Why do architects need to know how large their wings would have to be for unaided flight? Well, it's all to do with the gentle art of keeping engineers in hand
Shortly after standing down as president of the Institution of Civil Engineers at the end of last year, I gave a talk to art, architecture and engineering students at Newcastle University, along with with Eric Parry and Antony Gormley. Actually, it was less of a talk and more a discussion about the overlapping relationships we had as engineer, architect and sculptor.

Prior to the lecture, a small group of architectural students asked me to give a more informal talk, and I offered them a quick run-through of some projects, or a more light-hearted discussion of how to design aeroplanes. They asked for both, so we crammed the slides into 20 minutes and spent the rest of the hour on aeroplanes.

They were fascinated. Why should they be interested in calculating the wing span and engine size of a jumbo? Or how light and large their wings would have to be for the fittest among them to be able to fly under their own power? The sums required are surprisingly simple so that, ultimately, it was possible for us to calculate whether an albatross could fly using the energy it gained from photovoltaic cells on its wings.

What I was seeking to illustrate to the students was that the fundamental principles of engineering are simple and logical. But the meat of engineering is not so much in concept but delivery. Here, it gets fiendishly complicated as one moves from the principle to the practical. Aerodynamics, thermal movements, fatigue stresses, variations in material properties and, dare I say, dynamics, all make the art a science.

Flight took off 100 years ago this December and although the early aeronauts used the same calculations that I showed the students, as far as other calculations were concerned, they literally flew on a wing and a prayer. In this country, powered flight was first promoted by a flamboyant American cowboy, "Wild Bill" Cody (possibly the originator of the cowboy builder). However, as Neville Shute recalls in his autobiography Slide Rule, civil engineers with a little knowledge of aerodynamics soon came to the rescue and pioneered the design of aeroplanes in a rigorous way. Their work played a major part in the development of modern-day structural analysis.

That was a golden age, where, without computers, engineers such as Barnes Wallis and Shute, working for Vickers, traded calculations to create vast structures such as the R100 airship. In competition, the government was building the R101 with a slightly different approach and disastrous consequences.

We calculated whether an albatross could fly using energy from photovoltaic cells on its wings – the sums are surprisingly simple

When you consider the challenge of the discipline, it is a wonder that most good engineers don't all want to make aeroplanes. But, in fact, buildings and bridges are the stuff of life. Aeroplanes today are refined structures lasting decades and subject to limited design iteration. Once they work, there is little reason to change them. One of my colleagues is an aeronautical engineer who realised that he would be lucky to make a single design decision in his lifetime. In the design of buildings and bridges, it is a daily – if not an hourly – delight.

There are times, however, when one has the chance to go back literally, as with the aeroplanes, to first principles. A lovely example for me was a recent request to review a design for the restoration of Lord Cobham's Memorial at Stowe. A slender stone gazebo had stood at the top of a 115-foot column, which had supported his statue from 1749 until 1957, when it had blown down in a spectacular manner. We were asked to comment on a design to rebuild it, which would incorporated considerable metal reinforcement.

It had been reinforced before but my instincts were that it was this Victorian intervention that had contributed to its collapse. It looked like it shouldn't stand up, but it had. I dug out my college notebooks and returned to Dr Dougill's "work done and energy stored" calculations. We concluded that, if well maintained, the gazebo would withstand hurricanes, provided Lord Cobham himself weighed at least seven tonnes. Not totally satisfied, we got our calculations checked by Jacques Heyman, the pre-eminent engineering professor at Cambridge.

Back in Newcastle, the students were wondering how to put their new knowledge to good use. I explained that, as architects, they would need to keep their engineers under control. And what better way than to ask them if they knew how to design an aeroplane, and when they replied "no", take a few moments out to explain it to them?