HISTORY OF FLIGHT On December 24, 2014, about 1225 Pacific standard time, a Cessna 172, N8518B, impacted an access road in hilly terrain in Sutter Creek, California, about 2 miles north of Westover Field Amador County Airport (JAQ), Jackson, California. The private pilot and one passenger were fatally injured, and the airplane sustained substantial damage. The pilot/owner was operating the airplane as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed along the flight route for most of the flight, and instrument flight rules (IFR) conditions existed at the destination airport at the time of the accident. No flight plan had been filed. The flight departed from San Martin, California, at an undetermined time and was destined for JAQ. A couple in a valley near the accident site reported hearing a low-flying airplane with an engine that seemed like it was "struggling" or not producing power. They then heard a loud "boom," and one of the witnesses went to search for the airplane. Once he found the wreckage, he called his wife, who called 911. Another witness in the area stated that she heard, but did not see, a low-flying airplane circling overhead and that the engine sounded like it was cutting out. The airplane then descended below a cloud layer, and she saw it heading in an eastbound direction. Local law enforcement reported that, upon arrival at the accident site, heavy fog was present with light rain and that the visibility was about 100 to 200 ft; there was no fire. PERSONNEL INFORMATION The pilot, age 52, held a private pilot certificate with an airplane single-engine land rating that was issued on February 23, 2010. The pilot was issued a third-class medical certificate on September 26, 2014, with the limitation that he must have available glasses for near vision. At his last medical examination, the pilot reported 900 hours of total flight time with 20 hours accrued in the past 6 months. According to the pilot's personal flight logbook, he completed a flight review on May 10, 2013. AIRCRAFT INFORMATION The four-seat, high-wing, fixed-gear Cessna 172 airplane, N8518B, serial number 36218, was manufactured in 1958. It was powered by a Continental Motors Inc., O-300-A 145-horsepower engine and was equipped with a McCauley model M74DR-0-56, serial number 41996m, two-bladed metal propeller. Review of maintenance logbook records showed an annual inspection had been completed on June 12, 2014, at a recorded tachometer reading of 168.4 hours, airframe total time of 3,929.3 hours, and an engine total time of 2,999.3 hours with 1,591.3 hours accrued since major overhaul. The tachometer and the Hobbs meter were observed at the accident site; however, damage precluded determination of the current readings. METEOROLOGICAL INFORMATION AIRMETs Sierra, Tango, and Zulu were issued at 0645 for the accident time and site. They forecast IFR conditions with ceilings below 1,000 ft agl and visibility below 3 miles in precipitation and mist, mountains obscured by clouds, and precipitation and mist, with moderate turbulence below flight level (FL) 180, and moderate icing between the freezing level (between the surface and 8,000 ft) and FL200. (Altitudes 18,000 ft and above are indicated in FL. FL200 is an altitude of 20,000 ft msl.) No record was found that indicated that the accident pilot received an official weather briefing from Lockheed Martin Flight Service or any other official source. During the time surrounding the time of the accident (from 1224 to 1240), JAQ reported wind from 340° at 6 to 9 knots, visibility 1/4 mile with an overcast ceiling at 100 ft agl, temperature 10° C, dew point 9° C, and an altimeter setting of 30.01 that declined to 29.99 inches of Mercury between 1224 and 1240. The weather observations from JAQ indicated that both low instrument flight rules (LIFR) ceilings and visibilities existed at the time of the accident. (LIFR refers to general weather conditions of a ceiling below 500 ft and/or less than 1-mile visibility that pilots can expect at the surface.) These conditions were present at JAQ as early as 1200 with IFR ceilings and visibilities as early as 1110. Conditions improved above IFR conditions by 1400 with ceilings lifting to 1,200 ft agl. There were no SIGMETs or Center Weather Service Unit advisory or meteorological impact statements valid at the time of the accident or for the accident site. A review of the Federal Aviation Administration (FAA) carburetor icing probability chart indicated that conditions were conducive to moderate icing at cruise power settings or serious icing at glide power settings. WRECKAGE AND IMPACT INFORMATION The entire airplane was located about 2 miles from the intended destination at an elevation of 1,590 ft mean sea level (msl). The airplane impacted near the top of a hill on a dirt access road; the surrounding area was open land with rolling hills. The airplane had come to rest upright in a nose-down, right-wing low attitude on a magnetic heading of 180°. A large crater was identified just below the lower edge of the road with imprints of the landing gear, the airplane's belly, and the right wing. Wreckage debris from the left and right main landing gear and right wing were identified at the initial impact site. The airplane came to rest a couple