ANC23FA074

The pilot’s decision to operate the airplane above its maximum certificated gross weight, and his installation of an unapproved external load that degraded takeoff performance and flight characteristics resulting in a loss of airplane control during takeoff into an area of mechanical turbulence and downdrafts.

The pilot ferried a group of hunters into a remote wilderness area over the days leading up to the accident flight. The hunters then killed a moose, and the pilot ferried the first of two loads of meat back to the departure airport. The first ferry flight was uneventful, with the airplane departing to the north before initiating a climbing right turn toward the destination. During the second flight, the airplane was more heavily loaded with meat and the pilot had mounted a set of moose antlers to the right wing strut. The hunters observed that the accident takeoff was more labored than before; the airplane took off in the same direction, and they watched as it rolled to the right after rotation and flew out of sight behind an adjacent ridgeline. They were all initially relieved that the airplane had managed to become airborne, but it did not reappear from behind the ridge, and had crashed just beyond their view in the opposite direction of takeoff. The initial takeoff phase of both the accident and a previous flight were captured on video. Audio analysis of the recordings indicated that the engine was operating at the same high power setting during both flights; it was not trailing any smoke or vapor. Postaccident examination of the airframe and engine did not reveal any anomalies that would have precluded normal operation. Examination of the cargo at the accident site indicated that it was still secured within the airframe, but was not secured within the cargo pod. Review of the takeoff video indicated that the airplane did not pitch up aggressively enough during the takeoff to have caused the unsecured meat in the cargo pod to shift. The antlers were still secured to the right wing strut and did not impede any of the flight control cables. The pilot did not use scales to weigh the cargo, and the airplane was loaded 117 lbs, or about 6%, over its maximum takeoff weight. It was so heavy that, even after consuming fuel enroute, the airplane still would have been about 180 lbs over its maximum landing weight upon reaching the destination. The runway was situated at the crest of a hill, where terrain rapidly fell away into a valley at the northern departure end. The terrain then began to rise such that within about ¾ mile it was 400 ft higher than the runway. The wind at the time of takeoff was out of the north, and while this would have helped during the initial ground roll, once the airplane had left the runway and began a right turn over the valley to the south, it would have encountered downdrafts and mechanical turbulence induced by the terrain to the north and the runway drop-off. The downdrafts, along with the overweight airplane and the added drag and lateral weight imbalance caused by the antlers on the right wing, would likely have resulted in the airplane having insufficient power and/or control authority to maneuver above terrain. Although carrying antlers externally is a common practice in Alaska, it requires formal FAA approval with a notation in the airplane’s airworthiness and maintenance logbooks. There was no evidence that such approval had been granted for the accident airplane. The airplane was manufactured about 70 years before the accident and had undergone dozens of major repairs and alterations such that at the time of the accident, almost none of the original airplane existed. Although the repairs and alterations were approved through supplemental type certificates (STCs), at the time those alterations were performed the FAA did not provide guidance for installers to determine the interrelationship between all STCs incorporated into an aircraft. Therefore, the airplane’s true flight performance characteristics under normal operations, and particularly when the airplane was flying outside of its weight envelope, were unknown. The pilot had cardiovascular disease, including focally severe narrowing of a branch coronary artery. Such disease may develop without major symptoms, but conveys an increased risk of sudden impairing or incapacitating cardiovascular events, such as arrhythmia, chest pain, or heart attack. There was no autopsy evidence that such an event occurred, although such an event would not leave reliable autopsy evidence if it occurred just before death. Based on the circumstances, there was no evidence that the pilot’s medical condition or use of medications contributed to the accident. Although the pilot survived the initial impact, he succumbed to his injuries within a few hours. The occupiable space within the cabin was compromised by impact to such an extent that it could no longer provide protection to the pilot even with the use of a shoulder harness. Given the remote location of the accident site, which was about 400 miles from a hospital, and accessible only by air, providing the pilot with prompt medical treatment following the accident was not possible.

