HISTORY OF FLIGHT On May 13, 2002, about 1115 Pacific daylight time, a Cessna 152, N48512, experienced a partial loss of engine power and made an emergency landing in the Ohlone Wilderness area about 15 miles south of the Livermore Municipal Airport (LVK), Livermore, California. The airplane, operated by Flying Particles as an instructional flight under the provisions of 14 CFR Part 91, sustained substantial damage. The certified flight instructor (CFI) and the student pilot received minor injuries. Visual meteorological conditions prevailed for the local area flight, and no flight plan had been filed. The flight departed LVK about 1020, and was scheduled to terminate at LVK. The CFI and student pilot provided the following information. The CFI reported that they departed from LVK with full fuel tanks, and the purpose of the flight was to practice maneuvers in the local area. They practiced touch-and-go landings for about 45 minutes before departing to the south to do air work. The CFI stated that they were about 2,500 to 2,800 feet mean sea level while doing the air work. He and the student decided to fly down to the Bay before terminating the flight. The CFI indicated that they had to cross a ridge in mountainous terrain before they could fly directly to the Bay. As the airplane climbed over the ridge, both the CFI and the student noted that the engine was running rough, "like a rough running magneto." Both the CFI and student reported that the engine was producing power, but not enough to sustain flight. The airplane started to sink. The CFI instructed the student to increase the power; however, the airplane continued to sink. The CFI took the flight controls and maneuvered the airplane to a clearing area for a forced landing. The main landing gear touched down and the airplane bounced into the air. The airplane went over a crest line where it came to rest upright after colliding with trees about 30 feet down from the crest. METEOROLOGICAL INFORMATION The closest official aviation weather observation station is the Livermore airport, which is 15 miles north of the accident site. At 1053, the station was reporting the following conditions: Wind 280 degrees at 13 knots; sky clear; visibility 10; temperature 64 degrees Fahrenheit; dew point 44 degrees Fahrenheit; and altimeter 30.16 inHg. The report for 1153 listed a temperature and dew point of 67 and 43. A carburetor icing probability chart indicated that the temperature/dew point at Livermore were favorable for moderate icing conditions in cruise power. TESTS AND RESEARCH A Federal Aviation Administration (FAA) inspector arrived on site 2 hours after the accident. He reported that there was a strong odor of fuel present. The right fuel tank was intact and contained an estimated 5 gallons of fuel. The left tank was compromised in the impact sequence and an estimated 1.5 gallons remained. Following recovery of the aircraft to a storage yard, it was examined by Safety Board investigators with technical assistance by Cessna and Textron Lycoming. The outboard right wing was separated at the flap/aileron joint. A 24-inch diameter semicircular impression was centered in the leading edge at a point 44 inches inboard from the tip rib. Brown organic material transfer was evident in the crush folds of the impression, which extends back through the main spar. The vertical axis of the impression crush folds were oriented at 15 degrees to the vertical (105 degrees from horizontally level at the wing's leading edge). The inboard right wing remained attached to the center section and was bent aft about 10 degrees. At the inboard/outboard wing separation point, a semicircular impression with a 24-inch diameter was observed. The left wing remained attached to the center section. Multiple semicircular impressions were observed along the leading edge, with crush lines extending aft to the main spar. The flap actuator jack screw was measured at 1-inch extension. According to Cessna, this equates to a flap position of 10 degrees extension. The McCauley 1A103 propeller remained attached to the engine crankshaft. Blade No. 1 exhibited leading edge nicks, with cordwise striations and scratches. The blade is torsionally twisted toward the cambered side and bent in the rotational plain opposite the direction of normal rotation. Blade No. 2 exhibited heavy leading edge damage and tip end polishing (paint worn off to bare metal). The blade has a 15-degree twist trailing edge toward the cambered side, with a forward curled bend at the tip of about 110 degrees. Both blades exhibit a trailing edge sine wave pattern. No obstructions or foreign objects were found in the fuel tanks. The vents in the fuel tank caps were clear. The crossover vent between tanks was clear and the wing vent tube was unobstructed. No obstructions were found in the fuel lines from the tanks to the carburetor. The fuel selector was confirmed to be in the BOTH position detent.. About 20 ml of blue colored liquid with an aroma like aviation gasoline was drained from the carburetor bowl. The carburetor venturi was intact and the inlet screen was clean. No obstructions were found in the induction system from the inlet filter to the cylinders. The engine crankshaft was rotated by hand with thumb compression developed in each cylinder. The right and left magnetos were timed at 21 and 23 degrees, respectively. The engine was removed from the airframe and mounted in a test stand. It started on the first attempt and was exercised throughout the normal range of power from idle to full power with no anomalies found.