Ah, the famous Chickenpox Plane.

If you’re on any social media and are interested in aeroplanes (and this clearly applies to you), then you know this story. Some typically dumb military officers approach Abraham Wald, a mathematician working with airplane survivability, with data showing how bombers get shot by fighters in their wingtips and tails, and asking him to help work out how much armor they should add there so that they will lose fewer bombers.

Bill Sweetman

Wald then points out that the airmen are looking at the bombers that survived and that those that were shot down were hit somewhere else. Enlightened, the Army Air Force installs armor according to Wald’s ideas and more bombers survive.

The story is usually accompanied by the same drawing (see above)

I first saw this story no more than a few years ago, and I thought, wow, I never heard that before. Which, given that I wrote a book about the A-10 and read the Good Book on aircraft survivability, and attended a conference or two devoted to survivability, piqued my curiosity, not to mention my amour-propre.

There was another piece to the tale that did not fit. The aeroplane in the universally used drawing is a Lockheed PV-1 Ventura. Nothing at all against the Ventura, but almost the entirety of its career was spent chasing submarines or shooting up ships with the Navy, rather than getting shot down en masse over Germany. Why would it be the focus of a survivability study?

Since I have an ADHD proclivity for internet rabbit holes, off I went and found more.

Wald did important mathematical work on survivability. But in 1943. Why is this important? By the time it was completed and reported, the final operational versions of the B-17 and B-24, after getting hammered over Berlin and Schweinfurt &c, were already flying, with essentially the same protection (self-sealing gas tanks and selective armour) that they used for the rest of the war. And where is said armour?

I found this story, too.

Wald did really good work, but the story got embellished. How?

A statistician, author and lecturer called Howard Wainer used the story in lectures and books, back in the late 1990s. He also had a very simple version of the drawing, which was later elaborated into today’s ubiquitous image.

But Ground Zero was where Wainer’s story got Glabared – Gladwellized* beyond all repair – by a best-selling mathematician, Jordan Ellenberg.

“The officers saw an opportunity for efficiency; you can get the same protection with less armor if you concentrate the armor on the places with the greatest need, where the planes are getting hit the most. But exactly how much more armor belonged on those parts of the plane? That was the answer they came to Wald for. It wasn’t the answer they got.”

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Whoa! Who’s missing from this account? Fighter pilots, that’s who. As far as I know, they didn’t go shooting at wingtips and tails. They knew damn well what the crucial bits of a bomber were: the engines and the cockpit. Nobody had told the bomber designers, or the USAAF requirement-writers, that?

“Wald’s recommendations were quickly put into effect, and were still being used by the navy and the air force through the wars in Korea and Vietnam.”

Put into effect how and where? Nobody says. Nobody points to a certain block of B-17G or B-24J production where changes were introduced.

And the survivability lessons of WW2 had mostly been abandoned by the time of Korea. Indeed, jet airplanes were so sensitive to weight and burned fuel so fast that self-sealing tanks (which cost fuel volume) and armour were ditched. It was also assumed from the late 1950s that if you were hit, it was by a missile and Goodnight Nurse. Vietnam proved this to be wrong, and its lessons were incorporated in the A-10 ‘Warthog’ and, more subtly, in many other aircraft.

Lessons:  as Abraham Lincoln said, don’t believe everything you see on the Internet. And mathematicians, like fighter pilots and first violins, are not immune from telling stories about how important they are.

*Malcolm Gladwell, Norden, Lenin and strategic bombing is a whole different story

Bill’s new book Trillion Dollar Trainwreck: How The F-35 Hollowed Out The U.S. Air Force is available to buy here.

The Hush-Kit Book of Warplanes Vol 3 is available to pre-order here