Bell

Bell Model 30
Bell Model 47
Bell Model 48
Bell Model 61
Bell Model 204
Bell Model 205
Bell Model 206 Jet Ranger
Bell Model 207 Sioux Scout
Bell Model 209 Huey Cobra und Sea Cobra
Bell Model 212 Twin Two-Twelve
Bell Model 214B Big Lifter
Bell Model 222
Bell Model 301 (XV-15)
Bell Model 409 (YAH-63)
Bell Model 412
Bell/Boeing Model 609

Bell Model 30

History of development
The Bell Model 30 – the first in a series of first-class helicopters – was an experimental construction to test the rotor system. During World War I, the Bell Helicopter Corporation – as it was formerly called – designed and built at least five copies of an experimental helicopter. The first Bell Model 30 (NX-41867) was first flown in the middle of the year 1943. It consisted of a fuselage on a fixed three-wheeled landing gear with an open cockpit in the nose and the engine in the inside behind the pilot. The two-bladed main rotor contained the stabilizer that later became a typical characteristics of Bell helicopters and the two-bladed torque-tail rotor was sitting on a slim tube coming from the tail. The second Model 30 had to undergo several improvements like a modified landing gear and a new tail rotor attachment that became necessary after early test flights. The most remarkable modification was the closed cabin for the pilot with the passenger sitting aside. The Bell Model 47 widely-used in the world is based on this type.

Bell Model 47

Bell Model 48

History of development
In 1946, Bell started the development of a new helicopter that was actually a larger version of the Model 47. The USAAF ordered two copies of the new Bell Model 48 designated XR-12; the machines were equipped with a 540 shp (403 kW) R-1340 Wasp radial engine and provided place for five persons. Another aircraft with a stronger R-1340 engine and eight seats was ordered designated XR-12B. After renaming the R (rotary) aircraft in H (helicopter) models, they were called XH-12 and XH-12B. Apparently the tests were not satisfactory, because later orders of 10 pre-series models YH-12 and 34 series models R-12A were cancelled.

Bell Model 61

History of development
On 4 March, 1953, Bell flew the prototype of a helicopter called Bell Model 61, which was developed for a tendering of the US Navy for a new submarine defence weapon. The model won the US Navy contest in June 1953, and three units of the XHSL-1 were ordered. As the first model designed for submarine fighting , this machine went down in aircraft history, and with its tandem rotors it is unique in the Bell series. The Model 61 is basically a construction with a rectangular fuselage, four-wheeled landing gear, tandem rotors with manually retractable blades and a Pratt & Whitney R-2800 radial engine in the tail of the fuselage. It provided place for two pilots and two sonar operators. A diving-sonar system and an electronic target-tracking system belonged to the instruments intended for fighting missions. When the target was located, bombs, water bombs and Fairchild Petrel AUM-N-2 antisubmarine missiles were deployed. After some test flights, 78 HSL-1 aircraft were ordered, 18 of these were intended for Great Britain to be used within the Mutual Defence Assistance Programme. The first aircraft started flying in January 1957 in the US Navy Squadron HU-1, but after the end of the Korean War no aircraft were delivered to the Royal Navy, and production was discontinued after only 50 machines. Due to its limited performance, the HSL-1 was in duty only for a short period of time.

