On March 24, 2007, at 1115 eastern daylight time, a Piper PA-28-140, N56124, was substantially damaged when it impacted trees and mountainous terrain during a forced landing near Catherine Township, Pennsylvania. The certificated private pilot and passenger were not injured. Instrument meteorological conditions prevailed, and no flight plan was filed for the flight that departed Penn Valley Airport (SEG), Selinsgrove, Pennsylvania, about 0930, destined for Ebensburg Airport (9G8), Ebensburg, Pennsylvania. The personal flight was conducted under 14 Code of Federal Regulations Part 91. During a telephone interview, the pilot stated that the flight originated at Blairstown Airport (1N7), Blairstown, New Jersey, about 0820, and the purpose of the flight was to visit family near Ebensburg. The flight proceeded uneventfully to Selinsgrove, which was about halfway between the departure point and the final destination. The pilot often flew this route, and typically would stop there for a break and to purchase fuel. After the airplane was serviced with 10 gallons of fuel, the pilot departed for Ebensburg. He did not note any problems with the airplane during the taxi, runup, takeoff, or climb. The pilot used the airplane's global positioning system to navigate directly to the destination, "keeping the airplane on the line." While cruising at 4,500 feet, and about 10 minutes from the destination, the engine started to "run rough." He applied carburetor heat, but that only made the roughness worse, so after about one minute, he turned the carburetor heat back off. He noted that the oil pressure was "fine," but the engine continued to lose power. The pilot then decided to "take emergency action," configured the airplane for best glide speed, and chose the top of a nearby mountain as a forced landing site. During the descent he actuated the throttle, with no reaction from the engine. He described the loss of power as being similar to reducing the throttle. By the time the airplane contacted the trees on top of the mountain, the propeller was "windmilling," and he thought that the engine had ceased running completely. In a subsequent interview with Federal Aviation Administration (FAA) inspectors, the pilot recounted the accident. About one-half to one hour after departing Selinsgrove, the engine, "…started losing rpm's. As it was dropping off, I was trying to increase it. I thought it was carb ice, so I cut it on and it didn't make much difference but continued to decrease rpm and added to the rate of decrease. About 30 seconds [later] I cut it off." The pilot held a private pilot certificate with a rating for airplane single engine land, which was issued on November 4, 1994. He did not hold an instrument rating. The pilot's most recent FAA third class medical certificate was issued on August 25, 2005, and on that date the pilot reported 425 total hours of flight experience. The airplane was examined by FAA inspectors on the following day at the accident scene. According to the inspectors, the airplane struck the tops of several trees, and the wreckage path was oriented in a north by northwest direction. The left wing and empennage were separated from the fuselage, while the remainder of the airplane came to rest on the ground inverted. Examination of the propeller revealed almost no damage, except for a slight bend near the tip of one blade. The engine crankshaft was rotated by hand, and compression was obtained on all cylinders. The bottom four spark plugs were removed and examined. All appeared "normal," except for the No. 1 cylinder plug, which was fuel soaked. The fuel strainer was absent of debris, the fuel filter bowl was dry, and both fuel tanks contained fuel. The weather conditions reported at Altoona-Blair County Airport (AOO), about 17 nautical miles southwest of the accident site, at 1109, included winds from 160 degrees true at 7 knots, visibility 3 statute miles in mist, an overcast ceiling at 300 feet, temperature 46 degrees Fahrenheit, dewpoint 45 degrees Fahrenheit, and an altimeter setting of 30.28 inches of mercury. During an interview with FAA inspectors, the pilot stated that prior to the accident flight he checked the weather using the Direct User Access Terminal Service (DUATS). The FAA inspectors then asked the pilot to read the printed weather report to them; however the pilot was unable to interpret the data. When asked about the weather conditions during the flight, the pilot stated that there was at least 1-mile visibility, and that he stayed clear of the clouds, as he was in "class G" airspace. Subsequent examination of a sectional chart revealed that the pilot was actually flying in "class E" airspace. FAA publication P-8740-24, "Tips on Winter Flying," discussed carburetor icing and some of the hazards associated with it. The publication stated in-part, "In general, carburetor ice will form in temperatures between 32 - 50 degrees F [Fahrenheit] when the relative humidity is 50 percent or more. If visible moisture is present, it will form at temperatures between 15 - 32 degrees F." The publication warned that a loss of engine rpm in airplanes equipped with a fixed pitch propeller is one sign that carburetor ice may be present. In order to counteract carburetor icing, the pilot should apply full carburetor heat immediately. The publication noted that the engine "may run rough initially for a short time while ice melts." Interpolation of a carburetor icing probability chart contained within the publication revealed that the atmospheric conditions were conducive to "moderate icing" at cruise power or "serious icing" at glide power.