Airbus Helicopters is to further upgrade the H135 light twin with the addition of its Helionix avoinics suite - which includes a glass cockpit and four-axis autopilot - and has signed up Norwegian emergency medical services operator Norsk Luftambulanse (NLF) as launch customer.

Delivery of the first of three examples equipped with the enhanced avionics ­- and which also gain a modification to the aft cabin roof - to Drobak-based NLF will take place in 2017, says the manufacturer.

Initial flight tests of the upgraded helicopter have already begun at its Donauworth, Germany facility, says programme head Axel Humpert, with the modified rotorcraft currently being equipped with the four-axis autopilot.

Certification is targeted for the end of 2016, with deliveries starting the following year.

The avionics upgrade brings the H135 in line with other members of the Airbus Helicopters range which are already fitted with Helionix including the H145, H175 and developmental H160.

Production of rotorcraft to the previous standard will continue into 2017 - or even 2018 if there is sufficient demand - says Humpert to "allow customers fleet commonality" but eventually Helionix will be the only option.

A previous upgrade to the type, raising it to the P3/T3 standard, focused on the helicopter's respective Pratt & Whitney Canada and Turbomeca engines. However, earlier T2+/P2+ models are still being produced, although these will be phased out in a similar 2018 timeframe, says Humpert.

Announcing the upgrade, Dominique Maudet, executive vice-president global business and services at Airbus Helicopters, said it would give the H135 "even more performance" for EMS missions.

Lars Kobberstad, chief executive of NLF, says the enhancement "will be a benefit for us and, last but not least, for our customers", through improved safety and capability.

NLF operates a 16-strong fleet of Airbus Helicopters types.