Eurocopter EC135

The Airbus Helicopters H135, formerly Eurocopter EC135, is a twin-engine civil light utility helicopter produced by Airbus Helicopters. It is capable of flight under instrument flight rules and is outfitted with a digital automatic flight control system. First flying in February 1994, it entered service in 1996. 1,400 have been delivered up to September 2020, to 300 operators in 60 countries, accumulating over 5 million flight hours. It is mainly used for air medical transport (medevac), corporate transport, law enforcement, offshore wind support, and military flight training. Half of them are in Europe and a quarter in North America. The H135M, certified under the name Eurocopter EC635, is a military variant, so the overall design is known as the Airbus Helicopters H135 and the military version, as the Airbus Helicopters H135M. The EC135/H135 is a development of the prototype Messerschmitt-Bölkow-Blohm (MBB) Bo 108.

The H135 started development prior to the formation of Eurocopter, under Messerschmitt-Bölkow-Blohm (MBB) under the designation Bo 108 in the 1970s. MBB developed it in partnership with Aérospatiale, the Bo 108 was initially intended to be a technology demonstrator, combining attributes of the successful MBB Bo 105 with new advances and an aerodynamically streamlined design. Technologies included on the Bo 108 included the first full-authority digital engine controls (FADEC) on a helicopter, a hingeless main rotor, and the adoption of a new transmission. The first prototype made its first flight on 17 October 1988, powered by two Allison 250-C20R/1 engines. A second Bo 108 followed in June 1991, this time with two Turbomeca TM319-1B Arrius engines. Unlike later production aircraft, both technology demonstrators flew with conventional tail rotors.

In the late 1990s, the design was revised with the introduction of the Fenestron tail rotor system, an advanced rigid main rotor, composite materials, and resonance isolation systems. It was decided to pursue a full certification program, resulting in the production of two pre-production prototypes. At the same time, the Bo 108 was given a new designation of EC135, to correspond with the newly created Eurocopter company. At this point, it was decided that the EC135 should be developed with the option of being powered by two competing engines, the Turbomeca Arrius 2B and the Pratt & Whitney Canada PW206B engines. Two pre-production prototypes were built in 1994 powered by either engine, both powerplants proved to be successful and were used on subsequent production aircraft.

In January 1995, the EC135 made its first public appearance at the Heli-Expo convention at Las Vegas, at which prospective buyers were reportedly impressed with its appearance and performance figures. Another feature which became apparent upon entering service was the low noise levels produced, in part due to its Fenestron tail, the EC135 was the quietest aircraft in its class for more than 15 years. Despite the helicopter's design being primarily oriented towards emergency medical operators, the EC135 had considerable appeal to a wide range of operators. European JAA certification was achieved in June 1996, with FAA approval following in July.

In December 1999, the EC135 was granted single-pilot instrument flight rules certification by Germany's Luftfahrt-Bundesamt. In December 2000, the United Kingdom's Civil Aviation Authority also gave the EC135 single-pilot instrument flight rules certification.

In 2000, Eurocopter announced the start of certification work on the EC135P2, powered by the Pratt & Whitney Canada PW206B2, offering improved single-engine performance and 30-second emergency power. The Luftfahrt-Bundesamt certification was achieved in July 2001, and the first EC135 with the new engines was handed over to the Swedish Police Authority in August 2001. In September 2002, the EC135T2 equipped with the improved Turbomeca Arrius 2B2 was made available, providing for improved single-engine performance.

In 2002, the EC135 active control technology demonstrator/flying helicopter simulator (ACT/FHS), a research aircraft designed to test fibre optic-based flight control systems, undertook its first flight. In 2014, Airbus Helicopters began flying the Bluecopter demonstrator aircraft, built to explore more efficient design elements, including economy-optimised single-engine operations, Blue Edge swept rotor blades to reduce noise and increase efficiency, a relocated horizontal stabiliser outside the main rotor's downwash, an active rudder, and new water-based external paint; these changes were aimed at cutting fuel consumption by 40%. In December 2014, the single-engine operations portion of the Bluecopter tests were delayed to summer 2016 to make necessary avionics changes, such as to the engine's FADEC systems.

In March 2007, at the NBAA in Atlanta, Eurocopter unveiled 'L'Hélicoptère par Hermès, a special-edition VIP model designed by Hermès International, S.A. It features a customised luxury four-place main cabin, a sliding glass partition, a corporate baggage hold, redesigned skid landing gear and other external changes. The launch customer for the type is Falcon Aviation Services (FAS), based in Abu Dhabi, United Arab Emirates. In July 2014, Airbus Helicopters made further personalisation options available for the EC135 l'Helicoptere par Hermes.