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MBB / Airbus Helicopters

v1.0.4 / 01 jan 16 / greg goebel

* In the late 1960s, the German Messerschmitt-Boelkow-Blohm firm (MBB, later part of Airbus Helicopter) introduced a utility helicopter, the "Bo 105", that proved very successful on the global helicopter market. It was followed by an improved successor, the Airbus "EC 135", which is now in widespread service. MBB also collaborated with Kawasaki of Japan to develop a scaled-up derivative of the Bo 105, the "BK 117", which proved popular as well and, through technology cross-breeding with the EC 135, led to the Airbus "EC 145".

This document provides a history and description of the Bo 105, EC 135, BK 117, and EC 145 -- and also discusses the Indian HAL Dhruv helicopter, designed with MBB assistance and more or less a scaled-up BK 117.

Airbus EC 145


[1] BO 105 ORIGINS
[2] BO 105 CIVIL VARIANTS
[3] BO 105 MILITARY VARIANTS
[4] EC 135
[5] BK 117 / EC 145 (UH-72A LAKOTA)
[6] FOOTNOTE: HAL DHRUV HELICOPTER
[7] COMMENTS, SOURCES, & REVISION HISTORY

[1] BO 105 ORIGINS

* In 1948, Ludwig Boelkow opened a civil engineering office in Stuttgart, Germany; in 1956, Boelkow moved into aviation work with the formation of the company Boelkow-Entwicklungen KG, with the company head office moving to Ottobrunn, near Munich, in 1958.

In 1957, Boelkow-Entwicklungen worked with a team of helicopter experts -- known as the "German Helicopter Study Group (DSH in its German acronym)" and headed by Dr. D.W. Just -- on the development of a helicopter trainer. A prototype was built as the "P102" and was praised by students running it through its paces, resulting in the production "Bo 102", introduced in 1959. It was one of the more eccentric rotorcraft ever manufactured, a single-seat nonflying helicopter trainer that similar to a carnival ride. It had a 30 kW (40 HP) piston engine and a rotor system with Hiller-type control paddles with a half-blade main rotor, the other half being counterweighted; it rode on a pivoting arm mounted on a four-legged stand. It looked like it was fun to play with, though not necessarily something "real men" would have been happy to climb into; it did certainly prove useful, and the company did a fair business with the Bo 102, selling it to several European nations.

Of course, Boelkow-Entwicklungen wanted to build a helicopter that actually flew as well, leading to the first flight of the "Bo 103" on 14 September 1961. The Bo 103, designed by Hans Derschmidt, was effectively an airworthy version of the Bo 102, with landing skids instead of a stand and twice the engine power; it still had the half-blade / counterweighted main rotor and surprisingly flew perfectly well. It was strictly a demonstrator, never got out of the prototype phase, and it seems only one was built.

In the same year, 1961, Boelkow-Entwicklungen began work on two new helicopters, the "Bo 46" and the "Bo 105". The Bo 46 was a demonstrator for an advanced five-blade "rigid rotor" scheme invented by Derschmidt. Three were built for the German Ministry of Defense, with the first flying in 1964, but the design proved overly complicated and was not put into production. The Bo 105 proved more the way of the future, though it wasn't obvious that the company had a winner at the outset.

* The Bo 105 was conceived as a light helicopter with five or six seats, powered by twin turboshaft engines, featuring an innovative unarticulated rigid rotor system invented by Professor E. Weiland, with the rotor scheme evaluated in a collaboration with Sud-Aviation of France on an Alouette II helicopter.

The initial Bo 105 prototype -- designated the "V1", where "V" stood for "Versuchs (Prototype)" -- was powered by twin Allison 250-C18 turboshafts. It did not feature the new rotor system, instead using a conventional rotor system taken from a British Westland Scout helicopter. The V1 machine came to a bad end even before taking to the air, being wrecked during ground testing in 1965. The V2, the second prototype, featured the rigid rotor along with the Allison engines and performed its first flight on 16 February 1967, with Wilfried von Engelhard at the controls. By this time the company was known as "Boelkow GMBH", thanks to a reorganization following an infusion of cash from US aerospace giant Boeing.

