#kopp-etchells effect

It's a TRAP!

A Marine Corps MV-22 Osprey assigned to Special Purpose Marine Air-Ground Task Force-Crisis Response-Central Command stages on a hasty landing zone during a tactical recovery of aircraft and personnel drill at an undisclosed location in Southwest Asia, Nov. 16, 2015.

The abrasion strips on helicopter rotor blades are made of metal, often titanium or nickel, which are very hard, but less hard than sand. When a helicopter is flown near to the ground in desert environments abrasion occurs from the sand striking the rotor blade. At night, the sand hitting the metal abrasion strip causes a visible corona or halo around the rotor blades. The effect is caused by the pyrophoric oxidation of eroded particles.

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In 2009, photographer Michael Yon dubbed this phenomenon the “Kopp-Etchells effect" to honor Cpl. Benjamin Kopp and Cpl. Joseph Etchells, recently fallen American and British soldiers.