Bell Model 204

History of development
In 1955, the US Army initiated a competition for the concept of a new helicopter that could be used for evacuation of injured, instrument training and general purposes. In June of the same year, the US Army selected the model of the Bell Helicopter Company with the designation Bell Model 204. The US Army first chose the designation H-40 that was renamed later into HU-1 when the model also got the name Iroquois. This was also the first exemplar of the 'Hueys', the nickname developing in 1962 when the model was renamed within the framework of the Tri-Service rationalization to UH-1. Initially, the US Army ordered three prototypes with the designation XH-40 for experimental purposes. With the designation H-40, the model was assigned to the USAAF helicopter category. The first of these prototypes flew on 22 October, 1956; Bell used these aircraft for tests and further development. Shortly before the first flight, six aircraft of the type of the pre-series model YH-40 were ordered and delivered in August 1958. One machine remained in the possession of Bell, and of the remaining aircraft, one was sold to Eglin AFB, one to Edwards AFB and three to Fort Rucker for experimental purposes. After the production order, nine of the final pre-series models HU-1A were delivered on 30 June, 1959, followed by 74 series models, 14 of these were delivered to Army Aviation School in San Diego. The HU-1A with dual control was used as an instrument trainer. The first international operation was at the 55th Aviation Company in Korea; furthermore, the HU-1A was used as one of the first US Army helicopters in Vietnam. The Model 204, with its stabilizer in right angle to both main rotor blades and with the small elevator area at the tail, was a genuine member of the Bell family. The tubular skid landing gear was perfect for multi-purpose applications. The cabin provided place for two crew members and six passengers or two stretchers. The engine was a 700-shp (552-kW) Avco Lycoming T53-L-1A shaft turbine; thus, the Model 204 was the first helicopter with turbine propulsion ordered by the US Army. The HU-1A (182 machines were manufactured) was followed by the advanced HU-1B (1014 aircraft of this model were built). Early series models were provided with 960-shp (716-kW) Avco Lycoming T53-L-5 engines, later models with a 1,100-shp (820-kW) T53-L-11. Further improvements of the HU-1B were the modified main rotor blades and a bigger cabin with place for two crew members and seven passengers or two stretchers. In autumn 1965, the UH-1B was replaced in the production process by the UH-1C that was provided with an improved rotor and blades with a longer chord allowing an increase of speed and a better manoeuvrability. Some UH-1C helicopters – a total of 767 were produced – used in Vietnam were provided with missiles and a 7.62 mm MG for close air support. They succeeded and led to the production of the UH-1B with similar equipment that consisted mostly of a 7.62 mm MG or two cluster rockets with 24 missiles each. Other military versions of the Model 204 were the UH-1E for the US Marine Corps (in general similar to the UH-1B, but with winch, rotor brake and a special avionics equipment) the first machines of which were delivered to the Marine Air Group 26 on 21 February, 1964, and which got the new Bell rotor from October 1965 (192 units); the UH-1F for the USAAF, in general similar to the UH-1B, but with a 1,290-shp (962-kW) General Electric T58-GE-3 shaft turbine, an enlarged rotor diameter and big enough for a pilot and ten passengers (120 units); a similar TH-1F trainer version of the same model for the USAAF; an SAR version, the HH-1K SAR, for the US Navy, similar to the UH-1E but with a 1,400-shp (1,044-kW) T53-L-13 engine (26 units); UH-1L and UH-1L trainer and multi-purpose version of the UH-1E with T53-L-13 engines; and three UH-1M with night sensors to be tested by the US Army. The Model 204B was produced by Bell in a small number for civil customers and military export. In general, they were similar to the UH-1B and provided place for ten persons, an enlarged rotor of the UH-1F and a T53-L-11 engine. The Model 204B and the UH-1 were produced by Fuji in Japan under licence of Mitsubishi. In 1967, this company presented the Fuji-Bell 204B-2 with a stronger engine and a pull tail rotor. Augusta in Italy is as well producing under Bell’s licence. They built a great number of the Model 204B for civil and military purpose.

