WPR14FA044

The pilot's failure to maintain clearance from terrain while maneuvering in likely low-ceiling and low-visibility conditions in mountainous terrain.

Before departing on the cross-country flight over mountainous terrain, the accident pilot and two other pilots going to the same remote airstrip discussed the weather and checked webcams positioned throughout the passes. The accident pilot took off first and flew south before turning east to cross the mountains, while the other two pilots chose to fly north before crossing the mountains. Inflight radio communications from the accident pilot indicated that when he first turned east to cross the mountains, he encountered weather that required him to turn around and fly further south before turning east again. No further radio communications from the accident pilot were heard. The other two pilots reported encountering marginal weather with low clouds during their flights to the destination, which they completed without incident. Flight track data downloaded from the accident airplane's onboard GPS unit indicated that, during the final 40 seconds of the flight, the airplane made a left turn of about 90 degrees followed by a right turn of about 180 degrees while maintaining an altitude of about 8,150 ft. This flightpath suggests that the pilot was following the contour of the horseshoe-shaped ridgeline at that location. However, the ridgeline varied in elevation between about 8,000 and 8,200 ft, and the airplane impacted steep, heavily wooded terrain about 100 ft below the top of the ridgeline. A postaccident examination of the airframe and engine did not reveal any anomalies that would have precluded normal operation. Due to the location of the accident site, weather reporting stations and weather products were limited. Satellite imagery did not show low-level clouds because of a mid-level cloud layer at 15,000 ft. A weather model run to simulate relative humidity over the accident site revealed that the lower altitudes above terrain likely had a much lower visibility with relative humidity greater than 98%. Thus, it is likely that the pilot was maneuvering the airplane in or near low clouds when he lost visual contact with the ground resulting in controlled flight into terrain.

