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[2.0] Twin Hueys / Foreign-Built Hueys / Updates & Modifications

v1.2.2 / chapter 2 of 2 / 01 oct 13 / greg goebel / public domain

* The first-generation Hueys led to a series of twin-engine variants, the "Twinhueys". Further improved variants and updates followed, helping keep the Huey in service in the 21st century.

Bell Model 214ST


[2.1] MODEL 212 TWIN HUEY: USN-USMC UH-1N / MODEL 412
[2.2] MODEL 214
[2.3] FOREIGN-BUILD HUEYS
[2.4] HUEY UPDATES
[2.5] UNUSUAL HUEY MODIFICATIONS / VARIANT SUMMARY
[2.6] COMMENTS, SOURCES, & REVISION HISTORY

[2.1] MODEL 212 TWIN HUEY: USN-USMC UH-1N / MODEL 412

* In 1965, Bell had experimented with a single twin-engine Model 208 "Twin Delta" Huey prototype, which was a UH-1D fitted with a Continental XT67-T-1 engine module, consisting of two T72-T-2 turboshaft engined driving a common gearbox. This exercise was performed as an experiment using company funds.

In early 1968, Bell had discussions with the Canadian government and Pratt & Whitney Canada (PWC) that led to an agreement in 1969 to build a twin-engine version of the Model 205. Bell flew a UH-1D fitted with a new PWC "Twin Pac" engine, consisting of two of PWC's popular PT6 turbines driving a common gearbox, in 1969. This prototype led to the production "Twin Huey" or "Model 212 / UH-1N", essentially a UH-1H fitted with the PWC T400-CP-400 (PT6T-3) Twin Pac, providing a total of 1,140 kW (1,530 SHP). Each turbine of the Twin Pac could actually provide 670 kW (900 SHP), but the rotor system couldn't deal with 1,340 kW (1,800 SHP). However, in the event of a failure of one of the turbines, the remaining operational turbine could be run at its full 670 kW (900 SHP) output.

Bell began deliveries of the UH-1N to the US Air Force in 1970, which obtained 79 and used them for special operations. The US Navy and Marine Corps were particularly interested in the type, since the twin-engine configuration provided greater flight safety for overwater operations, and obtained a total of 221 by 1978. Marine UH-1Ns would gradually be fitted with countermeasures, infrared imager nose turrets, and other kit. Two standard Marine UH-1Ns were converted to "VH-1N" VIP transports, and six Model 212s were built new to this standard for the Corps as well. The USAF adopted the UH-1N for the crash rescue role as the "HH-1N", with about 52 machines fitted out much like the HH-1H.

Bell UH-1N, USMC UH-1N

The Canadian Armed Forces, which had backed development of the type, received their first Model 212 on 3 May 1971, with the last of 50 delivered about a year later. The CAF originally designated the type the "CUH-1N", but this was later changed to "CH-135". Small quantities of the Model 212 have been sold to other military operators as well as commercial users. The enhanced safety provided by the Model 212's twin-engine configuration also proved to be an excellent selling point for commercial operators working in offshore gas and oil exploration.

   BELL MODEL 212 / UH-1N TWIN HUEY:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   rotor width             14.69 meters        48 feet 2 inches
   footprint length        17.46 meters        57 feet 3 inches
   fuselage length         12.92 meters        42 feet 5 inches
   height                  4.53 meters         14 feet 10 inches

   empty weight            2,720 kilograms     6,000 pounds
   max loaded weight       4,535 kilograms     10,000 pounds

   maximum speed           205 KPH             125 MPH / 110 KT
   service ceiling         5,275 meters        17,300 feet
   range                   460 kilometers      285 MI / 250 NMI
   _____________________   _________________   _______________________

* The Bell "Model 412" program was announced on 8 September 1978, with initial deliveries in January 1981. It was essentially a Model 212 with a four-blade composite rotor for smoother and more efficient flight. The rotor system could be folded for compact storage. It was powered by a PWC PT6T-3B-1 Twin Pac engine providing a total of 977 kW (1,310 SHP). The Model 412 featured crashworthy seats, fuel tanks, and landing gear, and the fuselage also featured built-in maintenance steps and handholds to ease servicing in the field. It could carry up to 14 passengers, or six stretchers with attendants.