A third prototype, the V3, was built, featuring MAN-Turbo 6022 engines, with initial flight on 20 December 1967. Two preproduction machines, the V4 and V5, were flown in 1969, with initial deliveries of the first production machines, designated "Bo 105C", late in the year. By that time the company had evolved again, having merged with Messerschmitt in 1968 to become "Messerschmitt-Boelkow GMBH" -- and then merged again with Hamburger Flugzeugbau GMBH, an offshoot of the Blohm und Voss firm, to become "Messerschmitt-Boelkow-Blohm (MBB)" in 1969.

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[2] BO 105 CIVIL VARIANTS

* The initial Bo 105C variant provides a baseline for the series. It was utilitarian in appearance, with an egg-shaped body, twin landing skids, twin engines driving the four-blade rotor on top, and a tailboom with a twin-blade rotor and two rectangular tailfins mounted high on the rear. Few would have thought it particularly sexy in appearance, but it was businesslike; its successors would have much the same unadorned style.

Production machines were powered by twin Allison 250-C20 turboshafts providing 300 kW (400 SHP) each; the Allison 250-C18 and MAN-Turbo 6022 were offered as options early on, but nobody bought them. The folding four-blade main rotor was made of fiberglass and had a titanium hub; the tail rotor was also made of fiberglass. A rotor brake was standard. The rotor system provided considerable agility, including the ability to perform loops.

Accommodations included a pilot and passenger seat up front -- dual controls could be installed for training -- and a seat for three across in the back. In an alternate configuration, two stretchers could be carried, along with two medical attendants. There was a hinged door forward and a sliding door towards the back on each side of the fuselage; there were clamshell cargo doors in the rear. The landing skids could be fitted with four inflatable emergency floatation devices, or pontoons could be fitted in place of the skids. Other optional kit included a rescue winch mounted above the door and a cargo sling hook.

A variant designated the "Bo 105D" was produced for sale in Britain, being generally identical to the Bo 105C except for some minor differences as per UK Civil Aviation Authority (CAA) requirements. From 1975, production moved to the "Bo 105CB", which was generally the same as the Bo 105C except for uprated Allison 250-C20B turboshafts, along with an improved rotor system to handle the higher power ratings.


   MBB BO 105CB:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   main rotor diameter     9.84 meters         32 feet 4 inches
   tail rotor diameter     1.9 meters          6 feet 3 inches
   fuselage length         8.56 meters         28 feet 1 inch
   footprint length        11.86 meters        38 feet 11 inches
   height (rotor head)     3 meters            9 feet 10 inches

   empty weight            1,276 kilograms     2,813 pounds
   max loaded weight       2,500 kilograms     5,510 pounds

   maximum cruise speed    240 KPH             150 MPH / 130 KT
   service ceiling         5,180 meters        17,000 feet
   range                   575 kilometers      360 MI / 310 NMI
   _____________________   _________________   _______________________

The Bo 105CB led to a slightly "stretched" version, the "Bo 105CBS", with the fuselage extended by 25 centimeters (10 inches) to a length of 8.81 meters (28 feet 11 inches), permitting up to six passengers. It could be distinguished from "short" variants by a small additional side window at the rear of each side of the passenger compartment. A UK-spec version was sold, designated the "Bo 105DBS"; the Bo 105CBS was also marketed in the USA as the "Twin Jet II". The Bo 105CBS was sold in refined production blocks up to the "Bo 105CBS-4" and its stablemate, the "Super 5", which incorporated refinements developed for military variants of the Bo 105.

MBB Bo 105CBS

In the early 1980s, a variant of the stretched Bo 105CBS designated the "Bo 105LS" was introduced that featured still more powerful Allison 250-C28C turboshafts with 375 kW (500 SHP) takeoff power each and an uprated rotor transmission to handle the greater power. It was only built by MBB Canada. As with the Bo 105CBS series, the Bo 105LS was sold in production blocks, up to the "Bo 105LSA-3", which was sold along with a "flying crane" subvariant, the "Bo 105LSA-3 Super Lifter".

IPTN / Dirgantara of Indonesia assembled both the Bo 105CB and Bo 105CBS for local sale, with locally-assembled machines designated the "NBO-105CB" and "NBO-105CBS" respectively. At least 121 machines were built there. Some sources mention a production deal for the Bo 105 in the Philippines, but if it happened details are hard to find.

