996. “”The Hub of the Wheel”” – A Project Designer’s View of Weight

Paper

Abstract

This paper considers weight as the hub of the aircraft design ‘wheel’. The complex inter-relationships between weight and the other parameters influencing aircraft design are illustrated by pinpointing examples taken from the wide spectrum of Civil Aviation.
On short haul aircraft, changes in empty weight have a significant effect on aircraft performance. As range increases, drag and fuel consumption have an increasing influence and fuel weight becomes a major criterion.
Increasing emphasis on reduction of the noise nuisance to the community is discussed in relation to effects on aircraft weight, performance and economics. The introduction of wide bodied airliners with high B.P.R. engines led to aircraft which were both quieter and more economic. New techniques will be required if this downward trend of cost is to be maintained, whilst meeting the more stringent ‘noise-worthiness’ requirements forecast for the future.
Future developments in the fields of aerodynamics, systems, structures and materials can provide tools to assist the airframe designer in his continuing battle against weight.
Advanced aerodynamic wing design could be applied to reduce operating costs of subsonic airliners or to enable them to fly further out of shorter fields.
In the longer term, multiplex artificial stability systems may be developed for use in Control Configured Vehicles to provide a proportion of the aircraft stability. Acceptance of this technique in Civil Aviation is only likely after extensive proving flying in the military field.
Fuselage weight can be saved by integrating the functions of structure and soundproofing. Composite materials provide potential for weight saving on a wider scale. Although expensive during the introductory period, reducing material costs due to increased usage could lead to lower operating costs in the 1980’s. Vertical take-off aircraft highlight the necessity for minimizing weight and scope for the application of new materials in both the airframe and the engine is greatly increased.
The special relationships between static lift and weight are explored awl a suggestion is made for a vehicle combining the use of static and powered/dynamic lift.
Weight is a common denominator linking all aircraft design activities. Airworthiness, environmental and economic factors enforce a limitation on the realization of lower weights and place constraints on aircraft development. The aim of this paper is to provide pointers to the future which can ease these constraints and yet meet the ever present needs to improve safety and reduce costs.