Bell Model 205

History of development
The undoubted success of the Bell UH-1A/B Iroquois testified that basically everything was right with the construction of this multi-purpose helicopter. At the beginning of 1960, Bell proposed an advanced version of the Model 204 with a longer fuselage and additional cabin room (by relocation of the fuel cells) for a pilot and 14 passengers or six stretchers, alternatively a freight of 1,814 kg. In July 1960, the US Army ordered seven of these new helicopters for tests, the aircraft with the US Army designation YUH-1D was identified by the manufacturer as Bell Model 205. The first helicopter flew on 16 August, 1961, and was produced after an order of the US Army in 670 units after several successful test flights. The first UH-1D was delivered on 9 August, 1963, to the 11th Air Assault Division in Fort Benning, Georgia. The engine of the early series models was a 1,100-shp (820-kW) Avco Lycoming T53-L-11 turbine shaft, the normal fuel capacity of 832 l could be enlarged to a maximum capacity of 1,986 l with two auxiliary tanks at the outside. The UH-1D was produced in large quantities (2,000 aircraft) for the US Army and for armed forces of other countries, and 352 units were produced by Dornier for the German Bundeswehr and the German Air Force. The production of the UH-1D was followed by the more or less identical UH-1H with a stronger 1,400-shp (1,044-kW) Avco Lycoming T53-L-13 shaft turbine. The delivery of the UH-1H to the US Army began in September 1967, and this model represented the final version for the production. The UH-1H was produced in large quantities (5,435 units plus export) for the US Army, nine were sold to the Air Force of New Zealand (RNZAF) and under the condition of the licence agreement of 1969, Taiwan produced 18 of these helicopters for use in the Taiwanese army. Other versions of the UH-1H were the CH-118 (originally UH-1H) that was produced by Bell for the Mobile Command of the Canadian Armed Force, the first ten machines of which were delivered on 6 March, 1968; and the HH-1H rescue helicopter, 30 units of which were ordered by the USAF on 4 November, 1970, completed in 1973. The UH-1D/H was frequently used for different missions in South East Asia and was considered by many persons as the exemplary "workhorse" among the helicopters in Vietnam. The type played an important role in special operations in Laos, Cambodia and several isolated areas in South Vietnam; the chronicle of the USAF reports that nearly every one of the injured of the last theatre of war could be evacuated by this type of helicopter. Since then, some few machines of the UH-1H – designated EH-1H – were chosen to take over electronic defence missions, and since 1981 aircraft with extended equipment were delivered. Within the framework of the SOTAS (Stand-Off Target Acquision System) programmes of the US Army, four UH-1H helicopters were converted for tests. They had the task to record the radar data of movements on the battle field and transfer them to the ground command, as well as making available current information about the particular tactical situation. However, the US Army wants to keep a great number of UH-1H helicopters in duty until the beginning of the 21st century, e.g. for command and control purposes, electronic warfare, medical evacuation, minelaying, supply and troop transport. To realize this plan the fleet of UH-1H helicopters already existing had to undergo an extensive programme of a complete modernisation including an extended avionics equipment that provides the helicopters with the necessary possible applications and a higher service life. Furthermore, Bell produces a civil version of the UH-1H with the designation Model 205-A. It has a 1,400-shp (1,044-kW) Avco Lycoming T53-13B shaft turbine throttled to 1,250 shp (932 kW). Normal fuel capacity is 814 l and is extendible to 1,495 l. Therefore, the inside can be rebuilt very quickly depending on the application as freight, ambulance service, executive, flying-crane or searching helicopter. It provides place for a pilot and up to 14 passengers. Augusta also produces the Model 205 under licence with the designation AB.205A-1, which is virtually identical to the Bell Model. The Italian Army and the armies of other countries belong to its customers. A Fuji-Bell Model 205A-1 is available in Japan. More than 10,000 aircraft were produced of the Model 205 including the UH-1D and H.

Bell Model 206 Jet Ranger



Bell Model 206B



Bell Model 206L4



Bell Model 206LT

History of development
In 1960, the US Army initiated a competition for a new aircraft that was designated as LOH (Light Observation Helicopter). Actually the persons responsible were searching for a multi-purpose model, because the LOH was to be used for evacuating injured , close air support, observation, photo reconnaissance and transport operations. So far, no model met all these requirements. The announcement intended the aircraft to have a payload of 180 kg and a cruise speed of approx. 190 km/h. Twelve American helicopter companies sent in their designs and the companies Bell, Hiller and Hughes were engaged to build five prototypes each for comparative tests. After these tests, the Hughes HO-6 (later called OH-6A) was chosen as US Army LOH for production. Even if the US Army was in doubt about the Bell HO-4, this was not shared by the manufacturing company. After having lost the competition, Bell built a new prototype with the designation Model 206A JetRanger. Its first flight was on 10 January, 1966, and it gained a FAA certification in 20 October in the same year. After that the Model was produced for civil customers by Augusta in Italy. The JetRanger was basically identical with the OH-4A (formerly HO-4) prototype, apart from the modifications of the fuselage for five inmates. Since 1966, the model has been produced in a large number, and in 1981, it was in production under the designation Model 206B JetRanger III, after being completely re-developed and improved.

