[QUOTE=cdrmuetzel@juno.com;45336]
As I see it, the Order and the AC say the same thing with slightly different wording, basically: during Phase I, no person may be carried in the aircraft during
flight unless that person is essential to the purpose of the flight. Examples of essential personnel, as I understand it, are pilots, co-pilots, flight engineers, and navigators.
So, as I see it, there are no experimental amateur-built aircraft that would have an "essential" or "required" crew of more than one. The AC does allow for an exception to allow a non-flying pilot aboard a test flight, but that exception must asked for, granted, and written directly into the operating limitations, just like the Additional Pilot Program.
People have, and still do, interpret "person... essential to the purpose of the flight" however it suits them, and many people believe that there is wiggle room in the phrasing. I would only say that I would not want to be ramp checked after a Phase I test flight that had another pilot on board for whatever reason, unless that other person were accounted for in my ops limits. I am certain that the FAA inspector wouldn't buy the "essential" safety pilot/data recorder/radio operator gambit and my ticket and I would be temporarily separated.