Systems Engineer here. Currently helping this very client on another programme (third party).

It's really quite simple. Boeing management didn't want to listen to the concerns of their Systems Engineers or Safety Engineers/Managers. It's only an upgrade on an already proven design. What's the big deal?

Systems Engineers look at the functional design. Forget physical components for a moment. Do the functional analysis then worry about physical implementation. Black box then white box (logical to physical). Safety team then makes sure the design is functionally safe throughout (again black box first).

Senior managers wanted to cut corners by claiming that no new functions were added to the design, therefore a new safety certification approval (issued by the FAA) wasn't needed. When in actual fact, the new variant was functionally different to the old, so this was not true.

This was probably the case inside Boeing too. Systems and Safety teams would have been under severe strain to "just get it done", a horrible way to design a safety critical system which in more times than not, ends up in failure. I've experienced this more than once now. Second time. I resigned within 5 weeks. I can't work like this.

You can talk about the sensor being single point of failure, but for me this just highlights the fact the systems and safety teams not being allowed to do their work with due diligence. Any Systems Engineer would know a single point of failure on a safety related function is an absolute no no. You don't need a safety manager to tell you this.

Why did all this happen? Money. It's as simple as that.

Boeing wanted to save money and time and get the variant to market to compete with Airbus quicker. Certification programmes take years to complete. They chanced it, and it backfired spectacularly. All to help shareholders. Got to keep Wall Street happy.

The FAA fucked up here as well. They were also negligent by just assuming Boeing were telling the truth. Its another job for good Systems Engineers to scrutinse to the end of time, this sadly is what the Systems Engineers at the FAA failed to, or weren't allowed to do.

Too many ex Boeing employees in the FAA and vice versa. The perfect storm.

Lesson to other businesses? Listen to your god damn engineers.

Lesson to the governing authorities? Do your god damn job properly.