I thought it was a small transport and not a fighter...
Not a transport either. The S-3 was originally designed as an anti-submarine surveillance attack aircraft. It can act as a tanker and it has some electronic surveillence capabilities. It can carry up to 4 crewmembers, although I understand the current standard crew is only three, after the removal of some equipment. Since it can drop depth bombs, torpedoes, and some missles, it might be best to think of of it as an attack or bombing aircraft.