To Engineer is Human—A Review of Henry Petroski’s Classic Philosophy on Engineering

Setting up a new home office for my Vitech work in January of this year involved the cleaning out of a basement bedroom that had become a repository for long-forgotten items that surely would of course be needed some day. It was a shame I had let it get to that point, as the room is a nice one with plenty of sunlight through sliding glass doors which open to the stairwell and the back yard. My wife armed me with a brand new box of trash bags, a signal to get to work.

One of the many containers of old paperwork, floppy disks, and cassette tapes also had a few books from my school days at Norfolk State. I stopped a minute to take a trip down memory lane. Among them was a small black book entitled To Engineer is Human: The Role of Failure in Successful Design by Henry Petroski, a professor of civil engineering at Duke University in the 1980s. First published in 1982, this book was apparently required reading back in the day at Norfolk State. I vaguely remembered this as a kind of layman’s book on engineering and design.

I laughed to think how irrelevant my early engineer readings probably are in 2017; however, I decided to take a closer look to see if this book was even still available. This led me to Amazon, where I found that it is indeed still for sale. I decided to thumb through it once more for old time’s sake. An online review from the Defense Acquisition University had piqued my interest:

Henry Petroski’s 1982 classic is relevant today given the Department of Defense’s challenge to develop and deliver highly effective and reliable defense systems that are increasingly integrated and complex. A natural result of this increased complexity is increased risk and probability of failure. However, efforts to eliminate all risk would impede the Department’s ability to provide the warfighter with the technological superiority to dominate the battlefield in an economical and timely manner. Instead, Petroski challenges us to understand and learn from our failures, which allows us to push the technical edge of our defense capabilities even further.

That same review went on to give the following example of relevance to today’s technology.

It helps to put into perspective how the complex systems demanded by today’s warfighter cannot necessarily be developed and delivered in a fail-proof manner. It illustrates that our ability to learn from mistakes through risk reduction prototypes and “failing fast” during our development process can increase our ability to solve complex problems and deliver a safer capability in a more efficient and cost-effective manner.

This synopsis was written by Aileen Sedmak, Deputy Director for Systems Engineering Policy, Guidance, and Workforce in the Office of the Deputy Assistant Secretary of Defense for Systems Engineering at the Pentagon. Ms. Sedmark also discussed the fact that the author of the book warned against blind faith in computers. She likened this issue to the modern-day drawbacks of reliance on computer simulation, which coincidentally was a topic of discussion in a class I just taught on Model-Based Systems Engineering.

I decided to give the book a quick skim, if only to see how far we’ve come, and to review the concept of basing successful designs on failures. In addition, I liked Petroski’s strong inference that creative writing has a place in engineering. He may make a believer out of me yet on the merits of blogging! His “Design as Revision” discussion mirrors how one works on paper (or today on computer) creatively with a client, taking them on a path which integrates proven techniques and methods that we as engineers know work well, with client wants and needs.

The methodology Petroski uses certainly sets the tone of the book, and while dated, is an interesting read, especially if you like the history of the craft. He uses famous moments in engineering history to make his point. One of the cases he covers is that of the Tacoma Narrows Bridge in Washington State, which was designed by the engineer Leon Moisseff, who used the work of others to create the specifications for the bridge. While it was clearly recorded how wind damage had affected other bridges of his day, Moisseff gave the effects of this factor, called resonance, almost no consideration. The bridge famously failed, causing loss of life and a public outcry. The good news is that structural engineers now design for resonance, not only in bridges, but also in buildings.

Another moment in history Petroski cites is the collapse of the walkway at the Hyatt Regency in Kansas City in 1981. This was one of the largest engineering disasters in our country until the terrorist attacks in 2001 and the destruction of the World Trade Center. At the Hyatt, the pedestrian bridges which connected the huge main lobby of that facility with its rooms, fell, killing and injuring hundreds. This was a prime example of an engineering design which sought to please the vendor with aesthetics, not taking into consideration the use, as in how many people might use the walkway during a special event at one time. In addition, an original design change made to make the actual installation of the walkway a simpler process reduced the ability of the walkways to support even their own weight, and so it was a major accident waiting to happen from its inception.

With each chapter in the book, the author makes the following point:

I believe that the concept of failure…is central to understanding engineering, for engineering design has as its first and foremost objective the obviation of failure. Thus the colossal failures that do occur are ultimately failures of design, but the lessons learned from these disasters can do more to advance engineering knowledge than all the successful machines and structures in the world.

The book reiterates, and I agree, that most engineers have a desire to blaze new territory and do what has never been done before. Working with a client who is not an engineer and who has certain aesthetic or other expectations can lead one into the temptation of pushing the envelope of what’s possible from an engineering standpoint. The fundamental feature of all engineering theory, of course, is that the design will not fail if it is used as intended. However, that is not always what happens.

The most repeated point in the book is that engineers routinely rely on engineering designs of the past, without looking closely at failure of design. Petroski calls the new computers of the 1980s artificial intelligence, and reminds his readers that these programs are only as good as the logic which has been given to them by humans. He talks about installing the proper checking mechanisms, which today we call requirements.

One of the most interesting stories in the book for me was the reference to the engineering tools of the past and in particular, that most basic of tools, the slide rule. In Chapter 15, From Slide Rule to Computer: Forgetting How It Used to Be Done, Petroski relays the story of a well-known manufacturer of slide rules, Keuffler & Essler, who had been in business for years. In 1967, the company commissioned a study of what the future of engineering would look like in 2067. Their vision portrayed domed cities and three-dimensional televisions. It did not, however, predict the demise of the very slide rule they themselves manufactured within the next few years.

In the same chapter, he also worries that engineers who love computers would forget to ask the important questions. Petroski makes it clear without too much reading between the lines that he thinks any student of engineering should learn the old-fashioned way first, without depending on either calculators or artificial intelligence.

So, lessons learned or relearned from the book:

  • Smart practitioners of the art and craft of engineering know that failure-proof design does not exist.
  • Innovation almost always involves risk, and studying failure helps to move innovation and its accompanying technology forward so engineers can search for better solutions.
  • Tailoring to meet client needs and economics can subvert the design; it is the moral responsibility of the engineer to do what is right.
  • Successful design is certainly a delicate balancing act, but can be done without arrogance or hubris.

While the book is geared to civil and mechanical engineering, the points are a great review for those of us who work in other areas of engineering, particularly those of us responsible for integrated system designs. I believe that the book is a good read for DOD managers, but also for any program or project manager.

I enjoyed the broad philosophical questions that Petroski asked and then attempts to answer: What is it to be an engineer from a human point of view, and what is an engineer’s place in the world?

This book highlights both the challenges, poetry, and philosophy of the engineering profession, and shows how progress happens when we document what has gone before.

This quotation by George Santayana, which Petroski used to sum up his own writing, is a good description of his engineering philosophy: We must welcome the future, remembering that soon it will be the past; and we must respect the past, knowing that once it was all that was humanly possible.

What Petroski is really calling for is a study of failure, and for this to be part of the intellectual life of any would-be engineer. He reminds those already in the profession to be humble enough to take another look, because failure breeds innovation and the evolution of future engineering success. As a systems engineer, I know this to be true.

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