MBB Bolkow BO-105

MBB's small yet capable BO 105 has won a well-deserved reputation for performance and reliability since it first flew over 30 years ago. Today this adaptable craft is in worldwide military and civilian service.

To the pilot, the BO 105 is a delight to fly, offering good flying characteristics with great agility thanks to its rigid rotors. The current BO 105 with seating for six in an extended fuselage is regarded as one of the most sensible and effective light helicopters in the world, offering a superb view from its rounded contour nose.

Rescue versions of the BO 105 have saved thousands of people in life-threatening situations. It has made a great impact in construction, ambulance and police work, as well as forming the basis for one of the most capable tank-destroyers currently in military service.

Now being marketed by the multinational Eurocopter concern, the BO 105 is a classic design which copes admirably with every task to which it has been assigned.

Design of the Bo.105 lightweight, general purpose helicopter was begun in July 1962 utilising basic experience gained by the company in the preceding few years in building the Bo.102 and Bo.103. The former was a non-flying, ultra-light helicopter trainer, and the Bo.103, flown for the first time on 9 September 1961, was essentially the same aircraft minus its fixed base. An enlarged version of the Bo.103was proposed as the Bo.104, but this project was supplanted by the more promising Bo.105.

The first Bo.105 prototype, powered by a pair of Allison T63 shaft turbine engines and using a conventional hinged-rotor installation, encountered ground resonance problems which eventually caused its destruction. The second machine, which flew for the first time on 16 February 1967, was similarly powered but introduced the 4-blade rigid rotor intended for use in production aircraft. These will be powered by two 375shp MAN-Turbomotoren shaft turbine engines as fitted in the third prototype machine, which first flew on 20 December 1967. In addition to the pilot the Bo.105will accommodate 3 or 4 passengers with their baggage, and its development was still continuing at the end of 1967. The non-articulated rotor, whose fold-able blades are reinforced with glassfibre, has been developed over several years by Bolkow in association with Sud-Aviation and has been adopted by the French company for its own SA.341 light helicopter.

The Bo.105 general purpose helicopter project begun in 1962 can be regarded as the crowning of the experience acquired by Ludwig Boelkow's company with the Bo.46 and the subsequent Bo.102 and Bo.103. The Bo.105 started out as a lightweight five-six seater with twin turbines to improve flight safety and all-weather capabilities. The first aircraft, designated V-1, was ready for ground testing in September 1966. The helicopter had been fitted with a conventional Westland Scout articulated rotor, but in spite of this, it was destroyed by ground resonance during initial trials.

By the time the second prototype, the V-2, was ready, the rigid rotor had been thoroughly tested and was fitted to the new helicopter. The Bo.105 V-2 made its first flight at Ottobrunn (Munich) on 16 February 1967; it had a pair of Allison 250-C18 turbines and the four-blade rigid rotor, and from the outset demonstrated excellent controllability while hovering and at low flight speeds.

Further changes and modifications led to the third prototype — the V-3 fitted with two German-built MAN-Turbo 6022 turbines, and to two pre-production models, the Bo.105 V-4 and V-5, the first of which made its maiden flight on 1 May 1969. Two Allison 250-C20 turbines were later installed on the V-4, which thus became the prototype of the definitive Bo.105C. Meanwhile, from spring 1970, new "droop snoot" design blades, which had a marked downward curvature on the leading edge, were introduced. These were made by MBB, the Messerschmitt-Bolkow-Blohm und Voss group — of which Bolkow and its affiliates had become part.

In 1972, the Bo.105 went into full-scale production, and was offered with either Allison 250-C18 turbine engines or the more powerful C20. The helicopter was approved by the German Federal Authority LBA with the first power-plant in October 1970, after successfully completing autorotation trials in the autumn of 1969. Approval by the US Federal Aviation Administration followed in March 1971 and was extended to the C20 engines in August 1972, while the Canadian authorities certified the Bo.105 in April 1973. The German helicopter also received a British Certificate of Airworthiness in July 1973 and was recognized by the Italian Aeronautical Register in March 1974.

There was no doubt that, with its twin-turbine engines and spacious cabin, theBo.105 would be widely adopted for civil operations, and the German government in fact ordered 20 for its "Katastrophenschutz" programme, to ensure rapid assistance in the event of a disaster. The military version differs little from the civil one. The antitank version can carry six HOT missiles, three on either side of the cabin, with a stabilized sight on the port side.

