The main emphasis at the start of the ALFA project has been on converging and interpreting the stringent Natural Laminar Flow (NLF) requirements in relation to typical HTP structures. The driving NLF requirements are related to superior surface quality in terms of steps, gaps, waviness, profile, roughness etc. whilst still being competitive in weight, production cost/time, maintainability & reparability. During a close collaboration with the aircraft integrator, several conceptual design solutions were generated with high potential to comply with the NLF requirements whilst remaining competitive to all other HTP characteristics.
This has accumulated in a trade-off phase were the design solutions were evaluated in terms of NLF feasibility and cost, weight and maintainability aspects. The outcome of the trade-off phase was a selection of the technologies to be included on the Demonstrator.
The main features of the technologies focussed on were:
1) Optimized assembly processes to minimize the tolerances.
2) Two innovative manufacturing technologies for the leading edge, based on RTM technology (single sided tool) and autoclave technology, with different, promising multi-criteria evaluations, while both technologies have the potential to achieve the laminar criteria.
3) Automated masking operation for fastener heads.
A detailed Demonstrator lay-out has been generated and a detailed design phase has been initiated to further converge towards part-release. In parallel, mono-tool and assembly tool conceptual design has been started.