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I was told that most aircraft had depleted uranium on board as counterweights. I have not seen one myself. Do all current modern aircraft have depleted uranium on board?

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    $\begingroup$ Related: What is the reasoning behind using depleted uranium as counterweights in the 747?, most of the counterweights were replaced with tungsten, so no, most aircraft don't use DU weights. $\endgroup$ – Ron Beyer Feb 4 at 14:53
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    $\begingroup$ You don’t need anything that exotic; Steel or tungsten will work just fine for that role $\endgroup$ – Carlo Felicione Feb 4 at 18:35
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    $\begingroup$ Counterweight to what? I've never noticed any in my 1973 Cessna single engine 4 seater. $\endgroup$ – CrossRoads Feb 4 at 18:55
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    $\begingroup$ @CrossRoads - Why are “counterweights” used in aircraft production? $\endgroup$ – ymb1 Feb 4 at 19:23
  • $\begingroup$ I suspect small aircraft just use a big chunk of shaped lead, and not depleted uranium. That would be a nightmare for A/Ps out in the field if any trimming was needed for example. My parts manual does not appear to say what the parts are made out of. $\endgroup$ – CrossRoads Feb 4 at 19:45
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From my research, it looks like about 0.1% of all aircraft carry depleted uranium counterweights.

The Systematic Radiological Assessment of Exemptions for Source and Byproduct Materials (NUREG-1717), on page 3–260, gives a table showing that 430 domestic United States aircraft were delivered with depleted uranium counterweights, and says that "A reasonable estimate is that 50% of these aircraft still contain DU counterweights." So there are about 200 aircraft in the United States which contain depleted uranium counterweights.

Meanwhile, the FAA's "Air Traffic by the Numbers" publication says that there are over 200,000 aircraft in the United States currently.

So no, very few aircraft use depleted uranium counterweights.

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    $\begingroup$ … but those with DU are the very heavy and big beasts, so per mass the fraction is quite a bit higher. Still, it's insignificant. $\endgroup$ – Peter Kämpf Feb 4 at 22:40
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    $\begingroup$ Is this "all aircraft" in the US, or the world? $\endgroup$ – isanae Feb 4 at 23:58
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    $\begingroup$ @isanae Well, the 0.1% figure is for aircraft in the US, and it seems reasonable to guess that the number is similar for the rest of the world. In particular, the number is certainly not 100%. $\endgroup$ – Tanner Swett Feb 5 at 4:39
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That material is dangerous and expensive. It is used only in special situations where the design requirements are stringent and heavily constrained.

For example, the C-5A cargo plane used depleted uranium (DU) to counterweight its main control surfaces.

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    $\begingroup$ It's not really expensive, at least at acquisition time. "Tungsten markets for \$25 to \$45 per pound depending on the form of the metal" "Depleted uranium costs \$5 per pound from old stockpiles" and lead is \$1 per pound. DU likes to burn so I hope one would use it in oxide form. Being a very heavy metal doing nasty things to biological systems (Uranium Babies are horrendous) and somewhat radioactive, use gloves when handling. Do not inhale. Dispose at specialized municipal waste recycling centers. $\endgroup$ – David Tonhofer Feb 4 at 20:57
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    $\begingroup$ @DavidTonhofer, thanks for this, the maintenance techs on the C-5 were "on the clock" when working in proximity to the DU counterweights and had to cycle out after a certain number of hours which I cannot remember... $\endgroup$ – niels nielsen Feb 4 at 23:48
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    $\begingroup$ It's not super radioactive, not that I'd want to handle it all that much. I'd rather have to worry about a block of DU than, say, a radon build up or dust from uranium ore processing. I've read that the heavy metal toxicity of uranium will kill you long before the radiation exposure, chemical toxicity estimates put it on a similar LD50 to DDT and MDMA, not all that lethal but still not something to mess with lightly. $\endgroup$ – Kaithar Feb 5 at 3:27
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    $\begingroup$ Indeed. Consider also this C-5A fact: its main landing gear bogies are cast from beryllium, to save weight. this metal is so severely notch-sensitive for fatigue failure that there are NO radii in the structure less than 12" and the entire assembly is coated with a THICK layer of paint. Why? Because the oxides of beryllium, when inhaled, cause berylosis, a deadly disease. For this reason, maintenance techs on the C-5 are on the clock anytime they are in the main wheel wells, to minimize beryllium exposure via scratches in the paint... $\endgroup$ – niels nielsen Feb 5 at 3:40
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    $\begingroup$ @DavidTonhofer - Formula 1 cars used depleted uranium for ballast until sometime around 2001. It was disallowed not because of the toxicity, but because of cost. By the time teams got the depleted uranium, it cost about 7500 (US dollars) per kilogram. A team supporting 3 cars at around 22 kg of ballast per car would end up spending close to 500,000 (US dollars). $\endgroup$ – rcgldr Feb 5 at 15:29

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