BY THOMAS WITHINGTON, Aviation Aftermarket Defense

The environmental spotlight shining on the carbon footprint generated by aircraft engine emissions seems to be directed at the world’s airlines. However, helicopter operators and engine and airframe manufacturers also are coming under increasing pressure from governments and environmental activists to minimize the impact of rotorcraft.

Helicopters, be they civilian or military, cause environmental pollution in two ways. First, the emissions from their engines contain carbon dioxide (COs), or more generally so-called greenhouse gases that can contribute to global warming. In evaluating the carbon footprint of a helicopter, consider the fact that a Bell 206 will use around 16 gallons of fuel to travel 58 miles, while a van may burn only 5 gallons to cover the same distance.

Second, the sound of a helicopter’s engines and its rotor blades slicing through the air produces substantial noise pollution. Helicopters can produce sound levels of up to 110 decibels, which is just slightly less than the noise produced by a large chainsaw.  The pressure for helicopters to operate in a more environmentally friendly manner is increasing, and that pressure is likely to grow in the near future, as the number of rotorcraft expected to enter service around the world appears set to increase.

In February, helicopter engine builder Honeywell stated that it expects between 4,700 and 5,200 new helicopters to be delivered in the 2012 to 2016 timeframe. This represents an anticipated increase of a minimum of 400 airframes as compared to the 4,300 new helicopters that Honeywell delivered between 2007 and 2011.

Engine builder Rolls-Royce also is bullish regarding the number of new helicopters that it expects to see delivered over the next decade. The company’s 10-year Helicopter Industry Market Forecast 2011-2020 predicts that an industry-wide total of 16,970 civilian and military turbine-powered rotorcraft could be delivered by the end of the decade.

What is driving this demand? Rolls-Royce says that emerging markets for new helicopters include Brazil, China, and India, as those areas experience increasing affluence. Meanwhile, demand also is being driven by helicopter operators’ recapitalizing of their legacy fleets. Per Rolls-Royce, an estimated 43 percent of the global fleet is over 25 years old. Moreover, the company predicts that attractive financing will encourage market sales, as customers are being offered increasingly favorable terms for the acquisition of new helicopters.

While this is good news for many in the industry, an enlarged global fleet of helicopters could have a detrimental effect on the environment as the level of gaseous emissions from helicopter engines increases and people on the ground experiences a rise in aircraft noise. Several initiatives are ongoing in Europe and, to a lesser extent, in North America to reduce the environmental footprint of helicopters.

GREEN ROTORCRAFT

In Europe, the Clean Sky initiative is being run as a public/private partnership involving the European Commission – the executive body of the European Union (EU), which proposes and upholds EU legislation – as well as a range of private companies in the aviation market. The initiative commenced in 2008, and it is expected to run until 2017.

The program is tasked with developing technologies that can be used in the production of new aircraft to reduce their environmental footprint.  Clean Sky comprises a number of Integrated Technology Demonstrator (ITD) teams, each of which are led by two companies that have supplied expertise and funding to the Clean Sky programs.

One such program is the Green Rotorcraft project. The mission of the Green Rotorcraft ITD team is to reduce helicopter powerplant carbon dioxide (CO2) emissions by between 25 and 40 percent and to reduce a helicopter’s noise by half. European helicopter builders Eurocopter and AgustaWestland are leading the team.  The ITD’s work is divided into several segments: One aspect of the project is researching ways in which helicopter rotor blades can be made more energy efficient in order to help the aircraft burn less fuel.

The goal is to obtain a 3 percent reduction in fuel burn when the helicopter is cruising and an 8 percent fuel reduction when the aircraft is hovering.  Allied to this research, the project also is examining how the physical shape of the rotor blades could be changed while in flight so as to reduce the noise generated by the main rotor by 6 decibels.  While such research may seem the most obvious in terms of helicopter redesign, the Green Rotorcraft ITD is taking a broader approach.

The project leaders recognize that there probably is not one single technology that can do enough to reduce a helicopter’s environmental impact. Instead, a number of technologies will need to be developed, which working together can achieve these aims.  Therefore, the Green Rotorcraft program also is looking at the design of helicopter airframes in an attempt to improve their aerodynamic performance, as reducing drag will reduce fuel burn.

The goal of the work being performed in this part of the project is to design an airframe that could reduce a helicopter’s fuel burn by up to 5 percent. One mechanism that may help to improve aerodynamics is the utilization of active and passive vortex generators to delay vortex separation and reduce drag on the rear section of the fuselage.  Other efforts to improve fuel efficiency include reducing the electrical consumption of a helicopter so as to lower the power generation demands on its engines.

