The engineer will then run a few tests and simulations, green-light the change, a superior will check the maths, and they'll be good to go with making the part by hand.
> But there was worse to come: every part in the production process has to be signed off at each stage of its manufacture on a document called a "shop traveller". This records that each individual stage of manufacture has been carried out in accordance with the type design.
> The Boeing team discovered that Ducommun had apparently falsified these records: it had two sets of "books" - the official one recording that each part had been made by the computerised process and a second set recording the actual, handforming process which had really been used.
> What that meant, in the eyes of the Boeing team, was that every single chord and bear strap manufactured by Ducommun had to be viewed as unlawful.