On July 5, 1991, a Hughes 369D (registration N18KJ) operated by Nova Group, Inc was involved in an aviation accident near Napa, CA. Investigators recorded the probable cause as: THE PILOT'S FAILURE TO MAINTAIN THE PROPER ALTITUDE. CONTRIBUTING TO THE ACCIDENT WAS THE PILOT'S IMPROPER IN FLIGHT DECISION TO FLY IN THE BELOW VFR WEATHER CONDITIONS AND HIS MISJUDGED WEATHER EVALUATION. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A student helicopter pilot with an airline transport pilot certificate for airplanes collided with terrain after encountering ground fog on a short business flight.
Background
The pilot involved in the accident held a student helicopter pilot certificate and an airline transport pilot certificate for airplanes. The pilot's flight instructor had authorized the pilot to operate the helicopter only under visual flight rules (VFR).
Flight Sequence
The pilot departed on a business flight between his home and his office. At the time of takeoff, the pilot was aware of the weather conditions: a 500-foot ceiling and visibility of one mile. After flying for approximately five minutes, the pilot encountered decreasing visibility to 1/16 mile and ground fog. The pilot reversed course and subsequently collided with the underlying terrain.
The accident occurred during daylight hours, and the helicopter was not equipped for instrument flight. No further details about the aircraft or injuries were provided in the source.