The Messerschmitt-Bölkow-Blohm Bo 105 is a light, twin-engine, multi-purpose helicopter developed by Bölkow of Ottobrunn, West Germany. It was the first light twin-engine helicopter in the world, and the first rotorcraft that could perform aerobatic maneuvers such as inverted loops.Moll 1991, p. 96.looping capability according to the German Air Force museum at Gatow The Bo 105 features a hingeless rotor system, a pioneering innovation in helicopters when it was introduced into service in 1970. Production of the Bo 105 began at the then-recently merged Messerschmitt-Bölkow-Blohm (MBB).
The main production facilities for producing the Bo 105 were located in Germany and Canada; due to the level of export sales encountered, additional manufacturing lines were set up in Spain, Indonesia, and the Philippines.Moll 1991, pp. 103–104. MBB, acquired by DASA in 1989, merged its helicopter division with that of France's Aérospatiale to form Eurocopter in 1992 (rebranded Airbus Helicopters since). The latter continued production of the type until 2001. The Bo 105 was formally replaced in Eurocopter's product range by the newer Eurocopter EC135. By the close of production, over 1400 had been produced in Germany, and with license production 1640 had been produced in total.
Development
In 1964, development work began at Bölkow upon the helicopter that would become the Bo 105, although work on the hingeless rotor it would use had begun earlier.Rieck, Joan M. "Bölkow's Bo105." Flight International, 18 May 1967, p. 794. On 16 February 1967, the second Bo 105A prototype conducted its maiden flight at Ottobrunn in Germany; the first public demonstration was held in May 1967. The test program was broken down into stages as the Bo 105 comprised a new airframe, new rotor system, and a new engine; thus the flying Bo 105 prototype was initially equipped with a main rotor from Westland Helicopter's Scout rotorcraft and a pair of Allison Model 250 turboshaft engines instead of their production counterparts. Sud Aviation worked with Bölkow on developing the rotorcraft; an Alouette II helicopter was modified with the Bo 105's rotor and used to test its performance envelope. The third Bo 105 prototype was equipped with the initial production standard MAN Turbo 6022 turboshaft engines; six pre-production Bo 105s were constructed for testing.
On 13 October 1970, the German Civil Aviation Authority certified the Bo 105; initial deliveries for the first customers, ADAC Air Rescue and the Bavarian State Police, took place shortly thereafter. In 1972, further type certification was granted by the Federal Aviation Administration (FAA) and the Civil Aviation Authority (CAA), enabling export orders from the United States and Britain respectively, which soon followed. In 1972, an improved version of the rotorcraft with more powerful engines, the Bo 105C, was developed; this model quickly superseded the Bo 105A. On 25 September 1973, the prototype Bo 106 performed its first flight;Taylor 1976, p. 73. the Bo 106 shared many similarities to the Bo 105, the principal difference being a widened cabin area, capable of seating three abreast in the front row and four abreast in the rear of the cabin. However, nothing further came of the Bo 106 project.Air International May 1976, p. 246.
In 1976, the Bo 105CB, equipped with more powerful Allison 250-C20B engines, was introduced. The Bo 105C was further developed to become the Bo 105CBS, the primary change being a fuselage stretch of 10 inches to meet American demand for emergency medical service (EMS) operations; this version was often referred to as the Bo 105 Twin Jet in the United States. US aerospace firm Boeing-Vertol served as a partner in the type's production and further development, and marketed the BO 105 in the US.Weeghman 1975, p. 54."A Marriage that Lasted." Flight International, p. 30. 31 May 2004. The Bo 105 CB and the Bo 105 CBS variants were also subject to license manufacturing agreements, leading to them being produced by the Philippine Aerospace Development Corporation in the Philippines which produced 44 units from 1977-1997, Indonesian Aerospace (IPTN) in Indonesia, and Construcciones Aeronáuticas SA (CASA) in Spain in addition to the main production line in Germany.
In 1984, the Bo 105LS was developed with the enlarged fuselage of the Bo 105CBS combined with uprated Allison 250-C28C engines to increase the maximum take-off weight as well as hot-and-high flight performance; the Bo 105 LS was manufactured under a cooperative arrangement with Eurocopter Canada. Improvements and modifications to the Bo 105 LS continued until 1995.
Production of the Bo 105 by Eurocopter formally ended in 2001, principally due to the type having been superseded by the more modern Eurocopter EC135, itself a direct development from the Bo 105. By the end of production, 1,406 rotorcraft had been manufactured and delivered to operators in 55 nations worldwide.Gotzhein, Christina. "Eurocopter Celebrates the 40th Anniversary of the Maiden Flight of the BO105, the World's First Light Twin-Turbine Production Helicopter." Eurocopter, 15 February 2007. Including the license production in Canada, Indonesia, Philippines and Spain the total is about 1640; of that 1404 were made in Germany.
