I just finished watching National Geographic's Megafactories: Boeing 747-8.
During the test flights, a bunch of engineers are on board the plane, presumably controlling the water tanks that distribute weight, and collecting the data.
Another time I'd seen it was when they were testing detection systems for microbursts. There were about a dozen engineers sitting on the plane, watching monitors while the crew deliberately flew into hazardous conditions.
Why do they risk the safety of these engineers, when presumably the work they're doing could be automated or controlled remotely? For data to be observed, couldn't they do that from the ground?
Is this a case of "we've always done it this way?" Even now that we probably have the technology that would allow the engineers to avoid having to go on test flights, I'm guessing that changing this procedure would be a lengthy and difficult process.
Besides the pilots, why does anyone else need to be on board?