AIRCRAFT ECONOMY FOR DESIGN TRADEOFFS

A. Van der Vclden
Synaps Inc., Atlanta. GA, USA

2.1 Abstract

Before the go-ahead is given on the further development of a new transport aircraft design a number of questions need to be answered The airframe manufacturer needs to know whether it can breakeven on its initial investment easily. The airline will only order this new product if it can expand its market, reduce its cost and increase its revenues. The traveller wants a low ticket price and high comfort The society as a whole wants this new technology to improve the econ­omy while safeguarding the environment.

Since all of these views arc in conflict we can only evaluate a new design by comparing it with existing transports, keeping in mind that the life of a new design can span a quarter of a century or more. The content of this section follows is loosely based on my report [ 38J “An Eco­nomic Model for Evaluating High-Speed Aircraft Designs” of 1989. This report has been updat­ed and reevaluated after my experiences at Airbus.

The present model has been developed to give realistic results to tradeoff engineering features of a design to improve aircraft economy. It is not intended to present an accurate picture of pricing policies of airframe manufacturers and airlines

The first sections of the paper deal with a market in equilibrium The economic view ­points of the manufacturer, airline and pussenger arc based on the commodity product jet travel is today. These equilibrium market conditions can also be used to make design trade offs for a supersonic transport but we would have to be very careful to infer more. The question of whether such a supersonic aircraft can be sold and at at which price is very much a different

issue. Daimler Benz Aerospace and other companies use very refined forecasting models to assess the marketability of a new aircraft and such models are highly proprietary In the last see – lion of the paper I will present a highly simplified qualitative overview of such a non equilib­rium market model

2.2 List of Principal Symbols

engine price operating cost airframe block hourly material cost airframe flight cycle material cost Maximum takeoff lift coefficient aircraft and paris deflator relative to 1994 engine and parts deflator relative to 1994 fuel deflator relative to 1994 labor deflator relative to 1994 engine labour hours per flight hour airframe flight cycle labour cost (h) airframe block hourly labour cost (h) insurance rate loudfactor maximum takeoff mass ikg) airframe mass (kg) block fuel (kg) engine mass (kg) number of engines depreciation period to 10 of value range (km) number of scats

AFM

ACM

Ljmaxjo

D

D < IK

D.

m

m

P R s

wing planform reference area maximum uninstalled sea level static thrust

time (h) block time (h)

maximum turbine entry temperature

yearly uuliiation aircraft speed Mock speed (km / h)

aircraft weight Greek Letters mean time between repairs

Subscripts

aircraft

airframe

block

engine

fuel

high subsonic

labour

takeoff