|Quoting prebennorholm (Reply 3):|
Vacuum tubes were nothing special for the A2D. All military planes (and ships, tanks etc.) of the A2D era carried hundreds or thousands of vacuum tubes for electronics such as communication, radar, bomb aming computer, jamming equipment and all such things.
Thousands? Certainly not. The power needs of such an assembly would be huge, it'd be throwing off heat like mad so that cooling would also be a huge issue, and it'd be unreliable as hell in anything that moved.
Hundreds would be quite improbable as well. Perhaps maybe on the B-29, which was the most advanced aircraft of its time in terms of systems, and cost more to develop than did the atom bomb!
Keep in mind that most tubes were dual-function, they had 8 pin sockets, so one could implement two triodes inside one envelope, or a pentode and a diode, and various other combinations/permutations of interest.
For instance, here's a description of a common WWII aviation receiver and transmitter, with a total of 10 tubes for both Rcvr and Tmtr:
LF/MF/HF receivers all use a similar same 6-tube superhet design: r.f. amplifier (12SK7), converter (12K8), two i.f. stages (two 12SK7's, or 12SK7/12SF7), diode detector/BFO (12SR7), and one audio stage (12A6). Transmitters use four tubes: 1626 oscillator, two 1625 finals, and 1629 magic-eye tuning.
Many of the tubes are pentodes, like 12SR7:
But the 12K8 was a diode/pentode setup:
Also keep in mind these folks were very clever (and they didn't have an Internet to waste time on!) and knew how to minimize their design, which made it more rugged and less heavy. The main amount of weight came from the transformers needed to provide the high voltages needed for the tubes.
The above says all it did was control prop pitch, which is far less than anything remotely resembling a FADEC.
ObOldManRef: I was an electrical engineering student in the early 80s when one of our profs, who had been trained in the 50's, gave us an hour lecture on vacuum tube circuits! Funny thing is I already knew a lot about them, since I had been using them for amateur radio for years by then!