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[3] BO 105 MILITARY VARIANTS

* The Bo 105 proved popular as a military helicopter, generally in the utility role, but with a good number built in combat configurations. The biggest military user was the West German Army, which bought both scout and anti-armor variants:

The evolution of the German Army Bo 105s is a somewhat confusing subject. Upgrades were implemented for the PAH-1 early on, with an AN/APR-39 radar warning receiver (RWR) fitted from the mid-1980s. That led to a more thorough upgrade in the early 1990s, featuring a new digital sighting system for the HOT missiles; a new lightweight launch rack arrangement for the HOTs; a modified engine installation; and an updated main rotor, with rounded-off tips. All surviving PAH-1s were upgraded and redesignated "PAH-1A1". It was simple to tell the two variants apart: the HOT launch tubes of the PAH-1 were arranged in a row straight out to the sides of the helicopter, while the launch tubes of the PAH-1A1 were mounted on a rack angling down from each side.

MBB Bo 105 PAH-1A1

The VBH fleet was retired since the machines were heavily utilized and had reached the end of airframe life. The PAH-1A1 has been replaced by the Airbus Tiger gunship helicopter; the PAH-1A1s had not been so heavily utilized, so some of them were stripped of armament and refitted for the VBH role.

To confuse the topic further, several combat variants of the Bo 105 were proposed for German service, but not actually obtained:

* The Spanish Army acquired 60 military Bo 105CBs in 1979, with 57 assembled by CASA in Spain from knockdown kits provided by MBB. They included:

The HA.15 anti-tank machines were never upgraded to a spec comparable to the PAH-1A1. They are being replaced by the Airbus Tiger. The armed HR.15 scout machines were retired early in the 21st century, having gone beyond their safe airframe life. The unarmed HR.15 scout machines are being phased out, with some passed on to civil security forces; the EC 135, discussed below, is being obtained as a replacement. Incidentally, CASA also assembled a batch of Bo 105s for Iraq.

Swedish HKP-9A with TOW launchers

* In 1987, the Swedish Army ordered 20 Bo 105CB machines in an anti-armor configuration, carrying four TOW antitank missiles on pylons, with a SAAB HeliTOW night-capable sight on the cockpit above the pilot position. They were also fitted with cable cutter blades. The Swedes designated the machine the "HKP 9A", where "HKP" stood for "helicopter". The Swedish Air Force also obtained four "stretched" Bo 105CBS machines for SAR operations, designating them "HKP 9B".

* The Mexican Navy obtained 12 Bo 105CBs in a navalized configuration, with Sperry Primus 500 radar in the nose, doppler radar under the tail boom, rescue hoist, folding rotor blades, floatation kit, and facilities for lashing the machines to the deck of a naval vessel. It does not appear that they were armed; they were used in the utility / SAR role. Colombia acquired a number of Bo 105s to a similar spec.

Mexican Navy Bo 105CB

While the Bo 105 series was popular with world military arms, it is unclear just how many services other than those listed above obtained variants with combat optimizations instead of in the "plain" utility configuration. Photos exist of a Bo 105CBS with stores pylons, cannon and rocket pod warloads, and a spherical roof-mounted sight; or with a roof-mounted sight along the lines of that of the Swedish HKP 9A, and carrying four Hellfire anti-armor missiles on pylons. These machines appear to have been demonstrators, however, and there's little evidence that anybody bought them.

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[4] EC 135

* Production of the Bo 105 series ended in 2001, after delivery of over 1,400 helicopters to over 40 countries. The Bo 105 was obsoleted because a better replacement was available. In the late 1980s, MBB had begun work on a follow-on to the Bo 105, essentially performing a "clean sheet" reconsideration of the design. The initial flight of a technology demonstrator, designated the "Bo 108", was on 15 October 1988. It had the same general arrangement as the Bo 105, but featured better streamlining; like most Bo 105s, it was powered by two Rolls-Allison 250-C20R turboshafts. A second prototype, with twin Turbomeca Arrius turboshafts, performed its initial flight on 5 June 1991.

In late 1992, work began on a significant redesign of the Bo 108, one objective being to increase passenger capacity. By this time MBB had, though a series of acquisitions and mergers, become part of the Eurocopter company, effectively joining MBB with the helicopter division of Aerospatiale of France; Eurocopter would later become a segment of the giant European Aerospace & Defense Systems (EADS) conglomerate, which became in turn the Airbus Group at the beginning of 2014, Eurocopter becoming Airbus Helicopter. The Airbus name is used here for simplicity.

