Aircraft and technology for low noise short take-off and landing

Abstract

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.

Flight Mechanical Challenges of STOL Aircraft Using Active High Lift

“…Therefore, the SFB 880 gathers all relevant research fields to efficient clusters. In other contributions to this conference overviews of the "aerodynamics", "aeroacoustics" and "flight dynamics" clusters will be presented as well [3][4][5]. A configuration for a turbo-propeller powered aircraft equipped with a micro-compressor blown flap system has been designed combining circulation control with deflected propeller slipstream effects, depicted in Figure 1 with the basic aircraft data given in Table 1.…”

Modification of Porous Aluminum by Cold Rolling for Low-Noise Trailing Edge Applications

“…Being in approach for landing, a major part of noise is generated by the circulation of air along the airframe. The trailing edge of the wing is one of the main acoustic sources at the airframe, which can be diminished by using open porous materials in the trailing edge [4][5][6]. Herr et al [6] used different porous materials in an acoustic wind tunnel experiment, to analyze the effects of porous materials as trailing edges.…”

“…It must be pointed out that due to cold rolling, porosity and pore size decrease and consequently specific flow resistivity increases. The specific flow resistivity has a major influence on the reduction of trailing edge noise [4][5][6]. It is a main goal to produce material with specific flow resistivity similar to PA 80-110 which was used by Herr et al [6].…”

Production and characterization of experimental low noise trailing edges made of cold rolled porous aluminum with special attention to the influence of cold rolling on the mechanical stability of the investigated materials

“…Porous materials soften the aforementioned discontinuity of the trailing edge. First tests in the acoustic wind tunnel (AWB) of the DLR in Braunschweig as well as simulations with different materials showed promising results, especially for a porous aluminum (PA) produced by a salt infiltration technique [1,9,12,13].…”