WPR23FA153

The pilot's failure to maintain sufficient altitude for undetermined reasons while maneuvering to land in dark night conditions, which resulted in collision with terrain.

The pilot and passenger departed for a cross-country flight in dark night conditions, with the moon below the horizon. The pilot’s friend recorded the accident flight departure, which appeared normal. They were communicating over the radio, and the pilot did not report any problems. The airplane continued toward an unpopulated, hilly area for about 11 minutes before the pilot initiated a 180° turn back to the departure airport. Security camera footage captured the airplane’s lights as it approached the runway before descending rapidly into terrain. The airplane came to rest in desert terrain about 3,350 ft from the north end of the runway, with the wreckage path leading away from the runway. The airplane impacted the ground in a near-level pitch attitude with the flaps extended. During the landing roll, the propeller struck the ground and separated from the engine, yet the airplane retained enough airspeed to briefly become airborne, traveling about 920 ft before contacting the ground again. The pilot’s pre-event cardiac testing revealed an abnormal nuclear stress test with evidence of reversible ischemia. This indicates the pilot likely was at increased risk of a sudden distracting, impairing, or incapacitating cardiac event, including angina, arrhythmia, or heart attack. There is no forensic evidence that such an event occurred. However, such an event could not be excluded given the limitations of the autopsy due to fragmentation. Therefore, whether the pilot's heart disease contributed to the crash could be determined. The reason for the airplane’s return to the airport was not determined. The airplane’s flight path and ability to maintain altitude during its return to the airport is inconsistent with a loss of engine power. Examination of the airplane was limited due to the extensive fragmentation of the airframe. During the examination, the engine fuel supply line was found to have a loose b-nut; however, it is unknown if the loose b-nut affected the performance of the engine. The pilot’s logbooks and the airplane’s GPS information indicated that the pilot likely did not have recent night flying experience. The area of the accident flight was rural, with little terrestrial lighting present. Given the dark night conditions and the airplane’s rapid descent into the ground, the pilot likely experienced visual illusion or spatial disorientation while maneuvering back to the airport for undetermined reasons.

