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.