Impact of spanwise non-uniform discrete gusts on civil aircraft loads

Abstract

The drive for increasing flight efficiency is resulting in wing designs that are of higher aspect ratios, lower in weight, increased wingspans and, consequently, require greater attention in the disciplines of aeroelastics and loads. This trend in aircraft design, along with past research experience with flexible aircraft, motivate a review of assumptions in gust models; especially, that of the gust maintaining a uniform spanwise profile. In this paper, the authors investigate the use of spanwise varying 1−cos gust models for loads prediction using a non-linear aeroelastic model of a conventional large transport aircraft. The comparison between a test case using conventional uni-dimensional approach and another, using multidimensional gusts, illustrates the impact of stepping away from traditional discrete tuned gust processes and adding a spanwise varying gust component. A methodology for processing and analysing the loads data arising due to the added dimension is also developed and both envelope and correlated loads are considered. Gust characteristics and resulting load factor are, respectively, considered for comparison between the two models, as both metrics define realistic gust encounters. In this case, it has been shown that spanwise variation of gust profiles leads to lower envelope loads if viewed in terms of conventional gust gradients. However, higher envelope loads are found if the maximum load factors are matched.

Identification of In-Flight Wingtip Folding Effects on the Roll Characteristics of a Flexible Aircraft

“…Aircraft position is used in both gravity and atmospheric models to complete the simulation environment. For a more detailed description of the framework, the reader is referred to the dedicated literature [16,17,[20][21][22][23]. The Matlab/Simulink based tool can also be used for handling qualities investigations, and was previously used to study realistic pilot models, effect of manual controls on flexible structures [24] and flight loads [25].…”

“…The aircraft selected for this investigation is the Cranfield University AX-1 model, which is more extensively described in past literature [16,17,20,21]. Additional geometric details of the aircraft are given in Appendix D. Figure 3 illustrates the beam-stick model used to model and compute aircraft structural deformations, aerodynamic loading distribution and overall flight dynamics, with structural node (in grey), aerodynamic station distribution (profiles shown in blue), control surface position (shown in red) and different wingtip sizes.…”

Verification of a low fidelity fast simulation framework through RANS simulations

“…The CA 2 LM framework is an aeroservoelastic simulation framework that couples structural dynamics and unsteady aerodynamics in the time domain to capture the aircraft dynamics such as structural loads. It can be used for real-time pilot-inthe-loop simulations and additional aspects such as investigating handling qualities, effect of manual controls, on flexible aircraft [29,30] along with maneuver and gust loads [8]. The framework was developed to model a large transport aircraft known as the AX-1, as shown in Fig.…”

“…2 and the reader is referred to Refs. [2,3,8,28,30,34] for a thorough discussion of this aeroservoelastic framework.…”

Comparison of Two Methods to Calculate External Loads at Flight in Continuous Turbulence

“…Such common software tools as NASTRAN (Rodden & Johnson, 1994) and ZAERO (ZONA Technology, 2017), are not suitable for detecting loads and reactions from non-uniform gusts (Karpel et al, 2005). Therefore, the study of two-dimensional discrete impulses has recently become popular (Yang et al, 2019;Lone & Dussart, 2019).…”