Originally Posted by
Longtimer
With a lot of 737 Max8s flying, you have to wonder what was different about this bird? If an overall design problem, then why has there not been more incidents? If with only that bird, perhaps new suppliers or even a manufacturing flaw.
Not necessarily, it is entirely conceivable that a design flaw has been lurking there since day one of commercial operation. It just takes a specific sequence to cause an accident. I mentioned earlier the
Lindy Effect, which is an observation that the longer something lasts, the higher the probability that it will continue to last.
The 737 STS design is very old, the MCAS is not. The STS dataset is enormous, it is well proven technology that has survived the test of time through huge numbers of potential failure modes. The MCAS is a new technology, with only 220 aircraft in service, it has a much smaller reliability dataset in the real world compared to the STS system. There haven't been a large enough sequences of failure modes to truely test the design of the MCAS, compared with the STS.
This is about a series of probability paths (multiple events in a unique sequence) that lead to an adverse outcome, STS has proven itself to be a solid design over an enormous range of these paths, and we can probably conclude it is unlikely to have a significant design flaw based on time in service. MCAS has not been around for long, and it appears that a unique series of events has demonstrated a flawed design early on in the service life.