EBACE Convention News

Helo research targets engine, airframe mods

 - April 28, 2010, 7:36 AM

Financial results for 2009 showed that AgustaWestland (Booth No. 7020) is spending more on research and development than its rival Eurocopter (Booth No. 7010). The latter gives a high profile to its R&D efforts, while the former has consistently been much quieter. Nonetheless, Europe’s leading helicopter manufacturers have joined forces for Clean Sky, a major research project partly funded by the European Commission (EC).

According to 2009 figures reported by AgustaWestland parent company Finmeccanica, the Anglo-Italian helicopter manufacturer spent €328 million ($443 million) on R&D. Meanwhile, Eurocopter parent company EADS reportedly spent exactly half that: €164 million ($221 million) on R&D.

However, Eurocopter CEO Lutz Bertling said in January he expects that figure to increase by 20 percent this year to almost €200 million ($270 million). Part of that amount will bespent on the still-to-be-launched X4 program, a Dauphin replacement in the 9,000- to 11,000-pound category.

This new rotorcraft’s head-to-head competitor will be AgustaWestland’s XX9, a 9,000-pound-class twin. R&D spending of €650 million ($878 million) in the 2010-2012 time frame will be for the XX9, the BellAgusta BA609 tiltrotor and the military AW149. Total AgustaWestland R&D spending for this period is expected to be €750 million ($1 billion).

Clean Sky Project
The Clean Sky joint technology initiative, a ?1.6 billion ($2.2 billion) private-public partnership in European aeronautical research, is focused on innovative helicopter technology, including an electric taildrive, conversion of otherwise-wasted heat to electricity, as well as new diesel engines and rotor heads. All of these should contribute to the ambitious cuts in noise, as well as reductions in carbon dioxide (CO2) and nitrous oxide (NOx) emissions that European authorities are demanding.

Eurocopter and AgustaWestland are working together on the Green Rotorcraft project, which is one of Clean Sky’s six integrated technology demonstrators. This accounts for 10 percent of a seven-year budget total of ?160 million ($216 million) ending in 2015.

The EC has targeted a noise reduction of 10 EPNdB and a 26-percent reduction in CO2 emissions by turbine-powered helicopters, with 10 percent of that reduction coming from engines alone. This means R&D teams are trying to cut specific fuel consumption (SFC) by 10 percent, and improvements in aerodynamics and aircraft systems should account for the remaining 16 percent. NOX emissions are set to be cut by 65 percent.

For a light helicopter powered by a diesel engine, the expected reduction in CO2 emissions is 40 percent, with the engine’s better SFC accounting for 30 percent. NOX emissions should be cut by 53 percent.

The objectives were determined by taking into account the wider Acare (advisory council for aerospace research in Europe) environmental goals for aviation and keeping in mind what can be realistically achieved within Clean Sky’s time and budget limits. In 2000, Acare set goals for 2020, including a 50-percent cut in CO2 emissions per passenger mile and an 80-percent reduction in NOx emissions. As for perceived noise, the envisaged reduction is to 50 percent of 2000 average levels.

Powering a light helicopter with a diesel engine seems to be more difficult than expected. The goal has already been part of the first call for Green Rotorcraft proposals but came to a dead-end because none of the R&D proposals complied with the permitted budget. However, the Green Rotorcraft consortium has accepted that the beefed-up specifications made it impossible for a bidder to keep within the budget, so it is to relaunch a call for R&D proposals later this year.

This project should eventually materialize into a demonstrator derived from an existing aircraft. The engine maker that the Clean Sky partners select must already have some experience in general aviation and diesel technology, but not necessarily in helicopters. The main challenge is controlling weight.

In addition, the Green Rotorcraft consortium is launching a wide-ranging study on diesel engine integration. One aspect of this is to focus on the entire helicopter architecture, rather than just engine performance.

The company selected to do the R&D work will have to analyze the loads that the engine generates as well as methods for reducing vibration in engine installation. It also will have to perform a thermodynamic analysis of the engine to understand how to cool the engine and the engine bay.

In aircraft systems, the firm entrusted with the diesel project will be expected to optimize electrical, oil and fuel systems for the new powerplant. A Fadec control system is also part of the development.

Further major changes involve the electric taildrive. The plan is to replace the mechanical transmission shaft with an electrical motor, which would allow the tailrotor’s rotation speed to vary across a wide range and would be independent from the main rotor.

The concept is expected to cut both noise and a lower fuel burn. But again the challenge is to achieve the new design without creating weight penalties, and the Green Rotorcraft consortium is calling for a full-size ground demonstrator.

At the same time, finding some use for wasted heat also may improve efficiency. The consortium hopes to gain 1 to 10 kilowatts (1.35 to 13.5 horsepower) and it has two approaches in mind. One is the Peltier-Seebeck thermoelectric effect, through which different metals or semiconductors areconnected and the connections transform differences of temperatures into electrical current. This reversible thermoelectric effect is already implemented in portable refrigerators, for example. One benefit is that there are no moving parts; however, the efficiency of the process still needs to be increased.

The second approach is to use a conventional thermal machine with a fluid loop and a generator. The challenge is to make a robust, simple, light device that can yield higher power. Its heat source would be in the engine bay or the oil system. Temperature differences there are relatively low–100- to 200-degrees C–so the machine could use a Sterling thermodynamic cycle.

The consortium is targeting drag reduction as a result of fuselage and rotor-head improvements. One aspect of this R&D effort concentrates on a light helicopter with a blunt aft-body region and landing skids; perhaps a rotorcraft that looks like a Eurocopter EC135 or EC145.

Drag Reduction
Rotor-head drag usually accounts for 20 to 50 percent of the total drag. A rotor head normally has no fairing and is composed of mechanical parts that rotate and interfere, acting like an airbrake and causing relatively more drag on smaller aircraft.

The company selected to do this work will use a wind tunnel to test new shapes supplied by the Green Rotorcraft consortium. It will have to build a model no longer than two meters (just over six feet), with a simplified fuselage. The model should be modular so that the mast fairing, the landing skids, the rotor hub and hub cap can be replaced easily.

The rotor hub must be realistic in terms of shape and adjustable in both collective and cyclic pitch, but it does not have to be controlled in real time. There also is a requirement to keep the hub fixed or have it rotate. Moreover, it should be possible to tilt the rotor mast about its nominal position both forward and backward by five degrees.

In addition to the basic configuration, the consortium will provide two sets of landing skids, two rotor heads and one or two mast fairings. It also reserves the option to provide spoilers, strakes and vortex generators so their impact on airflow characteristics around the aft body can be studied.

Further R&D work on tiltrotors will focus on drag reduction. The areas of interest are the fuselage/wing junction, the nose, the landing gear sponsons and the empennage.

The selected applicant for this slice of the Green Rotorcraft R&D pie will have to use computational fluid dynamics (CFD) to optimize these areas. It will have to take into account possible impact on lift and moments. Such negative impact would have to be avoided or kept to a minimum. Bidding companies are also being asked to create an “optimal design procedure” that could be used in an actual program.

The Green Rotorcraft project also wants to limit efficiency losses from engine installation and so includes a topic called “contribution to the optimization of a heavy engine installation.” Research engineers are going to work on the shape of the air intake and the inlet particle separator. They will endeavor to minimize pressure loss and distortion, as well as workon hot gas ingestion and air intake de-icing.