/*Karen Johnson*/ was flying the aircraft early Wednesday morning to help keep crops from freezing -- when the helicopter disappeared from radar.
About four hours later, an air unit with the Kern County Sheriff's Department located the wreckage in a vineyard.
Investigators say the search was difficult because of thick fog and limited visibility at the time.
A spokesperson with the Federal Aviation Administration said Johnson was returning to the Delano airport when her chopper went down.
During cold spells, helicopters move warmer air down onto threatened crops.
The National Transportation Safety Board and the Federal Aviation Administration are investigating the cause of the crash.
