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, Peru, Spain, Turkey, and
Venezuela.
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.
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