Soapbox - Greener, Lighter Airframes
Rafael Palacios, Department of Aeronautics, Imperial College London
Airworthiness certification rules give an extraordinary degree of safety to the process of designing, building, and operating new aircraft. But they must be adapted in the coming decades if the aviation industry is to solve the conflicting requirements of an ever increasing demand with minimum environmental impact.
The recently published European Commission’s Vision for Aviation predicts a six-fold increase in total passenger numbers worldwide by 2050 while demanding a 75% reduction per passenger in CO2 (90% for NOx). We will likely need to redraw many of the rules of the game to meet those targets.
At the design level, the transition to airframes built with composite materials, wings with wingtip devices, and high bypass ratio engines is well under way. But only truly revolutionary solutions will allow us to fulfill the quest for ever lighter, more efficient aircraft.
Advanced programs in computational structural and fluid dynamics have reached a high level of maturity. When combined with state-of-the-art computing power they can be used as part of the design process from the conceptual stage onwards. But, while aircraft and engine manufacturers make significant weight savings and performance improvements by using these ‘virtual design environments’, the benefits are only incorporated in the latter stages of the design cycle, once the basic frame of the aircraft has been established.
These virtual designs must be introduced earlier so that non‑conventional configurations can be explored in detail from the outset of the creative process. It is easy to distinguish the exterior design of a 1960s car from one built in 2010, but the same cannot be said for commercial aircraft. Innovation from the outset would allow for aircraft design approaches built around active control strategies. Currently, airframe designs are built around passive rules, using design approaches not unlike those used by civil engineers to size bridges.
We also have a rather good understanding of load and flow control technologies, as well as embedded systems and actuators for performance optimization and structural health monitoring. Although they offer potential for a reduction in airframe weight and an increase in vehicle performance, aircraft are not yet sized with these technologies in mind. Their full adoption by aircraft manufacturers will require a fundamental change of mindset in design practices, which are still strongly sequential between mono-discipline teams, as well as the development of suitable skills among the engineering workforce.
The results may go beyond the existing accepted limits in the aircraft certification process, which may need a paradigm shift, provided safety is not compromised. Without doubt, they will affect the aircraft operation. These are not easy tasks, and the challenge is considerable, but 2050 is not far compared with the life of new aircraft. We must take action now.
The Department of Aeronautics at Imperial College has initiated a Green Aviation forum that aims to stir the debate between researchers, manufacturers, certification authorities and operators to develop sustainable solutions to society’s demands of air travel.
For more information visit: www3.imperial.ac.uk/greenaviation