The results of tests with the Bo.105 HGH were particularly interesting. These were completed in 1975 after two years' research aimed at improving the helicopter's performance. With special fairings, a modified tail unit and smaller skids, this helicopter reached a maximum speed of 372km/h, 100km/h more than the conventional Bo.105. The same aircraft was also given a 6.20m span wing, which enabled it to reach a speed of 404km/h.

The German Army has ordered the following numbers of the military version of the MBB helicopter: Bo.105M liaison and observation, 227; Bo.105 / PAH-1 antitank, 212. Other military Bo.105s have been supplied to Iraq, the Gulf States, Spain, the Philippines and Indonesia, and the Bo.105 has been built under license in these latter three countries by the CASA, NAM and Nurtanio companies, respectively.

The civil version has also been a major export success and was initially marketed through Boeing in the United States before MBB set up its own US facilities. By the end of 1981, total production of the Bo.105 exceeded 1100. More than 100Bo.105s are now in operation in the United States and these were joined in 1982 by the more recent Bo.105CBS Twin Jet II variant, with 420shp Allison 250-C20B turbines, which, apart from having better flying capabilities, has 20 per cent more cabin room.

Further development of the Bo.105CBS led to the introduction in 1981 of theBo.105LS (Lift Stretch) which combines the enlarged cabin with the uprated transmission of the military version and more powerful 550shp Allison 250-C28C engines to provide a much improved hot/high performance and external lift capability.

Design of the MBB BO 105 light utility helicopter began in 1962 and, under German government contract, ground rig testing of its radical rigid rotor and construction of the first prototypes began in 1964. The first prototype airframe, powered by two Allison 250-C18 turboshaft engines and using the rotor from a Westland Scout, was destroyed on the ground at an early date by resonance problems; the second prototype, first flown on 16 February 1967, was the first to take to the air with the new rigid rotor. Initial production version was the BO 105 C, superseded in 1975 by the BO 105 CB which remains the current standard production version.

Suitable for all-weather operations, the military BO 105s are particularly valuable because of the remarkable nap-of-the-earth flight capability provided by the rigid rotor, and the Federal German government has authorised production of a total of 439 BO 105s for service with the German army. These comprise 227 of the BO 105 M(VBH), a liaison and light observation version of which deliveries began in 1980; and 212 of the BO 105 P(PAH-1) anti-tank version, each able to carry six Euromissile HOT missiles. Initial deliveries of this latter version, to Heeresfliegerregiment 16, began in December 1980. MBB has also developed an anti-tank version able to deploy eight Hughes TOW missiles. Other military operators include the Mexican navy with six radar-equipped versions used for maritime patrol, and the Spanish army with 60 BO 105Ps, 57 of them assembled by CASA. The Spanish company is also assembling 80 105s for other customers, and there are active licence-assembly programmes underway in Indonesia as the Nurtanio NBO 105, and Chile. Others are in use in Brunei, Canada, Ciskei, Colombia, Holland, Iraq, Nigeria, Peru, Sierra Leone and Sweden. By 1991 more than 1,300 BO 105s had been delivered to 37 countries and the type is scheduled to remain in production until replaced by the new BO 108 in 1995.

VARIANTS

BO 105 CBS: current version with slightly lengthened fuselage to provide increased seating or cargo capacity

BO 105D: version with modified equipment, supplied to customers in the UK and Nigeria

BO 105 LS: version for 'hot-and-high' operation, combining the larger cabin of the BO 105 CBS with two Allison 250-C28C turboshafts each with a maximum take-off rating of 373kW

Development of this lightweight helicopter began in July 1962 and the first prototype (V-1), fitted with conventional Westland Scout articulated rotor was ready for ground testing September 1969; destroyed by ground resonance during trials. Second prototype (V-2) with hingeless titanium rotor hub and composite rotor blades, powered by twin Allison 250-C18 turboshaft engines flew on 16 February 1967; V-3 fitted with two German-built MAN-Turbo 6022 engines, followed by preproduction models V-4 and V-5. V-4, which first flew 1 May 1969, became the prototype for the definitive production BO 105C, powered by Allison 250-C20 turbines. Full-scale production commenced in 1972; German LBA certification October 1970; FAA certification March 1971.

