The Takata air bag recall announced today is in some sense the largest product recall ever. The number of units recalled, 35 million, is not so large by itself, but these are cars, and the defective part is something that could blow up in your face.
An obvious problem in designing auto parts is making something that can last for the useful life of a car. How do you test the long-term strength and stability of a manufactured product, and then deliver it to market next year? Part of the answer is accelerated aging, a rubric that covers a wide range of testing techniques for making manufactured products break down faster than they would in actual use. The results are imprecise by nature, and it is hard to know how far you can rely on the conclusions. Unfortunately, this also means that business executives looking at accelerated aging test data can easily convince themselves that their latest designs are far more durable than they will turn out to be in practice.
Aging is a factor in the breakdown of the defective Takata air bags. It took years to discover the extent of the defects, and that was mainly because the air bags would develop the tendency to rupture spontaneously only after years of actual use. The aging of automobiles generally is also a factor. The expectation a generation ago that a car should run at least five years has stretched out to twenty, and as we go into the electric car era that number will only go up. As cars get older we continue to discover parts that we wish had been made a little tougher when the cars were first put together. Maybe the defective air bags fall into this category. I haven’t seen anything to indicate that Takata was designing products to last for just five years, but after the fact, some of the failure data looks like that of a five-year product. Most of the recalled cars are more than seven years old, a long enough time to discover that the air bag designs were not as physically stable and durable as they needed to be.