This was the second crewman in British carrier fighters like the Fulmar. The title seems similar to the radioman/gunner in planes like the SBD, but the rationale usually given is that the extra man was needed for overwater navigation. Was the TAG also a navigator? Were they using a radio navigation device like the American YE/ZB?
No, they appear to have been just TAGs. Telegraphist Air Gunners (wartimeheritage.com) The British used a similar system to the YE/ZB. article-part3a-1947-Quinn.pdf (nonstopsystems.com)
"A machinist is a tradesperson or trained professional who operates machine tools, and has the ability to set up tools such as milling machines, grinders, lathes, and drilling machines. Machinist. Machinist, operating a metal lathe. Occupation." I was a machinist mate (MM), and I never did a job like the one above. I swung .50s on my first permanent duty assignment. I wasn't a gunners mate. Military job titles can be a bit confusing.
The headsets allowed the crew to chat. The gunner didn't need to see where they're going, he kept track of headings and speed. Then it's just math.
In good part, the FAA wanted the second seat in planes to provide for a crewman that could assist the pilot in finding the carrier on a return flight. Whether or not the second seat was a navigator or not, he was certainly intended to have skills commensurate with getting the plane back to the carrier. The British system described in the above article was a simple homing beacon. On pg 957 of that article the following under the heading "Security" is given: There is generally no special security objection to operating the beacon whenever an aircraft is away from the aircraft carrier, because the presence of the ship is already revealed within effective optical distances by its radar and v.h.f. radio- telephony transmissions, but methods may be adopted to reduce the probability of detection by the enemy. YE/ZB was intended from the outset to provide a secure and very difficult to detect homing beacon that would keep the carrier's position hidden from the enemy. It was also largely automatic and could be used by a pilot in a single-seat aircraft. Included in the design were security features to render the signal useless to enemy pilots or receiving stations. Unlike the British Type 72 where the radio operator had to align the plane to the signal, with YE/ZB the system would receive a coded signal that when interpreted would tell the pilot what direction the carrier was from his current position without having to carefully align his flight direction to the signal. Thus, the workload using YE/ZB was minimal while using the Type 72 required considerable skill and effort, thus the need for the telegraphist. Microsoft PowerPoint - YE-ZB.pptx (ar88.net) In fact, once the US entered the war, YE/ZB was shared with the RN and replaced the Type 72 homing beacon in service.