US Army wanted 4,000 units of the OH-6A to be produced, but was disappointed by Hughes when the production costs rapidly increased whereas the production itself decreased. Eventually, the LOH competition was started (1967), and on 8 March, 1968, the Bell Model 206A was declared winner. Shortly after that production of this model started under the designation OH-58 Kiowa; until the end of the year 1973, 2,200 aircraft were delivered. The OH-58 differs from the civil JetRanger by its main rotor with a greater diameter, modified details of the interior equipment and military avionics equipment. The first delivery to the US Army was on 23 May, 1969, and within less than four months the Kiowa was in service in Vietnam. 74 of 2,200 aircraft originally ordered by the US Army were delivered under the designation COH-58A to the Canadian Armed Forces from December 1971; this designation was later changed into CH-136. In January 1973, an additional agreement over the production of 74 aircraft was signed with the US Army in order to replace the units delivered to Canada. In early 1971, Bell started the delivery of the improved Model 206B JetRanger II that was later replaced by the Model 206A in the production process. It had a stronger 400-shp (298-kW) Allison 250-C20 shaft turbine, for which the airframe had to be only slightly modified so that the construction kit for the conversion of the Model 206A into 206B could be produced. Australia bought this version under the designation Model 206B-1 Kiowa; 12 units were built by Bell, another 44 under a licence agreement. Commonwealth Aircraft Corporation was responsible for the assembly in Australia, the engine and the avionics equipment were produced in the U.S. In the context of the development agreement with the US Army, a machine of the OH-58A was equipped with a stronger 420-shp (313-kW) Allison T63-A-720 turbine and an improved glass cockpit; the aircraft received the designation OH-58C, and in the following two other conversions of a OH-58A were converted to this standard in order to allow Bell and the US Army to carry out more complex flight tests. Then, in March 1978, the modification of 275 aircraft of the type OH-58A into a more improved OH-58C configuration began. From 1978 to 1979, an OH-58C was tested with a visor attached to the mast, amongst others equipped with an automatic television camera and a laser rangefinder/target detection device. Other versions were twelve aircraft of the type OH-58B (delivered in 1976 to the Austrian Air Force, a model similar to the OH-58A) and 40 TH-57A SeaRangers for the US Navy. The latter are trainers with dual control and were ordered on 31 January, 1968, in order to make a trainer for beginners available to the Naval Air Training Command in Pensacola, Florida. The model is actually a civil Model 206A JetRanger with US Navy avionics. The production of the JetRanger II was discontinued in summer 1977, when the model was replaced by the Model 206B JetRanger III. In this process, a stronger version of the Allison shaft turbine, which makes a higher quality of performance possible, was introduced; the model is also available as installation kit for the Model JetRanger II. The power output and the reliability of the JetRanger series lead to the construction of the Model 206L LongRanger. It had the engine of the JetRanger III, and a 0.63 m longer fuselage for a total of five passengers. With a capacity of 2.35 m³, the LongRanger could apparently transport a remarkable cargo, and in order to simplify the loading of bulky cargo, a double door was installed at the port side. Further improvements included the re-developed main rotor and the patented Noda-Matic suspension system that reduced vibration in the cabin. Delivery of the LongRanger series models began in October 1975, and the model was replaced by the current Series Model 206B LongRanger II in the middle of the year 1978. This type differs from its predecessor model by the stronger Allison 250C-28B turbine with a maximum continuous power of 489 shp (365 kW), by a modified transmission and improvements in detail. In 1981, the company developed an improved LongRanger III with stronger engines and a new rotor. Furthermore, Bell initiated the development of a military multi-purpose version of the civil LongRanger that was designated Model 206L TexasRanger. The series models were equipped with a 650 shp (485 kW) Allison 250-C30P turbine shaft, and armed with anti-tank missiles, folding-fin aerial rockets or MG. The model is intended to be sold on the export market, reconnaissance and observation, command and control, medical evacuation, supply, as well as search and rescue flights belong to the range of application. At the end of 1983, delivery dates for the new type were still not fixed. Until today, the total sum of the production of all versions of the Model 206 series amounts to more than 7,000 units. Agusta in Italy also produced JetRangers and LongRangers, which are generally similar to their American counterparts, under the licence of Bell.

