NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The commercial pilot was conducting a 14 Code of Federal Regulations (CFR) Part 135 commercial air tour flight with three passengers onboard when the airplane impacted rising terrain below the entrance of a high mountain pass. The airplane was substantially damaged, and the pilot and his three passengers were seriously injured. Thirty-five days later, one of the passengers died as a result of his injuries. The pilot initially reported to first responders that he had encountered a severe downdraft while approaching the high mountain pass, which caused the airplane to lose altitude. Review of reported weather conditions at the time of the accident in the area of the pass indicated that the wind speed was 4 to 7 knots, and no indications of sudden downdrafts were discovered.When interviewed by investigators about 2 weeks after the accident, the pilot stated that the right front seat passenger was not wearing his shoulder harness and had slumped onto the flight controls and become unresponsive after taking a motion sickness drug. The pilot further stated that the two rear seat passengers (who had also taken the drug) were also unresponsive when this occurred. However, none of the three passengers recalled this, and the front seat passenger was found with his seatbelt and shoulder harness on when first responders arrived on scene.In a written statement dated about 2 months after his interview, the pilot stated that a propeller blade had separated in flight, as one propeller blade was missing and not recovered from the accident site. The passengers did not recall that this had occurred, and postaccident examination of the propeller hub, propeller blade pilot tubes, propeller blade clamps, and the remaining propeller blade indicated that the missing propeller blade had separated during the impact sequence. Evidence that the missing propeller blade separated on impact included the existence of power signatures on the remaining propeller blade and the presence of a large amount of grease in the hub, which was not thrown out in a centrifugal pattern from the missing propeller blade side of the hub as it would have been if the blade had separated in flight. Further findings indicating that the missing propeller blade separated on impact were a broken clamp bolt head found lying inside the clamp bolt cup of the clamp from the missing propeller blade, impact damage on that same clamp, and a shiny-crescent shaped contact mark on the hub butt in the aft quadrant where the trailing edge of the missing propeller blade would have been located; the crescent-shaped contact mark, which was indicative of aluminum transfer from the missing blade to the hub butt, is typically seen when propeller blades separate during impact. Additionally, metallurgical testing showed that the impact-damaged clamp from the missing propeller blade as well as both of the propeller blade tubes had failed due to overload, and no evidence of fatigue cracking was found.Postaccident examination of the airframe and engine found no evidence of preimpact mechanical malfunctions or anomalies that would have precluded normal operation of the airplane. Several discrepancies were noted with the engine, including the presence of metallic particulates within the oil filter, contamination of the fuel inlet screen with a rubber-like material, and damage to the oil pump consistent with hard particle passage; however, none of these discrepancies would have prevented the engine from producing power.Witness statements, passenger statements, photographs taken during the flight by one of the passengers, and GPS data recovered from a GPS receiver onboard the airplane indicated that, after takeoff, the pilot did not climb to a safe cruising altitude to cross through the mountain pass but instead remained at low altitude. After circling a town, he proceeded up a valley that led to the high mountain pass, flying below the tops of the surrounding mountains in close proximity to terrain and obstructions about 500 feet above ground level. This low altitude flying resulted in the airplane reaching the area of the pass, being boxed in by the surrounding terrain, and not having enough energy or performance to climb up and cross over the pass as the terrain at that point was rising faster than the airplane could climb.Examination of weight and balance information indicated that the pilot had taken off with the airplane loaded over maximum gross weight and that the airplane was near its maximum gross weight when the accident occurred. The pilot’s decision to operate the airplane near its maximum gross weight likely contributed to the accident because it reduced the margin of power available for climb.Review of Federal Aviation Administration (FAA) records revealed that, from 2007 to 2012, the pilot had a history of accidents, incidents, reexaminations, and checkride failures. Despite the pilot’s history and concerns voiced by numerous FAA personnel during the certification process, the FAA issued a certificate to the pilot in 2012 to conduct commercial air transportation pursuant to 14 CFR Part 135.