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Intelligent Design

Intelligent Design

This time I thought I might lighten up a little and have a look at some of the concepts involved when designing a complete aircraft.

Many years ago during the WWII era, an old time aircraft design engineer, Mr C. W. Miller, was doodling on his designer’s pad one day and came up with a classic cartoon titled ‘Dream Airplanes’. Although now somewhat dated in detail, the underlying concepts remain sound. This cartoon has been reproduced, published and altered many times over the intervening years, this is my variant:

In an aircraft factory environment the design of an aircraft is usually shared between many specialist groups involving engineers with expertise in different aspects of the design process. The reality is that the design of an aircraft is a very complex process and it is only human to believe that the most important part of the design is the bit that their group is responsible for. This, of course, means that all of the problems in the design are caused by the less important design groups – naturally!

A complete aircraft is a compromise of competing ideals. If each department or group involved in the process had its own way we could end up with an aircraft looking like one in the cartoon. Clearly the group designing the fuselage want a big box shaped fuselage – much easier to fit things in. The drafting group like to draw only straight lines, the stressing group would like to build it using steel ‘I’ beams, etc etc . . .What more can I say! Obviously, in the real world the competing requirements need to be balanced carefully and, in the end, no one design group can be allowed to prevail – all must meet their individual requirements, but not at the expense of the others.

It may seem silly but there are real life examples of some of these extremes. Probably the most notable example would be the Gee Bee Racer of the early 1930s. This was an aircraft designed and built for one purpose – to win air races. It had an extraordinarily large engine with a tiny wing and was one of the most controversial aircraft ever built. It was commonly known as the ‘killer plane’, 22 were built and, as far as I can determine, they all eventually crashed. You could say that the Gee Bee was probably designed by the ‘power plant group’ as engine power seems to be the predominant criteria of its design, however the ‘weight control group’ seems to have been consulted as look where they had to put the pilot to balance out the weight of the engine – in the fin!
For sure, some of the engineering groups in the cartoon would have difficulty accepting the compromise forced by other groups but compromise is necessary if the aircraft is ever to fly.
Today, in Australia at least, the majority of general aviation aircraft design is carried out by independent CAR 35 design engineers quite removed from an aircraft factory environment. Consequently they tend to act for all of the design groups, a bit like a veterinary surgeon who has to treat all types of animals for all types of complaints! I guess that has its advantages though – at least they get to see and consider all sides of the design compromise.
Unfortunately we will never have an aircraft that does everything that every operator wants: the desires and the reality are often just too far apart. New technology in avionics, electrical and radio see us constantly refitting our aircraft with the latest gadgets and that is an ongoing challenge.
But also beware the design engineer’s own private projects as he strives for perfection. As my wife will attest, there is extreme danger when leaving anything remotely aviation looking lying around in the hangar. Yes, it will often end up disassembled, redesigned and maybe, if you are lucky, eventually rebuilt. Engineers love projects and everything stationary has the potential to be one. She will also tell you that when engineers tell you they own an aircraft, what they really mean is they own a bunch of aircraft components. She insists that these should merely be viewed as ‘bits’, as unless they are fully assembled into an aircraft they do not constitute one!
So next time you take a look at your aircraft think about the time that went into the design process. Which engineering group dominated the design of your aircraft? Did one group dominate? I guess in the end, is it really safe to fly? That is the real question.

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