Increasind the Aerodynamic Efficiency of the Skyranger Microlight Through Shape Optimisation Methods

Topics: Aerodynamics, Wingtip device, Wing design Pages: 18 (4156 words) Published: March 8, 2011






Overview of the Project

The Skyranger along with other ultra-light home build plane are designed and constructed to be extremely cost effective due to the low price at which they are marketed. In this report the aerodynamic performance of the Skyranger’s wing is analysed and particular modifications such as the implementation of wing twist and the introduction of wingtip devices are discussed as possible retrofits. Issues being investigated: induced drag caused by the production of lift especially though take-off and landing configurations in aircraft, parasite drag caused by the modifications such as winglets, implementations of the modifications. Concluded is the success of the project and whether the proposed modifications are a realistic improvement to the Skyranger taking into account all design factors such as cost, complexity of the design and build and weight changes.

Aims, Objectives and Milestones.

The aim of the project is to improve the efficiency and effectiveness of the Skyranger wing using forms of shape control on the wing planform. This will be achieved through the following objectives.

Back Ground Research

This will be split into two sections that will look into the background wing tip devices and wing twist

Wing Twist

In 1899 the wright brothers were experimenting on wing twist as a means of controlling the rolling motion of an aircraft. This was accomplished though many hours of watching birds in flight when Wilbur Wright concluded that “regain their lateral balance when partly overturned by gust of wind by torsion of the tips of the wings” (Padfield and Lawrence 2005). This is considered as one of the most important discoveries of aviation and also the origins of wing twist. Ludwing Prandtl published the 1st theory of lifting wings which allowed us to mathematically analyse and predict the effects of wing twist. This was a crucial step in the development and Prandtl is often considered as one of the founding fathers of aerodynamics. From this theory it the effect of aspect ratio on the lift slope and induced drag was established. It also shows that the optimum (lowest) induced drag occurs for an elliptic lift distribution on the wings from tip to tip. Where the Oswald’s efficiency is 1 whereas for the Skyranger’s rectangular wing the efficiency factor is 7 (NASA, 2010). The graphs in the appendices show the variation of the induced drag between elliptical, tapered and rectangular wings.


In the 1920s Hermann Glauert discovered that twisting the two sides of a wing in a symmetric manner could affect the drag acting on the wing such that under some conditions the drag would decrease whereas in other conditions twist would increase the drag (Phillips 2005) .A newly developed solution to Ludwig Prandtl ‘s theory of lift that allows us to predict and maintain proper twist distribution and amount of wing twist has shown that with proper twist implementation wing of any planform shape can be designed to produce the same minimum induced drag as an elliptic wing.

In the report three ways of implementing the twist distribution will be discussed and these are:

• The Horten twist distribution.

• The Culver twist distribution

• The Pankinin twist distribution.

All three twist distributions have both positive and negative aspects and their equations are in found at the appendix for further comparisons and reference.

The Horten twist distribution is based on the work of Prandtl and others, and has been supported by the more recent works of R.T. Jones and Klein and Viswanathan. The Horten paradigm has the potential to reduce induced drag and eliminate adverse yaw, but is computationally intensive and the twist distribution itself must be...

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