First Story

It was to be 84 feet long, 23 feet high, and 35 feet from wing tip to wing tip. And we have met it already. It was called the P.17A, and it was designed by English Electric in 1958 to replace the Canberra.

I will talk about the design of its wings. Like a paper dart, these were to be delta-shaped, their leading edge swept back at 50 degrees. They were to be thin, their thickness only 2.5 percent of their breadth at the tip. They were to be short and broad; their aspect ratio (the span from wing tip to wing tip divided by gross surface area) was to be 2.77. And their gross surface area was to be 597.3 square feet.3

So why were they to have this shape? An answer will take us to design, and to the heterogeneity of design, its distributions. To the patterns in its overlaps and interferences.

Look at the following. It comes from the English Electric brochure on the P.17A (English Electric/Short Bros. 1958, 2.1.9):

Let’s define the terms, for these are terms that can be linked to the words that appear in the less formal part of the expression.

—M is Mach number, the speed of sound, so M =2 would be twice

the speed of sound, and so on.

— at is transonic lift slope; more about that in a moment.

— W is the weight of the aircraft.

— S is the wing area.

—And G is a measure of the response of the aircraft as it flies

through vertical gusts of wind.

So the equation expresses what aerodynamicists call ‘‘gust re­sponse.” It quantifies the susceptibility of an aircraft to vertical buf­feting. The aircraft, or so the expression tells us, will be buffeted less if it weighs more, and it will be buffeted more if it flies faster, if it has a larger wing, and if its lift slope is higher.