Airbus Helicopters unveiled the Bluecopter demonstrator on July 7 in Donauwörth, Germany. The modified EC135, which has been flying since April last year, incorporates a number of technologies intended to shrink a helicopter’s environmental footprint. Through changes in engine operation and airframe modifications, engineers hope to cut fuel burn by 35 to 40 percent compared with the current model and to take perceived noise levels 10 dB below ICAO standards.
Perhaps most radical is single-engine operations (SEO), under which one of the helicopter’s two engines is shut down for portions of the mission where the power of one engine can suffice. The capability recognizes that one highly loaded engine operates much more efficiently than two lightly loaded engines.
SEO can be activated only in a defined window inside the flight envelope: cruise speed should be 10 knots below the best-range speed and altitude should not exceed 5,000 feet. In addition, SEO requires a height of at least 1,600 foot agl to provide an altitude cushion for reacting to the unexpected. The system continuously monitors the flight conditions and helps the crew decide when to shut down and restart one of the engines.
Largely a software exercise in terms of equipage, SEO is still in early testing and the pilots simply shut down one engine when the system indicates the helicopter is in the right window. Eventually an “eco mode” will shut it down automatically, AIN understands. The system will also automatically command reactivation of the dormant engine in the event it detects an emergency such as failure of the operating engine.
The Bluecopter’s turboshafts are Pratt & Whitney Canada PW206B3s. The engine manufacturer, which collaborated with Airbus on SEO, describes the system as “intelligent engine power management.” The expected improvement in fuel burn is in the range of 22 to 27 percent.
A Turbomeca spokesman told AIN that his company is also considering “new power management modes” for twin-engine helicopters and that the work is well advanced.
Modifications to the airframe are expected to reduce fuel consumption by a further 13 percent. New engine air intakes, lateral as opposed to frontal, reduce so-called installation losses that deprive the engine of some intake airflow. The Bluecopter’s intakes are better than those on the latest version of the H135 and have restored 4 to 7 shp, said Marius Bebesel, Bluecopter program manager.
Blue Edge swept blade technology raises efficiency and cuts noise on the Bluecopter’s bearingless (rigid) main rotor. CTO Jean-Brice Dumont explained that the design engineers faced challenges in materials and in reducing rotor rpm by 16 percent. With its five blades (one more than usual) and greater diameter (three feet more), the Bluecopter’s main rotor is oversized for an H135 but should be regarded only as a technology “brick,” according to Airbus.
The program uses the H135 as a platform on which to develop technologies that can be transferred to any other model. “Bluecopter is platform agnostic,” Dumont emphasized. Some of the “bricks” are limited in size, though, such as the Fenestron tail rotor, thought to be unsuitable for helicopters larger than the H160.
As of July 7, the Bluecopter had flown 28 hours. Most of them were logged during the first test phase (April to October last year), which focused on the main rotor. The rotorcraft was then further modified with the SEO system, rotor hub fairing and optimized Fenestron for the second phase, which started recently. “The helicopter is very smooth,” chief test pilot Volker Bau said. Phase two will last until year-end, by which time all the technology bricks will be at technology readiness level six and fit for launch as products, Dumont predicts.
Several aerodynamic improvements are visible on the airframe. The main rotor hub has a new fairing, inspired by the one that helped the X3 compound helicopter unofficially break a speed record in 2013. The new fairing improves drag but inhibits access for maintainability, Dumont conceded. The aft body, where the rear door is located, sports a new shape to break vortices. Skid struts have been fitted with aerodynamic covers.
An active rudder “unloads” the Fenestron. The tail rotor will thus draw less power, especially in cruise. So far, the rudder’s position is set manually but Airbus Helicopters plans to morph it into an automated system. The active rudder is said to be a failsafe design, as it returns to neutral in the event of a problem.
Engineers have removed several stator vanes on the Fenestron, reducing their number to two for better efficiency. With the same goal, the blades feature a new, swept leading edge. To cut or even eliminate the tail rotor’s buzz noise, engineers have replaced the current-generation noise-attenuating shapes (cavities that act as Helmholtz resonators) with an acoustic liner. The change cuts noise by 50 percent, according to Bebesel. The T-shaped empennage moves the horizontal stabilizer out of the main rotor downwash, adding lift equivalent to 110 pounds. Finally, the external paint is water-based, further reducing the helicopter’s environmental footprint.
Dumont says the program is on target to validate a 35- to 40-percent cut in fuel burn: 13 percent attributable to the various aerodynamic, rotor and other improvements, and 22 to 27 percent to SEO. The baseline operating conditions for measuring the benefits are 4,500 feet, ISA+10, 138 knots and 5,837 pounds.
The project started in 2011. Airbus Helicopters self-funded “a lot” but also received financial support from Europe’s Clean Sky joint technology initiative and Germany’s LuFo-IV research program. Bluecopter technologies could enter service two to six years from now, depending on their complexity, Dumont said. The main rotor and the intelligent power management system are seen as “the trickiest ones.”
H135 Next in Line for Helionix
Airbus Helicopters is adapting its Helionix avionics suite for the H135 light twin, after the H145 (formerly known as the EC145T2) and the H175 medium twin. The H135’s cockpit, like the H145’s, will have three main displays, and the information will be displayed in the same way. Changes include the links to the fuel tanks, electric systems and so on, a design engineer explained.