WPR21FA321

The pilot, who owned the dual-flight-control airplane, planned to take the other two occupants (one of whom was also a pilot) on a local tour flight to celebrate their 1-year wedding anniversary. The planned route could not be determined; however, friends and family members stated that they intended to fly past the temple where they were married. Automatic dependent surveillance broadcast (ADS-B) equipment data indicated a nominal climb profile after takeoff, as the airplane flew past the temple and toward the entrance of a canyon. The airplane then entered the canyon while initially level with the top of its walls. However, as the flight progressed, the top of the canyon walls began to increase at a rate that exceeded the airplane’s climb performance. Escape from the canyon during the initial stages would have required a precise and coordinated 180° turn that would have resulted in the airplane flying very close to terrain. Instead, the airplane continued until it reached a 1-mile-wide bowl at the end of the canyon that was surrounded by steep rising terrain. Data indicated that the airplane appeared to begin a left turn, possibly in preparation for a 180° turn to escape the canyon but by this time it was approaching the stall speed. The wreckage was located just beyond the final ADS-B target and damage to the airplane and surrounding vegetation was consistent with a near vertical impact, likely after the occurrence of an aerodynamic stall and resultant spin. Propeller damage signatures along with the airplane’s climb performance indicated the engine was operating throughout. The airplane’s final flap position and observed speed as it passed the halfway point through the canyon were consistent with that required for best angle-of-climb performance. Therefore, the pilots were likely aware of the predicament not long after they entered the canyon. Weather data indicated that the airplane would not have encountered mechanical turbulence often associated with mountain flight and that no downdrafts or updrafts were in the area. A forest fire had resulted in smoke and reduced visibility in the entire area with visibility of 5 miles in smoke and haze. However, due to the prevailing wind direction, which pushed smoke toward the rising terrain, it is possible that visibility may have been even lower at the end of the canyon. Video footage of the mountains, along with the statement of a witness who was close to the accident site appeared to confirm this. An airman's meteorological information report indicating mountain obscuration due to smoke and haze was current at the time of the accident. It could not be determined which pilot was flying the airplane at the time of the accident or why they chose to fly up the canyon. Both pilots were locally based and aware of the terrain. However, it is possible that the limited visibility caused them to misjudge the terrain and entry altitude. An established mountain pass, located 5 miles north of the accidentlocation, followed a route that was about parallel to the accident flight. Although the entrance was indicated by a well-defined reporting point, it is possible that, with the low visibility and potential distractions related to the tour, the pilots may have missed this cue. Although the owner had more experience flying the airplane, the other pilot had more flight experience and had previously provided the owner with flight instruction. It is possible that a diffusion of responsibility occurred; however, it was not possible to determine the command and decision-making power hierarchy during the accident flight.

None of the local pilots interviewed during the investigation reported having ever flown through the accident canyon. A mountain pass was about 5 miles north of the accident location. That pass followed a route that was approximately parallel to the accident flight, however the entrance to that canyon was indicated by the “Lagoon Amusement Park”, which was a well-defined reporting point documented in the FAA Salt Lake City terminal and sectional aeronautical charts. The airplane, which had dual flight controls, was purchased by the owner about 6 months before the accident. At that time, a prebuy and annual inspection was performed. Aircraft maintence logbook records were not recovered, however, a local mechanic who had performed two oil changes on the engine since it was purchased stated that the airplane was in good condition. Purchase data indicated the engine had accumulated about 1,230 hours since overhaul, and the mechanic stated that it had flown in excessive of 100 hours since purchase. Airplane Performance Maximum rate-of-climb data from the airplanes owner’s manual indicated that with flaps retracted, at 5,000 ft and 41° F, the climb rate would be about 745 ft per minute (fpm) at maximum gross weight (2,800lbs), and 