EXPERIMENTAL RESEARCH OF THE CONFIGURATION OF WING－TIP DRAG REDUCTION FOR LIGHT AIRCRAFT

hree kinds of devices of drag reduction are presented swept wingtip,stage by stage swept wingtip and downbend wingtip. The effects of changing geometryparameters of the swept wingtip on the drag reducing are also presented. Wind-tunnelexperiment results indicate that a properly designed swept wingtip results in an incre-ment in induced efficiency of 4%～ 7% and that swept wingtip can increase longitudinalstatic-stability. Water-tunnel experiment results indicate that the reason for drag re-ducing of swept wingtip is that when the angle of attack is not zero, the strong end vor-tex of the wing is weakened by the combined effect of the leading edge and trailing edgevortices of the swept wingtip.

THE CANARD-WING INTERFERENCE AND STALL SAFETY OF LIGHT CANARD AIRCRAFT

In this article, the interference between canard and wing is discussed on the basis of wind-tunnel test, with a brief review of the development of aerodynamic configurations of AD-100 / 200 (two light canard aircraft designed by NAI) .The safety against stall of a canard is also discussed based upon flight test.The rule 'canard stall first'is introduced as an effective measure to improve safety against stall. It has been pointed out that the rule may threaten the flight safety at low-altitude. Finally,what a designer can do to remove the threat is presented.

Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA

In this study,a process for establishing design requirements and selecting alternative configurations for the conceptual phase of aircraft design has been proposed.The proposed process uses system-engineering-based requirement-analysis techniques such as objective tree,analytic hierarchy process,and quality function deployment to establish logical and quantitative standards.Moreover,in order to perform a logical selection of alternative aircraft configurations,it uses advanced decision-making methods such as morphological matrix and technique for order preference by similarity to the ideal solution.In addition,a preliminary sizing tool has been developed to check the feasibility of the established performance requirements and to evaluate the flight performance of the selected configurations.The present process has been applied for a two-seater very light aircraft（VLA）,resulting in a set of tentative design requirements and two families of VLA configurations：a high-wing configuration and a low-wing configuration.The resulting set of design requirements consists of three categories：customer requirements,certification requirements,and performance requirements.The performance requirements include two mission requirements for the flight range and the endurance by reflecting the customer requirements.The flight performances of the two configuration families were evaluated using the sizing tool developed and the low-wing configuration with conventional tails was selected as the best baseline configuration for the VLA.