The study of the motion of manoeuvring aircraft has traditionally considered the aircraft
to be rigid. This simplifying assumption has been shown to give quite accurate results for
the flight dynamics of many aircraft types. As modern transport aircraft have developed
however, there has been a marked increase in the size and weight of these aircraft. This
trend is likely to continue with the development of future blended-wing-body and supersonic
transport aircraft. This increase in size and weight has brought about a unique set
of aeroelastic and handling quality issues.
The aerodynamic forces and moments acting on an aeroplane have traditionally been
represented using the aerodynamic derivative approach. It has been shown that this quasisteady
aerodynamic model inadequately predicts the aircraft’s stability characteristics,
and that the inclusion of unsteady aerodynamics “greatly improves the fidelity” of aircraft
models.
This thesis thus presents a novel numerical simulation of an aeroelastic aeroplane for
real-time analysis. The model is built around the standard six degree-of-freedom equations
of motion for a rigid aeroplane using the mean-axes system, and includes unsteady
aerodynamics and structural dynamics. This is suitable for pilot-in-the-loop simulation,
handling qualities and flight loads analysis, and control law development. The dynamics
of the structure are modelled as a set of normal modes, and the equations of motion are
realised in state-space form. The unsteady aerodynamic forces acting on the aeroplane
are described by an indicial state-space model, including unsteady tailplane downwash
and compressibility effects. An implementation of the model is presented in the MATLAB/
Simulink environment.
The interaction between the flight control system, the aeroelastic system and the rigidbody
motion of the aeroplane can result in degraded handling qualities, excessive actuator
control, and fatigue problems. The introduction of load alleviation systems for the management
of loads due to manoeuvres and gusts is also likely to result in the handling
qualities of the aeroplane being degraded.
This thesis presents a number of studies into the impact of structural dynamics, unsteady
aerodynamics, and load alleviation on the handling qualities of a flexible civil transport
aeroplane. The handling qualities of the aeroplane are assessed against a number of
different handling qualities criteria and flying specifications, including the Neal-Smith,
Bandwidth, and CAP criterion. It is shown that aeroelastic effects alter the longitudinal
and lateral-directional characteristics of the aeroplane, resulting in degraded handling
qualities. Manoeuvre and gust load alleviation are similarly found to degrade handling
qualities, while active mode control is shown to offer the possibility of improved handling
qualities.
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/7705 |
| Date | 03 1900 |
| Creators | Andrews, Stuart P. |
| Contributors | Cooke, A. K. |
| Publisher | Cranfield University |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Doctoral, PhD |
| Rights | © Cranfield University 2011. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. |
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