Over the past fifty years, the main driver for aircraft design was to improve aircraft operational efficiency, which led to converging to an almost universal configuration, which now dominates the commercial airplane market. Given that air traffic is forecast to more than double in the next twenty years and that both environmental and economical pressure will strongly increase, significant progress will need to be achieved in both improving the efficiency and minimising the environmental impact of aircraft. This may not no longer be achievable with today's configuration. Designing suitable Novel Aircraft Concepts will require developing capabilities in the complete range of aeronautical disciplines and technologies.
NACRE will address these issues, and will take full benefit of the preliminary activities initiated in Europe on Novel Aircraft Concepts in the frame of the FP5 projects ROSAS, VELA & NEFA.
The NACRE Integrated Project aimed at integrating and validating technologies that will enable new aircraft concepts to be assessed and potentially developed. As such, it did not concentrate on one specific aircraft concept, but aimed at developing solutions at a generic aircraft component level (cabin, wing, power plant system, fuselage), which will enable the results to be applicable for a range of new aircraft concepts.
For each of the major aircraft components, the multidisciplinary investigations explord the different associated aspects of aerodynamics, materials, structure, engines and systems with the goal of setting the standards in future aircraft design, thus ensuring improved quality and affordability, whilst meeting the tightening environmental constraints (emission and noise), with a vision of global efficiency of the air transport system.
As a result, a set of unconventional aircraft concept configurations was developed:
- Pro Green aircraft;
- Payload Driven Aircraft;
- Simple Flying Bus.
They featured advanced components or systems i.e., wings, empennage, power plant installation, fuselage and cabin. These major aircraft components will undergo specific multidisciplinary exercises in order to develop the associated innovative capabilities (aerodynamics, acoustics, structure and systems).
Integration at overall aircraft level was carried out in order to challenge the concepts' objectives.
In order to explore the most relevant capabilities and meet the widest range of challenges, the NACRE project proposed to identify a set of concepts tailored to address specific subsets of design drivers:
- the Pro Green (PG) aircraft concepts, paying major emphasis on the reduction of environmental impact of air travel;
- the Payload Driven Aircraft (PDA) concepts, aiming at optimised payload and appreciable quality of future aircraft for the end users;
- the Simple Flying Bus (SFB), which puts the biggest emphasis on low manufacturing costs and minimum cost of ownership.
Irrespective of what final future product configurations might look like, these concepts were to act as basic vectors, describing and stimulating the whole of future capability developments. More than the intrinsic value of the single concept, what is of importance is the consistent capability enhancement that they prepare.
The rationale is that each of these concepts allows the exploration of alternative routes for the major aircraft components (fuselage, wing, engine integration) that are better suited to their specific targets and which would have been rejected in a balanced approach. The associated envelope of innovative designs (fuselage, wing, engine integration) and associated technologies provides better answers to the full range of requirements, or expected ones. NACRE was therefore in essence a focused multi-disciplinary approach.
The NACRE consortium was composed of 35 partners from 13 countries (including Russia), providing an impressive spread of expertise throughout the EU. The permanent assessment of alternative concepts, to be performed within NACRE, will guarantee both that the best capabilities are available and that the spirit for engineering innovation is preserved and developed for further exploitation.
New Aircraft Concepts Research in NACRE are summarised below:
- The two Pro-Green concepts have enabled relevant work on Powered Tails and Advanced Wings aiming at high environmental performance (noise and CO2 emissions):
- Contrafan and Open Rotor propulsion systems were integrated with a noise-shielding empennage and assessed;
- Advanced Wings, both high aspect ratio low sweep wings and forward swept wings (with natural laminar flow), have contributed to achieving good fuel efficiency at aircraft level.
- The Flying Wing configuration work has progressed the understanding of these complex configurations and opened a new path for the promising over-body-engine configuration;
- Finally the IEP concept was fully developed into a demonstrator but not flight-tested yet;
The amount of further preparation and adaptation work will require setting up a new project with a formal customer base.
Key technical achievements:
- Multidisciplinary Design and Analysis Capabilities for Components:
- Open Rotor propulsion systems & integration
- Powered Tail innovative integrated design & analysis
- Natural Laminar Flow wing design & transition prediction
- Flying Wing configuration design and multidiscplinary assessment
- Experimental Validation & Testing Techniques:
- Rear-engine integration (Aerodynamics & Noise)
- High-Energy Absorption
- Flying Wing cabin evacuation
- Innovative Evaluation Platform development