What is the visibility requirement for mountainous cross country flights at night when using NVGs or TAWS?

The visibility requirement for mountainous cross-country flights at night when using Night Vision Goggles (NVGs) or Terrain Awareness Warning Systems (TAWS) is 5 miles. This standard is established to ensure safety by allowing pilots to maintain visual reference necessary for navigation and to avoid obstacles, especially in complex terrain.

Flying at night poses unique challenges due to reduced visibility and increased difficulty in identifying topographical features. The requirement for 5 miles of visibility ensures that pilots using NVGs or TAWS can adequately perceive their surroundings and react to potential hazards. This level of visibility is deemed sufficient to enhance situational awareness, allowing for effective navigation through mountainous areas where terrain can be particularly dynamic.

This standard takes into account not just the basic need for sight but also the additional demands that night flying presents, especially in the context of mountainous terrain where elevations and potential obstacles can quickly become dangerous if not seen in advance.