On January 6, 1998, about 2034 eastern standard time, a Bell 206B, N333FC, registered to Skyline Aviation, collided with trees while approaching to land at Savannah International Airport, Savannah, Georgia, while on a Title 14 CFR Part 91 personal flight. Instrument meteorological conditions prevailed at the time and no flight plan was filed. The helicopter received substantial damage and the private-rated pilot and one passenger received minor injuries. The flight originated from Stuart, Florida, the same day, about 1815. The pilot stated he obtained a weather briefing via computer prior to departing Stuart, Florida. After departure he flew a direct course to Savannah, Georgia, at 2,500 feet. At a position 20 miles southeast of Savannah International Airport, he contacted the FAA Savannah Approach Control. They informed him that the weather at Savannah International Airport was ceiling 500 feet overcast, visibility 1 mile, and altimeter setting 30.05. He requested and received a special VFR clearance to Savannah International Airport. He flew north of the airport and then made a left turn to land into the wind. His altimeter was reading 400 feet at this time. About 1 mile north of the airport the helicopter collided with branches of a tree and an emergency landing was made in a field about 1 mile northwest of the airport. The passenger stated that the flight from Stuart, Florida to Savannah was conducted at 1,500 feet. When the flight was about 50 miles from Savannah, they obtained the weather from Savannah, which was visibility 1/4 mile, cloud ceiling 100 feet, and altimeter setting 30.05. About 25 miles from Savannah the pilot began a shallow descent. There was a thick layer of ground fog below them and they had no visual contact with the ground. The pilot obtained a special visual flight rules clearance from the FAA Savannah Approach Control. When 10 miles from Savannah and below 1,000 feet, the pilot obtained a heading direct to Savannah from LORAN. They flew over an area of lights and then into darkness. The altimeter read 500 feet at this time. A short time later he observed the altimeter at 480 feet and looked out the front windshield where he observed the silhouette of large trees. They collided with the trees and the windshields and chin bubbles broke. The helicopter continued to fly and a short time later began to spin uncontrollably. He placed his feet on the torque pedals and the spinning stopped. They made a forced landing in a field and shutdown the helicopter. The passenger stated that at no time during the flight did he observe the pilot reset the altimeter with the current seeting. Examination of the helicopter by an FAA inspector showed there were oak tree branches sticking out of the main rotor hub. The outer 18 inches of each main rotor blade had impact damage to the under side. Both front windshield and lower chin bubbles were broken. The pitot tube had been knocked off and the left cockpit door post was separated from the aircraft. The anti-torque pedals were damaged. See attached inspector statement.