Probably not coincidentally, the redesigned Bo 108 featured the enclosed "fenestron" tail fan rotor, a trademark of many Aerospatiale helicopters; the merger between the German and French helicopter companies would lead to an interesting as well as somewhat confusing technological cross-breeding between their product lines. The fenestron configuration was quieter, more efficient, and the rotor being screened off, also improved safety to a degree, the tail rotor being a traditional lethal hazard to the careless in helicopter operations.

Three preproduction prototypes of the "EC 135", as it was known, were built. The first performed its initial flight on 15 February 1994; it was powered by twin Turbomeca Arrius 1B turboshafts. The second prototype, powered by twin Pratt & Whitney Canada (PWC) PW206B turboshafts, performed its initial flight on 16 April 1994; and was followed by the third prototype on 28 November 1994, this machine reverting to the Arrius 2B powerplant. Certifications were awarded from 1996, with the type going into production in that year.

* The EC 135 followed the traditional MBB helicopter layout, aside from the French-inspired 10-blade fenestron tail rotor. It had the pod and boom configuration; a four-blade composite main rotor, though made of graphite epoxy instead of fiberglass; twin (swept) tailfins; clamshell rear doors; and skid landing gear. However, it featured an airframe made mostly of composite materials, as well as a "glass cockpit" with twin flat panel displays. The improved aerodynamics of the EC 135 made it substantially less "draggy" than the Bo 105, and overall the EC 135 was advertised as 25% cheaper to operate.

Airbus EC 135P1 with nose radar

There were seven seats in the normal transport version, including seats for one or two pilots, with forward-hinged doors on each side for the pilots and sliding doors on each side for the passengers. Typical air ambulance configuration was a pilot, two stretchers, and two medical attendants. Optional kit included a cargo sling hook, rescue winch, inflatable floatation gear, loudspeakers, searchlight, day and night video imagers, and a weather radar in a pimple nose radome.


   EUROCOPTER EC 135:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   main rotor diameter     10.2 meters         33 feet 6 inches
   fenestron diameter      1.0 meter           3 feet 3 inches
   fuselage length         10.2 meters         33 feet 6 inches
   footprint length        12.16 meters        39 feet 11 inches
   height (tailfin)        3.51 meters         11 feet 6 inches
   height (rotor head)     3.35 meters         11 feet

   empty weight            1,495 kilograms     3,284 pounds
   max loaded weight       2,900 kilograms     6,393 pounds

   maximum cruise speed    255 KPH             160 MPH / 135 KT
   service ceiling         3,050 meters        10,000 feet
   range                   630 kilometers      390 MI / 340 NMI
   _____________________   _________________   _______________________

Production has run through a series of variants:

Special EC 135 fits for police, VIP transport, and other applications have been offered. The type is used for training, sometimes being given the military service designation of "TH-135". The EC 135 proved popular with civil and government users, with license assembly deals in Romania, Spain, and Switzerland.

One EC 135 was configured for trials as the "Active Control Technology / Flying Helicopter Simulator (EC 135 ACT/FHS)", performing its first flight in 1999. One of the EC 135 prototypes was modified as an "eco-demonstrator" named the "Bluecopter" to test advanced technologies for reducing fuel consumption, with the machine performing initial flights in the new configuration from 2015. It featured a new five-blade rotor and tailfan, plus other tweaks. Early trials demonstrated fuel burn improvements of 12% to 15%; further work was expected to improve substantially on that figure by modifying the engine control system to permit cruise flight on a single engine.

* A combat variant, the "EC 635", was offered from early on. It featured militarizations such as stores pylons, sighting systems, and cable cutters. An initial contract for the EC 635 with the Portuguese Army fell through; the Jordanian Army became the launch customer, ordering a total of 13, with deliveries from the first batch beginning in 2003. Switzerland was the second customer, obtaining a total of 18, with Iraq ordering 24 in 2009.

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[5] BK 117 / EC 145 (UH-72A LAKOTA)

* In the mid-1970s, MBB was working on what amounted to a scaled-up and improved derivative of the Bo 105, the "Bo 107". In the meantime, Kawasaki of Japan was working on a helicopter with similar specifications, the "KH-7". The two companies got in touch and decided to collaborate, resulting in an agreement in early 1977 to develop a common "MBB-Kawasaki BK 117".

