Pioneering a Pedigree
By the late 1960s, the helicopter had proven itself as a mature technology with clear potential for further development. The Korean War of the early 1950s and the then‑raging Vietnam War had demonstrated beyond doubt the helicopter’s value in military operations. During the same period, the civil sector was also warming to the benefits of rotary‑wing aviation.
The Bölkow Bo 105, which first flew in 1967, represented a major milestone in helicopter development and has had a far‑reaching influence on rotorcraft design ever since. It is fitting that such a revolutionary machine should have come from the company founded by the visionary Ludwig Bölkow.
Ludwig Bölkow (1912–2003) was, in a sense, born into aviation. His father worked as a foreman at the Fokker aircraft company. Ludwig began his aviation career with Heinkel before studying aeronautical engineering in Berlin. After graduating in 1939, he joined Messerschmitt, where he played a key role in developing both the Bf 109 fighter and the Me 262, the world’s first operational jet fighter.
In 1948, Bölkow established his own company and built it into one of the largest and most respected aviation firms in post‑war Germany. He is remembered not only as a principal architect of the reconstruction of the German aerospace industry, but also as a founding figure whose company would eventually become part of today’s Airbus Group.
Bölkow’s vision extended well beyond aviation. He was an early advocate of alternative energy and devoted much of his later life to researching hydrogen and solar power. As an employer, he was equally progressive, championing employee mentoring, company pension plans, and flexible working hours at a time when such ideas were considered remarkably forward‑thinking.
Advancing the Blade
Messerschmitt‑Bölkow‑Blohm (MBB), the company formed through the merger of Bölkow with Messerschmitt in 1968 and the subsequent merger with the aircraft division of Blohm + Voss in 1969, is generally credited with creating the Bo 105. In reality, however, the helicopter’s design had already been finalized and its maiden flight completed before those mergers took place. The Bo 105 was conceived and developed in the Bölkow workshops.
The Bo 105 was the world’s first production light helicopter powered by two turbine engines. This gave it impressive performance for its class while significantly improving reliability and operational safety.
Even more significant was Bölkow’s introduction of the rigid, or hingeless, rotor system. The design centred on a compact titanium rotor head connected to flexible composite rotor blades that were lighter, stronger, and more fatigue‑resistant than the all‑metal blades commonly used at the time. Rather than relying on traditional hinges between the rotor head and blades, the new system used the natural flexibility of the composite blades to accommodate the movement previously provided by mechanical hinges.
The advantages were numerous. The rigid rotor system reduced weight, simplified maintenance, and lowered manufacturing complexity. Its greatest contribution, however, was the extraordinary agility it gave the helicopter. The flexibility and torsional strength of the composite rotor blades allowed the Bo 105 to perform loops, rolls, and other aerobatic manoeuvres that had previously been considered impossible for a production helicopter. Those demonstrations became one of the aircraft’s defining characteristics and remain impressive today.
As the Bo 105 was an entirely new design, its development followed a careful and methodical programme. The fuselage, rotor system, and twin‑engine installation were all tested independently before being integrated into a complete aircraft.
The first three prototypes, intended primarily for systems and dynamics testing, were fitted with German‑built engines and the rotor system from a British‑built Westland Wasp. Meanwhile, the rigid rotor system itself underwent flight testing aboard a French‑built Sud Aviation Alouette II.
Later pre‑production prototypes were fitted with American‑made Allison 250 engines.
Six prototype aircraft were ultimately constructed before the Bo 105 entered production in 1970.
Building a Legend
The Bo 105 remained in production for three decades before the final aircraft was completed in 2001. Approximately 1,640 examples were built at assembly lines in Canada, Germany, Indonesia, the Philippines, and Spain.
Although originally intended for the civil market, the Bo 105’s agility and impressive rate of climb quickly attracted military interest. Over its long career, the helicopter appeared in roughly 25 different variants and found widespread success with both civilian and military operators.
To many casual observers, the Bo 105 is best known for its role as an air ambulance, a task at which it excelled for many years before gradually being replaced by newer designs.
In civilian service, it also proved highly effective in police operations, corporate transport, film and television work, and a variety of other utility roles.
Military operators employed the type in both land and maritime environments for missions that included training, anti‑tank warfare, infantry support, maritime reconnaissance, and border patrol.
The largest operator was the German Army, which retired the type in 2016. During the height of the Cold War, West Germany fielded the PAH‑1 variant as a dedicated anti‑tank platform. Its speed, agility, small size, and excellent low‑level handling made the Bo 105 particularly well suited to operating below treetop level in that role.
The Bo 105 Family Tree
The Bo 105 family includes a number of variants, but they are relatively straightforward to sort. The type was designed first for the civil sector and later branched into military versions.
The following list shows the major variants separated into civilian and military models:
Civilian Models
- Bo 105A: The first civil production model. It debuted in 1970 and was powered by a pair of 317‑horsepower Allison 250‑C18 engines. The Bo 105A was considered underpowered and was quickly superseded by the Bo 105C.
- Bo 105C: First appearing in 1972, this was an improved version powered by 400‑horsepower Allison 250‑C20 engines.
