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‏When the helicopter propellers spin and speak to with the sand dust, sparks fly. This phenomenon is called Kopp-Etchells Influence. — contemporary

‏When the helicopter propellers spin and contact with the sand dust, sparks fly. This phenomenon is called Kopp-Etchells Effect.

‏When the helicopter propellers spin and call with the sand dust, sparks fly. This phenomenon is called Kopp-Etchells Effect. – stunning