Daily Design Inspirations 33: Abraham Wald and the Missing Planes (#dailydesigninspirations)

During World War II, the UK and U.S. focused their air warfare plans on the use of strategic bombing, employing long- and short-range aircraft to lead the way and provide ground infantry with an upper hand. Much of the industrial war complexes of both these nations were focused on producing planes, and ensuring the safe return of an expensive, slow-to-produce bomber was a priority. After all, a plane that can make five or perhaps ten runs was worth much more than one which failed to return after a mission or two.

And many planes were being shot down by German fire, and the casualties were huge. In some years of World War II, the chances of a member of a bomber crew making it through a tour of duty were about the same as calling heads in a coin toss and winning. As a member of a World War II bomber crew, you flew for hours above an entire nation that was hoping to murder you while you were suspended in the air, huge, visible from far away, and vulnerable from every direction above and below as bullets and flak streamed out to puncture you. “Ghosts already,” that’s how historian Kevin Wilson described World War II airmen.

Where to Armour?

So here was the question. You don’t want your planes to get shot down by enemy fighters, so you armour them. But armour makes the plane heavier, and heavier planes are less manoeuvrable and use more fuel. Armouring the planes too much is a problem; armouring the planes too little is a problem. Somewhere in between there’s an optimum.

The Statistical Research Group (SRG) was a classified program that yoked “the assembled might of American statisticians to the war effort—something like the Manhattan Project, except the weapons being developed were equations, not explosives. The military came to the SRG with some data they thought might be useful. When American planes came back from engagements over Europe, they were covered in bullet holes. But the damage wasn’t uniformly distributed across the aircraft. There were more bullet holes in the fuselage, not so many in the engines.


The officers saw an opportunity for efficiency; you can get “the same protection with less armour if you concentrate the armour on the places with the greatest need, where the planes are getting hit the most. But exactly how much more armour belonged on those parts of the plane?

220px-abraham_wald_in_his_youthEnter Abraham Wald, who was working at SRG at that time. Born in Hungary in 1902, the son of a Jewish baker, Wald spent his childhood studying equations, eventually working his way up through academia to become a graduate student at the University of Vienna where the great mathematician Karl Menger mentored him. As he advanced the science of probability and statistics, Wald’s name became familiar to mathematicians in the United States where he eventually fled in 1938, reluctantly, as the Nazi threat grew. His family, all but a single brother, would later die in the extermination camp known as Auschwitz.

And Wald came up with an interesting idea to the question of how much armour, and where.

The armour, said Wald, doesn’t go where the bullet holes are. It goes where the bullet holes aren’t: on the engines.

Wald’s insight was simply to ask: where are the missing holes? The ones that would have been all over the engine casing, if the damage had been spread equally all over the plane? Wald was pretty sure he knew.

The Missing Planes

The missing bullet holes were on the missing planes. The reason planes were coming back with fewer hits to the engine is that planes that got hit in the engine weren’t coming back. Whereas the large number of planes returning to base with a thoroughly Swiss-cheesed fuselage is pretty strong evidence that hits to the fuselage can (and therefore should) be tolerated. If you go the recovery room at the hospital, you’ll see a lot more people with bullet holes in their legs than “than people with bullet holes in their chests. But that’s not because people don’t get shot in the chest; it’s because the people who get shot in the chest don’t recover.

Wald put together a crude before-and-after diagram. The “after” image — the plane on the right — showed where the majority of the damage was, as indicated by the shaded regions. Wald determined that most of the plane — the wings, nose, and fuselage — had taken the worst beating, while the cockpit and tail were generally unharmed.



Wald theorized that the fact that the planes lacked damage in the cockpit and tail was more telling. Certainly, the Axis’ targeting of Allies’ planes was both indiscriminate and imprecise; there was little reason to believe that the Axis forces were aiming for, say, the nose, and intentionally avoiding striking the tail. Some planes had to have taken significant damage to the tail and cockpit, and all of those planes had something in common: they, unlike the ones in Wald’s data set, did not return back to base.

On Wald’s advice, the U.S. military leadership reinforced the cockpits and tails on its planes. The number of planes (and lives) saved during the World War and Korean and viet Nam wars are difficult to estimate, but the impact of this idea was huge.


Design News: Engineering as a Driving Force Behind the Design-Thinking Movement


It’s wonderful that design thinking is now applied to so many different problems: designing better experiences for hospital patients, designing and implementing better client experiences at social-service agencies, starting new companies, teaching leadership, inventing new radio shows, changing organizational structures, and developing new products and services for people at the bottom of economic pyramid — to name just a few. Design thinking focuses on uncovering human needs, and doing so by not just relying on what people say, but by watching what they do as well. It entails developing a point of view about what needs to address, generating quick and rough solutions, prototyping like crazy and testing ideas with the users, customers, patients, employees or whomever the solutions are intended to help — and doing it all very quickly and not being overly attached to ideas.

