t is capable of flight under instrument flight rules (IFR) and is outfitted with a digital automatic flight control system (AFCS). First flying on 15 February 1994, it entered service in 1996 and 1,300 have been delivered up to January 2018 to 300 operators in 60 countries, accumulating over 4.5 million flight hours. It is mainly used for helicopter emergency medical services then for corporate transport, law enforcement, offshore wind and military flight training. Half of them are in Europe and a quarter in North America. The Eurocopter EC635 is a military variant. The EC135 is a twin-engine rotorcraft. It can be alternatively powered by a pair of Turbomeca Arrius 2B or Pratt & Whitney Canada PW206B engines, dependent on customer's preference (which gives either a T or a P, respectively, in the variant name). The main rotor is of a four-bladed, hingeless fiber-composite design; progressive improvements to the main rotor have increased its performance and reduced maintenance costs since the type's introduction. The EC135 holds the distinction of being the quietest helicopter in its class, featuring an anti-resonance isolation system to dampen vibration from the main rotor. The type's fenestron anti-torque device can be actively regulated via a HI NR rotor optimization mode, which provides for greater controllability during higher weight take-off and landings. It is capable of performing Category A operations throughout its full flight envelope. For further details of the design, development, operational history and variants, click here. Specifications below are for the EC135 P2+/T2+ model.