An Airbrake Design Methodology for Steep Approaches

Abstract

By performing steeper approaches to an airport the noise impact on the ground can be significantly reduced. The steep approach capability of an aircraft (A/C) mainly depends on its high-lift system, while additional means can also help to increase this capability by generating drag. However, a desirable drag generation method should not degrade the high lift performance of the A/C. Otherwise, in order to achieve the same amount of lift force as before, the approach speed would have to be Increased. This would In turn increase the noise generation and the landing distance required. Therefore, fuselage airbrakes can beneficially assist the existing high lift system since they are located away from the wing and do not disrupt the lift. In the course of this study, aimed to enable steep approach capable A/C, a specific type of fuselage airbrakes, namely ”Dorsal Airbrakes”, were designed. Being mounted over the wing region, dorsal airbrakes utilise the accelerated flow field around the airframe and generate a high amount of drag. Neither the lift nor the pitch-moment are influenced considerably through deployment of the dorsal airbrakes. This paper presents a methodology and principles that underlie the current aerodynamic design of dorsal airbrakes and provides a summary of the results from wind tunnel (W/T) tests conducted at the German-Dutch wind tunnels (DNW) on an experimental short range A/C. The discussion of the W/T tests excludes the corresponding acoustic analysis, which is documented in [5] and [6].