- Bo 105CB: This was the major production variant from 1975. The main change was fitting it with 420‑horsepower Allison 250‑C20B engines. This is the most significant member of the Bo 105 family, as it forms the basis for all subsequent variants.
- Bo 105CBS: This was a stretched version designed primarily for emergency medical services (EMS). It featured a 25 cm (9.8‑inch) cabin stretch to accommodate medical litters and equipment.
- Bo 105LS: This is the Canadian‑built variant. It debuted in 1984 and was intended to address the performance degradation the Bo 105 experienced in high‑temperature/high‑altitude environments. It had the stretched fuselage of the CBS version and was powered by the more powerful 550‑horsepower Allison 250‑C28C engines.
Military Models
- Bo 105M / VBH: A stripped‑down, unarmed observation platform delivered to the German Army. It had a military‑optimised transmission system and a simplified cabin interior for basic utility and communications work.
- Bo 105P / PAH-1: The primary Cold War anti‑tank variant deployed by Germany. It featured external weapon outriggers configured to carry six anti‑tank missiles.
- Bo 105P / PAH-1A1: This was a mid‑life upgrade programme for German attack helicopters. It featured structural reinforcements, modernised cockpit interfaces, integrated GPS navigation systems, and advanced digital weapon‑aiming equipment.
- Bo 105E4: Ex‑German military Bo 105s that were modified, structurally refurbished, and provided to the Albanian military.
Progeny of a Pioneer
As one would expect from a successful design, the Bo 105 became the progenitor of a family of light utility helicopters that inherited both its rigid rotor system and its excellent handling characteristics.
Due to the many mergers and rebrandings that have reshaped the European aerospace industry over the decades, tracing the Bo 105’s descendants by name can sometimes be confusing.
MBB remained an independent company until it was acquired in 1989 by the German aerospace group DASA. Through a series of reorganisations and mergers, DASA later became part of EADS (European Aeronautic Defence and Space Company), which subsequently evolved into the Eurocopter Group and, in 2014, Airbus Helicopters.
While Airbus Helicopters now carries the legacy of the Bo 105 and its descendants, the family lineage can be summarized as follows:
MBB/Kawasaki BK 117 → Eurocopter EC 145 → Airbus H145
The first major development of the Bo 105 was the BK 117, a joint project between MBB and Kawasaki of Japan. Both companies had been working independently on light utility helicopter designs before agreeing to combine their efforts into a single aircraft.
MBB assumed responsibility for the rotor system, tail assembly, flight controls, and hydraulics, while Kawasaki handled the landing gear, fuselage, transmission, and several other major components. The prototype first flew in 1979, and production began in 1982. BK 117 production continued until 2004.
While the BK 117 was in production, the European side of the programme came under the control of Eurocopter in 1992, though the partnership with Kawasaki remained unchanged. In 1999, following a series of upgrades to the BK 117, Eurocopter introduced the EC 145.
The EC 145 later became the basis for the UH‑72 Lakota, selected by the U.S. Army in 2006 as its new light utility helicopter to replace ageing Bell UH‑1 Iroquois and OH‑58 Kiowa aircraft. A separate military variant was designated the EC 645.
After Eurocopter was rebranded as Airbus Helicopters in 2014, the EC 145 and EC 645 were redesignated the H145 and H145M, respectively.
MBB Bo 108 → Eurocopter EC 135 → Airbus H135
MBB began work on a refined successor to the Bo 105 during the 1970s under the designation Bo 108. Much of the programme focused on streamlining the aircraft’s fuselage, improving its flight controls, and incorporating emerging technologies that would define the next generation of light helicopters.
Development proved to be a lengthy process, during which France’s Aérospatiale joined the project. The first of two Bo 108 prototypes made its maiden flight in 1988.
Initially intended solely as a technology demonstrator, the Bo 108 showed enough promise during testing that full production was eventually pursued. By then, Eurocopter had been established, and the aircraft was redesignated the EC 135. A military version followed under the designation EC 635.
When Eurocopter became Airbus Helicopters in 2014, the EC 135 and EC 635 were redesignated the H135 and H135M, respectively.
The Bo 105 Today and Learning More
Although production ended in 2001, the Bo 105 remains far from retirement. Hundreds continue to fly in both civilian and military service around the world.
With well‑established technical support networks, a reputation for reliability and excellent handling, and continued demand in specialist roles, the Bo 105 is likely to remain in the skies for years to come. Depending on where you live, your chances of seeing one in active service are still quite good.
The following resources provide additional information on the Bo 105, its development, and the people behind its success.
The Flying Bulls operate one of the world’s best‑known Bo 105s and regularly demonstrate the helicopter’s remarkable aerobatic capabilities. Their website includes information about the aircraft and its display pilots.
The Ludwig Bölkow Systemtechnik website also contains an informative biography of Ludwig Bölkow and his work in both aviation and alternative energy research.
The Pilots Who Ask Why website has a very informative article about different helicopter rotor systems. It gives a clear explanation of how the rigid rotor system compares to semi‑rigid and fully articulated systems.
Pickled Wings 