CHI86MA071

The purpose of the flt was to take a news crew to a location to cover a story. The news crew had attempted to hire another helicopter, but that operator refused due to forcast low visibility. This plt, however, agreed to fly. Altho he was certified for intrument flt in airplanes, the plt was not qualified for instument flt in helicopters, nor was thehelicopter certified for instrument flt. During a wx briefing, the plt was advised of adverse wx cond. While N1498W was in flt, 2 witnesses obsd a helicopter flying along a hiway on the plt's planned route at a very low alt. A truck driver estimated the acft had passed aprx 2' ovr his 13' rig; he said he could feel the downwash fm the rotor blades. Witnessesestimated the ceiling to be at or below 100' AGL & the visibility to be 1/8 to 1/4 mi with hvy fog. The helicopter crashed & burned aprx 100' fm the hiway near a pwr line crossing. Impact occurred while the helicopter was in a shallow dscnt, hdg away fm the hiway & parallel with the pwr line. Wreckage was not fnd until 1150 CST. No ELT was installed.