On 12/09/2009 08:52 AM, Horace Heffner wrote:
On Dec 8, 2009, at 9:09 PM, William Beaty wrote:
On Tue, 8 Dec 2009, Horace Heffner wrote:
Titanium dust oxidizing.
http://en.wikipedia.org/wiki/Helicopter_rotor
"When operating in sandy environments, sand hitting the moving rotor
blades erodes their surface. This can damage the rotors; the erosion
also presents serious and costly maintenance problems.[9]"
I'd have to track down the article and see if it's speculation. Or in
other words, if we use a sandblaster on titanium, do we get the glow?
Perhaps.
Maybe the eyewitness report was wrong about the glow extinquishing when
the copter ramp hit ground.
I doubt the eyewitness report was wrong, nor that it was inconsistent.
As the copter nears the ground the vortex flattens out and the radius
widens. The air flow hugs the ground and carries the sand outward. The
amount of heavy grains of sand or rocks returning to the blades
diminishes. Also, tip speed drops after landing.
And, as was mentioned somewhere (maybe in the original story), as soon
as the helicopter touches the ground, the blades are feathered. So,
they're still spinning, but lift goes almost instantly to zero, and the
dust cloud will presumably thin out immediately, as there's no longer a
blast of air coming down from the blades.