Four prototypes were built, with the initial flight of a German prototype on 13 June 1979 and of a Japanese prototype on 10 August 1979. A preproduction machine, made in Germany, performed its initial flight on 6 March 1981, with the first production machine, made in Japan, performing its initial flight on 24 December 1981. International certifications followed in late 1982 and early 1983, with deliveries of the initial "BK 117A-1" variant from both partners quickly following.

A "BK 117A-3" model -- there was no production BK 117A-2 -- was introduced in 1985, featuring maximum takeoff weight increased from 2,850 kilograms (6,285 pounds) to 3,200 kilograms (7,055 pounds), plus an updated tail rotor with greater diameter and twisted blades. Production then moved to the "BK 117A-4" in 1987, with minor improvements including a more robust power transmission, updated tail rotor head, and more fuel capacity.

* A general description of the BK 117 almost exactly matches that of the Bo 105. It had a conventional main-tail rotor configuration, with the main rotor system effectively borrowed from the Bo 105 but with larger blades (made of carbon composite instead of fiberglass), and a two-blade carbon composite tail rotor. The BK 117 had the same "pod and boom" configuration, with a somewhat more streamlined fuselage featuring skid landing gear and rear clamshell doors along with the side doors, plus twin swept fins on the tailboom. It was powered by twin engines, the powerplants being Avco Lycoming LTS 101-750B-1 turboshafts, each rated at 440 kW (590 SHP) for takeoff.

BK 117 of German Polezei

Like the Bo 105, few would have accused the BK 117 of being particularly sexy, though it had a certain clean utilitarian appearance. It was mostly made of aircraft aluminum, though it featured a few composite and titanium assemblies. Standard load was a pilot and seven passengers, with fewer passengers in executive versions. There was a forward-hinged door on either side of the cockpit and a rearward-sliding door on each side of the passenger compartment; the doors could be jettisoned in an emergency.


   MBB-KAWASAKI BK 117A-4
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   main rotor diameter     11 meters           36 feet 1 inch
   tail rotor diameter     1.96 meters         6 feet 5 inches
   fuselage length         9.91 meters         32 feet 6 inches
   footprint length        13 meters           42 feet 8 inches
   height (tail rotor)     3.85 meters         12 feet 8 inches
   height (rotor head)     3.36 meters         11 feet

   empty weight            1,705 kilograms     3,760 pounds
   max loaded weight       3,200 kilograms     7,055 pounds

   maximum cruise speed    255 KPH             160 MPH / 135 KT
   service ceiling         4,575 meters        15,000 feet
   range                   585 kilometers      365 MI / 315 NMI
   _____________________   _________________   _______________________

Of course the BK 117 could be configured for air ambulance, SAR, cargo transport, and other duties. Optional kit included dual controls, a rescue winch, a belly cargo hook, weather radar in a nose pimple radome, searchlight, loudspeaker, inflatable floatation kit, skis, folding main rotor blades, and sand engine filters.

In 1985, MBB displayed a combat version of the BK 117A-3 designated the "BK 117A-3M" at the Paris Air Show. Kawasaki had nothing in particular to do with it: the Japanese constitution traditionally raised barriers to weapons export. The BK 117A-3M featured:

A wide range of alternate weapons fits was offered. There was polite interest, but nobody bought it.

In the late 1980s, MBB flew a BK 117 with a composite fuselage under a German government experimental program. In the early 1990s, Kawasaki also flew an advanced technology demonstrator, the "BK 117-P5", with a "fly by wire" flight control system. There were discussions with IPTN to assemble the BK 117 as the "NBK-117", but only three Indonesian machines were produced.

BK 177B-2

In 1987, production moved to the "BK 117B-1", with improved Avco Lycoming LTS 101-750B-1 engines and increased takeoff weights compared to the A-series. The follow-on "BK 117B-2" raised takeoff weight even more. The "BK 117C-1" series was introduced in 1992, featuring a modernized cockpit and twin Turbomeca Arriel IE turboshafts with 528 kW (708 SHP) each, replacing the Avco Lycoming powerplants.

* In 1997, work began on rethinking the BK 117 design, incorporating refinements derived from the EC 135. Initial flight of the prototype was on 12 June 1999 in Germany, with a second prototype performing its initial flight in Japan on 15 March 2000; two more prototypes later joined the development program. Certifications of the "EC 145", as the type was designated by Airbus, or the "BK 117C-2", as it was originally known and was designated in Japan, was in 2002, with production shipments beginning in that year.

