For large transport aircraft, ditching analysis is requested by EASA. The respective requirements are primarily devoted to a minimisation of risks for immediate injuries and the provision of fair chances for an evacuation. A significant part of average air travel is over water and historically a planned or unplanned water-landing event occurs grossly speaking every 5 years.
The objectives of the SMAES project are "Aircraft Safety" and "Aircraft Development Cost". The primary outcome of the project will be advanced methodologies and simulation tools to support aircraft development from pre-project phase to certification. These will enhance future innovation in aircraft design through ensuring that innovative designs are compliant with safety requirements.
The key developments addressed in the work programme are:
- Improved models for the calculation of ditching loads including both analytical and detailed fluid dynamics models. Inclusion of the effects of the complex flow physics in ditching is critical to prediction of ditching loads;
- Reliable and predictive aircraft models for structural behaviour under dynamic fluid loads;
- Demonstration of the methods on representative future aircraft design concepts.
The consortium brings together aircraft manufacturers, analysis software developers, research organisations and universities. The consortium partners form a strong team covering the required expertise in aircraft design, numerical methods and simulation, ditching analysis and supporting experimental methods to achieve the project objectives.
New tools to ensure aircraft stays afloat during ditching
EU-funded researchers developed a set of simulation tools that should permit cost-effective design of aircraft able to protect passengers in emergency situations such as ditching. The team addressed problems of passenger survival during all phases of a water landing: from the moment of approaching water up to the actual floating.
The current drive towards greener, safer and lower-cost aircraft requires manufacturers to come up with innovative design solutions and new structural concepts. Empirical methods traditionally used to design aircraft with respect to emergency situations are becoming obsolete. New methodologies and predictive numerical tools are necessary to mitigate safety and economical risks.
Within the project http://www.smaes.eu/ (SMAES) (Smart aircraft in emergency situations), researchers developed advanced simulation tools for use at different stages of the design and certification processes. Through optimising the ditching response, these newly developed tools should reduce design and test costs, increasing innovation to create safer, lighter and less expensive structures.
The ditching process can be categorised into four phases: approach, impact, landing and floatation. Ditching generates high hydrodynamic loads on the structure. Because of the high forward velocity, effects such as cavitation and ventilation influence hydrodynamic loads.
Amongst project achievements was the development of improved analytical and numerical models for predicting fluid loads and local pressures acting on aircraft during ditching. Researchers produced complex fluid models that can represent important physical phenomena such as air cushioning, ventilation, cavitation and suction force.
Another part of the work focused on the successful development of reliable models predicting an aircraft's structural behaviour and rupture under dynamic fluid loads. The deformable structural models were then coupled with the improved fluid models. The outcomes of this task were validated methodologies for performing fluid-structure coupled with aircraft ditching simulations.
The SMAES team established a new experimental high-speed water impact facility that can support future research and development in water impact response. An extensive set of test data was produced, covering high-speed water impact and the response of composite structures.
Apart from upgrading safety, SMAES is expected to contribute to the competitiveness and primacy of the European aeronautics industry thanks to an array of novel tools for aircraft design. Finally, improved understanding of the complex physical phenomena that occur during aircraft ditching will be useful in other structure-fluid applications such as landing rotorcraft on water and high-speed planning.