During a postaccident airframe and engine examination that included representatives from the NTSB, FAA, Textron Aviation – Cessna Aircraft company, Continental Motors, and McCall Aviation did not reveal any anomalies with the airframe or engine that would have precluded normal operations. Airframe Examination An airframe examination revealed that all of the airplane's components were present; with the exception of the outboard portion of the right wing, which was not found on scene. Flight control continuity was established throughout. All of the breaks in the cables were either consistent with tension overload, or cut by the recovery crew. The flap jackscrew was examined and the flaps were in the retracted position. The elevator trim position indicator was severely damaged, and the position could not be determined. The fuel selector valve was found and was positioned on the right fuel tank. The inside of the right fuel bladder was mostly clear with the exception of some small particles. The propeller hub was fractured and separated from the propeller flange, and the blades were separated from the propeller hub. None of the blades sustained leading impact damage. One blade was bent forward about 10 degrees midspan in a small radius bend, and chordwise scoring was present on the cambered side of the blade. The outboard six inches of the second blade was twisted about 20 degrees with the leading edge being twisted aft. The third blade was bent aft about 10 degrees in a large radius bend starting 10 inches from the hub. The outboard seven inches were bent aft about 45 degrees in a small radius bend. Engine Examination The engine remained attached to the firewall by the fuel lines and control cables; there was no evidence of catastrophic failure. Both magnetos were separated from their attachment points. The magnetos were manually rotated and the right magneto sparked on all six magneto towers; however, the left magneto only sparked on three of the six towers. The spark plugs were removed and exhibited "normal" wear signatures when compared to the Champion Spark Plugs "Check-A-Plug" Chart AV-27. The gascolator was removed from the firewall; the screen was clear with the exception of a small amount of pinkish-gray lint. The engine driven fuel pump remained attached to the engine; once removed it rotated freely with no anomalies or binding. The throttle body/fuel metering unit was fractured and deformed. The throttle plate was found in the full open position, and the throttle and mixture controls remained attached to their levers. The fuel inlet screen was removed and it was covered in pinkish-gray lint; light could be seen through the debris. The oil pump and oil filter were removed and disassembled; no anomalies were noted. The crankcase sustained impact-related damage and the number 5 cylinder was displaced outward from its attachment point. All cylinders were removed from the crankcase and showed no signs of distress or oil starvation to the cylinder barrels, cylinder heads, pistons, valves, valve springs, or rocker arms. The starter adapter needle bearing boss displayed a witness mark that was consistent with crankshaft gear teeth. The crankshaft was visibly distorted to the left side of the engine, which inhibited rotation of the engine. The crankshaft was removed from within the crankcase and there was no evidence of oil starvation or operational distress. The camshaft remained intact, but was bent; neither the camshaft, nor cam lifters displayed signs of corrosion, excessive wear, or rubbing. Magneto Examination The left magneto was taken to Aircraft Magneto Services located on Bainbridge Island, Washington for further examination. The magneto was installed onto a test bench and was operated; one out of the six terminals sparked. The magneto was removed from the test bench and disassembled; it was noted that the distributer block-rotor-screws were bent aft. It was also noted that the rotor gear was fractured in half in what appeared to be overload. Fuel Metering Unit Examination – NTSB Materials Laboratory The fuel metering unit was sent to the NTSB Materials laboratory for an examination of the debris found on the inlet screen. The debris was removed and collected; using a spectrometer to process infrared wavelength absorbance spectra of each sample of debris. The gray material was a strong match to dimethylsiloxane. Siloxanes (silicones) are used in lubricants, fire sleeving, and sealants. The red fiber was a strong match to cellulose, which is found in natural fibers such as wool and cotton. An autopsy was performed on the pilot on November 9, 2013, by the Valley County coroner's office, McCall, Idaho. The autopsy indicated the pilot's cause of death was severe blunt force trauma. The Federal Aviation Administration (FAA) Civil Aerospace Medical Institute performed forensic toxicology on specimens from the pilot with negative results for carbon monoxide, cyanide, and tested for drugs. Ethanol was detected in various concentrations: 22 mg/dL detected in the liver, 100 mg/dL detected in muscle, 30 mg/dL detected in the heart, and 12 mg/dL detected in the lung. N-Propanol was also detected in the liver. The nearest weather reporting facility, MYL, was located about 14 miles to the northwest of the accident sight. At 0851, weather was reported as calm wind, 9 statute miles of visibility, few clouds at 300 feet above ground level (agl), broken clouds at 2,500 feet agl, and overcast clouds at 3,200 feet agl. The temperature was -1 degrees C, and dewpoint was -2 degrees C, with an altimeter setting of 30.29 inches of mercury. The other two pilots reported that the weather was not perfect. The valley where MYL is located was good and started to clear to a broken overcast. The weather along their particular route was marginal the entire way, clouds hung low in various locations; however, it became clearer as they neared C53. At no point did they have to divert from their path because of the weather. Due to the location of the accident site, weather reporting stations and weather products are limited. Satellite imagery was unable to show low level clouds because of a mid-level cloud layer at 15,000 feet. With lack of ground instrumentation in the accident area other weather sources were unable to show cloud conditions. There were AIRMETS for IFR and MTN Obscuration, however, there are no indications that those conditions were occurring near the accident site. A weather model and algorithm were used to simulate and approximate the weather conditions in the area of the accident site. A weather model that simulated relative humidity over the accident site was ran and revealed that the lower altitudes above terrain likely had a much lower visibility with relative humidity greater than 98%. An algorithm that uses satellite, radar, surface, and pilot reports to calculate the probability of icing was used; the algorithm revealed "light" to "moderate" severity icing threat, with a high probability of that threat. The airplane came to rest about 100 feet from the top on the western most ridgeline of a horseshoe shaped ridge. The airplane came to rest on the inside of the horseshoe, with the heading of the airplane consistent with the opening of the horseshoe. The terrain was steep, and was heavily covered with trees and about two and a half feet of snow, some of which was fresh. The first identified piece of debris was the inboard portion of the right elevator. It was found about 20 feet to the south of the main wreckage at the base of a small tree that did not appear to be topped. In between the first identified point of debris and the main wreckage were several topped trees. The airplane came to rest at the bottom of, and in between, two trees with a heading of about 299 degrees. One of those two trees sustained about 10 feet of scratching and scoring extending from the base of the tree; the airplane came to