Bell 412 Twin Huey

The initial 412 led to several improved variants:

There was talk of a "412 Plus" but it is unclear if it ever entered production. Bell did develop a prototype of an attack helicopter variant, the "Model 412AH", introduced in 1986. It featured a Lucas turret mounted under the nose fitted with a single 12.7 millimeter (0.50 caliber) machine gun, and could also carry rockets and other stores. Little seems to have come of this exercise.

   BELL MODEL 412EP:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   rotor width             14.02 meters        46 feet
   footprint length        17.12 meters        56 feet 2 inches
   fuselage length         12.70 meters        41 feet 8 inches
   height                  3.48 meters         11 feet 5 inches

   empty weight            3,100 kilograms     6,835 pounds
   max loaded weight       5,400 kilograms     11,900 pounds

   maximum speed           260 KPH             160 MPH / 140 KT
   hover ceiling           3,100 meters        10,170 feet
   range                   745 kilometers      465 MI / 400 NMI
   _____________________   _________________   _______________________

Total sales by Bell of Model 412s amounted to some 530 by 1998. The Canadian Armed Forces were a big customer, buying 100 "CH-146 Griffons", which were Bell-built "Model 412CFs" with the PT6T-3D Twin Pac engine.

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[2.2] MODEL 214

* In 1970, Bell announced the introduction of an improved derivative of the Model 205 / UH-1H to be designated the "Model 214 Huey Plus". The single Model 214 prototype featured the Lycoming T53-L-13 turboshaft engine providing 1,044 kW (1,400 SHP); a new wide-chord "Nodomatic" rotor system with no teeter bar that could handle the full power of the engine; structural strengthening to permit higher load weights; and various detail changes.

The prototype led to the production "Model 214A", which was similar but had a much more powerful Lycoming LTC4B-8D turboshaft engine providing 2,186 kW (2,930 SHP). The Model 214A was demonstrated to the Iranians, and in late 1972 the Shah's government placed an order for 287 of the type for the Iranian Army, who named it the "Isfahan", after the town where the Iranian Army's helicopter training school was based. After this batch, the Iranian Army ordered six more Model 214As, while the Iranian Air Force ordered 39 Model 214Cs, which were similar but fitted for the SAR role. The Iranian Model 214s served in the country's war with Iraq in the 1980s.

* The Model 214A itself was basically a single-engine Model 212 and looked it, but Bell began to consider a "stretched" derivative with a "Twin Pac" type engine configuration and other much more visible changes. The company began discussions with the Shah's government for license production of the Model 214A and the new "Model 214ST (Stretched Twin)", but in 1979, the same year the first of three Model 214ST prototypes flew, the Shah's government was overthrown and the production scheme never happened.

Bell continued development of the Model 214ST anyway, redefining the "ST" suffix to stand for "Super Transport", leading to initial deliveries of the new variant in 1982. The Model 214ST had a modernized and more streamlined appearance than other versions of the Huey; featured a "roll ring" built into the fuselage for crew protection; and was fitted with a glass-fiber rotor with titanium leading-edge strips and stainless steel end caps. It could carry a crew of two and up to 18 passengers.

Bell Model 214, Model 214ST

The Model 214ST was fitted with twin GE T700 turbines providing a total of 2,424 kW (3,250 SHP), and could carry nearly 3,630 kilograms (8,000 pounds) of payload. It was fitted with an automatic rotor stabilization system that eliminated need for the classic Bell teeter bar. It proved popular in commercial service, particularly for offshore oil and gas exploration, and was purchased by a number of foreign military services. The Iraqis bought 45 Model 214STs in the late 1980s, and small numbers were sold to Brunei, Oman, Peru, Venezuela, and Thailand.

