T'as mal cherché !
Rahul .Gokhale, Program Manager at Lockheed Martin
Answered October 5, 2016 · Author has 117 answers and 101.8K answer views
To the best of my knowledge, MIG 25 was the last plane to use micro vacuum tubes. The reasons for that are not publicly known but people speculate that this was done to “nuclear and EMP” harden the electronics. Vacuum tubes are not produced in north america anymore but interesting work is being done on vacuum transistors (mash up of silicon xsistor and vacuum tubes) so who knows, we might see more use in futuristic military hardware.
Doug Hanchard, worked at Aviation
Answered March 10, 2015 · Author has 3.1K answers and 8.8M answer views
Originally Answered: Aircraft: do any modern aircraft use vacuum tubes?
Mikoyan-Gurevich MiG-25's have not been in front line fighter service in any National Air Force since 2006.
Vacuum tubed early radar systems were replaced by electronic versions in the mid-1990's. While it is true, early generation vacuum tubes can survive an EMP, in 99% of the tests the Russian's carried out, the electronic board the vacuum tubes were attached were fused (short circuited) and severely damaged. The only way to increase the odds of its survival is to turn off any device during the EMP event (and it is not guaranteed to work), which means its weapons sensors are turned off, something pilots are not going to do and how would they know when to turn it off. EMP effects occur 1/1,000,000th of a second after they occur.
Modern aircraft do not use vacuum tube based systems for three primary reasons;
Reliability (poor) and size (huge)
Power consumption (massive) and quality of power (sensitive to any noise)
Accuracy (timing) is 10% compared to solid state - silicon based systems.
The one plus of a vacuum tube based radar is its power output. I wouldn't stand in front of one during a test op as some versions were Smerch-A, 600 Kilowatt versions. (Yes, you read that right, kilowatt...) Today that would be a huge drawback. You would be 'painted' from thousands of miles away by a AWAC's E-3 Sentry in a nano-second.