Radioactive materials in flight instruments
This post is addressed to the many visitors of this site who repair, restore or simply collect old instruments like altimeters, turn and slip indicator, compasses, etc. However, former pilots and current airliners crew and frequent flyers could find something interesting in this article. Here’s the reason why.
A friend of mine, who’s keen on aviation, recently bought on eBay an old ADI (Attitude Indicator). This friend has also a small Geiger counter that he uses to inspect all the items he receives from abroad because he was taught nuclear physics at school. His Geiger counter is able to detect alpha and bravo particles, and gamma rays. He neared the counter to the glass of the instrument and got no audible tone (the Geiger counter has a gas-filled tube that conducts electricity when a particle or photon of radiation makes the gas conductive. The tube amplifies this conduction and outputs a current pulse, which is heard as a “clickâ€; if you hear a click every now and then, you should not worry but if clicks become frequent it means you are near a radioactive source). RadioactivityMy friend opened the instrument in order to clean it and when he used the counter again to detect radiation, to his surprise, he heard multiple frequent clicks, meaning that the portable device was next to “something†emitting either radioactive particles or rays. Since he previously hadn’t detected anything (when the instrument was closed) he was sure that alpha particles were causing that large amout of “clicksâ€, since alpha particles may be completely stopped by a sheet of paper (in his case, by the glass of the instruments), beta particles by aluminum shielding while gamma rays can’t be stopped and can penetrate deeply unless stopped by a thick layer of lead.
With the same procedure, but without removing any glass, the Geiger counter found gamma radiation being emitted by another instrumment.
https://theaviationist.com/special-reports/radioactive-materials-in-flight-instruments/
