Is Vdp regulatory if published?

[Doc Holiday]

If you pass the VDP (which can be identified using time OR distance...so no excuses!) and then begin a descent from MDA, your glidepath will exceed 3 degrees. You may set up an excessive rate of descent.

In such a case you are not "continuously in a position from which a landing may be made using normal maneuvering" etc..etc..

Think like an airline pilot. Go-arounds pay more than landings.

This is incorrect, a true VDP is assessed for obstacle clearance and PUBLISHED on an IAP at a fixed point in space. It is not determined by time.

You are referring to what is sometimes referred to as a Planned Descent Point or Time To See point, and often used interchangeably with the term "VDP". While these are a great tool for non presicion IAPs where a VDP is not published, they are neither regulatory nor do they necessarily provide for obstacle clearance.

 

[Amish RakeFight]

VDP and PDP are different things.

VDP's are published - PDP's are calculated.

Published VDP's have all of math and geometry hammered out so you don't collide with something on that particular approach.

 

[PURPLEHAZE21]

I thought VDP's pertained more towards larger aircraft who would be unable to descend prior to the MAP, while at MDA, and land under 91.175 ? The "stable" concept, which has been around for awhile (Part 135/121), appears to be making a big come back. Under part 91 ops. does the "stable" concept apply or do you just have to adhere to 91.175 ?

 

[Amish RakeFight]

VDP's can and should be used by everyone including light aircraft.

Aside from ensuring a stabilized descent, let's say you're at MDA and acquire the runway environment prior to reaching the published VDP. It wouldn't be wise to begin descent prior to reaching this point. Your descent angle would be more shallow and if you did use a 3 degree (300' descent per mile) you might run into obstacles which penetrate this angle from your MDA if begun prior to reaching the published VDP or calculated PDP.

 

[PURPLEHAZE21]

Good information....There recently was an accident in which a plane flying a LOC approach only saw the runway at MDA and decided to descend to 100 ft above TDZ (It was night). You probably figured it out...they hit an obstacle prior to the runway....maybe a VDP would have helped ?