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MikeD · September 24th, 2004, 02:33

[ QUOTE ]
Can anyone explain how to calculate a VDP? I know VDP stands for visual descent point and it's a point on a non precision approach where you may begin descending if you have the runway in sight. Other than that, I know nothing. Any help?

[/ QUOTE ]

GuS wears a HAT. Take the desired glidepath you wish to calculate for (ie 3 degrees) and divide it into the Height Above Touchdown. Take that figure as miles, and count back from the beginning of the runway to get where your VDP would be.

Easy example: You have an airport where the HAT is 600', and your desired glidepath is 3 degrees. Take 3 degrees (300) and divide it into the HAT of 600. That gives you 2. Lets assume that the missed approach point depicted is at the beginning of the runway at, for example, 7 DME (with the FAF being the VOR for example). Your VDP would be 2 miles short of this, or 5 DME......which would make sense since if you desire a 300 to 1 descent profile, it would take 2 miles to descend 600 feet.

That's a very simplified example, but the equation works well when you have DMEs (miles) compute to things like 1.7, 2.4, etc.

Clear as mud? [img]/ubbthreads/images/graemlins/smile.gif[/img]

September 24th, 2004, 02:33	#3
MikeD Administrator Join Date: Feb 2003 Location: Pinal Airpark Posts: 6,897	Re: How to calculate a VDP? [ QUOTE ] Can anyone explain how to calculate a VDP? I know VDP stands for visual descent point and it's a point on a non precision approach where you may begin descending if you have the runway in sight. Other than that, I know nothing. Any help? [/ QUOTE ] GuS wears a HAT. Take the desired glidepath you wish to calculate for (ie 3 degrees) and divide it into the Height Above Touchdown. Take that figure as miles, and count back from the beginning of the runway to get where your VDP would be. Easy example: You have an airport where the HAT is 600', and your desired glidepath is 3 degrees. Take 3 degrees (300) and divide it into the HAT of 600. That gives you 2. Lets assume that the missed approach point depicted is at the beginning of the runway at, for example, 7 DME (with the FAF being the VOR for example). Your VDP would be 2 miles short of this, or 5 DME......which would make sense since if you desire a 300 to 1 descent profile, it would take 2 miles to descend 600 feet. That's a very simplified example, but the equation works well when you have DMEs (miles) compute to things like 1.7, 2.4, etc. Clear as mud? [img]/ubbthreads/images/graemlins/smile.gif[/img]