There is, however, a part of the story that seems to be slipping away — especially in the business press and in business schools, as well as in areas such as education and healthcare where design thinking is being used. Many executives, students and journalists don’t seem to realize that engineers and engineering schools were among the main driving forces behind the start of this movement. David Kelley, the main founder of the innovation firm IDEO and the Stanford d.school, has been teaching mechanical engineering at the university for over 35 years(he is pictured above, with the Apple mouse that IDEO designed); and Bernie Roth, our academic director at the d.school has been teaching mechanical engineering at Stanford since 1962 (he is a pioneer in the field of robotics).

And consider two of the most revered design thinkers and teachers I know:Diego Rodriguez at IDEO and Perry Klebahn at the d.school (officially, the Hasso Plattner Institute of Design at Stanford). When I first met Diego, some 20 years years ago, he had just graduated from Stanford, where he earned a degree in mechanical engineering and was working at IDEO. Diego did get increasingly interested in business, got a Harvard MBA, and now — back at IDEO for years as a partner — has become one of the most imaginative business thinkers I know (check out his blog and tweets). Yet, when I talk to Diego, listen to his ideas, and watch his masterful teaching and coaching, I can always see how the magnificent engineering designer inside him remains the strongest guiding force. His relentless advice to do things like get out and talk to and watch some real human beings, to develop a sharp point of view, to brainstorm, to “prototype until your puke,” and to view ideas as easy to get, important to throw away, and ultimately best to be judged by users and the market (rather than experts) all go back to his product-design roots. This really struck me when, a few years back, Diego was designing a new organizational structure for a client that, many years before, he had designed a product for when working as a young IDEO designer. He remarked to me, “The end product is a lot different, but the process I am using is remarkably similar.”

I see the same thing in how Perry approaches problems. Perry has always been a product guy, as he invented the modern snowshoe as a Stanford product-design student and then went on to grow a company that sold and spread the product called Atlas (the above grainy picture is of Perry on CNN with his invention back in 1997). Then Perry was a senior executive at Patagonia, and most recently was CEO of Timbuk2. Perry has also taught numerous product-design classes at Stanford over the past 25 years, and in the last decade, taught over a dozen classes for students and executives at the Stanford d.school. In fact, Perry has taught more d.school classes than any other faculty member since the d.school was founded in 2004 (even though he was CEO of Timbuk2 for five of those years, he kept teaching).

Over the years, I have watched Perry move beyond and expand his engineering-design skills to an ever broader set of problems, like helping software executives gain empathy for what millennials want and rethinking the strategy of a Fortune 500 company. Lately, Perry’s students in his d.school classes — which he teaches with others including Kathryn Segovia,Jeremy Utley and me — tackle problems ranging from finding ways for the San Francisco Opera to attract younger customers to improving the experience of buying a bra for women who have had mastectomies.

Yet Perry’s engineering roots are always evident. I remember watching Perry use his product-engineering background to guide a class exercise aimed at improving employee selection, recruitment and socialization practices for our d.school fellows program. He pressed the students to look for unmet needs, to identify the problem they were trying to solve, to brainstorm ideas for prototypes quickly, and then to test the emerging ideas with users — even though those ideas were unfinished and crude approximations of organizational practices. This process, although modified by Perry and many others to fit problems of all kinds, is simply a variation of the design process that Perry used as a Stanford engineering school student years ago to invent the modern snowshoe — and then to grow the company and customer base required to make the product succeed.

Yes, I am a tenured professor in the Stanford School of Engineering, but I am not an engineer. The core of what we do at the d.school, and of much of what they do so well at IDEO, is rooted most strongly in product-design engineering — especially the flavor taught at the engineering school. That is why, frankly, I feel better when I work with “real” engineering product designers like Diego and Perry in the d.school classes I help to teach — even though I recognize that there are master design thinkers from all kinds of backgrounds, including lawyers, journalists, computer scientists and psychologists. The aforementioned Kathryn Segovia has a Ph.D. in communication (she did her thesis on the psychology of avatars), and Jeremy Utley is a Stanford MBA and former management consultant). Both have developed into two of the most skilled design-thinking practitioners, teachers and coaches I know.

Like many people at the d.school, I get in regular arguments about what design thinking is, how it ought to be applied, and the times when it isn’t right to use it. It’s healthy for all of us to question what we do and how to do it better. But one thing we all share at Stanford, whether our students and faculty realize it or not (and some don’t, as the history is fading a bit), is that the brand of design thinking that we teach is a mindset and set of methods that was developed and refined at Stanford’s engineering school for decades — especially by product designers — before design thinking was ever a hot topic in business, entrepreneurship, education, healthcare and so many other places.

Original Post here

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Bob Sutton
Stanford Professor who studies organizations. Books include bestsellers Good Boss Bad Boss, The No Asshole Rule, The Knowing-Doing Gap and Scaling Up Excellence. He first wrote this post about five years ago and update it every now then. The iteration before this one appeared a couple weeks back at the Stanford Technology Ventures Program eCorner site.