VDP Limitations

Say youre flying to Asheville, North Carolina on a rainy IMC day. The visibility is hovering around a mile and a half and the ceiling is 1200 feet. ATC has you on vectors for the RNAV (GPS) RWY 34. Without a WAAS GPS in your Turbo Bugsmasher, youre stuck with the LNAV minimums. The weather is above the Category B minimums that youll be using, so you shouldnt have any problems. Right?

Key Takeaways:

• Pilots may encounter situations where reported visibility on a non-precision approach is above minimums but less than the Visual Descent Point (VDP) distance, making a normal, safe descent to landing difficult or impossible if the runway isn't in sight by the VDP.
• This issue arises because VDPs are calculated based on descent angle and threshold crossing height, while visibility minimums are determined by MDA height and approach lighting, creating a disconnect between the two.
• Not all straight-in non-precision approaches have published VDPs due to factors such as obstacle penetrations or remote altimeter settings, sometimes necessitating pilot estimation, which carries inherent risks.
• The VDP is critical for flying stabilized non-precision approaches (CANPA), but pilots must carefully manage their descent to avoid dropping below the Minimum Descent Altitude (MDA) when initiating a missed approach.

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