It seems that for forever, the advice was to chop the power at the final approach fix and dive for the minimum descent altitude, with the goal of seeing the runway as early as possible, and then starting a descent.
The visual descent point (VDP) is a tool to stop the madness and bring some stability to nonprecision approaches. Missed approach points are often near the end of the runway. This gives you the latitude to drop down to the minimum descent altitude and then drone along until the bitter end. If you don’t see the runway, the decision to start the missed approach is easy. But what if you do see the runway? Now you have to decide if you want to dive down in order to make it. In a slow, draggy airplane, this might not be a problem. But as you step up to bigger and faster airplanes, it’s easy to see how you could skid off the end of the runway in such a scenario.
The VDP is a marker on the approach from which a normal descent and landing can be made, and in certain applications takes away the needs for such a hasty last-minute decision. It generally reflects the intersection of a 3-degree glideslope with the missed approach altitude.
When you arrive at the VDP you have three options:
Not every nonprecision approach has a VDP. If an obstruction rises into the visual segment of the approach, a VDP won’t be published, for example. In these cases you can mentally create your own VDP by taking the difference between the minimum descent altitude and the touchdown zone elevation and dividing by 300. This will give you a general point at which to begin the descent or go missed, but remember that the absence of the VDP may mean there’s an obstruction to avoid. Also keep in mind that for this calculation you are looking for distance from the end of the runway, not the GPS center point or DME of the airport. Usually these are in the middle of the airport. You may need to subtract this distance from your VDP to make sure you end up with a stabilized approach to the runway and not a phantom marker in the middle of the airport.
With the VDP there’s no longer a reason to dive for the runway at the missed approach point. Especially in instrument conditions, stability is the goal, and a VDP offers just that.