All BO 105 helicopters for the world market are manufactured and assembled at the company's Donauwörth facility in Germany, with the following exceptions: those for the Spanish market, which are assembled in Spain by CASA; those for the Indonesian market, which are manufactured and assembled in Indonesia by IPTN; and BO 105 LS helicopters produced at Eurocopter's Fort Erie facility in Ontario, Canada.

VERSIONS

BO 105C: Initial production version offered with either 236kW Allison 250-C18 or 298kW 250-C20 turboshaft engines.

BO 105 CB: Standard production version from 1975, with two Allison 250-C20B engines, operable in air temperatures ranging from -45 to +54°C. LBA certification received in November 1976.

BO 105 LS B-1: One-off testbed C-FMCL, powered by two 307kW Pratt & Whitney Canada PW 205B turboshafts, made first flight 13 October 1988.

BO 105 LS: Canadian-built version of BO 105 CBS with increased power. First flight 23 October 1981, German LBA certification July 1984, followed by FAA and Canadian DOT type approval. In Spain, CASA assembled 57 of an initial 60 for the Spanish Army and has continued assembly.

BO 105 M (VBH): Liaison and light observation helicopter for the Federal German Army, with strengthened transmission gearing, reinforced rotor components, a tail rotor with improved thrust and performance, a rupture-proof fuel system and a landing gear able to absorb higher energy levels. Production of 100 approved by the Federal government, to replace Alouette II. Deliveries completed in 1984.

BO 105 P (PAH-1): Anti-tank version of the BO 105 M, with same airframe improvements as BO 105 M, outriggers to carry six Euromissile HOT missiles, a stabilised sight above the co-pilot and a Singer AN/ASN-128 Doppler navigation system. The Federal German government gave its approval for the procurement of 212 PAH-1s for the Federal German Army. Deliveries began on 4 December 1980 and were completed in mid-1984.

KWS-1 upgrade programme implemented in late 1980s, including installation of a digital weapon system, reduction in launcher weight, improved cooling unit, newly developed main rotor blades, and an increase in MTOW to 2,500kg.

CURRENT VERSIONS

BO 105 CBS-4: Version with increased rear seat leg room in a cabin extended by a 0.25m plug. Available in five-seat executive or six-seat high-density configurations. Identified by small additional window aft of rear door on each side. Marketed in the USA by MBB Helicopter Corporation under the name Twin Jet II. First CBS version certified in early 1983 by FAA for IFR operation in accordance with SFAR Pt 29-4, requiring two pilots, radar, Loran C and a separate battery, but not a stability augmentation system, although SAS is available as an option.

BO 105 CBS-5: Military army/naval version for armed and non-armed missions; can be equipped with anti-tank missiles, rocket launchers. Gun pod or turret. First 12 ordered by the Republic of Korea Army; most being assembled from kits by Daewoo. Include Boeing IR/optical sights and defensive aids suite.

BO 105 D: UK CAA-certified offshore version.

BO 105 LSA-3: Hot-and-high version, certified 7 July 1986 and first delivered February 1987. Uprated transmission and Allison 250-C28 turboshaft engines, rated at 410kW for 30 seconds. Built solely by Eurocopter Canada at its Fort Erie, Ontario plant.

BO 105 LSA-3 Super Lifter: Optimised for external load and heavylift missions; max T-O weight 2,850kg; upgraded tail rotor derived from BK 117C-1. Type certification granted October 1995. Built solely by Eurocopter Canada.

EC Super Five: High-performance version of BO 105 CBS-4, derived from German Army PAH-1 upgrade programme; certified late 1993. New main rotor blades, improved performance and reduced vibration; dual flying controls as standard.