For instance, the ITD team is investigating ways in which heat from a helicopter’s nozzles can be siphoned off and used for aircraft heating.  The team also is considering the feasibility of using a diesel powerplant, and it is working on such a prototype, which may become available in 2014.

TRANSPARENCY AND BLUE EDGE

Along with Eurocopter’s involvement in the Green Rotorcraft ITD, Eurocopter is making additional efforts to enhance the environmental credentials of its current product line. It recently revealed that it plans to publish emission and sound level figures for its existing range of helicopters.

The company also has stated that it seeks to establish a globally standardized system for measuring helicopter performance in terms of greenhouse gas emissions and helicopter acoustic signatures. The proposed system includes the adoption by helicopter manufacturers of a color-coded scale, ranked from A+ to D, rating a helicopter’s noise and greenhouse gas emission levels, which could be included in the manufacturers’ promotional literature.

In an official statement released by Eurocopter on February 15, its President and Chief Executive Officer Lutz Bertling said that he believes, “Transparent environmental communications by the rotary-wing aircraft industry is essential to building a relationship of trust with the public.” He added that such open communication also “encourages industry stakeholders . . . to invest heavily in the protection of the environment.”

Away from its work on the Clean Sky initiative, Eurocopter is developing quieter rotor blade technology as part of its Blue Edge rotor blade design program. The Blue Edge rotor blades are shaped to minimize the blade vortex interaction caused by a helicopter’s rotors, which creates much of the noise generated by its rotor blades.

The Blue Edge blades contain piezoelectrical motors that vibrate the blade edges up to 40 times a second, thus reducing blade vortex interaction and therefore noise. Test flights of the Blue Edge blades mounted on a Eurocopter EC155 helicopter have demonstrated a sound reduction of 3 to 4 decibels.

Eurocopter also is a member of the Helicopter Association International’s (HAI) Acoustic and Environmental Committee. This committee is tasked with monitoring developments regarding helicopter acoustic standards and advising the HAI on matters relating to government and local rotorcraft acoustic standards and regulations.

NORTH AMERICAN EFFORTS

Although ongoing research and development regarding the reduction of the environmental impact of rotary aviation is arguably most visible in Europe, similar efforts are moving forward in North America, according to the HAI’s Acoustic and Environmental Committee.  Moreover, on March 28, Sikorsky Innovations became the first rotorcraft member of the Lindbergh Foundation Aviation Green Alliance.

Sikorsky Innovations is part of the Sikorsky Aircraft Corporation, and it includes Sikorsky employees working along with colleagues from other companies to develop technological solutions to improve helicopter design and operation. (The broader Aviation Green Alliance works to fund research and efforts for the development of new technologies aimed at reducing the environmental impact of aircraft, while also “developing suggested best practices for achieving measurable aviation-related conservation and sustainability initiatives,” according to the organization’s Web site.)

Sikorsky is making other significant moves in a green direction. According to Bob Araujo, Manager of Sustainable Development and Environmental, Health and Safety Programs, “It takes a holistic environmental approach in terms of the technology we incorporate in an aircraft.” Accordingly, current Sikorsky helicopter designs have environmental mitigation built into them from the start. Jonathan Hartman, Program Manager for Sikorsky’s Firefly (a concept helicopter based on the S-300C), describes this innovative machine.

Outfitted with an electric motor and lithium iron battery pack, it claims zero carbon emissions. This aircraft currently is undergoing bench testing and is expected to take to the skies by the end of the year. In the meantime, Hartman says, the noise levels of the company’s S-76D utility machine have been reduced by up to 4 decibels using new gearbox technology, along with a quieter tail rotor.

In the case of helicopters, engine manufacturers clearly play a central role in reducing their environmental impact.  For example, Pratt & Whitney is promoting its PW210 1,000 shaft horsepower engine as a helicopter propulsion system offering such advantages as reduced fuel burn and improved power-to-weight ratios over other engines on the market. This supports the view that today’s dual priorities in helicopter – or any aircraft – engine design are improving an operator’s bottom line while reducing environmental impact.

GROWTH AHEAD

While helicopter environmental initiatives are not yet as extensive in North America as current efforts in Europe, the movement clearly is underway.  Although the helicopter engine builders’ predictions say that Asia and Europe will both be key growth areas in terms of new helicopter deliveries in the coming decade, they also expect North America to witness growth in helicopter demand.

And the more rotorcraft entering service, the more pressure is likely to emanate from governments, local communities, environmental activists, and ultimately operators regarding the green credentials of helicopters in service. With this in mind, helicopter engine and airframe providers worldwide are expected to continue to deepen their research and development efforts. The undoubted effect will be that of reducing the environmental footprint of rotorcraft even as the market grows in years to come.