On October 11, 2003, about 0800 Pacific daylight time, a Luscombe 8F, N1918B, collided with terrain just after departure from the French Valley Airport (F70), Murrieta, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot was not injured; the airplane sustained substantial damage. Visual meteorological conditions prevailed, and no flight plan had been filed for the personal cross-country flight. The NTSB investigator-in-charge (IIC) reviewed a copy of the Riverside County Sheriff's Department police report. The responding deputy interviewed the pilot. The pilot reported that he and his friend [in another airplane] were en route to Phoenix, Arizona. After takeoff the pilot decided to land because he had "a strange feeling about the flight." The pilot made a right turn to the south in an attempt to land to the north. During the turn, he saw a hill. He added power and attempted to turn to the right; however, the airplane impacted the hillside. Witnesses to the accident reported that dense fog conditions were present. In a written statement, the pilot reported that when he departed, the sky was clear in his direction of flight. As he departed, a fog bank closed in and he attempted to return to the airport. While in the turn, the airplane impacted the ground. He noted that there were no mechanical malfunctions. In a phone conversation, the pilot stated that his friend departed prior to him. His friend reported clear weather conditions. The pilot did not obtain a weather briefing prior to departure.