Calculating Your Venture Departure Point without a specified Instrument Approach
In the world of aviation, Visual Descent Points (VDPs) play a crucial role in non-precision straight-in approaches. These points, defined as the final approach course points from which normal descent to the runway touchdown point may be commenced, are not always published on charts. However, pilots can calculate VDPs using a simple geometric method when they are unavailable.
To calculate a VDP, you first need to find the height difference between the Minimum Descent Altitude (MDA) and the runway elevation. This height difference, in feet, is then divided by 300 feet per nautical mile to get the distance from the runway threshold in nautical miles.
For instance, if the MDA is 500 feet above the runway elevation, the VDP would be approximately 1.67 nautical miles from the threshold. This means that a pilot should not descend below MDA until this point if they have the required visual references. Descending below MDA before this distance could potentially risk obstacles, as no obstacle clearance protection exists below MDA unless a VDP is published.
This method aligns with the guidance provided by the Federal Aviation Administration (FAA), which states that VDPs serve as references for the optimal location to begin descent from MDA assuming visual cues exist. Below MDA, obstacle clearance is not assured unless a VDP is published.
It's important to note that VDPs are only published for straight-in instrument approaches to specific runways. If an approach has a VDP, pilots should not descend below MDA prior to reaching the VDP.
In some cases, VDPs may not be published due to terrain or obstacles. For example, on the Crookston (KCKN) VOR/DME Approach to Runway 13, the lowest MDA is 344 feet above the touchdown zone elevation. Dividing the MDA AGL value by 300 gives an approximate distance of 1.15 nautical miles from the runway where you can start a 3-degree descent to the runway.
However, it's essential to remember that not all non-precision approaches have published VDPs. In such cases, pilots should ensure they have enough visibility to see not only the runway but also any obstructions that might be in their path before starting their descent down from MDA to the runway.
In summary, calculating a VDP when none is charted involves finding the height difference between the MDA and runway elevation, dividing this value by 300 to get the distance from the runway, and using this point to start descent below MDA if visual references are established. This technique is a standard practice among pilots when no VDP is published and aligns with safe operational practice on non-precision approaches.
[1] Operational Guidance by NBAA and FAA documents on non-precision approaches and VDPs. [3] Pilot training videos illustrating the calculation of descent angles and VDPs for non-precision approaches.
- Utilizing the geometric method, pilots can calculate Visual Descent Points (VDPs) when they are unavailable, aiding in non-precision straight-in approaches.
- To calculate an approximate VDP, pilots first figure out the height difference between the Minimum Descent Altitude (MDA) and the runway elevation in feet.
- By dividing the height difference by 300 feet per nautical mile, pilots can obtain the distance from the runway threshold in nautical miles.
- For instance, with an MDA 500 feet above the runway, the VDP is approximately 1.67 nautical miles from the threshold.
- As a pilot should not descend below MDA until this point if they have the required visual references, descending below MDA before this distance could potentially risk obstacles.
- In accordance with FAA guidance, VDPs serve as references for the optimal location to begin descent from MDA assuming visual cues exist.
- VDPs are only published for straight-in instrument approaches to specific runways, so pilots should not descend below MDA prior to reaching the VDP.
- With no VDP published, pilots must ensure they have enough visibility to see both the runway and obstructions before starting their descent down from MDA to the runway.
- In the aerospace industry, education and self-development materials like NBAA and FAA documents, along with pilot training videos, illustrate the calculation of descent angles and VDPs for non-precision approaches.
- The finance and business sectors offer resources to acquire industry-specific knowledge and continue learning relevant aviation practices, such as the calculation of VDPs for enhancing safe flight maneuvers.
