I have a co-worker that has his rotorcraft private certificate and wants to get his fixed wing rating. What are the requirements to add on a fixed wing rating for someone that already has a rotorcraft license? My initial research looks like he may at a minimum need 20hrs with an instructor and 10hrs solo?
That's essentially it, with the specifics for the various night, XC, etc., as stated in 61.109(c ). But you won't need an additional written test.
Since he already holds a private certificate, 61.109(a) does not call for a specific number of hours required, except as I will note here. He does need to get to solo, whatever that takes, and by regulation, he needs 3 hours dual in each of these - cross-country, night, instrument training, and test prep (can be combined as the instructor sees fit). He also needs 10 hours of solo time.
Since he is adding a category rating, 61.63(b) requires the proper aeronautical experience I noted and a flight test; a knowledge, or written, test is not required, as Ron noted.
A successful flight test will count as a flight review, and all subsequent flight reviews may be taken in either a single engine airplane or a helicopter; he need not take a flight review in both.