Hacker News Reader

And why you design such parts so they cannot be physically installed upside down. http://en.wikipedia.org/wiki/Poka-yoke

It's also why you design the parts so that they are impossible to install upside down. No matter how clearly things are labelled, even the most experienced people will make mistakes.

The shuttle had a similar problem with a large piece of round metal that had more than one way to install of which only one was right. The mechanics knew this and asked for some markers on the piece to ease the process. The markers were never added not because of the cost of four paint points but because of the documentation that had to be updated.

So there is your problem - bureaucracy. I'm sure that an engineer knew about the sensor mounting problem but nobody cared enough to make the change because of the paperwork.

Or why this goes into configuration management and is verified before shipping. Seems not just the "young technician" failed but the process failed to catch the defect.