Engineers are not omniscient

What I wish people knew about engineers: we don’t know everything.

There we were: the next best thing to a dozen of us volunteers standing around a heavily-laden van and trailer. Someone turned to me: “Shannon, you’re an engineer. How much do we have to take off to make it safe?”

A half dozen questions immediately sprang to mind: How much did the load weigh? What were its dimensions? Its density? What was the trailer rated to carry? What about the van? Including passengers or not? What safety factors were used?

In the end, my attempts to dig up all the relevant information were too slow, and the others unloaded the van until the suspension worked again.

Why didn’t the engineer come up with that simple solution?

Because it’s complicated.

A system like a car, a rocket, or a building has a lot of parts. In order to ensure the system will perform safely, you have to identify the weak links in every situation it might encounter and check that those links won’t snap. (Or, more accurately, fail.) With experience analyzing the weak links, you can start making educated guesses about systems that are very similar to ones you’ve analyzed in the past. This is how you develop “engineering judgement.”

People also develop judgement by hearing about or observing under what situations components fail. (Call this “considering case studies” instead of “I once heard of a guy…”) After hearing enough stories of consequences of component failure on a particular system, even those who aren’t engineers can develop an intuitive sense of how to fix problems. That’s how our loading situation got fixed: someone observing the springs’ compression had experience that told him that as long as the springs had compression left, the van was safe to operate. Not being familiar with cars myself, I didn’t have the experience to agree.

The problem with both engineering judgement and more informal “case study” judgement is that they inherently rely on more assumptions than standard analyses. You assume that this new system is going to behave exactly like the others you’re comparing it to. You also assume that you know everything about it you need to know.

In the van example: we assumed we knew everything we needed to know and that the suspension was the weak link. It could have been the brakes. It could have been the tongue supporting the overloaded trailer. It could have been the transmissions, depending on the terrain along our route. But experience said the suspension was the only concern.

(Point of order: once you fix the weakest link, there’s always a new weakest link. You only have to ensure the weakest link is strong enough.)

Experience and engineering judgement go a long way toward helping engineers solve problems quickly. They also help raise hoards of questions, especially where safety is concerned, that may extend the time it takes to find a final answer.

And since experience and judgement apply only to similar problems, consider the breadth of problems in any given field of engineering:

Aerospace engineers work on airplanes, helicopters, wind tunnels, jet engines, propellers, rockets, satellites, icing, and more. Some parts spin; some don’t. Some have air flowing over them, some through them–and some have no air at all. Sometimes heat is a problem; other times, it’s a solution.

Civil engineers work on roads, bridges, tunnels, single-floor buildings, skyscrapers, dams, water treatment facilities, canals, and storm sewers. In some projects, water is dominant. In some, wind and earthquakes. Some need particular attention to natural frequencies; others, to large, cyclic loads.

Mechanical engineers, in my opinion, are the Swiss Army Knife of engineers. They do everything from building heating and cooling systems and air circulation to car and blender design. They work on refrigerators, prosthetics, helmets, and various other contraptions.

There are at least another half dozen general engineering types, including chemical engineers, biomedical engineers, electrical engineers, computer engineers, and nuclear engineers. Each field has specialties, and each specialty has a number of dissimilar types of problems. While engineers from different backgrounds can learn to work on the same problem, engineering judgement developed from, say, aerospace test environments may have limited applications in automotive troubleshooting. Engineers, like anyone else, can’t know it all. But if you have the time to wait for a solution, we can give you the most thorough results you’d ever want!

Special kudos to Diana Delk, consulting civil engineer for this article. You guys don’t seem to get the kudos you deserve. Thanks for keeping society working and–dare I say it–civil!

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