Final answer:
The normal range of the tri-color VASI at night is a 'red over white' indication, which signifies that the aircraft is on the correct glide path for a safe landing. The lights are typically visible from several miles away under clear night conditions.
Step-by-step explanation:
The normal range of the tri-color Visual Approach Slope Indicator (VASI) at night varies, but typically the VASI provides a visual glide path of safe altitude over certain airplane landing obstructions. The VASI consists of light units arranged to provide a visual indication of an aircraft's position on the glide path for a safe approach to the runway, both during the day and at night. At night, the VASI is especially critical as it assists in providing the pilot with altitude guidance.
The VASI system uses red and white light colors to indicate whether the aircraft is on the correct glide path. A "red over white" indication means the pilot is on the correct glide slope, while an indication of "white over white" means the aircraft is too high, and "red over red" indicates that the aircraft is too low. Therefore, the normal and safe range at night is to see a red over white indication.
It is important for pilots to understand this system as it greatly enhances safety during night operations. The range at which these lights are visible varies, depending on weather conditions and the intensity of the lights, but generally, the lights can be seen from a distance of several miles at night under clear conditions.