Calculating Your VDP Without a Provided One in an Instrument Approach procedure

Calculating Your VDP Without a Provided One in an Instrument Approach procedure

In the world of aviation, a Visual Descent Point (VDP) plays a crucial role in non-precision approaches, especially for straight-in instrument approaches to specific runways. However, it's essential to note that a VDP is not published on every non-precision approach.

When VDPs are not published on charts, pilots can manually calculate one using the Minimum Descent Altitude (MDA) above the runway elevation and a typical descent angle of 3°. The formula involves dividing the height above the runway by the tangent of the descent angle. For instance, if the MDA is 500 feet above the runway elevation and a 3° descent angle is used, the VDP would be approximately 1.6 nautical miles from the runway threshold.

This calculated VDP marks the point where a pilot can begin a normal descent from the MDA down to the runway, assuming adequate visual references, and helps ensure a stable and controlled descent. Approaches without a published VDP, however, have not been thoroughly evaluated for obstacle clearance below the MDA, so greater pilot vigilance is necessary below MDA to avoid obstacles.

The Crookston (KCKN) VOR/DME Approach to Runway 13, for example, has an MDA of 344 feet Above Ground Level (AGL). Dividing 344 by 300 results in an approximate distance of 1.15 from the runway threshold where a 3-degree descent can begin. However, it's important to note that this value is not the actual DME (Distance Measuring Equipment) value but rather the VDP's distance from the runway threshold.

In some cases, VDPs may be denied during approach chart design due to terrain or obstacles. In such situations, pilots must exercise additional caution and ensure there is enough visibility to see both the runway and any potential obstructions before starting a descent down from MDA to the runway.

The Boldmethod Instrument Procedures course aims to help pilots earn their instrument rating and improve their IFR skills, providing valuable insights into the importance of VDPs and other aspects of non-precision approaches.

In a recent incident, a pilot elected to go-around after realizing they were too high, having not briefed a Visual Descent Point (VDP) for the approach. This underscores the importance of proper briefing and understanding of VDPs during non-precision approaches.

The VDP is a defined point on the final approach course of a non-precision straight-in approach procedure. It provides an advisory reference but does not imply additional obstacle protection beyond what is published. The VDP helps ensure a stable and controlled descent on non-precision approaches, making it an essential tool for pilots navigating these types of approaches.

1. In the aviation industry, a Visual Descent Point (VDP) is significant for non-precision approaches, especially straight-in instrument approaches to specific runways.
2. When no VDP is published on charts, pilots can manually calculate one using the Minimum Descent Altitude (MDA) and a typical descent angle of 3°.
3. The calculated VDP indicates the point where a pilot can initiate a normal descent from the MDA to the runway, presuming adequate visual references.
4. Approaches without a published VDP might not have been tested for obstacle clearance below the MDA, necessitating increased pilot vigilance below MDA to avoid obstacles.
5. The Boldmethod Instrument Procedures course aims to aid pilots in attaining their instrument rating and enhancing IFR skills, focusing on the importance of VDPs and other aspects of non-precision approaches.
6. In some cases, VDPs may be omitted during approach chart design due to terrain or obstacles, requiring pilots to exercise extra caution and verify visibility to spot both the runway and potential obstructions before descending below MDA.
7. A recent flight incident involving a pilot choosing to perform a go-around after recognizing they were too high, absent the briefing of a Visual Descent Point (VDP) for the approach, highlights the importance of proper briefing and understanding of VDPs during non-precision approaches.
8. The VDP is a defined spot on the final approach course of a non-precision straight-in approach procedure, offering advisory reference but not implying additional obstacle protection beyond what's published.
9. The VDP is an essential tool for pilots navigating non-precision approaches, ensuring a stable and controlled descent on these types of approaches, by providing a reference point for initiating the final descent phase.

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