BO 105 Celebrates 40th Anniversary

On February 16, 1967, the BO105 took off for its maiden flight in Ottobrunn (near Munich), Germany. At the controls was Wilfried von Engelhardt, test pilot at MBB (Messerschmitt-Bölkow-Blohm), the German predecessor company of Eurocopter. The BO105 was the world’s first light twin-engine helicopter and the world’s first to feature a hingeless titanium main rotor without flap and lag hinges, and composite rotor blades. Trademarked “Rotor System Bölkow”, this innovative four-blade system gave unparalleled manoeuverability to the BO105, which laid the foundation to the German helicopter industry after World War II and was to become an aviation legend.

Over the years, license agreements for the BO105 CB/CBS versions with the Philippines, Indonesia and Spain were concluded, and for the BO105 LS, a cooperation agreement with Canada. Until production ended in 2001, as the BO105 was superseded by Eurocopter’s EC135, a total of 1,406 BO105s had been delivered to 55 customer nations – a remarkable commercial success considering that two engines for a light helicopter were a novelty at the time, and the use of composites for the rotor blades and some structural parts was a pioneering feat.

Production preparations for the BO105 began in 1969, and type certification for the BO 105 Amodel, equipped with two Allison 250-C18 turbines, was granted by the German LBA (Luftfahrt-Bundesamt) on October 13, 1970. Deliveries of Germany’s first production helicopter began, with the first customers being ADAC Air Rescue and the Bavarian Police. MBB’s production line soon gathered momentum. In April 1972, the A-model was certified by the FAA, resulting in first exports to the United States. The A-version was superseded by the BO105 C, featuring two Allison 250-C20 engines and a take-off weight of 2,100 kg. In the course of 1972, take-off weight was upped to 2,300 kg and certifications obtained from the LBA, FAA and the British CAA.

In 1977, the German Ministry of Defence selected the BO105 as a light observation helicopter (VBH) of which 100 units were procured, and as the German Army’s first anti-tank helicopter, designated PAH-1 and armed with six HOT missiles. A total of 212 PAH-1 were procured. Another conversion to a higher-powered engine, the 250-C20B, took place in 1976. The helicopter was designated BO105 CB and became known as the “standard version”. Chiefly in response to American market requirements, the BO105’s fuselage was stretched by 10 inches, thereby launching the CBS version which was marketed in the United States as “BO105 Twin Jet” and became vastly successful in the EMS (Emergency Medical Service) market. In 1980, the take-off weight of both the CB and CBS versions was increased to 2,400 kg, giving the aircraft even more scope and mission capability. A further take-off weight increase to 2,500 kg was performed in 1984 and finally, in 1993, the last modification up to CB/CBS-5 standard, called BO105 Super Five and featuring new airfoil main rotor blades, was carried out.

Concurrently in 1984, a hot-and-high version, the BO105 LS, was certified, which combined the stretched fuselage of the CBS version and the power of two 250-C28C engines. The LS A1-version was followed in 1986 by the A3- version, with 2,600 kg maximum take-off weight, and in 1995 the final version BO105 LS A3 “Superlifter” was certified, with a maximum mission weight with external cargo of 2,850 kg and a maximum external load capability of 1,350 kg.

From the outset, the BO105 was designed as a multi-role helicopter, combining flight safety, reliability, and high agility with a multi-purpose concept and about 50 available optional equipment kits. It featured large rear clamshell doors and high-set main and tail rotors for easy access and loading as well as ground handling safety.

Many of the BO105’s features and concepts have been adopted in Eurocopter’s new generation of light twins, notably the EC135 and EC145. More than that – the BO105 was already an early example of Franco-German cooperation. The MBB engineers had been experimenting with composite blades and designed their first hingeless rotor - a three-bladed version - before they had a suitable helicopter for it. Thus, initial flight tests of the system were carried out in 1966 on an Alouette 2 at Sud-Aviation in Marignane, France, which later became a division of Aerospatiale. The respective helicopter divisions of MBB and Aerospatiale merged in 1992 to establish Eurocopter.

Source: Eurocopter celebrates the 40th Anniversary of the Maiden Flight of the BO105, the World’s first light twin-turbine Production Helicopter