Helicopters - The French did it again - Safe single-engine cruise in a twin

Airbus Helicopters promises safe single-engine operations with Bluecopter demonstrator

By: DOMINIC PERRY

MUNICH

Source: Flightglobal.com

12:23 8 Jul 2015

Airbus Helicopters has unveiled a new demonstrator aircraft that brings together a basket of new and existing technologies aimed at drastically cutting fuel consumption, carbon dioxide emissions, and noise levels. For the first time, these include the possibility of safely operating a twin-engined helicopter in normal flight using just one engine.

In gestation since 2011, Bluecopter, as the manufacturer calls it, is targeted at cutting fuel burn by as much as 40-50%, says chief technology officer Jean-Brice Dumont.

Speaking at the public unveiling of the Bluecopter at an event at its Donauwörth, Germany site, Dumont said Airbus Helicopters had faced the choice over whether to develop a “brutally disruptive” rotorcraft –- for instance altering the position of the main rotor – or employing several incremental technology improvements, “techno-bricks”, in his words, to achieve the same goal.

Dominic Perry/Flightglobal

Using the original EC135 test airframe as a base, the company has chosen the latter course, adding so much new equipment “that there is not so much left from the original aircraft”.

Modifications include a next-generation shrouded Fenestron tail rotor which features optimised blades and stators, a T-tail to bring the horizontal stabiliser out of the path of the rotor wash improving stability and lift, an active rudder to reduce the power required for the Fenestron, a reshaped rear fuselage, aerodynamic skid covers, a bearingless main rotor featuring five curved Blue Edge-style blades – some 50cm (20in) longer than those in the regular EC135 – and a main rotor hub fairing.

The changes, notably the increase in rotor efficiency, have reduced the required power by around 15%, says Dumont, as well as increasing payload.

However, the most transformative technology is single engine operation (SEO), he says, which raises the potential fuel consumption saving to the 35-40% level.

At present, the system simply alerts the pilots that they are within certain parameters – a speed of about 120kt (222km/h) and altitude of between 1,640-5,000ft – to enable one engine to be safely shut down. Restart takes about 20-30s, says Marius Bebesel, programme manager research and innovation.

However, Dumont says the eventual goal is to automate the system, “to add intelligence” that allows the FADEC to control the shutdown or restart once “eco mode” is selected.

Airbus Helicopters

Airbus Helicopters has been working with engine supplier Pratt & Whitney Canada to implement the change to the FADEC software on the latter’s PW206 powerplants and hopes to trial a more automated system later this year, says Bebesel.

The enhancement could be applied to any twin-engined helicopter without the need for changes to dynamic components and additional certification work, says Dumont: “We don't see that as a risk.”

In addition, the engine manufacturer also worked with Airbus Helicopters to help reduce the engine and rotor RPM by 16% to reflect the improved rotor efficiency.

Dominic Perry/Flightglobal

Phase one of the flight-test campaign ran from April to October 2014, with a second effort kicking off in early 2015 that will terminate towards year-end.

So far it has accumulated 28 flight hours using the testbed, the majority during the initial period last year.

Although trialled on a light-twin rotorcraft, Airbus Helicopters says the technologies are largely platform agnostic and could be applied to any helicopter in its range, both those in production and in development.