1,005 fpm at a weight of 2,400 lbs. A friend of the pilot, who flew with him routinely, and during a flight earlier in the morning stated that in the Salt Lake City area, the airplane generally climbed at 500-700 fpm while flown at an airspeed between 80 and 90 knots with two occupants and full fuel. Review of the ADS-B data indicated that as the airplane entered the canyon, although it continued to climb, because of the rising terrain it was unable to maintain a lateral separation from the canyon walls of more than 700 to 1,000 ft. The bank angle required to maintain a turn radius of 1,000 ft, at a true airspeed of 80 knots would have been about 30°. About 45 seconds after entering the canyon, the airplane had slowed to 75 knots, and the lateral separation decreased to 700 ft. The required bank angle to perform a 180° turn based on these parameters would have been 35°. The airplanes Owner’s Manual indicated that with flaps retracted, the airplanes stall speed was 64 knots (calibrated) in level flight, 69 knots in a 30° angle of bank, and 91 knots in a 60° bank. The Owner’s Manual provided the following climb recommendations: If it is necessary to climb rapidly to clear mountains or reach favorable winds at high altitudes, the best rate-of-climb speed should be used with maximum power. This speed is 88 MPH at sea level, decreasing 2 MPH for each 5000 feet above sea level. If an obstruction ahead requires a steep climb angle, the airplane should be flown at the best angle of climb with flaps up and maximum power. This speed is 70 MPH. An impact damaged Appareo Stratus 2S GPS and ADS-B receiver was recovered from the airplane. The unit, which was capable of recording position, attitude, and heading information was sent to theNTSB Vehicle Recorder Division for data extraction. The data revealed multiple flights occurring over the two days before the accident over and through the mountainous areas of Southern Utah, specifically within the vicinity of Kanab, Zion National Park, and the Canaan Mountain Wilderness Area. The accident flight was not recorded. On August 15, 2021, about 1847 mountain daylight time, a Cessna 182H, N8477S, was destroyed when it was involved in an accident near Bountiful, Utah. Two pilots and one passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to friends of the occupants, the airplane owner planned to take the other pilot and passenger on a local tour flight, in celebration of their 1-year wedding anniversary. The planned route could not be determined; however, friends and family members stated that they planned to fly past the temple where they were married. Skypark Airport is at an elevation of 4,237 ft mean sea level (msl) and located within the northern confines of the Salt Lake Valley between the Great Salt Lake and the Wasatch Mountain Range. Automatic dependent surveillance broadcast (ADS-B) data indicated that the airplane departed at 1841 and, after reaching the end of runway 35, began a climbing right turn to the northeast toward the foothills of the Sessions Mountains. For the next 3 minutes, the airplane continued to climb at a rate of about 700 ft per minute (fpm) and a ground speed of 90 knots until it reached the entrance of a canyon located about 4.5 miles northeast of the departure airport and 2 miles north of the temple (see figure 1). Figure 1 – ADS-B track of the airplane entering the canyon at 1844:43. The shaded area depicts terrain below the airplanes altitude. For the first minute as the climb continued, the airplane remained about level with the tops of the canyon walls. The airplane continued its northeast track up through the canyon, at a speed between 75 and 80 knots while maintaining the same climb rate. As the flight progressed, the height of the surrounding terrain continued to increase such that by 1846:28, although the airplane had reached an altitude of 7,300 ft msl, it was now about 800 ft below the rims to the north and south. The airplane then entered a 1-mile-wide bowl at the end of the canyon where, for the last 8 seconds, it slowed to about 64 knots and turned left to the north (see figures 2, 3, 4). The last ADS-B target was recorded at 1846:36 (see figure 5). Figure 2 – ADS-B track at 1845:35. The shaded area depicts terrain below the airplanes altitude. Figure 3 - ADS-B track at 1846:01. The shaded area depicts terrain below the airplanes altitude. Figure 4 - ADS-B track at 1846:28. The shaded area depicts terrain below the airplanes altitude. Figure 5 – ADS-B track and accident location. A witness, who had stopped on a road that ran along the ridge on top of the range heard an airplane sound and looked down into thecanyon. He could see an airplane was flying below him and he pointed out to his associates how low it was. He then heard an engine accelerating and lost sight of the airplane. He