how do you calculate a VDP?

HAT/3 will give you the DME from the end of the runway. Groundspeed/2 will give you the vertical speed to descend at.

So for a sea level airport with an MDA of 600 feet you'd start down 2 miles from the runway (600/3) and if your ground speed was 100 knots you'd use 500 feet per minute down.

It's sort of quick and dirty but it mostly works assuming you can identify the distance from the end of the runway.
 
2 ways.

Timing. Take 10% of HAT and substract that from the time to the MAP. Ex: HAT 600' (10% = 60s). Time to MAP 2:30. 2:30 minus 60 seconds equals 1:30 to the VDP.

DME. HAT/300 equals DME to the MAP. Ex: HAT 600'. 600/300 equals 2 miles.
 
Or you can look at the LIDO chart. One of the nice things I noticed about them is most (if not all) have VDPs on the charts already....
 
taseal said:
yah but, they're not so easy to buy from a store lol
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Haha, that's what I was thinking. Anyone know where I can find them? I had a chance to hold some in person when a guy came to give a presentation about his company. They were pretty cool, mostly because they were something new, hehe.
 
AngelFuree said:
Haha, that's what I was thinking. Anyone know where I can find them? I had a chance to hold some in person when a guy came to give a presentation about his company. They were pretty cool, mostly because they were something new, hehe.
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something new is def cool :D

I have nothing to complain about my jepps though.
 
One thing about the formulas above is that they all assume a 3 degree glideslope. But if you use HAT/ (GS*100) you can change them for any desired glideslope. (Of course, most airplanes use 3 degrees anyway, but there are some fighters out there that use steeper ones and I think helos use really steep glideslopes, too.)

Anyways, I always remember it by "GuS wears a HAT. "
 
killbilly said:
What's HAT?
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HAT= "height above touchdown". It's calculated by subtracting the touchdown zone elevation (TDZE) from the MDA or decision height. It's sort of like the DH or MDA in AGL, but not exactly. The terrain at the point where you get to the MDA could be above or below the terrain at the first 3000' of the runway.

HAA= "Height above aerodrome". Similar to an HAT, except used for circuling approaches. It's MDA- field elevation, rather than MDA - TDZE.

TDZE is the highest point in the first 3000' of the specified runway.

Field elevation is the highest point on ANY runway on the field.
 
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