Design
The Bo 105 has a reputation for having high levels of maneuverability; certain variants have been designed for aerobatic maneuvers and used for promotional purposes by operators, one such operator in this capacity being professional pilot Aaron Fitzgerald, flying for Red Bull.Wise, Jeff. "How to Fly a Helicopter—Upside Down." Popular Mechanics, 25 May 2012. During the 1970s, the Bo 105 was known for having a great useful load capacity and higher cruise speed than the majority of its competitors.Weeghman 1975, pp. 54–56. While not being considered a visually attractive helicopter by some pilots, the Bo 105 was known for possessing steady, responsive controls and a good flight attitude.Moll 1991, p. 105. Most models could perform steep dives, rolls, loops, turnovers, and various aerobatic maneuvers; according to MBB the Bo 105 is cleared for up to 3.5 positive G force and one negative. One benefit of the Bo 105's handling and control style is superior takeoff performance, including significant resistance to catastrophic dynamic rollover; a combination of light weight and the twin-engined configuration enables a rapid ascent in a performance takeoff.
Perhaps the most significant feature of the Bo 105 is its rotor blades and rotor head. The rotor system is entirely hingeless, the rotor head consisting of a solid titanium block to which the four blades are bolted;Moll 1991, pp. 98, 101. the flexibility of the rotor blades works to absorb movements typically requiring hinges in most helicopter rotor designs.Moll 1991, p. 101. The rotor blades are made from reinforced-plastic glass-fiber composite material; the flexibility of the main rotor allows for active elements other than rotor pitch changes to be removed, greatly simplifying maintenance and extending blade lifespan.Weeghman 1975, p. 56. The reliability of the advanced rotor system is such that, in over six million operating hours across the fleet, there was a total of zero failures (as of 1991).Moll 1991, p. 98. The rigid rotor design adopted on the Bo 105 has been partially responsible for the type's agility and responsiveness; it remained an uncommon feature on competing helicopters throughout the Bo 105's production life.Moll 1991, p. 103.
Military operators would commonly operate the type at a very low altitude to minimise visibility to enemies, the Bo 105 being well matched to such operations, as the helicopter's flight qualities effectively removed or greatly minimised several of the hazards such a flight profile could pose to pilots.Moll 1991, pp. 102–103. When outfitted with optional auxiliary fuel tanks, a basic model Bo 105 had a flight endurance of roughly five hours under load.Moll 1991, p. 104. In the event of a single engine failure, the Bo 105 could typically continue its flight, albeit with a reduction in cruise speed and range. Besides the two pilots, the cabin can be configured to accommodate up to three passengers on a single rear bench, which can be removed to make room for cargo or a stretcher, which can be loaded and unloaded via the large clamshell doors located at the rear of the fuselage.Weeghman 1975, p. 57. In a maritime context, the BO 105 can be equipped with auxiliary fuel tanks, emergency flotation equipment, an inflatable life raft, folding rotor blades and high skid landing gear."Characteristics of the Messerschmitt-Bolkow-Blohm (BO-105-CBS) helicopter." Canadian Coast Guard, Retrieved: 6 November 2015.
Operational history
In 1975, the German Army decided to procure a specialist anti-tank version armed with up to six Euromissile HOT missiles, designated as the Bo 105 PAH-1 (Panzerabwehrhubschrauber, "anti-tank helicopter"). A total of 212 Bo 105 PAH-1s were delivered between 1979 and 1984. German Army leaders saw the PAH-1 as a temporary measure only, having originally sought a more capable anti-tank helicopter; they were particularly dissatisfied with the PAH-1's inability to perform nighttime combat missions and its self-protection capabilities; ultimately, the Eurocopter Tiger was developed as a replacement.Krotz 2011, pp. 59–61. In 1977, the German Ministry of Defence selected the Bo 105C for its light observation helicopter (VBH) program, leading to the procurement of another 100 rotorcraft. The helicopter was retired from German Army service on 13 December 2016, the occasion was marked by an 18-aircraft formation flyby from their base in Celle. The Bohicans, as their pilots were called, had clocked over 1.38 million flying hours.Last Of The Bohicans - Aviationweek.com, 23 December 2016
During the 1970s, MBB issued a license to produce the Bo 105 to Indonesian Aerospace (IPTN) as part of a wider agreement to help develop Indonesia's aviation industry. Within ten years, manufacture of the Bo 105 had been entirely localised within IPTN's own facilities.Amir 2012, p. 106. The Bo 105 has been used by various branches of the Indonesian National Armed Forces; military-operated Bo 105s have been reportedly used during the 1999 East Timorese crisis and the Papua conflict."STOP Arming Indonesia." European Network Against Arms Trade, 1994. Indonesian Bo 105s have also participated in several large-scale joint exercises.Keck, Zachary. "Indonesia to Conduct Massive Military Drill." The Diplomat, 21 May 2014.Rahmat, Ridzwan. "Indonesian navy conducts first helicopter landing on USN LCS." IHS Jane's Navy International, 18 August 2015.
The Mexican Navy operated a number of armed Bo 105s to perform maritime reconnaissance duties; during the early 1980s, Mexico procured a number of a Uribe-class patrol vessels which were equipped to handle the Bo 105 for off-shore operations."Mexico Study: Chapter 5. National Security." marines.mil, Retrieved: 1 November 2015. In 2005, work was completed on a series of upgrades to 11 of the Mexican Navy's Bo 105s, having received Forward looking infrared (FLIR) sensors, Global Positioning System (GPS) receivers, search radars, new rotor blades, armament pylons, and other changes."Procument, Mexico." Jane's Sentinel Security Assessment , 11 February 2011. In November 2014, Jet Rescue Air Ambulance inaugurated Mexico's first dedicated civil air ambulance rotorcraft using a Bo 105."First full HEMS for Mexico." AirMed & Rescue Magazine, 26 November 2014.