Exactly what's the deal with instructing and medicals? I know you need at least a third class if the instructor will be the PIC ie primary or initial multi. What about if instructing commercial or CFI's? At least a second class. Right?
Technically, no. Part 61 only requires a 3rd class medical to instruct, regardless of the certification or rating sought. Now, what kind of medical do you need to get paid as an instructor? You'd think at least a second class, right? This was my understanding until recently. Apparently, the FAA feels that you, as an instructor, are being paid to instruct, not to fly. Now keep in mind, if you operated as a CFI with only a 3rd class medical, you would be limited as to what you could do (ie. no scenic flights, no photo flights, etc.) Lastly, to muddy the waters even further, if the student can act as PIC, you don't need a medical at all to instruct.
You need a medical anytime the person you are instructing can't act as legal PIC, IE student pilots. Giving a biannual to a person whos biannual has run out. However you could give instrument instruction to a person that is current and and has a medical as long as you did'nt file (assuming he does'nt have his ticket yet). So there are a few instances where you can instruct without a medical, not many though.
Are you sure about giving Instrument instruction w/o a medical? I was under the impression that you needed a current medical whenever you were instructing someone under the hood or acting as safety pilot. At that point arent you PIC/required crewmember?