In the late 70's, me 'n my team went to collect a new Skyvan from Belfast. The aircraft was, as usual, not ready as promised, so we stayed at Shorts' expense for a week. One evening the Head of Design (or whatever the title was) got the job of entertaining us.
We asked how and why the Skyvan was designed, a fair question if you look at a Skyvan.
"Well," he said, "it was like this. The military wanted to carry a Landrover into short strips, so we thought we'd need a box for it." He drew a box on a tissue, with a Landrover inside.
"Then we put a wing on top, to keep it out of the way, and so that the middle bit could carry the fuel." He drew a wing cross section.
"Then we thought about a pilot," he drew a chair with a pilot on it, on a development drawing below, "and to keep him warm we put a sort of nose around the front." He drew a shape to enclose the pilot.
"Then we thought that it would take a bit of keeping straight, so we put two bloody great fins and rudders well back from the main bit," he drew a fin/rudder on another development drawing, "and then we sort of connected them to the main body". He drew the connecting structure.
"And finally we gave it a couple of engines and a fixed undercarriage with huge wheels to make it an ATV, and Bob's your uncle." He finished the design in the 4th drawing.
Now that, my children, is how a real aircraft is designed. And it worked*, with a better STOL take-off performance than a Twin Otter with a lower payload.
I've managed to preserve his drawings ever since. Here, exposed for the first time, is the very sheet of paper. You must appreciate that the drinks were flowing freely while this was going on, so the drawing accuracy began to reduce.
* Once it got a decent engine, the TPE 331, although even that had a habit of exploding unexpectedly.