WPR17FA213

The pilot's decision to fly into a canyon during wind conditions conducive to turbulence and downdrafts, and his subsequent loss of aircraft control while maneuvering in the canyon. Contributing to the accident was the pilot's limited canyon flying experience.

The pilot had received his private pilot certificate about 7 months before the accident. He had told family members that he was planning to fly with his friend, the passenger, and stay in the airport traffic pattern performing touch-and-go takeoffs and landings. Contrary to the pilot's stated plan, radar data indicated that the airplane departed toward a meandering river canyon immediately after takeoff. The radar data ended just before the airplane entered the canyon, likely due to terrain masking along the route of flight as a result of the airplane descending below the canyon walls. The wreckage was located about 2 miles beyond the entrance to the canyon, at a tight turn of the river. The wreckage was on the steep face of a boulder-strewn cut bank about 500 ft above the river and 200 ft below the canyon rim. Wreckage debris indicated that the airplane impacted the ground in a near-vertical attitude with low-energy impact signatures, consistent with a low-speed collision and likely the early stages of a spin. The majority of the primary airframe structure was consumed by fire, but postaccident examination did not reveal any anomalies with the remaining airframe or engine components that would have precluded normal operation. Performance calculations indicated that, while it was theoretically possible to negotiate the canyon bend in the airplane, the pilot would have needed to fly with precision and factor for tailwinds along with turbulence and downdrafts that were likely present in the canyon at that time and would have made escape from the canyon difficult. The pilot had flown through the canyon with his instructor once before in another, slower, airplane but in the opposite direction of flight than that he took on the day of the accident. The wreckage was located in an area the instructor had specifically warned the pilot about due to the tight radius of the river bend and the close canyon walls, and during that flight they had bypassed the area. It is possible that the pilot did not recognize the turn during the accident flight because he was approaching from the opposite direction. It could not be determined why the pilot chose to fly into the canyon instead of remaining at the airport as he had stated he planned to do. One possibility was that the airplane would soon need refueling, and the exit of the canyon was in the general direction of the airport where the pilot typically purchased fuel. Additionally, although by all accounts the young pilot was a conscientious and conservative aviator, having his friend on board may have influenced his decision to take a more exciting, yet less safe route. There were no witnesses to the accident, and no one realized that the airplane was missing until the day after the accident. The airplane was ultimately discovered a few hours after the search was initiated. Although the airplane was equipped with an operational emergency locator transmitter (ELT), it failed to provide timely notification of the accident for at least two reasons. First, the ELT transmitted on the frequencies (121.5/243 MHz) that are no longer monitored by the Air Force Rescue Coordination Center; instead, they are only monitored randomly by some overflying aircraft. Second, the ELT signal was severely attenuated by the combination of its antenna location in relation to the final resting attitude of the airplane. However, due to the nature of the injuries incurred by both occupants, a timelier response to the accident site would not likely have increased their chances of survival.