Bell Model 207 Sioux Scout

History of development
Because of the participation of the USA in the Korean War, the production of helicopters in the American aviation industry increased strongly. At the beginning of the Vietnam conflict when an intervention of the United States was foreseeable, Bell decided to take the initiative of developing a lightweight attack helicopter for close air support. The result – the Bell Model 207 Sioux Scout – was based on the OH-13S Sioux of the US Army being a military version of the proven Bell Model 47, and it was presented for the first time in September 1963. The Sioux Scout was equipped with the drive system – the 260 shp (194 kW) TVO-435 engine – and the skid landing gear of the OH-13; its dimensions were also similar. Apart from that it differed considerably from its predecessor in its completely new designed, closed and streamlined fuselage that provided place for two inmates on tandem seats. Furthermore, it had smaller tail fins and horizontal stabilizers; but the tail rotor and the fins at the bottom of the fuselage were identical to those of the OH-13S. Stub-wings with a small wing span were attached to the top of the fuselage directly behind the main rotor. They did not only serve to stabilise the main rotor during the flight, or to improve manoeuvrability, but were also used as attachment for various weapons. Two 7.62 mm M60 MG were attached under the nose; from there, they were operated by a shooter sitting underneath the pilots so that both had an excellent field of view. The Model 207 only remained a prototype. It is interesting that the ideas developed for this type and those for the multi-purpose model UH-1B (Modell 204) led to the production of the successful Bell Model 209 HueyCobra series.

Bell Model 209 Huey Cobra and Sea Cobra

History of development
In March 1965, Bell initiated the further development financed by the company of the already tested Model 204 (UH-1B/-1C) in order to produce an armed helicopter for close air support/ground combat. The model was intended to intermediately serve the US Army as an AAFSS (Advanced Aerial Fire Support System) helicopter and had a new, narrow, low-profile, tandem-seat fuselage and the rotor, transmission system and engine of the UH-1C. The prototype’s first flight was on 7 September, 1965, and the new Bell Model 209 was tested by the US Army from December of the same year. In April 1966, the order of two pre-series models and 110 series models followed. The AH-1G HueyCobra was delivered to the US Army in June 1967 and was operational in Vietnam two months later. The US Marine Corps was interested in the model as well and received 38 aircraft of the type AH-1G from the US Army production (1969). The delivery of 49 units of the AH-1U SeaCobra version ordered by the US Marine Corps in May 1968 started later. Several machines – similar to the US Army‘s AH-1G – were delivered to the Spanish Navy (eight aircraft under the designation Z. 14) and to Israel (six). The HueyCobra had short stub-wings that supported both the rotor in flight and the carry of weapons, in the case of the AG-IG missiles with folding fins or Minigun pods. Furthermore, this version carried beneath the nose an M-28 turret that could house two Miniguns or two 40-mm grenade launchers. Armour protection was provided for the crew in the form of Noroc side panels and seats, with other vital areas of the helicopter protected by panels of the same material.

