Help with VDP

[propilot1983]

Here is the question:

How do you calculate VDP?

A.) By DME - 300 Ft per nautical mile (from end of the runway) Ex. Say the MDA = 600 FT and MAP is 1 DME. Your VDP = 3 DME. 600/300 = 2 DME plus the 1 DME = 3 DME. So when the DME reads 3, that's your VDP and you can start your decent.

B.) By time- Take 10% HAT off your time. Ex. Let's say the published HAT is 800 Ft and the time for the approach is 5:20. Your VDP will be when your timer hits 4:00. (10% of 800 = 80 seconds, subtract that from 5:20 and you get 4:00.) Start your descent for the airport when the timer reads 4:00.

Here is what (I think) I know, perhaps you all will tell me differently.

VDP is a defined point on the final approach course of a non-precision, straight-in approach procedure from which normal descent form the MDA to the runway touchdown point can be commenced, provided the approach threshold of that runway, or approach lights, or other markings identifiable with the approach en dof that runway are clearly visable to the pilot.

According to the AIM, the VDP is indicated by a "V" on the profile view on the approach plate.

After doing some more research while compliling this post, it was mentioned on a web site that VDP is used as only a reference where a 3 degree glideslope can be attained for a normal approach to landing? I guess i was under a false impression the reason for the VDP was because of a possible conflict with an obstacle. I'm having a little trouble wrapping my mind around the concept. Please help!

 

[propilot1983]

the 4:00 is supposed to be 4 mins even. Stupid emoticon shortcuts.

 

[TheGuat]

You are a "propilot" and yet you don't know about vdp's?

 

[propilot1983]

You are a "propilot" and yet you don't know about vdp's?

Thanks for the help, sport.

 

[propilot1983]

Nevermind, ya'll...I have figured it out on my own.

 

[rjacobs]

not for obstacle clearance, if you see the runway and lights and stuff you can leave MDA way earlier than the VDP if you want. The only thing the VDP gives you like you already said is the 3 degree glide slope. If on an approach and you hit the VDP and still havent seen anything, chances are you are going around because it will be kinda tough to get down to the runway and still stay stabilized. When I fly a NP approach and hit the VDP and dont see anything I shift mentally to thinking missed even though I might have 2 or 3 miles before my MA point.

 

[Joe Schmo]

Another way I understand it as a point to where you should begin to leave the MDA for an approach to land. If all goes well on a non-precision approach and you have the airport enviroment you maitain the MDA until reaching the VDP then make a normal 3 degree approach path to a landing.

I believe it was brought about to help prevent pilots from descending to prematurely from the MDA to landing while shooting certain non-precision approaches. Hope that helps a bit

 

[rjacobs]

I agree with not descending to early, but what if your ceiling is very ragged and you see the runway then pop back into the clouds, then back out, etc... I personally leave MDA as soon as I see the lights if conditions are very iffy. Even if leaving a 600 foot mda and only going down 100 foot, it still gives you a better chance of keeping what ever you see in view. The VDP is actually a point, as I believe it, to keep people from diving at the runway at the last second and either not being able to arrest the descent or landing so far down the runway they cant stop. It assures a landing can be made with a minimal amount of maneuvering.

 

[olympus593]

I got to say, you guy's are a bunch of dorks!!! UND or Riddle?

 

[bailout]

We dont use VDPs anymore, we use the CANPA procedure.

 

[rjacobs]

I got to say, you guy's are a bunch of dorks!!! UND or Riddle?

Neither, I went to CMSU(call me stupid university). It is between KC and Whiteman AFB and our mascot was a big ASS(i.e. mule). I am not proud of where I went to college accept for the fact that it wasnt UND or Riddle.

 

[suupah]

only going down 100 foot,

your midwest roots