| Summary: | Today's high competitiveness in the airline industry urges for the development of even
more efficient transport aircraft. In many cases lower operating costs are the key to survival.
Although the introduction of emerging advanced technologies has shown improvements both
in safety levels and performance, with the associated reductions in costs, the search for more
economical aircraft must also take into consideration changes in current design practice. The
study of novel configurations is a contribution to this view.
In this research project, advantage was taken from multidisciplinary synergism to
design and optimise conventional and three-surface configuration commercial aircraft, to
satisfy the same mission and operational requirements. An integrated conceptual design
synthesis approach was employed where typical aeronautical disciplines, as well their complex
inter-relations, were taken intoaccount. All these considerations, together with both cruise and
field performance, and static stability and control requirements, resulted in different baseline
configurations of the two concepts, although sharing the same fuselage and the same
technology standard, but with different Maximum Take-off Weights (MTOW), lifting surfaces,
turbo-fan engine sizes, and economics. After coupling the design synthesis program to a
gradient based numerical minimization routine, optimisation of these designs was performed
for minimum Direct Operating Costs (DOC) and minimum MTOW, and their performance
and economics were compared on an equal basis. Trade-off studies were conducted on all
aircraft for 1000 through 3000 NM design mission ranges while keeping the same fuselage
size, lifting surface planform shapes and same static longitudinal stability margin (inherently
stable designs), as obtained for the respective datum designs (Range = 1250 NM).
Thus, using the same comprehensive design tool, built on the same primary
assumptions, and using the same analytical methods and principles which include many real
life considerations, a systematic and conýistent study of both design concepts was conducted.
The potential merits of a realistic three-surface transport design were clearly established, when
comparison was made with an equivalent mission conventional twin turbo-fan airliner. Within
the usual limitations of any initial conceptual design study, it appears that the concept of the
three-lifting surface transport can effectively improve in terms of performance and direct
operating costs, when compared to conventional aircraft designed for the same operational
environment and mission profiles, and may show a promising future.
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