Ride Comfort Investigation of an Elastic Transport Aircraft with Gust Load Alleviation in Preliminary Aircraft Design

Abstract

New fuel-efficient aircraft designs have high aspect ratio wings with lower structural mass. Consequently, they are more flexible, which is further amplified since aircraft manufacturers strive to reduce structural loads by including load alleviation functions which results in an additional reduction of the structural stiffness. This impacts the acting acceleration on passengers during turbulent flight and therefore the passenger discomfort and has to be considered in aircraft design. This is particularly interesting since the implemented load alleviation functions are designed to reduce loads, and not explicitly to reduce ride discomfort. For an efficient design process, it is important to assess such coupling effects in the early preliminary aircraft design phase. However, current methods are not accurate enough for this task. To address this issue, a loads analysis and structural optimization process, which is based on the MONA process (DLR), and the flight mechanical assessment tool MITRA (TUB) are linked. This tool chain allows the investigation of structural optimization impact on passenger discomfort criterion. This paper describes the tool chain and its application on a generic long range reference aircraft to investigate the effects of load alleviation functions coupled with Flight Control Laws on ride comfort. At the beginning, the process with iterative loads analysis featuring load alleviation functions and subsequent structural optimization is carried out to match the structure with the design loads. The resulting structural aircraft data is then exported to MITRA, which uses the resulting structural data to generate an elastic flight mechanical model and equips it with Flight Control Laws and Gust Load Alleviation functions. In the next step, MITRA integrates those elements in its flight simulation test environment. There, it conducts flight simulations to investigate the acceleration on passengers during flight in continuous turbulence with different flight conditions and flight control modes using passenger discomfort criterion.