initially thought it had departed the area, but a short time later he heard an explosion followed by rising smoke. Due to the hazardous nature of the terrain at the accident site, the occupants were removed by the search and rescue department of the Davis County Sheriff's Office. They were unable to ascertain the seating locations. Although, photographic evidence indicated that the two pilots were in the front seats, which side either pilot occupied could not be determined. The non-pilot rated passenger was in the rear of the airplane. According to the autopsy performed by the Utah Office of The Medical Examiner, the cause of death for all occupants was determined to be combined blunt force and thermal injuries. Toxicology tests were negative for all screened drug substances and ingested alcohol. A forest fire had resulted in smoke and reduced visibility within the entire Salt Lake City area. The closest aviation weather observation station to the accident site was at Salt Lake City International Airport, 14 miles southwest of the accident site. An aviation routine weather report recorded at 1854 indicated visibility of 5 miles with smoke and haze. An airman's meteorological information (AIRMET) for mountain obscuration due to smoke and haze was current at the time of the accident. A security video camera positioned on the wall of a fixed base operator on the west side of the airport included the accident mountain range in its field of vision, along with the accident airplane being refueled by the occupants just before the flight. The recording indicated that about noon, smoke and haze were in the vicinity, but the peaks of the mountain range could still be identified. As the day progressed, visibility decreased such that about the time of the airplane’s departure, the entire mountain range was obscured. The witness on the ridge who observed the airplane just before the accident took a photo at 1911 of the smoke rising from the wreckage; the photo showed that the smoke in the area was so dense that it was almost indistinguishable from the smoke from the wreckage. A High-Resolution Rapid Refresh model sounding was created for the accident time and location, with the modeled surface elevation at 7,552 ft msl. The model indicated at that elevation, the temperature was about 22.9°C and the dewpoint was about 3.4°C, with a relative humidity of 28 percent, and wind from 307° at 7 knots. The wind remained between 7 and 12 knots through 9,000 ft msl with the wind direction from 307 to 339°. The model did not indicate any downdrafts or updrafts below 11,000 ft msl. The airplane’s owner had recently received his commercial pilot certificate. Both pilots had trained at the same flight school where the owner had received multiple flight lessons from the other pilot, who was aflight instructor at the school. The majority of the second pilot’s flight experience was in the Diamond DA40 series airplane. According to family members, she had never flown in the accident airplane type before nor did she have mountain flying experience. Neither pilot had received formal mountain flight training. The wreckage was located at an elevation of 7,225 ft, about 150 ft below and 350 ft beyond the last ADS-B target. It came to rest facing downhill on a 50° southwest facing slope, about 1,100 ft below the summit of the surrounding canyon walls. The wreckage was within a densely forested area composed of loose shale, rock, and pine trees. The debris field was confined within a 30 by 30 ft perimeter, at the base of a 70-ft-tall pine tree. A near-vertical slash mark was observed cutting through the upper limbs of the tree, leading directly to a ground disruption and the wreckage, which was surrounded by freshly cut tree branches. The entire cabin from the firewall through to the leading edge of the vertical stabilizer, along with both inboard wing sections was consumed by fire. The remnants of both wings were located on either side of the cabin. Remnants of all control surfaces were present, and there was no evidence of in-flight structural failure, or bird strike. The wing flap drive actuator was in a position that corresponded with the flaps being fully retracted. The elevator pitch trim servo indicated neutral trim. The engine remained attached to the firewall by its aft mounts. The firewall sustained extensive crush damage and had formed around the rear of the engine. The propeller hub remained attached to the crankshaft; the spinner had formed around the hub and exhibited radial score marks. Both propeller blades exhibited similar leading-edge gouges, chordwise scratch marks and blade twist. The top spark plugs exhibited dark grey deposits consistent with normal operation and there was no evidence catastrophic engine failure. Fire damage prevented an assessment of the condition and setting of the altimeter.