A Fundamental Problem with Airframe Stress Analysis

I recall well my start in airframe stress analysis at Northrop Grumman in sunny Southern California in 1986. Educated, interested and ambitious is how I was described, and I was side by side with another ‘fresh-out’, named Jim. Jim was a nice guy – intelligent, easy to work with and easy to get along with. But we often wondered if he really had an engineering degree. It truly seemed as though he learned nothing while in college, scraped and clawed is way thru and somehow got a job. But there we were, side by side at the mighty Northrop Grumman analyzing military fighter jets, or at least trying. Stated bluntly, Jim screwed up everything he worked on. He left the company about a year later and I haven’t heard from him since. But to this day I think about my old hand-written analyses and my first finite element models and wonder ‘is any of that really right’? And then I think about Jim’s. All of that is definitely wrong. And does it matter? Of course it matters, we were analyzing military fighter jets.

Yes, arguments can be made that it was checked by more experienced people, we were given a lot of time, and it wasn’t flight critical structure anyway so it’s OK. But the point is that with essentially no screening or training or testing, we were writing margins of safety on flyable aircraft. And what’s happening today at major aerospace companies? From my experience, the exact same thing. There is one company, and only one of the many I’ve worked for that have a formal training program for both new and experienced analysts well beyond attending some after-hours course or looking at an on-line Power Point with a 20 point questionnaire at the end.

Why don’t all companies have a rigorous program requiring training, difficult testing and peer review that takes years to work thru and complete instead of three days? Is it really because we just choose to put money before safety? Again. I don’t think so. It’s more complicated than that. While engineering may be the heart and soul of an aircraft major, what it really takes to compute a margin of safety accurately is foreign to those who need to know. Profile is the answer, and unfortunately the larger the company the less profile the fresh-out has. It’s the responsibility of the senior engineers to inform ‘management’ of these shortcomings. Who else will?


By Glenn Armellino, 8/23/2018


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