Expert: Ray Wilkinson - 10/1/2006

Question
Hi,
I wanted to know what makes the wings of new military aircraft such as the F-22
superior to older military aircraft? How does the shape and the material of the
wing impact aircraft speed and safety?

Thanks!
-Daniel

Answer
Hi Daniel

There are several major changes that have improved wings over the last few years:

1. A move to composite materials rather than metals. These offer superior strength/weight ratio, and can also be used more efficiently - as a colleague of mine told me, because you can lay up the fibres in any direction, it is possible to design the material as well as the structure, so the strength and stiffness can be optimised. Composites also have superior fatigue performance compared to metals.

2. Better aerodynamics. Computational fluid dynamics (CFD) now allows engineers to develop more efficient wing sections, and to test them in mathematical models over a wide range of conditions. The speed of computers means that CFD runs can be done relatively quickly (minutes rather than many hours), and with better resolution, which often means less validation work is required in wind tunnels.

3. Better analysis of structures, again using mathematical modelling to optimise the structure, leading to lighter, stiffer structures.

Another key issue for military aircraft is damage tolerance, although this is still relevant to civil aircraft for bird strikes and damage to fuselages from collisions with servicing vehicles. The structure can be analysed in a damaged state, from battle damage predictions, so design margins can be investigated.

There has been little change in aircraft speeds since the late 50s/early 60s, as the laws of physics don't change, but developments in weapon systems, particularly the beyond-visual-range (BVR) capabilities, and also fighter turn rates, have had a great impact, especially in the last decade or so. Having a greater turn rate means it is easier to bring an opponent into the firing window of a missile (or guns), which gives a great advantage.

I hope this answers your question.

Regards
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Eur Ing Ray Wilkinson
Senior Lecturer
University of Hertfordshire
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