The EC 145 retained the general configuration of early members of the BK 117 family, except for a revised fuselage that provided substantially more internal volume, partly obtained by removing the cabin center post and door supports. It also featured a new main rotor derived from the EC 135, with composite blades and a titanium hub, as well as a "glass cockpit" with flat-panel color displays.

UH-72A Lakota

The EC 145 scored a major win in mid-2006 when it was selected to fulfill the US Army's "Light Utility Helicopter (LUH)" requirement. The LUH program was focused on obtaining an off-the-shelf helicopter with minor military optimizations for non-combat roles, freeing up combat-fitted machines for frontline service. The EC 145 was given the Army designation of "UH-72A Lakota", with initial deliveries in late 2006; Joe Red Cloud, a chief of the Lakota Indian nation, was a participant of the initial acceptance ceremony.

The US Army expects to obtain 411 Lakotas in all, with two thirds of them going into service with the National Guard. Production is at an Airbus USA facility in Columbus, Mississippi. 187 of them will actually be configured as dual-control trainers, the Army having decided to use the UH-72A to replace the Bell TH-67 Creek / Jetranger in the training role. There's been little mention of changing the designation of the training machines to "TH-72A", suggesting the trainers will be employed in utility roles as needed. The first trainer UH-72A was handed over in March 2015; some of the trainers will be built new, while some will be conversions.

Airbus has more or less revived the unsuccessful BK 117A-3M with a proposal for an armed derivative of the UH-72A for the US Army's upcoming "Armed Aerial Scout (AAS)" competition, with three "AAS-72X" demonstrators being built by Airbus in collaboration with Lockheed Martin. The first flew in 2010. Illustrations of the production machine show it to have an imaging / targeting turret under the nose, plus a stores rack on each side, each rack capable of handing two Hellfire anti-armor missiles, or two 70 millimeter rocket pods, or a rocket pod and a gun pod. The AAS competition was suspended, but the requirement remains outstanding, and so AAS is likely to be revived sooner or later.

AAS-72X

Airbus is also offering a similar "EC 645" for other military requirements, with options for twin stores pylons, an electro-optic targeting system, and helmet-mounted sight.

In 2011, Airbus announced the "EC 145 T2" -- later redesignated "H145" -- with uprated Arriel 2E engines and drivetrain, fenestron tail rotor, updated avionics, and other new features. Initial deliveries were in mid-2014. The firm also has a militarized version, the "H145M" -- previously "EC 645 T2" -- on offer, with initial deliveries in 2015 to German Kommando Spezialkraefte (KSK) special-operations forces. In addition, the firm is working with the French Army on an "optionally piloted" configuration of the EC 145 for robotic resupply, initial test flights taking place in the spring of 2013.

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[6] FOOTNOTE: HAL DHRUV HELICOPTER

* The MBB family of helicopters includes an Indian relative. In 1984, Hindustan Aerospace Limited (HAL) of India signed a contract with MBB for development of what was then designated the "Advanced Light Helicopter (ALH)", leading to rollout of a nonflying test airframe in the spring of 1991, and initial flight of the first of five flying prototypes on 30 August 1992. The five prototypes included two engineering validation prototypes, plus one prototype each of army-air force, navy, and civil versions. The production machine was to be given the name of "Dhruv (Polaris / Pole Star)". Deliveries were delayed because of US objections to Indian nuclear tests that blocked delivery of LHTEC CTS800 turboshaft engines, but production machines were finally delivered to the Indian Army in 2002, with deliveries following to other users.

The resemblance of an army-air force Dhruv to the BK 117 is unmistakeable, though the Dhruv is a bigger machine, with an empty weight about 50% greater than that of the BK 117. Otherwise, the two rotorcraft are very similar, with the Dhruv featuring a pod-&-boom / main-tail rotor configuration, clamshell rear doors, skid landing gear, twin swept tailfins, and a four-blade main rotor. It does differ from the BK 117 in featuring a four-bladed tail rotor.

The Dhruv is powered by twin Turbomeca TM333-2B turboshafts, each rated at 788 kW (1,057 SHP). The ultimate goal is to fit the locally-built Ardiden 1H / Shakti turboshaft, built by HAL with Turbomeca assistance, providing 895 kW (1,200 SHP) each for enhanced "hot & high" operation -- an important consideration for the Indian Army and Air Force, since operations are often conducted in the mountainous northern regions of the country. Composite materials make up a large proportion of the rotorcraft's structure. Fuel tanks are bullet-resistant, crashworthy, and self-sealing.