of feet forward of the initial impact site. The empennage and tail sections were folded forward and to the right. Flight control continuity was established from the cockpit to all flight control surfaces, which remained attached at their respective attachment points. Both fuel tanks had ruptured, and no fuel was found onboard the airplane; however, the smell of fuel was present at the accident site. The propeller and engine were pushed aft into the cockpit. The engine sustained impact-related crushing damage from the bottom up. See the section of this report, "Engine Examination," for more information about damage to the engine and propellers. Both wings exhibited crush damage from the leading edge to the trailing edge. The lower portion of the wings were damaged with the top of the wings open at the rivet line, exposing the inside of the wing. The right wing and tail section remained attached to the airframe. The left wing had impacted uphill from the main wreckage, and a red lens fragment was found at the impact point. The emergency locator transmitter was in the "armed position," but it did not activate. It remained mounted inside the empennage. MEDICAL AND PATHOLOGICAL INFORMATION The Amador County Office of the Coroner conducted an autopsy of the pilot. The cause of death was reported as "multiple traumatic injuries." The FAA's Civil Aerospace Medical Institute performed forensic toxicology on specimens from the pilot. Carbon monoxide and cyanide testing was not performed; no volatiles or drugs of abuse were detected. TEST AND RESEARCH Engine Examination Visual examination of the engine revealed that the accessory housing plate had partially separated from the engine case, exposing the accessory gears. Due to the displacement of the Nos. 5 and 6 cylinders, their associated pistons and connecting rods, and the No. 4 main bearing, which had shifted aft during the accident sequence, the engine crankshaft could not be manually rotated. However, visual examination of the engine's internal components, which were visible through the bottom of the crankcase, revealed no preaccident anomalies or signs of operational distress. All the valve train components (camshaft, lifters, pushrods, rockers, and valve springs), except for the Nos. 5 and 6 intake pushrods, were in place with no preaccident anomalies noted. The No. 5 cylinder deck studs, located at the 4-, 5-, and 6-o'clock positions, had exposed threads. The cylinder retaining nuts for the three studs remained in place. The remainder of the No. 5 cylinder's retaining nut and stud bolts remained secured at the mounting pad. The exhaust area of the No. 6 cylinder head was partially separated. The remainder of the cylinders were unremarkable. The top and bottom spark plugs were removed. The side electrodes on the Nos. 3 and 5 bottom sparkplugs were fractured and offset from their normal positions, and the copper washers from the No. 3 top and bottom spark plugs and the No. 5 bottom spark plug had multiple crimping marks. The No. 1 top spark plug's central electrode and insulator were missing. The remainder of the spark plug electrodes exhibited normal patterns per the Champion Aviation Check-A-Plug Chart AV-27. The propeller remained connected to the crankshaft flange. The spinner had separated from the propeller assembly. Both propeller blades exhibited chordwise scratching along the length of the blades. Leading and trailing edge nicks and gouges were evident on the outboard half of one of the propeller blades that was twisted toward low pitch. One of the propeller blades also exhibited S-bending. The starter armature had separated from the starter housing. The generator had separated from the engine and was unremarkable. The carburetor had separated from the oil sump mount, and the carburetor bowl had fractured into multiple pieces. The throttle plate and floats were not identified. The oil pan had separated/fractured, exposing the camshaft, which remained intact. Both magnetos had separated from their respective mounting flanges on the engine. Additionally, both magnetos had impulse couplings. The left magneto remained connected to the ignition harness P-leads, which remained attached to the spark plugs. Manual rotation of the left magneto drive shaft produced spark at all posts. The right magneto was located in the wreckage and had sustained impact damage to the housing. Investigators could achieve spark at two of the six posts. The right magneto was disassembled, and the internal gears were intact, secure, and undamaged. Radar Data Information Radar data for the accident area was obtained from the FAA Northern California Terminal Radar Approach Control (NCT). According to the FAA, the accident airplane had not received air traffic control services from NCT and was not under radar contact. The National Transportation Safety Board Air Traffic Specialist identified an airplane squawking 1200 near the accident area; there were no additional aircraft in the area at the time of the accident. At 1215:00, a radar target was identified traveling to the northeast at a Mode C reported altitude of 4,900 ft msl. The radar target continued to the northeast and ascended to 5,200 ft before it turned toward Sutter Creek and began a westbound descent that ended at 1227:14.