System noise assessment of an aircraft with coanda flaps

An innovative aircraft design of the Collaborative Research Centre (SFB) 880 features a new active high-lift system. This high-lift system is comprised of a droop-nose leading edge device and a Coanda flap as the trailing edge device. It offers very high lift coefficients and thus the ability to operate at airports that have reduced runway lengths, such as regional airports. Consequently, the assessment of aircraft noise is of utmost importance. The overall system noise on the ground is predicted using a parametric aircraft noise prediction tool. Although a parametric noise source model for the Coanda flap does not exist, it is estimated with a conventional Fowler flap model to evaluate the qualitative noise reduction potentials. The new design is compared with a regular aircraft that is equipped with a conventional high-lift system. Both designs are tested on individually calculated continuous decent approaches. The results show that airframe noise of the new aircraft is decreased due to later flap deflection and reduced speed. The engine noise, however, is significantly increased, especially on the glide slope. Hence, it dominates the overall noise on the ground, eliminating the benefits of the airframe noise reduction in the proximity of the airport. It is shown that the noise reduction potentials can only be exploited if the approach trajectory is individually optimized for low-noise.Aircraft Noise and Climate Effect

Assessment of the Noise Immission along Approach and Departure Flightpaths for Different SFB880 Vehicle Concepts

The number of flight movements is further increasing in the future and some major airports are already at their capacity limit. Therefore, it becomes beneficial for short range aircraft to operate on regional airports as well. Short range aircraft with conventional high-lift systems, however, are not able to safely operate on the comparatively short runways of regional airports. Instead, new aircraft concepts are required that are equipped with an active high-lift system. Such an active high-lift system offers high lift coefficients and thus the ability for short take-off and landing. In order to ensure a sustainable growth in aviation, such new aircraft concepts also have to offer reduced fuel consumption and low noise on the ground. The Coordinated Research Center (SFB) 880 focuses on such an active high-lift system. This active high-lift system is comprised of a flexible leading edge device, referred to as Droop nose, and an internally blown flap at the trailing edge, referred to as Coanda flap. Within the SFB880, the active high-lift system is applied to several aircraft concepts. These aircraft concepts are equipped with different propulsion systems, that is, turbofan engines of different bypass ratio or a turbine-driven propeller engine. In this study, the noise prediction methodology for the noise assessment within the SFB880 is summarized and applied to the aircraft concepts. The assessment includes the noise at the three noise certification points as well as along a line of observers. The study also includes a preliminary uncertainty assessment in order to evaluate the reliability of the predicted noise on the ground. The results show that the SFB vehicles can provide significant noise reduction compared to a reference aircraft with a conventional high-lift system and turbofan engine. Most noise reduction can be achieved with the aircraft that is equipped with the ultra-high bypass ratio turbofan engine

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

This paper discusses characteristic multi-disciplinary issues related to quiet short take-off 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 e�cffient and flexible high lift. The research also addresses flight Dynamics of aircraft at takeoff and landing. 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