On July 21, 2001, approximately 0830 Pacific daylight time, a Cessna 120, N90077, collided with trees about seven miles east of Troutdale, Oregon. The private pilot, who was the sole occupant, received serious injuries, and the aircraft, which was owned and operated by the pilot, sustained substantial damage. The pilot departed Portland-Hillsboro Airport, Hillsboro, Oregon, about 30 minutes prior to the accident, and was en route to Baker City, Oregon. The 14 CFR, Part 91 personal cross-country flight, which the pilot intended to conduct under visual meteorological conditions, inadvertently entered instrument meteorological conditions just prior to impacting the trees. No flight plan had been filed. The ELT, which was activated by the impact sequence, was turned off at the scene. According to the pilot, he intended to fly just beyond the southern border of Troutdale Airport's Class Delta airspace, and then enter the west end of the Columbia Gorge at 1,500 feet MSL. At the time of the accident, the overcast layer covering the west end of the gorge was lower than what had been forecast for the airport itself. In his efforts to keep clear of the Class Delta airspace, the pilot became focused on the indications of his hand-held Global Positioning System (GPS), and inadvertently entered the overcast. When he realized he had entered the clouds, he switched his attention to the aircraft's attitude indicator, with the intention of making a 180 degree turn. However, the instrument had tumbled, and was not useable as a point of attitude reference. The pilot therefore immediately switched his attention to his turn coordinator, and was about to initiate a turn when the aircraft's left wing impacted a tree. The pilot estimated that it was less than 10 seconds after he entered the clouds that the aircraft collided with the trees.