   BELL MODEL 214ST SUPER TRANSPORT:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   rotor width             15.85 meters        52 feet
   footprint length        18.95 meters        65 feet 2 inches
   fuselage length         15.02 meters        49 feet 4 inches
   height                  4.85 meters         15 feet 2 inches

   empty weight            4,284 kilograms     9,445 pounds
   max loaded weight       7,940 kilograms     17,500 pounds

   maximum speed           255 KPH             160 MPH / 140 KT
   service ceiling         1,950 meters        6,400 feet
   range                   800 kilometers      500 MI / 435 NMI
   _____________________   _________________   _______________________

* Bell also developed a civil derivative of the Model 214A, the "Model 214B BigLifter", with modest changes including emergency escape windows in the cargo doors, an engine fire extinguishing system, and civilian avionics. It was offered for roles such as passenger transport, a "flying crane" with an external cargo hook, agricultural service, or firefighter. The Model 214B was certified in early 1976, but there were few sales, with small numbers sold to Dubai, Ecuador, Oman, and the Philippines. Production ended in 1981.

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[2.3] FOREIGN-BUILD HUEYS

* The Huey proved popular in foreign service. Bell sold small quantities of UH-1Bs and UH-1Ds to Australia and Norway, and UH-1Hs for Canada and New Zealand. The Canadians used their "CUH-1Hs" (later "CH-118") for training. At least 55 UH-1Hs were also shipped to Turkey.

However, most foreign-service Hueys were license-built. Dornier of Germany built 352 UH-1Ds for the West German Army; one was evaluated by the West German Army with pontoons. AIDC in Taiwan built 118 UH-1Hs for the Nationalist Chinese army. IPTN of Indonesia license-built the Model 412 as the "NBell-412".

German Army UH-1D

Fuji Heavy Industries of Japan began license production of the Huey in 1962, producing at least 90 UH-1Bs and 50 UH-1Hs, mostly for the Japanese Self-Defense Forces but also for a few civil operators. Fuji then went on to develop a unique Japanese variant of the UH-1H, appropriately designated "UH-1J". The UH-1J featured an Allison T53-L-703 turboshaft engine providing 1,343 kW (1,800 SHP), a vibration-reduction system, infrared countermeasures, and a night-vision-goggle (NVG) compatible cockpit. First delivery of the UH-1J to the Self-Defense Forces was in 1993, with 78 delivered into 1998.

* The most enthusiastic alternate source for the Huey was Agusta of Italy. Agusta obtained a license to build Model 204 Hueys in 1961, flying their first example on 10 May 1961, and then went on to produce the Model 205. Agusta-Bell Model 204s and 205s were sold to a large number of nations, including Australia, Austria, Greece, Iran, Italy, Morocco, Oman, Saudi Arabia, Singapore, Spain, Sweden, Tanzania, Tunisia, Turkey, Yemen, Zambia, and Zimbabwe.

Agusta adopted a "customer is always right" attitude, and provided a wide range of auxiliary gear kits for customers. These kits included additional fuel tanks, rescue hoist, rotor brake, engine sand and dust filters, engine winterization, fixed floats, emergency floatation gear, snow skis, and a number of weapons fits. Agusta even supplied AB-204s fitted with a Rolls-Royce / Bristol Gnome H.1200 turboshaft providing 895 kW (1,200 SHP), or a GE T58-GE-2 turboshaft providing 988 kW (1,325 SHP). The company also developed prototypes of their own "Twin Hueys" based on AB-205s with dual Gnome H.1200 or Turbomeca Astazous engines, but these variants did not reach production.

Austrian Air Force Agusta-Bell AB-204B

The company built a specialized maritime warfare variant of the Huey designated the "AB-204AS" (where "AS" stood for "Anti-Submarine" or "Anti-Surface Vessel"), fitted with search radar, dunking sonar, and the capability to carry homing torpedoes and other stores for maritime combat. This machine was sold to the navies of Italy, Spain, and Turkey.

* Agusta went on to license-build the Bell 212, and sold the type to Austria, Dubai, Italy, Lebanon, Morocco, Saudi Arabia, Somalia, Spain, Sudan, Yemen, and Zambia.

As a follow-up to the AB-204AS, the company produced a similar ASW variant of the Model 212, the "AB-212AS". Work on this version began in 1971, resulting in the flight of a prototype in 1973. The AB-212AS resembled a standard Model 212 Twin Huey except for a prominent radome above the cockpit. Early production had a dome-shaped radome, while later production had a flatter "drum" radome, apparently reflecting different radar fits, with the later fit being the Ferranti SeaSpray radar. A winch outside the left side was standard equipment, used for handling the rotorcraft's Bendix ASQ-18 dipping sonar. Other changes included structural reinforcement, shipboard deck tiedown attachments, and corrosion protection.

