Simulation of a dynamic system is known to be sensitive to various factors and one of
them could be the precision of model parameters. While the sensitivity of flight dynamic
simulation to small changes in aerodynamic coefficients is typically not studied, the simulation
of aircraft required to operate in nonlinear flight regimes usually at high angles of
attack can be very sensitive to such small differences. Determining the significance and
impact of the differences in aerodynamic characteristics is critical for understanding the
flight dynamics and designing suitable flight control laws. This thesis uses this concept
to study the effect of the differences in aerodynamic data for different aerodynamic models
provided for a same aircraft which is F-18 HARV combat aircraft. The aircraft was
used as a prototype for the high angles of attack technology program. However modeling
an aircraft at high angles of attack requires an extensive aerodynamic data which are
usually di cult to access. All aerodynamic models were collected from open literature
and implemented within a nonlinear six degree of freedom aircraft model. Inspection of
aerodynamic data set for these models has shown mismatches for certain aerodynamic
derivatives, especially at higher angles of attack where nonlinear dynamics are known to
exist. Nonlinear simulations are used to analyse three different types of flight dynamic
models that use look-up-tables, arc-tangent formulation and polynomial functions to represent
aerodynamic data that are suitable for high angles of attack application. To achieve
this, a nonlinear six degree of freedom Simulink model was developed to accommodate
these aerodynamic models separately. The trim conditions were obtained for different
combinations of angles of attack and airspeed and the models were linearized in each
case. Properties of the resulting state matrices such as eigenvalues and eigenvectors were
studied to determine the dynamic behaviour of the aircraft at various flight conditions.
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/9722 |
| Date | 01 1900 |
| Creators | Mohmad Rouyan, Nurhana |
| Contributors | Cooke, A. K., Whidborne, James F. |
| Publisher | Cranfield University |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Doctoral, MPhil |
| Rights | © Cranfield University, 2016. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. |
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