“They should consider themselves lucky, debugging the DC-10 and Electra occurred only after fatal crashes of each type. “
BS. Engineering does not have to result in failure. Bad mangement is most likely the cause. For every failure there is an engineer saying, “Told ya so.”
I've sat in many design reviews where the engineers insist their design is perfect even though it can be and was proven to be unproducible, faulty or just plain failed in concept.
That's why there are dash numbers and revision letters in engineering documentation, someone fixed a design flaw or implemented a work-around.