While making a non-precision approach, you’ll need to know what the Visual Descent Point is. Learn everything about the VDP in aviation in this expert guide.
Knowing how to make safe approaches and landings is without a doubt one of the most important parts of becoming a pilot. As you get more and more advanced in your flying, you’ll eventually start making non-precision approaches where you don’t have as much data to rely on as other planes might provide. That’s where the Visual Descent Point comes in.
The Visual Descent Point (VDP) is an important part of any non-precision instrument approach. It's a point on the approach where the aircraft should be at or below the minimum descent altitude. Pilots use the VDP to help them make a safe landing, even if they can't see the runway.
In this article, we will explain everything you need to know about the VDP. We'll discuss what it is, how to find it on approach plates, and how to use it safely during a landing. We'll also talk about what happens if you miss the VDP. So if you’re ready to dive in and learn about this vital part of non-precision approaches, then strap in and continue reading!
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What is a Visual Descent Point (VDP) in Aviation?
When you take a look at some non-precision approach plates, you’ll see a small black “V”, often on the localizer approach section of the plate. But what is this little black “V” and what does it really mean? This is the Visual Descent Point (VDP), and it’s one of the most misunderstood and misused aspects of approach plates.
So what is the VDP?
Let’s start by taking a look at the official definition from the Federal Aviation Administration (FAA). In Section 4 of the Aeronautical Information Manual (AIM), Arrival Procedures are outlined in detail. Subsection 5-4-5 Instrument Approach Procedure (IAP), paragraph (h) details exactly what the VDP is.
According to the AIM, the VDP is a “defined point on the final approach course of a nonprecision straight-in approach”. Right off the bat, this means that you won’t have to worry about the VDP on a circling-only approach since it’s only used for straight-in approaches.
The AIM goes on to say that it’s the point from which a stabilized descent from the MDA to the decision height (DH) or touchdown can be made using normal landing configuration and approach speed. So basically, it’s the point where you should be able to see the runway and make a normal landing.
Now that we know what the VDP is, let’s talk about how to find it on an approach plate.
How to Find the Visual Descent Point (VDP)
The VDP can be found on the final approach fix (FAF) or localizer back course (LBC) segment of non-precision approach plates. It will be marked with a small black “V” and will have a corresponding note next to it. This note will give you the decision altitude (DA), which is the same as the decision height (DH) on a precision approach.
The VDP will also have a minimum descent altitude (MDA) associated with it. This is the lowest altitude that you can go down to and still maintain visual contact with the runway. If you can’t see the runway at the MDA, then you must go around and try again.
Now that we know what the VDP is and how to find it on an approach plate, let’s talk about how to use it during a landing.
How Can Pilots Calculate the VDP on the Fly?
Now that we know what the VDP is and how to find it on an approach plate, let's discuss how pilots can calculate the VDP on the fly. This is important because sometimes the VDP isn't explicitly called out on an approach plate and pilots need to be able to calculate it themselves.
There are two main variables that go into calculating the VDP: the MDA and the rate of descent. The MDA is simply the minimum altitude that you're allowed to descend to on an approach. This is usually given in feet above mean sea level (MSL). You can find the MDA on the approach plate under the "Descend" or "Initial Descent" heading.
The rate of descent is a bit more complicated. There are two different rates of descent that you need to be aware of: the normal rate of descent and the maximum rate of descent. The normal rate of descent is simply the average rate at which you'll descend on an approach. This is usually given in feet per nautical mile (ft/nm). You can find the normal rate of descent on the approach plate under the "Rate" or "Normal Descent" heading.
The maximum rate of descent, on the other hand, is the fastest rate at which you're allowed to descend on an approach. This is usually given in feet per minute (ft/min). You can find the maximum rate of descent on the approach plate under the "Max Descent" or "Maximum Descent" heading.
Now that we know all of the variables that go into calculating the VDP, let's put it all together. The formula for calculating the VDP is simply the MDA divided by the normal rate of descent. So, if the MDA is 500 feet and the normal rate of descent is 400 ft/nm, then the VDP would be at 0.75 nautical miles from the runway threshold.
It's important to note that you should always use the normal rate of descent when calculating the VDP. The maximum rate of descent is only to be used if you're descending at a faster rate than normal for some reason (e.g., you're trying to make up for lost time).
Why is it Important to Understand What the VDP is?
The visual descent point (VDP) is a key concept in aviation, and it's something that every pilot needs to understand. The VDP is the point on an approach plate where the pilot begins their final descent towards the runway. This point is calculated based on the aircraft's rate of descent, and it's marked on the approach plate so that pilots can easily find it.
The VDP is used on non-precision instrument approaches, and it's a key part of making a safe and successful landing. If you miss the VDP, you may not have enough time or altitude to make a proper landing. That's why it's so important to understand how to calculate the VDP and where to find it on approach plates.
Here's a quick overview of what you need to know about the VDP:
- The VDP is the point on an approach plate where the pilot begins their final descent towards the runway.
- It is calculated based on the aircraft's rate of descent and MDA.
- The VDP is marked on the approach plate so that pilots can easily find it.
- This point is used for straight-in non-precision instrument approaches.
- If you miss the VDP, you may not have enough time or altitude to make a proper landing.
With such a technical concept as the VDP, it’s best if you go and check out an approach plate yourself after this to see if you can apply the concepts you just learned here. At the very least, keep these bullet points in mind and you’ll know more about the VDP in aviation than the vast majority of people out there!
About THE AUTHOR
After spending years watching every video I could find about flying, I finally scratched the itch and got my pilots license. Now I fly every chance I get, and share the information I learn, here.Read More About Joe Haygood