On October 4, 1996, at 1615 eastern daylight time, a Cessna 172, N5154E, sustained substantial damage when it collided with trees and descended into terrain near Coudersport, Pennsylvania. The certificated commercial pilot and the passenger/photographer both received serious injuries. Visual meteorological conditions prevailed for the aerial photography flight that departed Bradford Airport at approximately 1415. No flight plan was filed for the local flight conducted under 14 CFR Part 91. The purpose of the flight was to photograph a private residence in Coudersport. The house was located at the base of a hollow with steeply rising terrain on both sides. The general direction from the house to the accident site runs up the hollow. The distance between the two sites was approximately one-half mile. Both sites were located on a mountain that had a peak elevation of 2514 feet msl. In a telephone interview, a witness who was 600-900 feet from the accident site stated: "...heard the airplane fly ... overhead two or three times and I noticed they were quite low. The last time I saw them go over ...[the airplane] seemed to be working fine. I didn't perceive any motor problems. They gunned it to climb over the valley - seemed like they were climbing." The witness also stated that he heard "...a severe noise..." when the plane crashed. He said that when he arrived at the wreckage he found two men trapped inside; "...the man I couldn't see said, 'Pull up and land on the road'." An examination of the wreckage by FAA Inspectors and representatives of the airframe and powerplant manufacturers revealed no pre-impact anomalies. One FAA Inspector reported: "The aircraft was found in an inverted position and was substantially damaged. The distance from the first sign of impact to the aircraft was 60 feet. The propeller was buried making it impossible to view the front, however propeller cuts in the trees were found. The amount of fuel on board could not be determined because both tanks were damaged, but the odor of fuel was present. A review of the maintenance records and a control continuity check were both satisfactory." Interviews with the pilot and the passenger revealed that neither had any recollection of events from the accident flight.