The pilot was first issued his pilot certificate in 1993. His logbook was not recovered; however, at the time of his last FAA medical examination on August 11, 2023, he reported a total flight experience of 6,707 hours. The pilot was the operator’s sole pilot. He was added to the company’s operating specifications and underwent a checkride with an FAA inspector, in accordance with 14 CFR 135.293 and 135.299, ten days before the accident. The series of flights that preceded the accident were the first in his capacity as a pilot for the operator. He had been a friend of the operator for many years, and according to the operator he had flown the airplane many times before. The airplane was originally manufactured in 1952 as a Piper PA-18-105 (“Special”), under the Type Certificate number 1A2. At that time, it was equipped with a Lycoming O-235-C1 engine. A series of major alterations were performed through STC in 2013. These included a replacement fuselage and new horizontal and vertical stabilizers, rudder, and elevators. Additional major alterations and repairs included the replacement of the original engine with a Lycoming O-320, 160-hp engine; a belly-mounted cargo pod; new seats; replacement of both forward wing spars and one rear wing spar; replacement of a series of wing ribs; extended flaps; installation of vortex generators; and 35-inch Alaska Bushweel main wheels and tires (which included an upgraded landing gear strut/suspension assembly). The FAA released Advisory Circular (AC) 20-188 on December 9, 2016. The AC provided engineering guidance to installers for determining the compatibility of the installation of approved changes via STC where previously approved changes were installed on aircraft. The airplane was involved in an accident in 2017, which required replacement of the vertical stabilizer and rudder, along a series of wing ribs, the aft spar of the right wing, and the forward spar of the left wing. As a result of the major repairs and alterations performed at the time of the accident, almost none of the original airplane remained. At the time of the pilot’s last FAA medical examination, he reported having high blood pressure and using the prescription blood pressure medication atenolol. His high blood pressure was noted to be qualified under the conditions aviation medical examiners can issue (CACI) criteria. He was issued a second-class medical certificate limited by a requirement to use corrective lenses to meet vision standards at all required distances. According to the pilot’s autopsy report, his cause of death was the result of multiple blunt force injuries. His autopsy identified hypertensive and atherosclerotic cardiovascular disease, including thickening of the left cardiac ventricle and an area of plaque causing 90% narrowing of a proximal diagonal branch of the left anterior descending coronary artery. The coronary arteries were otherwise without evidence of disease. The remainder of the autopsy, including visual and microscopic examination of the heart, did not identify other significant natural disease. The FAA Forensic Sciences Laboratory performed toxicological testing of postmortem specimens from the pilot; this testing detected metoprolol in femoral blood and urine. Metoprolol is a prescription medication that can be used as part of treatment for high blood pressure, certain arrhythmias, and certain types of heart failure. Metoprolol is not generally considered impairing. Metoprolol and atenolol belong to the same medication class (cardioselective beta-blockers). On September 12, 2023, about 2047 Alaska daylight time (AKDT), a Piper PA-18-150, N109T, sustained substantial damage when it was involved in an accident near St. Mary’s, Alaska. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 135 on-demand flight. Two days before the accident, the pilot ferried a group of five hunters, a guide, and their equipment from the operator’s base in Holy Cross, Alaska, to an airstrip in St Mary’s. The group then set up camp next to the runway, which was oriented north-south within hilly terrain about 70 miles northwest of Holy Cross. The group planned to hunt for a moose and prepare it for transportation back to the operator’s base. The day before the accident, the group successfully hunted a moose and coordinated with the pilot via satellite messaging devices to ferry the meat the next day. On the day of the accident, the pilot arrived at the camp about 1540. The pilot and hunters loaded the airplane with the first batch of meat, and the airplane departed on the north runway. After takeoff, the airplane made an uneventful climbing right turn over an adjacent ridgeline that paralleled the airstrip to the east and then continued in the general direction of Holy Cross. The pilot returned to camp about 1940 for the second and final load. The meat was strapped into the rear passenger seat area by the pilot with both the seatbelt and rope and was also loaded into the airplane’s belly pod, which did not have tie-down provisions. The pilot then tied the moose antlers to the right wing strut; the antlers were cupped outward and perpendicular to the direction of flight. They discussed the weather and observed that the wind at the airstrip was generally calm and from the north, but was also intermittently variable and gusting. Members of the group reported to the pilot that the wind was gusting much stronger at the northern (departure) end of the airstrip. The pilot then boarded the airplane and positioned it for a takeoff to the north. The hunters noticed that the ground roll was slightly longer than before, and that the airplane appeared to be more heavily loaded and “labored” than during the previous flight. They stated that, as the airplane reached the end of the airstrip, it pitched up and turned sharply to the right; however, rather than climbing as before, it flew behind the adjacent ridgeline and out of view. The group initially thought that the pickup had been successful, and they cheered with relief, but the airplane did not reappear from behind the ridge. They ran to the top of the ridgeline, looked down, and saw that the airplane had crashed. One of the hunters recorded a video of the takeoff. The video showed that the airplane began the ground roll at the southern end of the airstrip and departed uphill to the north. The flaps were retracted, and the tail of the airplane came up as soon as the pilot applied engine power (see figure 1). The ground roll lasted about 530 ft, and immediately after takeoff, the airplane pitched up and rolled right (see figure 2). The airplane then rolled to a wings-level attitude, and the video ended a few seconds later. The engine was heard operating during the recording and the airplane was not trailing smoke or vapor. Figure 1. Airplane during the takeoff roll (Source: hunter video). Figure 2 - Airplane rolling right immediately after takeoff (Source: hunter video). The runway was situated at the crest of a hill, where terrain rapidly fell away into a valley at the northern departure end. The terrain then began to climb, such that within about ¾ mile, it was 400 ft higher than the runway. The airplane came to rest on a 30° downward slope on the other side of the adjoining ridgeline, at an elevation of 1,210 ft mean sea level, about 10 ft lower and 600 ft east of the departure end of the airstrip (see figure 3). The surrounding area consisted of rolling hills covered in tundra, grass, and low-lying shrubs and bushes. Figure 3 - Accident site. The fuselage came to rest on a northerly heading, and both wings remained partially attached and generally in line with each other on a northwest-southeast orientation. The first identified point of impact was located about 20 ft below the main wreckage, and consisted of a divot in the soil that contained blue a