What exactly is the runway "fence"?

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infrequentFlyer

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infrequentFlyer
Hello,

While reading about landings and approaches, I often see "pull power when you are over the airport fence" or something of the like.

What exactly is this fence? At first I thought it was a real fence, but that doesn't seem like something that would be standard or the same at most runways. Is "the fence" slang for one of the runway markings? (Runway width stripes look kinda like a fence, or maybe the chevrons?)

Please enlighten me!
 
No, it is just hyperbole not a literal fence.

It is just referring to a point that is short of the approach end threshold, and sometimes referring to the "50' obstacle".
 
Ha. Ok so it's basically the same location as those who say you can pull power "once you have the runway made". (No intention to discuss landing technique here - just trying to find this "fence").
 
infrequentFlyer said:
Ha. Ok so it's basically the same location as those who say you can pull power "once you have the runway made". (No intention to discuss landing technique here - just trying to find this "fence").
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Pretty much.

The term comes from airports that actually have a fence around the airport property. In order to maximize runway length, the end of the runway is fairly close to the fence.
 
There is a second definition for runway fence: that barrier you run/slid/fly through after a botched landing, just before leaving airport property. During the winter, this position is usually marked by a collection of broken off nose gear.
 
rhkennerly said:
There is a second definition for runway fence: that barrier you run/slid/fly through after a botched landing, just before leaving airport property. During the winter, this position is usually marked by a collection of broken off nose gear.
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We just call that side the arresting barrier. There's a reason fence companies put their name and phone number on the fence.
 
Doesn't this refer to the actual fence around the airport?
 
infrequentFlyer said:
Ha. Ok so it's basically the same location as those who say you can pull power "once you have the runway made". (No intention to discuss landing technique here - just trying to find this "fence").
Click to expand...
Sort of, but not really. You can have the runway made on downwind and pull power there too.

The term usually refers to an “over the fence speed“ that is slightly lower than Vref. It‘s really the point where you are just beginning your round out. Contextually, I’ve heard it applies to higher performance airplanes rather that 152s.

It’s physical location varies. In the standard 3 degree approach with touchdown on the 1000’ marker, it’s pretty much the threshold. On a short field, it might be well before the threshold.
 
S43.Harvy.Field.Fence.jpg
At my home drome, generally power is pulled before the fence. Google car took this from Airport Way.
 
midlifeflyer said:
Sort of, but not really. You can have the runway made on downwind and pull power there too.
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Ok, true. I thought it was implied that I was referring to someone like a CFI talking to you on final. I'm a newbie and have only flown with a couple CFIs so maybe that wasn't clear.

midlifeflyer said:
The term usually refers to an “over the fence speed“ that is slightly lower than Vref. It‘s really the point where you are just beginning your round out. Contextually, I’ve heard it applies to higher performance airplanes rather that 152s.
Click to expand...

With a little help from your reply I found this IFR magazine article saying that "the fence" is where you would cross 50 ft AGL. Then again who knows where this author learned that, but it agrees with what you said and works for me.


Out of curiosity I calculated the location of the "other fence". That is, where you could lose power and still make the runway (on final! :)). Assuming:

- 1:9 glide ratio (C172)
- You were following a 3° slope towards the 1000 ft markers before engine quit
- No obstacles in your new power off trajectory
- No wind

You could lose your engine about 890 ft before the threshold and still land on the runway. You will be about 99 ft off the ground, and if you pitch for Vglide immediately you will still have enough speed to flare and maybe land on the numbers.

However, coming in to land in a 172 you are probably at 30 - 40° of flaps. I have no idea what effect that has on glide ratio, but maybe cuts it in half??

So, rough guess, the "other fence" is about 4-500 ft before the threshold.
 
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infrequentFlyer said:
Ok, true. I thought it was implied that I was referring to someone like a CFI talking to you on final. I'm a newbie and have only flown with a couple CFIs so maybe that wasn't clear.



With a little help from your reply I found this IFR magazine article saying that "the fence" is where you would cross 50 ft AGL. Then again who knows where this author learned that, but it agrees with what you said and works for me.


Out of curiosity I calculated the location of the "other fence". That is, where you could lose power and still make the runway (on final! :)). Assuming:

- 1:9 glide ratio (C172)
- You were following a 3° slope towards the 1000 ft markers before engine quit
- No obstacles in your new power off trajectory
- No wind

You could lose your engine about 890 ft before the threshold and still land on the runway. You will be about 99 ft off the ground, and if you pitch for Vglide immediately you will still have enough speed to flare and maybe land on the numbers.

However, coming in to land in a 172 you are probably at 30 - 40° of flaps. I have no idea what effect that has on glide ratio, but maybe cuts it in half??

So, rough guess, the "other fence" is about 4-500 ft before the threshold.
Click to expand...
There are airplanes in which you keep some power in at touchdown for a normal landing.
 
infrequentFlyer said:
Ok, true. I thought it was implied that I was referring to someone like a CFI talking to you on final. I'm a newbie and have only flown with a couple CFIs so maybe that wasn't clear.



With a little help from your reply I found this IFR magazine article saying that "the fence" is where you would cross 50 ft AGL. Then again who knows where this author learned that, but it agrees with what you said and works for me.


Out of curiosity I calculated the location of the "other fence". That is, where you could lose power and still make the runway (on final! :)). Assuming:

- 1:9 glide ratio (C172)
- You were following a 3° slope towards the 1000 ft markers before engine quit
- No obstacles in your new power off trajectory
- No wind

You could lose your engine about 890 ft before the threshold and still land on the runway. You will be about 99 ft off the ground, and if you pitch for Vglide immediately you will still have enough speed to flare and maybe land on the numbers.

However, coming in to land in a 172 you are probably at 30 - 40° of flaps. I have no idea what effect that has on glide ratio, but maybe cuts it in half??

So, rough guess, the "other fence" is about 4-500 ft before the threshold.
Click to expand...
I think we might be overthinking a hand-waving generalization here a bit.

I guarantee you the vast majority of CFIs using this term haven't put 2% of the thought into it that you have.

"Er, right about here will do ya."
 
ElPaso Pilot said:
I think we might be overthinking a hand-waving generalization here a bit.

I guarantee you the vast majority of CFIs using this term haven't put 2% of the thought into it that you have.

"Er, right about here will do ya."
Click to expand...

Ha, yea - I see that very clearly now, but before I had asked I thought it might be some "lingo" which I had yet to learn. You know, there's way too much lingo in this business so I had to check.

My "calculation" was just to satisfy my own curiosity about having the runway made, since it's a thing people say.
 
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