Depleted Uranium has a half life of about 4.5 billion years. This means that the first decay in a long decay chain goes very slowly...1/2 of the DU decays every 4.5 billion years.
What this means is there are very few radioactive particles emitted. The first decay emits alpha particles (big and slow) that are stopped with a piece of paper or a few centimeters of air.
Many people counter this argument with the fact that the elements produced in the decay are more radioactive than U238. This is true however the elements are produced very slowly as well. All the by products have a half life that is substantially smaller than that of U238 so there is no significant buildup of other materials. The decay of the by products does include beta and gamma emissions, which take more than paper or a few centimeters of air to stop, but the rates of production are so low that even completely unshielded result in negligible radiation doses.
Am I saying this stuff is safe? Not at all. With enough quantity (much more than would be used as tip weights) the radiation dose could become a concern. In small quantities DU is highly toxic, same as most heavy metals. That is the big concern.
This is where ingestion is a factor. Any dust from this is not something to inhale. Wash hands if contacting it directly. I assume most of the stuff would be coated in a safe metal, as mentioned previously so dust or contact shouldn't be a concern.
The spinning of the blades won't produce any noticeable effect on whatever gamma emmisions (high energy photons) make it to the cockpit. Very little effect on beta particles (electrons), and a very small effect on alpha particles (helium nucleii), if any are even detected at the cockpit.
If there is any dust the spinning would help keep it away from the pilot. Recirculation would be bad but with the density of Uranium and the speed of the downwash, probably not a problem. The spinning would send the dust everywhere, diluting it and making it a very very small problem for everyone else, kinda like how we treat waste from hydrocarbon combustion (the solution to pollution is through distribution).
Long story short, if you don't touch it, don't worry about it.
Matthew.
[This message has been edited by heedm (edited 26 April 2001).]