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P O L Y T E C H . N U

Avionics safety!

radioactive dial paint
Avionic instrument dials can be coated with radiating paint. Don't be scared, but beware of the health risks!

The radioactive paint is used since Radium containing paint keeps illuminating for hours after removing a light source. So the dials are lit in the dark for a while. After years the illuminating effect fades away. but the radiation is still there. The radiation risk is relative low as long as a reasonable distance is big enough. The dose is four times less for each two times the distance to the source. A couple of centimetres should do the trick. The risk of contamination by inhaling/ingesting is much bigger!

warningSo don't open avionic instruments unless you are trained and have the equipment to handle this safe.
Avoid scratching, filing, sanding the paint to prevent spread of particles.

In the video below the radiation detection is very clear. Almost every dial radiates a relative low dose of radiation except one double dial. The background radiation is here 0,1 uSv/h. (The video starts at a higher number due to the measurement before the video in combination with the meter averaging.) The dose measurement peaks at 36 uSv/h. Since there's glass between the dial and the detection tube, only Beta and Gamma radiation is detected. The main radiation is Alpha radiation, but doesn't penetrate the glass. So the radiation is likely much more behind the glass. Therefore avoid breaking/damaging the glass. Radium decays to Radon (gas), so keep the instrument in a well ventilated place.

If no dose meter is available, uv-light can be used to detect radioactive paint. The paint will illuminate clearly if uv-light is applied. Usually old instruments are pained with Radium. Newer instrument are usually painted with white paint to avoid the health risks. White paint won't illuminate as much as Radium paint. On the image and animation below, the effect of uv-light is clearly visible.

noteAs long as the instrument are not damaged/opened, it's rather safe to handle them.



Sidenote: This instrument panel was installed in Saab 91D Safir with registration number PH-RLS. This plane was used for the Dutch 'Rijksluchtvaartschool'. (RLS = RijksLuchtvaarSchool) The airplane is out of service and can still be seen as an eycatcher at Eelde airport in the north of The Netherlands. The instrument panels are now in proud possession of a collector. The displayed instrument panel is shown in the middle of the cockpit on the photo below.

Source: Airplane photo PH-RLS: Collectie Nederlands Instituut voor Militaire Historie

Beryllium material
I was informed by Erik that it's possible that gyroscopes can be made of beryllium. High quality instrument grade beryllium can be used to get the desired level of performance. Gyroscopes are rotating with a very high speed so the gyroscope should be perfect balanced to avoid instability/damage. The desired performance and repeatability is possible using light weight materials like beryllium. Aluminium can also be used, but beryllium alloys like beryllium copper is probably used for high quality instruments. Beryllium copper is also known as BeCu (of CuBe).
Beryllium bronze and spring copper, is a copper alloy with 0,5...3 percent beryllium and sometimes other elements. Advantages of the combination is it's high strength so the gyroscope won't explode due to forces. Other advantages are that it is non-magnetic and non-sparking which is convenient for tools in explosive environments.

Beryllium alloys present a toxic inhalation hazard during manufacture. In solid form and as finished objects, beryllium copper presents no known health hazard. However, inhalation of dust, mist, or fume containing beryllium can cause serious health damage (lungs). IARC and NTP lists beryllium as a carcinogen.

warningBeryllium is carcinogen!
Avoid scratching, filing, sanding the metal to prevent spread of particles.

noteAs long as the metal is not damaged, it's rather safe to handle the metal.

On the image below is my Ferranti FTS 21T turn and slip indicator shown. Due to the copper coloured gyroscope, it's very likely that the gyroscope is made of an beryllium alloy. The cylindrical bronze coloured 'ring' is the rotating part of the gyroscope.

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