How do you calculate the Visual Descent Point (VDP)?

The Visual Descent Point (VDP) is a critical aspect of an instrument approach that indicates where a pilot can begin a visual descent to the runway, assuming they have the appropriate visual references. To calculate the VDP, one must first understand what MDA (Minimum Descent Altitude) is, as it's key in this calculation.

In this context, MDH refers to the Minimum Descent Height, and typically, the VDP can be calculated using the formula based on the altitude above ground level at which the aircraft would start descending. The relevant approach to finding the VDP is done by dividing the height of the MDA by the desired descent gradient. A standard descent rate is often considered to be around 300 feet per nautical mile.

Therefore, understanding that dividing the MDH by 300 gives a result that aligns with the feet per nautical mile descent rate helps pilots determine how many nautical miles from the landing runway they should begin their descent to establish a stable approach. This conversion ensures that the descent is initiated at a point where visual references to the runway can be established, thus facilitating a safe landing under VFR (Visual Flight Rules) conditions.

This calculation is particularly useful in an environment where visual conditions may be marginal, ensuring