Versions:
JAH-1G HueyCobra: a helicopter for armament testing that was tested with a Hellfire missile and multi-barrel cannon.
TH-1G HueyCobra: designation of a dual-control trainer conversion from the AH-1G.
AH-1U SeaCobra: original US Marine Corps version with T400-CP-400 twin engine; the shaft turbines were throttled to 1,100 shp (820 kW) for continuous operation, but with a take-off or emergency power of 1,250 shp (932 kW); until spring 1975, a total of 69 were delivered to USMC as well as 202 similar helicopters to the Imperial Iranian Air Force from 1974.
AH-1Q HueyCobra: designation of 93 aircraft of the type AH-1G converted to the launch of TOW anti-tank missiles.
AH-1R HueyCobra: version similar to the AH-1G, but with a stronger T53-L-703 shaft turbine.
AH-1S HueyCobra: collective designation for US Army AH-1 helicopters, which were converted to fulfil the TOW configuration and included other improvements; furthermore, designation of new series models with the same or higher standard; current designations include the Modified AH-1S (197 aircraft of the type AH-1G and 93 of the type AH-1Q with improved gearbox, power transmission, rotor, T53-L-703 engine and TOW); 100 similar aircraft of the type Production AH-1S, new series models with advanced avionics, instrumentation and systems; 98 Up-Gun AH-1S aircraft, generally similar to the Production AH-1S, but with improved turret and weapon system;
Modernized AH-1S with 396 series models built (and 54 by Fuji in Japan); the latter contain improvements of the other AH-1S aircraft as well as advanced nav/com equipment, avionics and protection systems.
AH-1T Improved SeaCobra: generally improved version of the AH-1J with a stronger T400-WV-402 engine, the drive system of the Bell Model 214 and a 1.09 m longer fuselage. A total of 57 were built, 22 were built each year between 1984 and 1986.
Model 249: internal designation of a Modernized AH-1S, it was equipped and tested with an advanced four-blade rotor like that of the Model 412.

Bell Model 212 Twin Two-Twelve

History of development
On 1 May, 1968, Bell Helicopter Company announced that following negotiations with the Canadian government and Pratt & Whitney Aircraft of Canada, it had been agreed to proceed with the development of a new helicopter based upon the air frame of the Bell Model 205/ UH-1H Iroquois. The first of ten units for the Canadian Armed Forces (CAF) were delivered on 6 March, 1968, under the designation CUH-1H. The engine of the UH/CUH-1H was a 1,400-shp (1,044-kW) Avco Lycoming T53-L-13 shaft turbine. The CAF considered the incorporation of twin engines to provide a number of benefits, and this led to the development of the first military Bell Model 212 with its Pratt & Whitney Aircraft of Canada (PWAC) PT6T engines. The programme was a joint venture, financed by Bell, the Canadian Government and PWAC.
The revolutionary feature of this new helicopter was the PT6T Twin-Pac designed and developed by PWAC, which consisted of two shaft turbines mounted side-by-side and driving a single output shaft via a common gear box. The performance of the initial production version had a dry weight of 4.66 kW/kg compared with 4.19 kW/kg of the already developed Lycoming T53 turbine. Another advantage was: as installed in the Model 212, the PT6T-3 is limited to an output of 1,290 shp (962 kW) for takeoff. In case of a failure of one turbine, torquemeters in the combining gearbox signal the remaining turbine to develop full power ranging from 1,025 shp (764 kW) to 800 shp (596 kW), for emergency and continuous operation, respectively.

In 1970, initial deliveries of military Model 212s were made to the USAF under the designation UH-1N; from 1971, some units of this type were sold to the US Navy and the Marine Corps. The arrival of the first CUH-1N (later renamed to CH-125) – for the CAF – was on 3 May, 1971. Furthermore, some aircraft of this type were sold to Argentina (eight) and Bangladesh (six). The airframe is in general similar to that of the UH-1H Iroquois, with an all-metal fuselage structure, landing skids, a semi-rigid two-blade main rotor and a two-blade all-metal tail rotor.

A civil version for 14 passengers with the name Twin TwoTwelve was developed at the same time; it differed from the military version in its cabin furnishing and avionics equipment. The Twin Two-Twelve gained its FAA Transport Type Category A certification on 30 June, 1971. It is also certified for IFR operations requiring a new avionics package, a new instrument panel and stabilisation controls for such use. In June 1977, it became the first helicopter to be certificated by the FAA for single-pilot IFR operation with fixed floats.

The enhanced safety offered by the Twin-Pac engine has resulted in many sales to operators who provide support to offshore gas/oil prospecting and production companies, as well as to air taxi organisations. Eight Model 212s were delivered to the Civil Air Authority of China during 1979, and were the first helicopters supplied to the People's Republic of China by a US manufacturer.

The Model 212 is also built under licence by Agusta in Italy as Agusta-Bell AB.212, with initial deliveries made during 1971. This model is in general similar to the American-built aircraft, but Agusta has developed an ASW version designated AB.212ASW. Structural strengthening took place, plus the provision of deck restraint gear, and the PWAC PT6T-6 Twin-Pac turbo shaft rated at 1,875 shp (1,398 kW) for take-off. In 1976, the first aircraft were sold to the Italian Marine.

