Runway Approach Ratio

MDeitch1976

MDeitch1976

Line Up and Wait
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MattCanFly
Noticed several airports displaying airport approach ratios. Could someone please explain these? For example one was 28:1. Would this be descending 280 feet for every 1000 feet forward?


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MDeitch1976 said:
Noticed several airports displaying airport approach ratios. Could someone please explain these? For example one was 28:1. Would this be descending 280 feet for every 1000 feet forward?


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28 feet forward for every 1 foot down. Or 280 feet forward, 10 feet down. Or 2800 feet forward for every 100 down.

I think that ratio is wrong.
 
Ron Levy said:
Where are you seeing these "approach ratios"?
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First I saw this in the airport info on Skyvector.com, and Air Nav, and also in the comments in foreflight. 7G4 is an example. And it states in the comments "approach ratio 28:1 to displaced threshold".


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MDeitch1976 said:
First I saw this in the airport info on Skyvector.com, and Air Nav, and also in the comments in foreflight. 7G4 is an example. And it states in the comments "approach ratio 28:1 to displaced threshold".


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That is in reference to obstacle clearance - in that instance its 23 ft trees, 332ft from the runway - 26:1 ratio to clear down to the displaced threshold.
 
SkyHog said:
28 feet forward for every 1 foot down. Or 280 feet forward, 10 feet down. Or 2800 feet forward for every 100 down.

I think that ratio is wrong.
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I thought ratios were rise over run.
What you wrote doesn't seem correct. Maybe you are. If I was at a 1000 foot pattern altitude. I would have to travel 28000 feet forward to descend to the runway. Surely, my pattern is not that wide.

At 7G4, the runway is between to mountains or large hills for the mountain folk in the middle.


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MDeitch1976 said:
I thought ratios were rise over run.
What you wrote doesn't seem correct. Maybe you are. If I was at a 1000 foot pattern altitude. I would have to travel 28000 feet forward to descend to the runway. Surely, my pattern is not that wide.

At 7G4, the runway is between to mountains or large hills for the mountain folk in the middle.


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You're right, I misspoke - its 28ft down for every 1 ft forward - which is very steep.
 
SkyHog said:
That is in reference to obstacle clearance - in that instance its 23 ft trees, 332ft from the runway - 26:1 ratio to clear down to the displaced threshold.
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That makes sense.
In practicality, is a pilot going to use these numbers at all?


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SkyHog said:
You're right, I misspoke - its 28ft down for every 1 ft forward - which is very steep.
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That is what I thought. I will bring along an instructor if I try this one out.


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MDeitch1976 said:
That makes sense.
In practicality, is a pilot going to use these numbers at all?


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I don't think I ever would - I'd just take it to mean "Once I clear those trees, I gotta be aggressive to land on the numbers at this airport."
 
SkyHog said:
You're right, I misspoke - its 28ft down for every 1 ft forward - which is very steep.
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No, you had it right. 28:1 is about a 2 degree glide slope. Most folks fly a 4-5 degree glide path out of the VFR traffic pattern if there's no VGSI. What they're telling us is if you go below that 28:1 slope on that runway, you might hit something. But since most folks fly more like a 4-5 degree path visually (about a 13:1 slope), they won't have a problem. Even the "standard" instrument glide path of 3 degrees is a 19:1 slope, still well above 28:1.
 
SkyHog said:
You're right, I misspoke - its 28ft down for every 1 ft forward - which is very steep.
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That would be an 88 degree glideslope. I think you were right the first time. 28 feet forward, 1 foot down, would be about 2 degrees.
 
Thank you for the clarification here.
Are there many airports that have an extreme approach angle?
 
MDeitch1976 said:
I do not mean this one. Just in general anywhere around the mid Atlantic.
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Steepest VGSI I know is Rwy 32 at Clearview (2W2) in Westminster MD -- 7 degrees, which is about 8:1. Your home 'drome at Freeway (W00) has a 6 degree VGSI, which is 9.5:1.
 
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There are a number of different approach slopes going to a runway. A visual runway has a 20:1 slope, a non-precision runway has a 34:1 approach slope and a precision runway has a 40:1 approach slope. Depending on the runway and any obstructions there might be there, the slopes may intersect with the threshold, or may gp to a point 200 feet off the end of the runway. There are also departure slopes off of instrument runways, which in some cases are extremely flat -- up to 80:1.

These slopes are part of the standards used to define airport design so that the airports know what obstructions they must light, remove or notam, so that the approach designers have a standardized clearance to work with.
 
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dmspilot said:
That would be an 88 degree glideslope. I think you were right the first time. 28 feet forward, 1 foot down, would be about 2 degrees.
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He was joking, dms. And it was the funniest thing I've heard all day :)
 
Ron Levy said:
Steepest VGSI I know is Rwy 32 at Clearview (2W2) in Westminster MD -- 7 degrees, which is about 8:1. Your home 'drome at Freeway (W00) has a 6 degree VGSI, which is 9.5:1.
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I have done 3 landings on Clearview. However on 32. Need to try out the other way.
My home crime is GAI. However, I did get to fly out and in with Jaybird to Freeway. 18 at Freeway looms like it would be fun.


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