On: The Norway Problem

[lixtra]

> 3. I used to work for Boeing on flight critical systems, so I speak about how these things are really designed. Critical systems always have a backup. An assert fail means the system is in an unknown, unanticipated state, and cannot be relied on. It is shut down and the backup is engaged.

I ask you to reconsider your assumptions. How did this play out in the 737 MAX crashes? Was there a backup AoA sensor? Did MCAS properly shut down and backup engaged? Was manual overriding the system not vital knowledge to the crew?

You don’t have to answer. I probably wouldn’t get it anyway.

But rest assured that I won’t try to program flight control and I strongly appreciate your strive for better software.

[WalterBright → lixtra]

> How did this play out in the 737 MAX crashes?

They didn't follow the rule in the MCAS design that a single point of failure cannot lead to a crash.

> Was manual overriding the system not vital knowledge to the crew?

It was, and if the crew followed the procedure they wouldn't have crashed.