Cessna 150L accident near Dunsmuir, California, October 20, 2021

The NTSB's narrative final · quoted from the NTSB record

The non-certificated pilot departed on a cross-country flight that required multiple fuel stops. The weather forecast called for clouds near the accident site. During the fuel stops, the pilot recharged the battery and, at one instance, refused assistance from witnesses to find and replace his alternator. Witnesses stated that he sparingly used the battery power for takeoff and landing and continued his cross-country flight with a known inoperable alternator. Postaccident examination of the cockpit revealed that the master switch was in the OFF position. With the master switch in the OFF position, the electrical system was not powered, and the airplane was not able to transmit its aircraft positions over its automatic dependent surveillance-broadcast (ADS-B) system. The field examination of the airplane wreckage did not reveal any mechanical malfunctions or failures that would have precluded normal operation. A witness near the top of the mountain reported that clouds and fog were present and provided a visibility of about 200 ft. He added that, about the time of the accident, he heard a low-flying airplane and was able to distinguish noise consistent with a running engine but did not hear the airplane’s impact with terrain. He further reported that the fog was present for most of the morning, lasting through the early afternoon. The pilot was likely flying the airplane low over the interstate to stay out of the clouds. He then likely entered instrument meteorological conditions as the airplane approached the mountain valley and turned back towards the departure airport before impacting trees in a wings-level attitude. No record was found indicating that the pilot received a preflight weather briefing; however, it could not be determined if the pilot obtained weather information using other sources. The pilot’s toxicology results indicate that he may have been experiencing impairing effects of diphenhydramine, such as sedation, at the time of the crash, and may also have been experiencing mild symptoms of uncontrolled diabetes, such as fatigue or blurry vision. However, the pilot’s decision to attempt the risky flight is unlikely to have been directly affected by these medical factors. Thus, given that the airplane was in controlled flight at the time of its collision with visually obscured terrain, there is low likelihood that the pilot’s diphenhydramine use or uncontrolled diabetes contributed to the crash.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.