Bell Model 214B Big Lifter

History of development
As described with the Bell Model 214ST, the company developed a multi-purpose helicopter of the type 214A, 293 machines of which were sold to the Iranian Air Force where the model got the name Isfahan. Later, 39 similar aircraft with special equipment for SAR applications were sold to Iran under the designation Bell Model 214C. After extensive tests of the military helicopters, Bell was convinced that a civil version would find a market, because this model would have a better performance as all other helicopters in the medium-range category. Therefore, the company announced the plan for the development of the Bell Model 214B Big Lifter, in spring 1974. In general, this model was similar to the military helicopter and had the same airframe, rotor and transmission systems as well as the engine. However, the Big Lifter had emergency exits in the windows, an engine fire system and avionics for civil instead of military applications. Two versions are available, and the standard Model 214B is applicable: as transport helicopter for up to 14 passengers with two crew members, as carrier with outside tanks for loads of max. 3,629 kg, also qualified for agricultural tasks (with a comparable load of chemicals) or for fire fighting with 2,725 l extinguishing agent in the cabin and in the tanks under the fuselage. The alternative Model 214B-1 is authorized for different standards that permit a higher maximum weight with a greater interior load. The Model 215B has been available for civil operators since it was officially certificated on 27 January, 1976.

Bell Model 222

History of development
In April 1974, Bell announced its intention of developing the Model 222, a new civil helicopter, which would be the first light twin-engined helicopter to be built in the USA. This was no hasty decision: at the beginning of the year, a design proposal had been exhibited at the annual convention of the Helicopter Association of America, giving potential customers an opportunity of making constructive suggestions for product improvement. The resulting interest was sufficient to warrant a decision to proceed with the construction of five prototypes, and the first of these flew on 13 August, 1976. Allocated the company designation Bell Model 222, these prototypes were used to complete the development and certification programme as quickly as possible. The FAA certification in VFR configuration was granted on 20 December, 1979. The Model 222 benefits from new-technology features developed at an earlier date for both, civil and military helicopters, and includes the transmission system described for the Model 214ST, and glass-fibre/stainless-steel main-rotor blades. The airframe structure is primarily of light alloy, the fuselage having a short-span cantilever sponson mounted on each side. These provide additional lift in forward flight and thus supplement the main rotor; in addition, they provide a housing for the main units of the tricycle-type landing gear when retracted. The design includes a bigger tail unit than most helicopters have, with both upper and lower sweptback fins and mounted further forward on the aft fuselage, a tail plane with endplate fins. It provides place for a maximum of ten inmates, one or two crew members and nine or eight passengers, respectively. Optionally, the aircraft are available in three versions, there is the Model 222 with a standard seating configuration for a pilot and seven passengers; the Model 222 Executive, fully equipped for IFR flight with a crew of one or two and luxury accommodation for six or five passengers, respectively; and the Model 222 Offshore equipped for IFR operation with a crew of two, and with an emergency flotation system and auxiliary fuel tanks as standard. The twin turbine engine selected for the Model 222 consists of two Avco-Lycoming LTS 101-650C-2 shaft turbines with a dry weight of only 110 kg each providing a maximum power of 4.58 kW/kg at maximum power. It is interesting that the weight of the LTS 101 shaft turbine is lower than that of the APUs (auxiliary power units) which provide electrical drive power and hydraulic pressure in case of emergency for aircraft such as the British Aerospace Trident. Initial deliveries of VFR-certificated Model 222s were made to Petroleum Helicopters and Schiavone Construction in January 1980. The Model 222 delivered to Omniflight Helicopters on 25 January, 1981, was the 25,000th helicopter built by Bell.

