WPR24FA298

The accident airplane was one of three airplanes traveling together on a cross-country flight. The pilots of the accident airplane and one of the other two airplanes chose to divert from the group’s typical route of flight to fly an alternate route through rising, mountainous terrain. As the two airplanes approached an area of higher terrain and a ridgeline that required a climb, the pilot of the second airplane flying the alternate route initiated a circling climb to gain sufficient altitude needed to cross the approaching ridgeline. He then continued on toward the intended destination, unaware that the accident airplane was not behind his airplane. When approaching the same ridgeline, the pilot of the accident airplane maintained an altitude that was lower than the elevation of the ridgeline and did not initiate a climb. The airplane maintained an altitude of about 2,900 ft mean sea level (msl) until it entered a left turn, followed by a rapid descent above the accident location. The airplane’s ground speed had slowed to 40 kts at the onset of the rapid descent and the left turn began about .63 statute miles from terrain that rose to 3,550 ft msl, which was the lowest available terrain ahead of the airplane’s position. The pilot likely initiated a left turn away from rising terrain and exceeded the airplane’s critical angle of attack. The investigation was unable to determine why the pilot did not initiate a climb earlier in the flight. The pilot of the second airplane flying the alternate route reported that “it wasn’t too smooth out,” which was consistent with terrain-induced wind and/or turbulence. He reported that at the initiation of his climb he added engine power, saw his ground speed decrease and then added additional engine power. He subsequently chose to circle climb to clear the ridgeline. The calculated density altitude near the accident site was 4,626 ft. Postaccident examination of the engine and airframe revealed no evidence of preaccident malfunction or failure.

According to the FAA Airplane Flying Handbook (FAA-H-8083-3C), The angle of attack (AOA) is the angle at which the chord of the wing meets the relative wind. The chord is a straight line from the leading edge to the trailing edge. At low angles of attack, the airflow over the top of the wing flows smoothly and produces lift with a relatively small amount of drag. As the AOA increases, lift as well as drag increases; however, above a wing’s critical AOA, the flow of air separates from the upper surface and backfills, burbles, and eddies, which reduces lift and increases drag. This condition is a stall, which can lead to loss of control if the AOA is not reduced. It is important for the pilot to understand that a stall is the result of exceeding the critical AOA, not of insufficient airspeed. The term “stalling speed” can be misleading, as this speed is often discussed when assuming 1G flight at a particular weight and configuration. Increased load factor directly affects stall speed (as well as do other factors such as gross weight, center of gravity, and flap setting). Therefore, it is possible to stall the wing at any airspeed, at any flight attitude, and at any power setting. For example, if a pilot maintains airspeed and rolls into a coordinated, level 60° banked turn, the load factor is 2G, and the airplane will stall at a speed that is 41 percent higher than the 1G stall speed. In that 2G level turn, the pilot has to increase AOA to increase the lift required to maintain altitude. At this condition, the pilot is closer to the critical AOA than during level flight and therefore closer to the higher stalling speed. Because “stalling speed” is not a constant number, pilots need to understand the underlying factors that affect it in order to maintain aircraft control in all circumstances. Records showed that the most recent annual inspection was completed on June 1, 2024. The most recent engine overhaul was completed on April 10, 2012. On September 6, 2024, about 1259 Pacific daylight time, a Boeing A75L3 airplane, N53466, was substantially damaged when it was involved in an accident near Yacolt, Washington. The pilot was seriously injured and the passenger was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he had no memory of the accident flight or the accident sequence. Two other pilots reported that the accident airplane was part of a group of three airplanes traveling together. The group departed Ed Carlson Memorial Field/South Lewis County Airport (TDO), Toledo, Washington, with an intended destination of Ken Jernstedt Airfield (4S2), Hood River, Oregon, and maintained loose trail with one another. Near Woodland, Washington, the accident pilot announced a previously undiscussed alternate route of flight to the group and instructed a turn to the east/southeast. One airplane turned with the accident airplane, and one airplane chose to maintain theoriginally planned, southerly course. The pilot of the airplane on the southerly course heard the pilot of the accident airplane state, “this is the cut we’re going to take” to the second airplane, then did not hear any subsequent communication from either of the other two pilots. The two airplanes on the alternate route of flight proceeded toward mountainous terrain and the accident pilot offered continued direction to the second airplane. As the airplanes approached a ridgeline in the rising terrain, the pilot of the second airplane realized that his airplane was not high enough to clear the ridge and initiated a climb. He observed a decrease in his airplane’s ground speed and added engine power to facilitate the climb. He subsequently added additional engine power and completed two 360° circles in a circle climb to clear the ridge. The pilot of the second airplane then continued the flight toward their intended destination and was unaware that the accident airplane had not crossed the previous ridgeline. The final 6 minutes of available ADS-B flight track data showed the accident airplane maintained a variable altitude between 2,600 ft and 2,900 ft msl. About .63 miles west of terrain at 3,550 ft, the data showed the initiation of a left turn followed by a rapid descent. The accident airplane’s ground speed had slowed to 40 knots at the onset of the rapid descent. The other two airplanes from the group arrived at 4S2. Their pilots subsequently reported the accident airplane overdue, and an Alert Notice (ALNOT) was issued at 1637. The wreckage was located about 12 miles southeast of Yacolt, Washington, in wooded, mountainous terrain by a United States Coast Guard rescue helicopter and ground search and rescue teams from Skamania County Sheriff. The closest available weather reporting station was located at Portland-Troutdale Airport (TTD), Portland, Oregon, and included a reported 10 miles visibility and temperature of 31°C near the time of the accident. Based on the available weather report, the calculated density altitude near the accident site was 4,626 ft. The pilot of the airplane who continued on the southerly course while enroute estimated the visibility to be about 7 statute miles, with wildfire smoke in the area. The pilot of the airplane flying the alternate route with the accident airplane reported that “it wasn’t too smooth out.” Examination of the accident site revealed that the airplane came to rest in a nose-low attitude on a heading of about 110° magnetic, at an elevation of about 2,751 ft mean sea level. The wreckage was at the base of an about 100-ft-tall tree. Multiple impact scars were observed from the base of the tree to about 50 ft, and several branches from the tree were observed around and within the wreckage. The engine was partially buried in the forest floor, nose low and beneath the fuselage. The propeller assembly was attached to the engine, buried in recently disturbed earth, directly beneath the engine. The mainlanding gear assembly was about 75 ft downhill from the main wreckage. All major structural components of the airplane were located at the accident site. Postaccident examination of the wreckage revealed no evidence of preaccident mechanical malfunction or failure that would have precluded normal operation.