THE PILOTS INTENTIONAL FLIGHT INTO ICING CONDITIONS WITH AN AIRPLANE NOT EQUIPPED FOR FLIGHT IN KNOWN ICING CONDITIONS. THIS RESULTED IN AN UNCONTROLLED DESCENT AND CONTACT WITH TREES IN INSTRUMENT METEOROLOGICAL CONDITIONS. FACTORS RELATED TO THE ACCIDENT WERE: THE PILOTS DISREGARD OF THE WEATHER BRIEFING WHICH INCLUDED FLIGHT PRECAUTIONS FOR MODERATE ICING, AND HIS OVERCONFIDENCE IN HIS ABILITY AND THE AIRPLANE'S LIMITATIONS.