Agusta-Bell AB-212AS

The AB-212AS carried a crew of four in maritime combat operations, including pilot, copilot, and two systems operators. It was fitted with an all-weather flight control system, which provided both navigation and "hands-off" autopilot capabilities, and was integrated with the helicopter's search and targeting systems to pinpoint both helicopter and target positions. The AB-212AS was also fitted with a defensive countermeasures suite.

In ASW operations, the AB-212AS could carry two Mk.44/46 or Moto Fides A-244/S homing torpedoes. For surface vessel attack operations, it could carry two Italian Marte Mk.2, British Sea Skua, or (now obsolete) Aerospatiale AS-12 light antiship missiles. The AB-212AS could also be fitted with a TG-2 Teseo data link to provide guidance updates to the Italian Otomat ship or shore launched antiship missile.

Although the AB-212AS was optimized for the maritime combat mission, it retained the ability to carry passengers and cargo, as well as perform SAR missions using its winch. It could accommodate four litters and a medical attendant for medevac operation, or up to seven passengers. The AB-212AS was sold to Greece, Iran, Italy, Spain, Turkey, and Venezuela.

* Agusta began production of the Model 412 in 1981, and quickly came up with a multirole military version designated the "AB-412 Grifone (Griffon)", which could be fitted for gunship, medevac, troop transport, or SAR roles. First flight of the prototype Griffon was in 1982, with initial delivery in 1983.

The Grifone differed from the standard production Model 412 in having crash-resistant seats, adding armor plating for pilot and copilot; high-impact landing gear; self-sealing fuel tanks; and permanent armament attachment points. Optional sensor and countermeasures systems could also be fitted. Possible weapons fits included two 12.7 millimeter gun pods; two 25 millimeter Oerlikon cannon; two 19-round launchers for 81-millimeter SNORA unguided rockets; four or eight TOW missiles; air-to-air missile pods for Stinger and similar weapons; or four BAE Sea Skua antiship missiles. The Grifone could also accommodate six stretchers and two attendants, or up to 15 troops. Agusta sold the Grifone to Dubai, Finland, Italy, Lesotho, Uganda, and Venezuela.

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[2.4] HUEY UPDATES

* With so many Hueys built, it is not surprising that several companies offered refurbishment and update programs. Bell offered a UH-1H update designated the "UH-1HP Huey II", which involved modifying the Lycoming T53-L-13 engine up to T53-L-703 standard, giving it 298 kW (400 SHP) more power for a total of 1,343 kW (1,800 SHP); a new dynamic system, derived from that of the UH-1N and the Model 212, to handle the greater power; and new avionics. The improved engine was more reliable, slightly more fuel efficient, and raised the payload from 450 kilograms (1,000 pounds) to 1,350 kilograms (3,000 pounds). Huey IIs have been obtained by US Customs, Iraq, and Yemen.

Global Helicopter offered a "Huey 800" update, which replaced the UH-1H's TF3-L-13 engine with an LHTEC T800-800 turboshaft. The new engine had the same power output as the old, meaning no dynamic system updates were required, but the new engine was lighter, more reliable, and much more fuel-efficient. UNC offered a "UH-1/T700" update very similar to the Bell UH-1HP update, but replaced the T53-L-703 engine with a GE T700-GE-701C engine with 1,413 kW (1,900 SHP) to provide improved fuel economy.

In 2004, Singapore Technologies Aerospace began delivery of 20 refurbished UH-1Hs to the Philippines. It appears these machines featured modest updates, including cockpit lighting compatible with NVGs.