HAL army Dhruv

Two flight crew are normal, with 12 seats for passengers or 14 seats in a high-density configuration. In the medical role, the Dhruv can fit four stretchers and two medical attendants. Along with the clamshell rear doors, there is a hinged cockpit door and sliding passenger door on each side.


   HAL DHRUV (ARMY-AIR FORCE VARIANT):
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   main rotor diameter     13.2 meters         43 feet 4 inches
   tail rotor diameter     2.55 meters         8 feet 4 inches
   fuselage length         13.43 meters        44 feet 1 inch
   footprint length        15.87 meters        52 feet 1 inch
   height (tail rotor)     4.98 meters         16 feet 4 inches
   height (rotor head)     3.93 meters         12 feet 11 inches

   empty weight            2,550 kilograms     5,622 pounds
   max loaded weight       4,500 kilograms     9,920 pounds

   maximum cruise speed    265 KPH             165 MPH / 145 KT
   service ceiling         6,500 meters        21,320 feet
   range, 10 passengers    220 kilometers      135 MI / 120 NMI
   _____________________   _________________   _______________________

The Dhruv can be configured as a gunship, with sensor turret on top of the nose; an undernose turret carrying a 20 millimeter cannon; and stores pylons for unguided rockets pods, anti-armor missiles, or air-to-air missiles. It is also possible to mount a light machine gun on a pintle in one or both doors; a defensive countermeasures system can be fitted as well.

The naval / coast guard version of the Dhruv differs from the army-air force version in having wheeled retractable tricycle landing gear -- skid landing gear is inconvenient for shipboard operations -- with the main gear assemblies retracting into sponsons. The naval version also includes a deck harpoon capture fixture; a sonar system; a stores attachment on each side of the fuselage for a torpedo or other munition; and a nose radar. A roof-mounted infrared imager is an option. HAL is working with Israeli Aircraft Industries to develop a drone version of the naval Dhruv.

The civil version uses the same wheeled landing gear scheme, but it differs from other versions in being fitted with hinged passenger doors. Civil Dhruves have been exported to Ecuador, Mauritius, Maldives, and Nepal. HAL has worked with Israel Aircraft Industries (IAI) on a military export version of the Dhruv, with a full "glass cockpit", a sensor system, a defensive countermeasures system, and an expanded range of offensive stores.

* The Dhruv is being used as the basis for a two-seat helicopter gunship, the "Light Combat Helicopter (LCH)". It is a direct descendant of the Dhruv, essentially taking a Dhruv in gunship configuration -- with undernose 20-millimeter cannon turret, day-night sight on top of the nose, and stores outriggers -- and replacing the normal forward fuselage with a stepped tandem seat fuselage. It features nonretractable wheeled tricycle landing gear. Initial flight of the first prototype was in March 2010. The Indian Air Force and the Indian Army expect to obtain 30 LCH gunship each, with the high power ratings of the engines making them particularly suitable for combat use under "hot and high" conditions.

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[7] COMMENTS, SOURCES, & REVISION HISTORY

* The primary sources for this document was a set of JANE'S ALL THE WORLD'S AIRCRAFT from my local library. Miscellaneous items were also obtained off the internet, particularly writeups from "aerospace-technology.com". Gorka Martinez, a fine source on things that fly over Spain, was kindly enough to field some questions on the Spanish Bo 105s on request.

I was actually intrigued to see both Bo 105s and BK 117s operating in the colors of a medical service in my original hometown of Spokane, Washington. There was a time when it was unusual to see foreign-built flying machines in the USA, but it is much less unusual than it was. Incidentally, the Red Bull brewing company, which has pumped a fair amount of money into flashy airshow flight demonstrations, operates a Bo 105 -- maybe more than one -- in airshow aerobatic demonstrations. I managed to finally see it in action at Marine Corps Air Station Miramar in California in 2012.

Red Bull Bo 105

* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

* Revision history:

   v1.0.0 / 01 jul 09 
   v1.0.1 / 01 apr 10 / Review & polish.
   v1.0.2 / 01 mar 12 / Review & polish.
   v1.0.3 / 01 feb 14 / Eurocopter became Airbus Helicopter.
   v1.0.4 / 01 jan 16 / Antitank Bo105s retired.
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