Question about markings on vpt. Approach.
Posted by Nouchka_captPA-28@reddit | flying | View on Reddit | 14 comments
So nobody at my flight school is able to answer this question so reddit is my last resort.
On this vpt approach there are two X with the altitudes 1477’ and 1897’. What are they meant to be?
I first thought that they were altitudes you should be at but this doesn’t make sense as they are lower than the mda. I looked in the jeppeson manual and for symbols it show this symbol under the routes & airways as a “mileage break / CNF”
Any help would be appreciated.
flyingron@reddit
The X marks where the various racetracks intersect the final approach course. The altittudes are what that would be on a standard (presumably 3 degree) glideslope.
anactualspacecadet@reddit
Its actually like a 5-6 degree glideslope if you do the math lol
flyingron@reddit
The further out X at 1897 on a three degree glideslope is 3.4 miles which looks about right visually (since it's between the 3 and 4 mile DME ring). Don't forget you need to subtract the field elevation from 1897 (yielding 1112).
anactualspacecadet@reddit
DME≠distance from the threshold of the runway. You should not calculate glideslope this way, the NAVAID and threshold of the runway are seldom in the same location
flyingron@reddit
At the altitudes we're talking about (1000-2000') we're talking well under 1% difference between slant range and horizontal distance. This is not a problem here.
anactualspacecadet@reddit
Its a 4.4° glideslope. 4.4-3(your predicted number)=1.4. 1.4>1 (the number you said the difference would be well under).
flyingron@reddit
As I pointed out in another comment when the fact that the DME is at the far end of the runway I redid my calculations.
Again the 1000' at 3 miles from a DME station yields a .15% error between slant range and ground distance. Despite your histrionics, this is not introducing a error in this calculation.
No-Version-1924@reddit
DME is at the other threshold, though, which is about 0.9nm away from threshold runway 32, so you have to take that into account.
flyingron@reddit
Throwing in another 6000', brings it to 4.3 degrees.
canyoutriforce@reddit
Its a visual approach. Once you are visual at MDA, you continue visually on the prescribed tracks to the runway. They are reference altitudes to show you a correct descent profile but are not mandatory in any way.
Nouchka_captPA-28@reddit (OP)
Thank you. It’s still kind of weird to me that this would be higher than the mda. But like you said at that point you should be visual.
anactualspacecadet@reddit
Stepdowns for the visual, the 1897 puts you at 1100 AGL for a 2.5nm final (for Cat c) and the 1477 puts you at 700 AGL for a 1.2nm final. As the other guy said this is a visual you can kinda do whatever you want.
KCPilot17@reddit
Those altitudes aren't lower than the MDA? They're recommended altitudes based on where you should be, as it's a visual approach.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
So nobody at my flight school is able to answer this question so reddit is my last resort.
On this vpt approach there are two X with the altitudes 1477’ and 1897’. What are they meant to be?
I first thought that they were altitudes you should be at but this doesn’t make sense as they are lower than the mda. I looked in the jeppeson manual and for symbols it show this symbol under the routes & airways as a “mileage break / CNF”
Any help would be appreciated.
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