MAD Boom, Observers in the RN do not just navigate, they are the airborne Principal Warfare Officer; the mission commander or mission systems/ weapon system manager- navigation is just a small part of their role, but I'm sure you knew that.
Don't Apache Aircrew swap roles between being the Pilot one mission and the Gunner the next?
Too simplistic a comparison? Hmmm, so is calling the Observer "a navigator". And no, I am not an Observer!