Kopp-Etchells Effect

Here is an interesting helicopter fact about the Kopp-Etchells Effect.

When helicopters pass through dust storms, contact of the particles with

the rotating blades produces either sparks or static electricity.

The phenomenon has been observed during combat operations in Afghanistan ;

Michael Yon has documented the effect, and has named it after two U.K.

soldiers who died there. "Kopp-Etchells"

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 . 

The abrasion strips on helicopter rotor blades are made of titanium, which

is very hard, but less hard than sand; so when a helicopter is flown near to

the ground in desert environments abrasion occurs, and at night there is a

visible corona or halo around the rotor blades, caused by the sand hitting

the titanium and causing it to spark and oxidize .