Bell Model 301 (XV-15)

History of development
In May 1973, the NASA and the US Army chose Bell Helicopters to build two tilt-rotor research aircraft; this plan followed the former project of a Bell Model 200 (US Army designation XV-3) that was tackled in the framework of the agreement with the US Army and USAF, in 1951. The basic concept includes rotors with a smaller diameter or propellers with a greater diameter providing a VTOL performance like helicopters as well as a drive of as in conventional flight of an aircraft that is constructed and used like an airplane with fixed airfoils. For this purpose, the XV-3 had cantilever monoplane airfoils with ailerons, a fuselage with landing skids and a conventional tail. Combined rotor/propellers were fixed at the wing tips and driven over axes and gearboxes by a 450 shp (336 kW) Pratt & Whitney R-985 engine in the fuselage. During take-off and landing, the rotors were in a vertical position; during flight in an appropriate height, they were slowly tilted forward (driven by an electro motor) until they could serve as a propeller, and the XV-3 flew as an airplane with fixed airfoils. For a vertical landing, the propellers needed to be transformed reversely into rotors. Despite numerous problems in the beginning (the XV-3 programme was discontinued in 1966), the concept had proven to be practicable; with 250 VTOL operations more than 125 flight hours were covered. The Bell Model 301 had been in production since July 1973, and is a far more practicable aircraft that benefits from the experience made with the XV-3. Designated XV-15 by the US Army, it is a cantilever high-wing aircraft with a conventional fuselage for pilot and co-pilot sitting side-by-side in the flight deck.

The tail unit contains a higher tail/elevator with endplate fins and rudders, and the retractable nose landing gear has twin wheels on all single units. The powerplant consists of two Avco Lycoming shaft turbines mounted on tilting wing-tip nacelles that drive each a three-blade rotor each. VTOL and change to horizontal position and back was gained from the XV-3, but was improved by wing flaps/ailerons, trailing edge flaps and a stability and control system. On 3 May, 1977, the first of the two XV-15 research aircraft had its first free hovering flight; the first change to horizontal flight position took place on 24 July, 1979. The following year, both XV-15 achieved approx. 100 changes from vertical to horizontal flight and set an inofficial record for rotor aircraft with 557 km/h. This demonstrates the potential of this type of aircraft. After a demonstration at the Paris Air Show in 1981, both prototypes of the Model 301 were incorporated in a current NASA and US Army test programme. In the course of this programme, the capacity of this model for civil and military transport is examined, and the supply of gas and oil platforms is planned to be its first field of application. In 1982, the XV-15 had its first operation from a helicopter carrier. In June 1983, Bell and Boeing Vertol joined together for further development of a vertical take-off and landing aircraft with tilt rotors; the project has the designation JVX (leading to the V-22 "Osprey") and is based on the XV-15. The research programme is limited to two years.

Bell Model 409 (YAH-63)

History of development
Under the internal designation Bell Model 409, Bell presented its proposal for the AAH (Advanced Attack Helicopter) programme of the US Army in spring 1973. For the prototype construction it was chosen with the designation YAH-63, built in competition with the Hughes Model 77/YAH-64 and in two prototype units that had to undergo flight, ground and static tests. The first flight of the first prototype (22246) took place on 1 October 1, 1975, the second followed about two months later. However, the winner of the US Army competition in 1976 was the Hughes Model; the Bell YAH-63 would have been equipped with a 30-mm triple-barrel General Electric with 600-1800 rounds per minute and with up to 16 anti-tank missiles carried under stub-wings as well.

Bell Model 412

History of development
Under the designation Bell Model 412, the company developed a version of the Model 212 that had an advanced four-blade main rotor. Each blade was made of glass fibre and in Nomex honeycomb construction with a protective strip of titan at the leading edge and a lightning protection in the blade’s structure as well as mounting possibilities for de-icing and anti-icing units. The rotor hub was completely new developed, of steel and light metal alloys, with bearings and dampers of elastomer plastics. For the development programme, two Model 212s were built that both gained their airworthiness certification for instrument and visual flights on 13 February, 1980. The first aircraft that had a visual airworthiness certification was delivered on 18 January, 1981, and two of these aircraft were delivered to the Venezuelan Air Force in the course of this year. Augusta that produced Bell helicopters under licence in Italy planned the production of this version as Agusta-Bell AB.412, with first delivery in 1982. Augusta also developed a multi-purpose military version

Bell / Boeing Model 609