What happened
A certificated commercial pilot and four passengers departed from a remote airport on a scheduled air taxi flight. The flight was conducted under VFR (visual flight rules) during dark night conditions over terrain covered in snow. Prior to departure, the pilot gathered weather information using personal observations, pilot reports, and his home computer.
Following takeoff, the pilot executed a deviation to navigate around a range of small mountains situated between the departure and destination airports. The pilot stated this deviation was intended to keep the aircraft at least 1,000 feet above the ground and to avoid icing conditions. During the flight, the aircraft encountered a snow shower.
The pilot reported having no outside visual references for navigation during this period. Relying on the airplane's directional gyro for course guidance, the pilot noted that the gyro rotated to the left, which placed the aircraft in close proximity to a mountain. The unspecified aircraft subsequently collided with snow-covered terrain at an altitude of approximately 900 feet MSL. The four passengers were not injured but reported they could not see the ground and were unaware of any impending danger until the aircraft came to an abrupt stop.
An area forecast for the flight period had included an AIRMET for mountain obscuration, as well as marginal VFR ceilings in mist and snow, along with light, isolated, moderate rime icing in clouds.