posted on Dec, 28 2004 @ 11:34 PM
Originally posted by spaceghost
1. Why would you uses depleted uranium on the wing tips, does this have any real effect as to stability or speed performance?
Do a thought experiment here with me. Okay, you are tooling along at 1000 feet AGL at 90 knots, chewing gum and wiggling your feet whilst twitching
your hands. Kopacetic. And then you hear: silence.
Oops. Motor off.
Maybe you ran out of fuel, the engine died, you took a hit, or whatever.
Now. How do you fly without a motor? Easy. You autorotate.
Slight aft cyclic, right pedal (assuming US rotor here), drop the collective all at the same time. Air comes up through the rotor as you drop in a 3:1
glide ratio, windmilling the blades. Watch your airspeed and RPM. As you near the ground, aft cyclic flare, forward cyclic level the skids, raise the
collective and keep the nose straight with the pedals. If all goes well, you are down all in one piece.
Problem is, reaction time. Until you drop that cyclic, the drag of the pitched rotor blades is eating RPM. If the RPM goes low enough before you do
something, blades stop lifting and you become a lawn dart. So you need some energy stored in the blades. Add weights (DU) to the blade tips, and you
buy time through stored centrifugal energy. So now it is easier to enter autorotation before you run out of RPM. Next problem: you've been trading
altitude for RPM all the way down. Now you are at the bottom, and you have nothing left to trade. Except that stored cetrifugal energy. With enough
energy in the blades, when you raise the collective at the bottom you can fly the ship down under control to a soft, controlled landing.
Weight adds stress to the rotating assemblies, so there is a limit to how much you can load on. It also has a damping effect, which can minimize some
of the numerical chaos up there in the world of vortices. So more weight at the blade tips is better up to a point.