The EC155B is a development of the AS365N3. In fact, during its development it was referred to as the AS365N4. However, this may have been a ruse to disguise the fact that a major redesign of both the dynamic system and the fuselage was in work. The AS365N series passenger compartment has restricted headroom in the aft part of the cabin. The EC155B redesign addresses this by increasing the headroom in the aft part of the cabin as well as widening and lengthening it. The redesign also squared up the cabin and improved access to the pilot seats. The cabin can accommodate up to 12 passengers in addition to two pilots. Alternatively, the large cabin can accommodate up to four stretchers placed longitudinally in the cabin, or a six-seat corporate interior. This helicopter uses composites for a substantial portion of the fuselage.
As part of the redesign, the number of main rotor blades was increased from four to five and the rotor diameter was increased by over 2 feet when compared with the AS365N3. A more powerful Turbomeca engine was also installed. The EC155B dynamic system, like that of the AS365N3, incorporates composite rotor blades, a composite rotor head and a 10-blade Fenestron tail rotor using composites. The drivetrain for the EC155B uses two Turbomeca Arriel 2C1 engines and a five-bladed composite rotor head and blades. The EC155B is certificated to the standards of both FAR and JAR 29 and is approved for single-pilot IFR operations as well as Category A single-engine operations.
The EC155B was certificated in 1999 and deliveries started shortly after that.