* The US Marine Corps has kept their UH-1N Hueys up-to-date, adding countermeasures such as infrared jammers and chaff-flare dispensers, forward-looking infrared (FLIR) turrets in the nose, a cable cutter above the cockpit, new armament fits, and revised avionics. The service has now obtained an updated variant of the Huey, the "UH-1Y Super Huey " AKA "Venom", based on the UH-1N, intended to extend the service life of the UH-1Ns, since many are about two-thirds of the way through their 10,000-hour design life, and to improve payload and performance. The upgrade fit included:

The UH-1Y was stretched to accommodate the new hardware and preserve their center of balance. The Super Huey had 800 kilograms (1,760 kilograms) more payload capacity, and a top speed of 295 KPH (185 MPH) compared to a previous top speed of 200 KPH (125 MPH).

Bell UH-1Y Super Huey

The first UH-1Y was rolled out in late 2001, with initial deliveries in 2008. Originally, the order envisioned that the Marines would obtain 100 UH-1Ys, all through upgrades of UH-1Ns, but the UH-1Ns were too heavily tasked in Iraq, Afghanistan, and elsewhere to be withdrawn from service for upgrade, and the price of new-build machines was only incrementally greater than that of rebuilt machines. The plan was changed to obtain 160 UH-1Ys, mostly new-build except, it seems, for ten upgrades from UH-1Ys for test and evaluation. The original UH-1Y upgrade program was part of a deal that also involved a parallel upgrade of 180 Marine AH-1W SuperCobra helicopter gunships to the new "AH-1Z" standard, with a fair degree of commonality between the two updated aircraft.

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[2.5] UNUSUAL HUEY MODIFICATIONS / VARIANT SUMMARY

* Hueys have been used for a number of research programs. One UH-1A was modified by Bell as a flying laboratory for new sensor and instrument configurations, and designated the "Research Helicopter 2 (RH-2)".

One of the YUH-1Bs was used as an aerodynamic test bed as the "Model 533" and modified to a number of configurations as part of a US Army program. The first series of modifications, flown in 1962, featured aerodynamic fairings, a new tail surface to offload the tail rotor, and a tilting rotor mast inside a large fairing structure. The Model 533 was then fitted with a swept wing, two Continental J69-T-29 turbojets with 7.55 kN (770 kgp / 1,700 lbf) thrust each, and a modified rotor blade with swept tips. This compound rotorcraft achieved a speed record of 370 KPH (236 MPH or 200 knots) in level flight on 15 October 1964, and on 6 April 1965 topped that record with a speed of 402 KPH (250 MPH) in level flight.

Bell Model 533 compound helicopter

The Model 533 was finally fitted with two wingtip-mounted Pratt & Whitney JT12A-3 turbojets with 14.7 kN (1,500 kgp / 3,300 lbf) thrust each. In this configuration, it achieved speeds of over 480 KPH (300 MPH). At last notice, the Model 533 was on display at the US Army Transportation Museum at Fort Eustis, Virginia.

* The following list summarizes Huey variants. Model 204 variants included:

* Model 205 variants include:

* Model 212 Twin Huey variants include:

* Model 412 variants include:

* Model 214 variants include:

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[2.6] COMMENTS, SOURCES, & REVISION HISTORY

* As an interesting note on the Huey, during fighting with Islamic militants in 2007, the Lebanese Army rigged up one or more Hueys to carry 225 kilogram (500 pound) aircraft-type bombs on each stores pylon. Apparently the "HueyBombers" proved very accurate and devastating in strikes.

* Although I have never seen a good number of the aircraft I write about, that is certainly not the case for the Huey. I don't think I can remember a year for the last three decades or so when I haven't seen them flying around. It is ironic, however, that although the Huey is one of the most heavily produced flying machines of the postwar era, it is hard to find information on it, and this writeup became something of a scavenger hunt. Helicopters just do not have that much sex appeal.

Bell 205 / UH-1H Huey

* Sources include:

* Revision history:

   v1.0   / 01 apr 01 
   v1.0.1 / 01 jan 02 / Added variant summary, plus minor tweaks.
   v1.0.2 / 01 jan 04 / Review & polish.
   v1.1.0 / 01 jan 06 / General cleanup.
   v1.1.1 / 01 dec 07 / Review & polish.
   v1.1.2 / 01 nov 09 / Review & polish.
   v1.2.0 / 01 dec 09 / Split into two chapters.
   v1.2.1 / 01 nov 11 / Review & polish.
   v1.2.2 / 01 oct 13 / Review & polish.
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