The following description refers to the BO 105 CBS-4 except where indicated:

DESIGN FEATURES: 
Four-blade main rotor, comprising rigid titanium head and GFRP blades, with titanium anti-erosion strip and pendulous vibration damper on each blade. NACA 23012 lifting aerofoil with drooped leading-edge and reflexed trailing-edge. Two-blade semi-rigid tail rotor. Tail rotor gearbox on fin. Main rotor 424 rpm. Tail rotor 2,220 rpm. Main transmission utilises two bevel gear input stages with freewheeling clutches and a spur collector gear stage. Planetary reduction gear; three auxiliary drives for accessories. Main transmission rated for twin-engine input of 257kW per engine, or a single-engine input of 283kW. Uprated transmission and Allison 250-C28 engines in BO 105 LS for exceptional hot-and-high performance. EC Super Five has new main rotor blades and performance improvements, including 150kg more rotor lift; better stability; and airframe vibration reduced to less than 0.1g.

FLYING CONTROLS: 
Main rotor has roller bearings for pitch change. Main rotor brake standard. Dual controls standard on EC Super Five.

STRUCTURE:
 Folding of two main rotor blades optional. Tail rotor blades of GFRP, with stainless steel anti-erosion strip. The fuselage is a conventional light-alloy semi-monocoque structure of pod and boom type. Glass fibre reinforced cowling over power plant. Titanium sheet engine deck. Horizontal stabiliser of conventional light-alloy construction with small endplate fins.

LANDING GEAR: Skid type, with cross-tubes designed for energy absorption by plastic deformation in the event of a heavy landing. Inflatable emergency floats can be attached to skids.

POWER PLANT:
 BO 105 CBS: Two 313kW Allison 250-C20B turboshafts, each with a maximum continuous rating of 298kW. Bladder fuel tanks under cabin floor, capacity 580 litres, of which 570 litres are usable. Fuelling point on port side of cabin. Auxiliary tanks in freight compartment available optionally. Oil capacity: engine 12 litres, gearbox 11.6 litres. EC Super Five additionally has scavenge oil filter and one-handed engine starting arrangement. 

BO 105 LS A-3: Two Allison 250-C2BC turboshafts, each rated at 410kW for 2.5 minutes, and with 5 minute T-O and maximum continuous power ratings of 373kW and 368kW respectively. Main transmission, type ZF-FS 112, rated for independent restricted input of 310kW per engine at T-O power or 294kW per engine for maximum continuous operation; or single-engine restricted input of 368kW at maximum continuous power, or 410kW for 2.5 minutes at T-O power. Fuel capacity as for CB/CBS. Oil capacity 4.5 litres per engine.

ACCOMMODATION:
 Pilot and co-pilot or passenger on individual longitudinally adjustable front seats with safety belts and automatic locking shoulder harnesses. Optional dual controls. Bench seat at rear for three or four persons, removable for cargo and stretcher carrying. A full EMS version is available. Both cabin and cargo compartment have panelling, sound insulation and floor covering. Entire rear fuselage aft of seats and under power plant available as freight and baggage space, with access through two clamshell doors at rear. Two standard stretchers can be accommodated side by side in ambulance role. One forward-opening hinged and jettisonable door and one sliding door on each side of cabin. Ram air and electrical ventilation system. Heating system optional.

SYSTEMS: 
Tandem fully redundant hydraulic system, pressure 103.5 bars, for powered main rotor controls. System flow rate 6.2 litres/min. Bootstrap/oil reservoir, pressurised at 1.7 bars. Electrical system powered by two 150A 28V DC starter/generators and a 24V 25Ah Ni/Cd battery; external power socket; stability augmentation system standard on BO 105 LS A-3, with hoist, firefighting kit, weapons fittings, mast-mounted sight and floats optional; EC Super Five has improved hydraulic system.

AVIONICS:
 Wide variety of avionics available including weather radar, Doppler navigation, SAS and autopilot.

EQUIPMENT: 
Standard equipment includes basic flight instruments, engine instruments, heated Pitot, tiedown rings in cargo compartment, cabin and cargo compartment dome lights, position lights and collision warning lights. Options include dual controls, heating system, windscreen wiper, rescue winch, landing light, searchlight, externally mounted loudspeaker, fuel dump valve, external load hook, settling protectors, snow skids and manual main rotor blade folding.

Technical data for MBB Bo-105CB

Engine: 2 x Allison 250-C20B turboshaft, rated at 313kW, main rotor diameter:9.84m, length with rotors turning: 11.86m, height: 3m, take-off weight: 2400kg, empty weight: 1256kg, cruising speed: 270km/h, ceiling: 5180m, range with max payload: 658km