Safran Arrius 1

The Arrius 1 is a turboshaft engine developed by the French manufacturer Turbomeca (now Safran Helicopter Engines) during the late 1970s to power light twin-engine helicopters. Introduced in the early 1980s, the engine was designed to provide improved power-to-weight performance, reliability, and fuel efficiency for new-generation rotorcraft. The Arrius 1 family has been widely used on helicopters such as the Eurocopter AS355 TwinStar and MBB Bo 105, supporting roles including law enforcement, medical transport, training, and utility missions. Its development later led to the more advanced Arrius 2 series.

Arrius 1A delivers approximately 466 shp (take-off power) and is used on the AS355N. The Arrius 1A1 is a modernized version certified in 2007 with a new high-pressure turbine for improved "One Engine Inoperative" (OEI) performance, powering the AS355NP.

Arrius 1M is amilitary-dedicated variant used on the AS555 Fennec, which is the militarized version of the AS355.

Arrius 1B: A variant historically used in experimental and early flight testing, such as on the Eurocopter BO 108 (the precursor to the EC135) to evaluate early digital engine control units.