A European Collaborative NLF Nacelle Flight Demonstrator.

Aero engine nacelles are an attractive candidate for the application of the continuing worldwide efforts in laminar flow technology. This paper describes the initiation of a unique, European collaborative programme to flight test a Natural Laminar Flow (NLF) nacelle. The programme combines the experience of two major European aero-engine manufacturers (Rolls-Royce and MTU) with the expertise of an established, national fluid dynamics institute (DLR). In addition, nacelle manufacture is being undertaken by Hurel-Dubois (UK) Ltd and some aspects of instrumentation are to be provided by the University of Oxford. Since transition is strongly affected by the Reynolds Number, Mach Number and freestream flow environment, a flight test provides the best means of achieving realistic flow conditions to evaluate the NLF nacelle performance and hence validate the design methods used. Flight testing also ensures that realistic experience of the operationa1·aspects of the NLF nacelle is obtained; for example, surface contamination by foreign objects, engine noise and vibration.