Designing successful commercial aircraft is a difficult business; the stakes are high and
the risks numerous. Researchers in the past have developed methods that assist the
designers in reducing these risks. In recent years such methods have benefited from
improvements in computer technology. The work described in this thesis extends these
methods to the design of commuter aircraft. These aircraft are more sensitive to
operational requirements than other types due in part to their high zero-fuel mass ratio. It
is essential that, for such aircraft, the best information possible is available to the
designers. The identification of the optimum aircraft configuration and mission
characteristics constitutes a vital part of this knowledge.
A review of literature, involving both modem computer-based and traditional search
methods, has shown continuing interest in aircraft project design methods from the
earliest times to the latest conference. The work presented in this thesis is seen to
compliment this interest in computer methods and to apply these techniques to the
relatively neglected area of commuter aircraft design.
A survey of commuter operation and aircraft types revealed the often conflicting
requirements and regulations which govern the design process in this area. Detailed
statistical analysis on a collection of commuter aircraft showed no consistent data
patterns, but did indicate the bouyant state of the market.
Earlier research work on the design of twin-engined turbo-prop aircraft had provided
some experience in the design of short-haul aircraft. The new work improves these
methods and applies them to larger and faster turbo-fan commuter aircraft. Since the
turbo-prop work, the optimiser developed at RAE (Farnborough) has been rewritten to
work more efficiently and allow larger problems to be tackled. This new optimiser s
linked to a new synthesis routine which simulates turbo-fan aircraft design. The
synthesis program was calibrated against industrial design calculations and shown to
give acceptably accuracte predictions. The resulting design program is fully described
and computer listings are presented.
To illustrate the use of the optimisation methods in the devleopment of a new aircraft, a
series of industrially related design studies is presented. These studies range from the
selection of the initial baseline configuration, through various parameters sensitivity
investigations, to the evaluation of aircraft and engine stretch options.
To demonstrate more general types of design study, a series of optimisations in which
the engine size is variable was conducted. This provides the designer with a knowledge
of the absolute (optimum) design surface and allows him to judge the 'penalties' inherent
in his chosen configuration.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.