This paper discusses characteristic multidisciplinary issues related to quiet short takeoff and landing for civil transport aircraft with a typical short to medium range mission. The work reported here is focussing on the noise aspects and is embedded in the collaborative research centre CRC880 in Braunschweig, Germany. This long term aircraft research initiative focusses on a new transport aircraft segment for operation on airports with shorter runway length in commercial air transport. This calls for a community-friendly aircraft designed for operations much closer to the home of its passengers than today. This scenario sets challenging, seemingly contradictory aircraft technology requirements, namely those for extreme lift augmentation at low noise. The Research Centre CRC880 has therefore devised a range of technology projects that aim at significant noise reductions and at the generation of efficient and flexible high lift. The research also addresses flight dynamics of aircraft at takeoff and landing. Two companion papers, reporting about the research in the field of "Efficient high lift" 1 and "Flight dynamics" 2 complete the presentation of the CRC880. It is envisaged that in general significant noise reduction-compared to a reference turbofan driven aircraft of year 2000 technology-necessarily requires component noise reduction in combination with a low noise a/c concept. Results are presented from all the acoustics related projects of CRC880 which cover the aeroacoustic simulation of the source noise reduction by flow permeable materials, the characterization, development, manufacturing and operation of (porous) materials especially tailored to aeroacoustics, new UHBR turbofan arrangements for minimum exterior noise due to acoustic shielding as well as the prediction of jet noise vibration excitation of cabin noise by UHBR engines compared to conventional turbofans at cruise.

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Over-the-wing mounted (OWM) engines, together with their design challenges and their potential in terms of aerodynamic benefits and positive installation effects, are investigated with CFD methods. The analysed reference configuration is a new concept of a civil transport aircraft with short takeoff and landing characteristics featuring a circulation control supported high lift system. The concept is intended to provide extraordinary airfield performance while meeting low noise standards. The reference aircraft will be firstly analysed in its wing/body layout. Successively, engine and pylon will be integrated and analysed. A description of the pylon design and parametrization will be given. The results of the wing/body/engine/pylon configuration computations will be discussed in order to assess the transonic flow phenomena taking place on the upper wing when an engine is integrated over the wing in cruise condition and the overall impact of the pylon on the flowfield. Particular attention will be reserved to the flow on the pylon, in order to identify aerodynamic characterisitscs, possible flow separations and to evaluate a strategy for an optimization process. The pylon optimization procedure will be described in detail, together with the tools used and the parameters defining the pylon shape. The preliminary results and trends of the Design of Experiment will eventually be discussed in order to provide an outlook on complete optimization scenarios for such configurations.

A CFD-based assessment of the low speed high lift performance of an over-the-wing mounted engine installations for a short range airliner with STOL capabilities is presented in this paper. The configuration is representative for a 100 passenger aircraft and characterized by pylon mounted over-the-wing installed UHBR-engines. The high lift system features active segmented and highly deflected Coanda flaps and a specifically designed droop nose at the leading edge of the wing. The study is part of the Collaborative Research Center 880 that develops technologies and configurations with quite STOL capabilities. The layout of the high lift system is described, together with the numerical approach and results for the considered test case. The objective of the present study is to investigate a short chord active plain flap in landing configuration and assess the maximum lift capabilities against target values from preliminary design studies of the CRC 880. It is a first step towards a more comprehensive assessment of variants of the high lift system. With the typical lift generation for a circulation control supported high lift system, the analysis of the stall behavior reveals a favorable smooth lift breakdown starting at the inner wing. Yet, the maximum lift properties fall short of the target value, so that an enlarged chord flap will be considered as a next step to comply with the maximum lift requirements.