Notes on To Engineer is Human

To engineer is human (see in Amazon or in Goodreads) is a 1992 book about how knowledge of past design failures is useful in current projects, strongly biased to civil engineering. Some examples are repetitive and not studied in depth, thus making the book a bit dull at times. Even then I found some very interesting reflections and quotes that I wanted to comment on or simply organize for later reviewing.

Galileo and wrong models

Galileo’s analysis of the cantilever beam illustrates an extremely important point for understanding how structural accidents can occur: he arrived at what is basically the right qualitative answer to the question he posed himself about the strength of the beam, but his answer was not absolutely correct in a quantitative way. He got the right qualitative answer for the wrong quantitative reason. Thus Galileo could correctly have advised any builders how to orient their beams for the best results, but should he have been asked to predict the absolute minimum-sized beam required to support a certain weight so many feet out from a wall, the answer he calculated from his formula might have been too weak by a factor of three.

— p. 51

I found a blog post about this subject, which you may find interesting.

On learning from mistakes, not successes

[…] the process of successive revision is as common to both writing and engineering as it is to music composition and science, and it is a fair representation of the creative process in writing and in engineering to see the evolution of a book or a design as involving the successive elimination of faults and error. It is this aspect of the analogy that is most helpful in understanding how the celebrated writers and engineers alike learn more from the errors of their predecessors and contemporaries than they do from all the successes in the world.

— p. 79

Should a young engineer look for models in weak-linked structures while they are still functioning, he could indeed design weak links into his own structures. However, if the cause of a failure is understood, then any other similar structures should come under close scrutiny and the incontrovertible lesson of a single failed structure is what not to do in future designs. That is a very positive lesson, and thus the failure of an engineering structure, tragic as it may be, need never be for naught.

— p. 97

Yet no disaster need be repeated, for by talking and writing about the mistakes that escape us we learn from them, and by learning from them we can obviate their recurrence.

— p. 227

Treating every case of failure as an opportunity to test hypotheses, whether embodied in novel designs or in theories about the nature and process of engineering itself, makes even the most ancient of case studies immediately relevant for even the most forward-looking of technologies. In the final analysis, there are aspects of the engineering method, especially those involving conceptualization and the design process itself, that transcend all eras and cultures. Thus every case study—no matter how obsolete its technology or how fresh its trauma, whether in a book or in tomorrow’s news—is potentially a paradigm for understanding how human error and false reasoning can thwart the best laid plans.

— p. 232

The electronic brain

The electronic brain is sometimes promoted from computer or clerk at least to assistant engineer in the design office. Computer-aided design (known by its curiously uncomplimentary acronym CAD) is touted by many a computer manufacturer and many a computer scientist-engineer as the way of the future. But thus far the computer has been as much an agent of unsafe design as it has been a super brain that can tackle problems heretofore too complicated for the pencil-and-paper calculations of a human engineer. The illusion of its power over complexity has led to more and more of a dependence on the computer to solve problems eschewed by engineers with a more realistic sense of their own limitations than the computer can have of its own.

— p. 195

It is not only in the high technological business of building mass-transit buses that our accelerating socio-economic system breaks down. Computer models that predict the behavior of the economy have come increasingly to be relied upon to justify major economic decisions, and yet these models are not necessarily any more infallible than the ones that predict the fatigue life of a bus frame. Thus the same tools that apparently free us from the tedium of analyzing the wheel condemn us to reinvent it. We have come to be a society that is so quick to change that we have lost the benefits of one of mankind’s greatest tools—experience.

— p. 220

On being an engineer

It us a great profession. There is the fascination of watching a figment of the imagination emerge through the aid of science to a plan on paper. Then it moves to realization in stone or metal or energy. Then it brings jobs and homes to men. Then it elevates the standards of living and adds to the comforts of life. That is the engineer’s high privilege.

The great liability of the engineer compared to men of other professions is that his works are out in the open where all can see them. […] The engineer simply cannot deny that he did it. If his works do not work, he is damned. That is the phantasmagoria that haunts his nights and dogs his days. He comes from the job at the end of the day resolved to calculate it again. He wakes in the night in a cold sweat and puts something on paper that looks silly in the morning. All day he shivers at the though of the bugs which will inevitably appear to jolt its smooth consummation.

— p. 215

Other recognized master often express the thought that they abandon a work rather than complete it. What they mean is that they come to realize that for all their drafts and revisions, a manuscript will never be perfect, and they must simply decide when they have caught all its major flaws and when it is as close to perfect as they can make it without working beyond reasonable limits.

— p. 78

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