According to the autopsy performed by the Yavapai County Office of the Medical Examiner, Prescott Valley, Arizona, the cause of death for both the pilot and passenger was thermal injury with smoke and soot inhalation, along with multiple blunt force trauma. Toxicology testing of both occupants was performed by the FAA Forensic Sciences Laboratory. Testing was negative for carbon monoxide and all screened drug substances and ingested alcohol. Refer to the toxicology report included in the public docket for specific test parameters and results. Surface Observations PRC (elevation 5,045 ft msl) was equipped with an Automated Surface Observation System (ASOS) augmented by the local tower controllers. The observation issued at 1653 indicated wind from 200° at 15 knots gusting to 22 knots, 10 miles visibility, clear sky below 12,000 ft, temperature 19°C, dew point -9° C, altimeter setting of 29.86 inches of mercury (Hg). Gusting wind conditions existed throughout the hottest parts of the afternoon, generally from 180° to 200°, sustained at 12 to 17 knots with gusts to 27 knots. Similar conditions existed at Sedona Airport (SEZ), 18 miles east of the accident site at an elevation of 4,830 ft msl. The automated weather observation at 1635 indicated wind from 210° at 16 knots gusting to 24 knots, 10 miles visibility or greater, clear skies below 12,000 ft, temperature 21°C, dew point 3°C, altimeter 29.84 inches of Hg. Sounding A High-Resolution Rapid Refresh (HRRR) numerical model was obtained from archived data from the National Oceanic and Atmospheric Administration Air Resource Laboratory database for the approximate location of the accident at 1700. The HRRR model depicted a surface temperature of 23.2°C, a dew point of -3.9°C, relative humidity 16%, density altitude of 6,255 ft, and a surface wind from 210° at 11 knots. The sounding supported strong thermals from the surface to 9,000 ft. The wind profile indicated south-southwesterly winds from 10 to 20 knots through 10,000 ft. Calculated conditions at the airplane's last radar-observed altitude of 4,550 ft included wind from 210° at 14 knots, a temperature of 21°C, and density altitude near 6,343 ft. The National Weather Service Flagstaff 1700 sounding, which was launched 28 miles northeast of the accident location, showed similar temperature structures, but with a temperature inversion at 6,240 ft above ground level (agl) and strong thermals from the surface to this level. The wind profile showed wind at the surface from 190° at 10 knots gusting to 26 knots, with wind speeds through to 1,000 ft increasing to 24 knots. The observed sounding indicated a moderate potential for low-level wind shear and a moderate and greater potential for turbulence below 1,000 ft agl. Pilot Reports and Local Observations There were no significant pilot reports (PIREPs) of turbulence below 8,000 ft surrounding the period of the accident. A flight instructor operating in the immediate vicinity of the accident at the time of the accident provided a statement of the conditions that he encountered. He reported south-southwesterly winds near 25 knots, with light turbulence through 9,000 ft. He stated that he did not encounter any significant weather, and indicated that it was an ordinary windy day for the area. Weather Research and Forecasting Model Simulation A Weather Research and Forecasting (WRF) numerical model was run to simulate the weather conditions during the period from 1600 through 1700 with regard to wind, vertical motion, and the Richardson number (Ri) for turbulence determination surrounding the time of the accident. The results of the model supported moderate turbulence over the area, with wind speeds of 18 to 20 knots at the accident site about 1630, with vertical velocities ranging between 300 fpm down to 500 fpm up. The airplane came to rest at an elevation of 4,290 ft msl on 45° sloping walls at a river turn on the north cut bank of the canyon (See Figures 3, 4). The airplane was located about 200 ft below the canyon rim and 500 ft above the river. The area was strewn with sandstone slabs, rocks, and boulders up to 8 ft in size. Figure 3 – View of the wreckage site (circled) toward the northwest Figure 4 – Wreckage site The airplane cabin and wings came to rest inverted on a heading of about 030° true. The aft fuselage and empennage had rotated 90° to the airplane's right, and the outboard right wing had folded underneath itself about midspan. Fire had consumed the main cabin and most of the right wing inboard of the aileron. The empennage and the left wing outboard of the pitot tube remained largely undamaged. The engine and firewall came to rest wedged between a set of boulders on the upsloping side of the wreckage (See Figure 5). Figure 5 – Wreckage site viewed downhill toward turn in river The wreckage was tightly contained within the immediate vicinity of the accident site, there was no damage to any of the surrounding terrain, and all control surfaces were accounted for. An examination of the engine and airframe was performed following recovery from the accident site. A complete report is contained in the public docket; the following is a summary of findings. Fuselage The fuselage from the firewall to the baggage door frame was consumed by fire. Remnants included the main landing gear, which was still attached to the lower box assembly. The left door had detached from the airframe and the right door was consumed by fire with only the window frame remaining. The forward seats, with the exception of the steel seat adjustment components, were consumed by fire. Both the left and right front seat lap buckles were found in the latched configuration and the belts were consumed by fire. Tail The empennage remained attached to the aft fuselage. The left side of the aft fuselage was largely undamaged, and the right side sustained thermal damage along its entire length. The elevator remained attached to the horizontal stabilizer by its hinges; the elevator trim tab was in place and its control rod had extended 1.25 inches out of the actuator, consistent with a 5° trim tab-down (elevator up) position. Left Wing The left wing was intact except for thermal damage to the inboard leading edge at the fuel tank. The flap remained attached at its rails and the aileron remained attached by its hinges. The stall warning horn at the wing root was consumed by fire. Right Wing The inboard section of the wing was consumed by fire, with only remnants of the fuel tank, flap actuator assembly, outboard flap and rail, and wing spar remaining. The wing sustained accordion-like crush damage to the underside, outboard of the lift strut attach point. The flap actuator jack screw exhibited an extension of about 1/8 inch, consistent with fully-retracted flaps. Engine The engine remained attached to its mount, which was still attached to the crushed firewall. The engine sustained thermal damage, consuming the right magneto, the spark plug harness, oil sump, alternator, and the right side of the accessory case. The carburetor sustained extensive thermal damage, melting the float and destroying all gaskets. The fuel inlet line fitting was in place, and the inlet screen was free of obstructions. Visual inspection of the combustion chambers was accomplished through the spark plug bores utilizing a borescope; there was no evidence of foreign object ingestion or valve damage and all combustion surfaces were coated in grey deposits. The crankcase did not exhibit any breaches indicative of internal catastrophic failure. Drive train continuity was established and the camshaft and magneto drive idler gears were intact. The camshaft lobes and corresponding tappet contact areas appeared undamaged. The propeller remained attached at the crankshaft flange. The tip of one blade had melted away about 24