The private pilot departed on a personal flight in visual meteorological conditions during the early evening and flew to a nearby airport, where he parked the airplane and walked to a nearby restaurant. He returned to the airplane about an hour later, which was about 20 minutes after the end of civil twilight. Surveillance video captured the accident airplane depart the runway and enter a right traffic pattern, which was the opposite of the published left traffic pattern and took the airplane over unlit pasture and hills. The imagery then depicted the airplane enter a rapid descent on what appeared to be the right downwind leg of the traffic pattern. The airplane disappeared from view consistent with ground impact. The descent duration was about 7 seconds.The airplane impacted a pasture north of the airport. The debris field indicated that the airplane impacted the ground with a relatively shallow flight path angle, in a nose- and right-wing low attitude, with a significant amount of horizontal energy. All major airplane and engine components were identified in the wreckage, and no indications of any pre-impact mechanical deficiencies or failures were observed. The flaps were in the fully retracted position, which was the climb-cruise configuration, likely indicative that the pilot was not attempting a landing when the impact occurred. The undamaged condition of the artificial horizon gyro rotor and internal case suggested a possibility that the device was not operating, but the actual operating status of the instrument at the time of the accident could not be determined. Even if the artificial horizon was inoperative, external visual references should have been sufficient to enable the pilot, albeit possibly with some difficulty, to maintain the proper airplane attitude and flight path.Some fibrous lint-like material was found in the carburetor fuel inlet screen; the material was foreign to the airplane fuel system, but it was not determined when or by what means the lint was introduced into the system. The lint did not appear to have any adverse effect on engine operation; propeller damage was consistent with the engine developing significant power at the time of impact. Airplane fueling information and published performance data indicated that the airplane had sufficient fuel onboard for a Page 2 of 13 WPR18FA035return flight to the airport of origin.About 5 weeks before the accident, the pilot had completed a night flight in the accident airplane from his home airport to the accident airport and back, which indicated that he was at least somewhat familiar with the accident airport. The reason for the pilot's use of a right traffic pattern instead of the designated left traffic pattern for his departure could not be determined. Although the pilot had documented color vision deficiencies, this condition likely did not contribute to the accident sequence. The pilot had relatively limited total and night flying experience, and the night and local terrain were very dark. Given the signatures of engine power and lack of mechanical anomalies found during postaccident examination, it is not likely that the accident was the result of a loss of engine power. Further, correlation of debris field information with the descent angle depicted in the surveillance imagery frames indicated that the descent path was too shallow to be consistent with an aerodynamic stall. Additionally, the airplane's impact attitude and the distribution of the wreckage were inconsistent with a loss of control due to spatial disorientation. It is possible that the pilot lost his situational awareness while maneuvering onto the right downwind leg which resulted in the airplane descending rapidly to ground impact.