A Natural Laminar Flow (NLF) aerofoil is considered to be one of the key technologies to reduce drag and improve the performance of an aircraft; it is also identified as a potential key technology for the next generation of aircraft. The ImpNLFFD project was a critical enabler that will, through mature design concept and stress justification, facilitate the manufacture of the starboard Upper Cover and Metallic Leading Edge of an A340-300 test aircraft and validate that the required level of aerodynamic surface quality can achieve Natural Laminar Flow.
The ImpNLFFD project objectives surround the finalisation and maturity of engineering data to enable subsequent manufacture of an advanced composite starboard Upper Cover and Metallic Leading Edge for installation on the flight test aircraft wing. To support this objective a number of work packages were identified that progress the current status of engineering through to delivery of hardware, concession support, permit to fly, and support operations during the final wing assembly and flight test campaign.
GKN Aerospace has delivered the critical leading edge assemblies and upper covers that form part of the NLF wing section on the starboard wing of the Airbus A340 flight test aircraft. These structures offer NLF levels of performance through the adoption, by GKN Aerospace, of a totally new design approach and the application of novel manufacturing technologies that deliver the ultra-high tolerances and exceptional surface finish required. The ImpNLFFD programme allowed GKN to progress innovative technologies, concepts and capabilities with the potential to bring about a step change in aircraft fuel consumption.
The key challenge with designing and manufacturing an NLF wing, with the many aerodynamic benefits that it promises, stems from the need to tightly control the wing surface. It was vital to eliminate features such as steps, gaps, surface roughness and waviness or fastener heads as these all lead to more traditional ‘turbulent flow’ performance levels. The GKN Aerospace team had created these integrated, co-cured composite upper covers and very high tolerance leading edge surfaces using the same structured design and development process applied in commercial aircraft programs. As a result, GKN’s first part was of very high quality and had been delivered for the flight test program.