Vertical Descent Angle, Mountain Airports

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t3chiman

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t3chiman
Perusing mountainous area airports, looking for extreme values of Vertical Descent Angle, I ran across Salmon, Idaho, Lemhi County: SMN RNAV (GPS)-D.
upload_2022-2-24_13-58-33.png
Charted VDA is 8.91 degrees. Using simple math (i.e. no correction for curvature of the earth), I get 8.86 degrees.
Descent: 7020 - (4044 + 40) = 2936 ft
Distance: 3.1NM, 18836 ft
Gradient: .1558
Angle: arctan (.1558) = 8.86 degrees

Previous POA discussions re VDA values pointed to Steamboat Springs, SBS RNAV (GPS)-E, at 7.75 degrees.

Any greater VDA values out there?
 
That's nothing. Take a look at Aspen ASE.
 
Anyone remember the old airport for Vail, located around Avon. Can't remember the name, but it had some colorful unofficial names.
 
..and I thought the 6.9 for the LOC D at SEE was high


/stabilized approach has left the chat/
 
It's a bit ambiguous, but Table 2-6-1 is in the "straight-in" context. Lemhi County is Circling, Step-down, and Offset, so differing (and not fully defined) rules apply. I think; I'm not instrument-rated yet.

The approach plate begins at 14000MSL; the airport is at 4044. Must be an absolutely spectacular experience. It's very pretty on the ground. I've driven it. Sacajawea was Lemhi Shosone, this area is where Lewis and Clark met with her brother, to bargain for fresh horses.
 
n00b question - for the helo pilots. What category are you? And do the VDAs mean anything? I would imagine a 90* VDA is theoretically possible..
 
Tantalum said:
..question - how are these not violating TERPS?

from https://www.faa.gov/documentLibrary/media/Order/Order_8260.3D_vs3.pdf
Click to expand...

First, you linked to the 8260.3D. Current version is 8260.3E, but the details for this discussion don't change: https://www.faa.gov/documentLibrary/media/Order/Order_8260.3E.pdf

They don't violate TERPS because since they do not have straight-in minimums, the maximum (uncharted) angle is calculated to the Circling MDA, not to the threshold crossing height. 8260.3E formula 2-6-3:

upload_2022-2-24_18-41-36.png

However, the 8260.19I, which controls how the procedure is documented, says to then publish the actual angle to the TCH. "Where straight-in minimums are not authorized..."

upload_2022-2-24_18-44-52.png

Crystal clear, right? :D
 
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