Maybe its something a pilot with a lot of experience becomes.
You said it first.
You cannot really become a worthwhile test pilot until you have suffecient knowledge and experience of the roles and missions you will be testing for,
The tp course teaches you (amongst other things) some of the tools to test aircraft to get quantitative data when its required, but the most important thing a test pilot brings to the table is his experience and knowledge of what the aircraft needs to be able to do.
Equally a transport pilot would not be expected to go off and test fighters and vice versa. Its called role relation.
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