According to the U.S. Naval Observatory, Department of Astronomical Applications, the phase of the moon was waning gibbous with 68.1% of the moon's visible disk illuminated. At the time of the accident, the moon was about 16° below the horizon (including refraction) on an azimuth (heading) of 246°. The pilot’s logbooks indicated that the pilot had a total time of 526.2 hours, of which 90.7 hours were in the accident Glastar; the logbook’s last entry was in November 2022. GPS data from the airplane revealed it completed nine flights (totaling about 5 hours), including the accident flight, after the last entry recorded in the logbook. These flights took place over seven separate days, with none occurring during nighttime hours. The experimental Glastar was equipped with a Eggenfellner Subaru H4 engine based on an EL-25, 2.5L Subaru water-cooled 4-cylinder engine that was rated at 160 horsepower. Power is transferred from the engine to the propeller speed reduction unit (PSRU) through a spline shaft. The unit was an Eggenfellner GEN 3, Ver 4 model. The PSRU is a geared reduction drive that provides for a propeller rpm that is about ½ that of the engine rpm. The last 100-hr inspection was recorded as being completed 6 days before the accident on April 05, 2023. The mechanic who signed the entry stated that he wasn’t familiar with the engine and the pilot performed all the maintenance on the airplane. He was conducting the inspection to look for leaks and the overall condition of the airplane. A review of the maintenance records revealed that in March the pilot installed new fuel injectors and changed the manifold, temperature, and oxygen sensors. The tachometer at the accident site was not recovered, but the last inspection indicated the airplane had a total time of 446.6 hours. The fuel system consisted of two wing tanks that were plumbed to header tanks (located on the upper left and right vertical cage structures). From the header tanks, the fuel lines were routed down to a sump and then were routed to an Andair “RIGHT” “LEFT” and “OFF” selector valve. The fuel line continued forward from the valve to the firewall. At the firewall there was a braided fuel line to a fuel filter (mounted on the firewall). The fuel then continued through two different parallel electric fuel pumps and then joined into one line and continued to a paper fuel filter. The fuel was routed to an engine rail and injectors. All 4 fuel injectors were affixed to their respective cylinders. The fuel return was routed after the engine rails to a fuel pressure sensor. From the sensor, the fuel was routed back to the fuel selector and would return to the tank selected. An autopsy of the pilot was performed by the Clark County Office of the Coroner/Medical Examiner. According to the pilot’s autopsy report, his cause of death was blunt force injuries, and his manner of death was accident. Due to the extent of his injuries, the brain, heart, and lung examinations were limited. Within these limitations, the autopsy did not identify significant natural disease. The pilot had pre-event medical testing that showed a large area of cardiac muscle reperfusion abnormality and ventricular dilatation on cardiac nuclear stress testing. The main wreckage was in the desert terrain about 3,940 ft north-northwest from the end of runway 33, at an elevation of 2,660 ft; the initial impact was 3,550 ft from the end of the runway. The terrain was composed of dry, soft dirt and dense brush. The wreckage was found distributed over 970 ft on a median magnetic bearing of about 050° (figure 4).   Figure 4: Impact sites in reference to the runway The first identified points of contact, located 3,350 ft from the runway surface, consisted of disrupted cacti and dirt on the flat desert terrain making up the far southwestern end of the debris field. The parallel disruptions in the terrain were consistent in size and spacing with the right wheel impacting first, followed by the left wheel. Those markings continued down the debris field on a heading of about 22°. Located between the markings were slashes in the dirt perpendicular to the direction of travel, consistent with propeller slashes. Fragments of propeller blades were found in that area embedded in the soft dirt.   The second identified debris field started 920 ft from the end of the initial debris field and consisted of disrupted dirt and vegetation. The markings started as a 5-inch wide indentation in the vegetation dirt with a blue/green lens and almost the entirety of the right-wing tip fragments embedded. There was a crater about 35 ft from the right-wing tip followed by the main wreckage, which was upright facing the opposite direction of the debris field.   As part of the postaccident examination, a majority of the engine and the propeller speed reduction unit (PSRU) were disassembled. There were large plastic shards found in the No. 4 intake (entering the cylinder) and smaller pieces were in the No. 3 intake, consistent with the plastic connection at the air intake fragmenting while the engine was still running at impact. The entire drivetrain was intact. The deposits on the pistons and spark plugs were all consistent with normal operation. The PSRU splines and bearings were all intact. Fine metallic shavings were found in the oil. The examination of the engine and PSRU revealed no evidence of pre-impact anomalies or failures that would have precluded normal operation (figure 5). Figure 5: Engine and PSRU disassembled There was fluid in both wing tanks consistent in odor and color with that of 100LL Avgas. The fuel selector was in an over-extended position and sustained crush damage with the selector post bent. There was white Teflon tape on all the selector fittings that had the appearance of being recently installed. The fuel lines were all fractured in various places consistent with impact deformation. The fuel line from the selector through the firewall was broken and the b-nut was loose; there were marks on the nut (figure 6 below). The fuel filter was punctured open; the fluid inside was grainy and dirty and tested positive for containing water. The cooling reservoir was located above the filter and was punctured. Power was applied to the fuel pumps and investigators could feel them clicking and there was suction on the inlets. The paper filter was cut open and found to be discolored. Figure 6: Firewall fuel fitting Complete control continuity could not be established due to the fragmentation of the airframe from impact. There was no evidence of disconnect or failure of the flight control system. The flaps were in the full extended position visually on the cockpit Johnson bar and on the control surface. On April 11, 2023, about 0419 Pacific daylight time, an experimental amateur-built Glastar airplane, N8488, was substantially damaged when it was involved in an accident near Cal-Nev-Ari, Nevada. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.   The purpose of the flight was for the pilot and his spouse to depart from their winter residence in Nevada and fly to their primary residence in Iowa. The first day of the trip he had a plan to terminate in Dalhart, Texas, where they would overnight and refuel. On the morning of the accident, the pilot’s friend filmed the departure on his cellular phone and was in radio contact over the common traffic advisory frequency (CTAF). A review of that video revealed that the airplane departed runway 33 about 0406 (figure 1 below). After the initial climb, the airplane made a left turn (to the west). The airplane’s lights remained visible in the video and the airplane could be seen to make a right turn and continue to the east in a level attitude until disappearing out of the frame. Shortly after turning to the right, the pilot made a goodbye call t