Evolution has played almost as important a role in the development of aircraft as it has in the development of birds, although the timescales are very different, argued Boeing 787 Dreamliner chief test pilot Ricardo Traven at the recent 2019 Aeronautical Society of South Africa conference, in Pretoria. (Traven had previously been chief test pilot for the Boeing F/A-18 Hornet fighter.) He dated the start of aeroplane evolution to the Wright Flyer of 1903, which was the first heavier-than-air powered aircraft to successfully fly.

“There are some moonshot designs, which I call revolutionary,” he said. “Then there are evolutionary designs which have developed with time.”

Revolutionary designs can be risky. “There are revolutionary things that can be done, that are successful,” he observed. But, sooner or later, revolutionary technologies are going to be copied, emulated or (if military) countered.

Like birds, aircraft (whether military or civil) exist in environments. “The environment can change rapidly for us,” he pointed out. “What was great for one environment, can be a disadvantage in another.”

Just as changing environments can result in bird species becoming extinct, so too can changing aviation environments make aircraft types or even categories (such as flying boats) extinct. Thus, the Lockheed SR-71 Blackbird strategic reconnaissance aircraft, which could fly higher and faster than any other operational aircraft, became “extinct” (was withdrawn from service) because of the development of ever more effective spy satellites, and because it was too specialised to be adaptable to other missions.

(The two-seat SR-71 first flew in December 1964, following from the very similar but smaller single-seat A-12, which made its maiden flight in 1962 and was code-named Oxcart, and was developed for, and operated by, the Central Intelligence Agency. The SR-71 could maintain a sustained speed of Mach 3 – that is, three times the speed of sound – at altitudes of 85 000 ft, or 25 908 m. It was withdrawn from service in 1990, after only 26 years.)

On the other hand, the Boeing B-52 Stratofortress bomber and the Lockheed Martin C-130 Hercules transport were and are great examples of evolutionary aircraft designs. Both have been in service for decades, and both have been extensively modernised.

(The original production version of the Stratofortress, the B-52A, first flew in 1954, or 65 years ago. The last one produced, a B-52H, was delivered in October 1962, or 57 years ago. The US Air Force now operates only the B-52H version. The first production Hercules model, the C-130A, was first delivered in December 1956, or nearly 63 years ago. It was followed by the C-130B, which is still operated by the South African Air Force. The other main production versions are the C-130E and the C-130H. In 1999, the much-improved new-generation C-130J version was first delivered in 1999 and remains in production.)

The aviation environment will evolve, stressed Traven. It was a matter of evolve or perish. “[To] evolve rapidly . . . [with] aircraft . . . you have to have a design that allows rapid technology insertion.”