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jutes85
Topic Author
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Arrows On Runways

Sat Dec 13, 2003 7:22 am

What is the point of the arrows that lead up to the runaway?


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This seems to reduce the runway length as the aircraft have to land about 1/4 down the runway.
nothing
 
Leskova
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RE: Arrows On Runways

Sat Dec 13, 2003 7:24 am

Aren't those the areas of the runway that are reserved only for planes exceeding specific weights?
Smile - it confuses people!
 
ConcordeBoy
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RE: Arrows On Runways

Sat Dec 13, 2003 7:30 am

the arrows indicate that the threshold is displaced, thereby cautioning airliners not to land at the very end of the runway.
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
NWA ARJ
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RE: Arrows On Runways

Sat Dec 13, 2003 7:30 am

Those arrows you refer to are for the displaced threshold. That part of the runway is to be used only for takeoff, taxiing, or the rollout. That part of the runway cannot be used for landing because it may not be suitable for all of that weight or it is just too worn down, etc.
Nightmare 68, Fargo Tower, Runway 36, Fly Runway Heading, Mantain 10,000, Cleared For Takeoff, Change To Departure
 
potomac
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RE: Arrows On Runways

Sat Dec 13, 2003 7:31 am

that's a displaced threshold - usable for takeoff but not for landings (you must land ahead of those arrows past the "piano keys"). from the other direction, however, your landing roll may continue thru a displaced threshold.

these are commonly found where there is some sort of obstacle at the end of the runway.
 
InnocuousFox
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RE: Arrows On Runways

Sat Dec 13, 2003 7:31 am

That's a displaced threshold. The arrowed area is only for takeoff rolls. The landings still need to take place beyond the solid white line (the real threshold). The difference is that the real threshold is placed there for obstacle clearance on the approach path. Some genious realized that you don't need the clearance on that end if you are just starting your takeoff roll. Therefore, you can buy an extra 500 feet or 1000 feet or whatever for taking off (where you really need it).
Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
 
Tom in NO
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RE: Arrows On Runways

Sat Dec 13, 2003 7:33 am

The arrows help to designate a "displaced threshold". That stretch of pavement may be used by aircraft departing on that runway, but landing aircraft have to land beyond the area where the arrows end (hence that is where the runway end bar and the runway indentifier are painted). The purpose of a displaced threshold is for adequate airspace clearances on the runway approach.

Our runway 28 has a displaced threshold.

Tom at MSY
"The criminal ineptitude makes you furious"-Bruce Springsteen, after seeing firsthand the damage from Hurricane Katrina
 
Leskova
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RE: Arrows On Runways

Sat Dec 13, 2003 7:36 am

Is obstacle clearance the only reason? Because at my "hometown airport" (HAJ), they've got a displaced threshold (is that "threshold" or "threshhold"?) - but the only obstacle that a plane could encounter would be grazing cows...
Smile - it confuses people!
 
InnocuousFox
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RE: Arrows On Runways

Sat Dec 13, 2003 7:39 am

Well, there needs to be a 3 degree glide slope there... you can't have fences near the threshold at all... a lot of things.
Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
 
Leskova
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RE: Arrows On Runways

Sat Dec 13, 2003 7:43 am

Hmm, there is a fence some - I'd guess - 30-50 meters away from the beginning of the runway, but that's less than 2 meters high... the next real obstactle in the direction I'm thinking of would be the city of Burgdorf - but that's about 20 kilometers away... Big grin
Smile - it confuses people!
 
InnocuousFox
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RE: Arrows On Runways

Sat Dec 13, 2003 7:48 am

Maybe it WAS an extention for longer takeoff rolls. Is it a different pavement than the rest? I've seen that before.
Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
 
Tom in NO
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RE: Arrows On Runways

Sat Dec 13, 2003 7:51 am

It gets a little more complicated with the different types of approaches to a runway. The 3-degrees mentioned is not an obstacle clearance guide, it is the average glide angle for an approach.

Obstacle clearances are done more on a foot out/foot up basis. In other words, the most basic runway usually requires a 20:1 clearance. In other words, for every 20 feet you extend from the end of the runway, go up 1 foot in the air. Extend further out at that angle, and the only things that are allowed to penetrate that slope are frangible (easily breakable) approach lighting arrays. That is what designates what is called the RPZ (Runway Protection Zone).

For most instrument related approaches, the approach slope can be as shallow as 50:1.

The slope angles can also vary based on if you are off the side of the runway.

This can all be found in Federal Aviation Regulations Part 107: Obstructions to Navigable Airspace.

Tom at MSY
"The criminal ineptitude makes you furious"-Bruce Springsteen, after seeing firsthand the damage from Hurricane Katrina
 
Leskova
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RE: Arrows On Runways

Sat Dec 13, 2003 7:52 am

Actually I think it is different pavement - but I'd have to look at some of my pictures to be sure of that (I usually just see it from the right hand window of a plane not using the extension)...

But I think I remember reading about that part of the runway only being "opened" for long-haul flights (as if there were that many from HAJ  Sad), although I'm not sure if that was about the west- or east-end of the runway...
Smile - it confuses people!
 
Southamerica
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RE: Arrows On Runways

Sat Dec 13, 2003 8:34 am


I think based on the healthy replies you can build yourself a good concept.

Strange though nobody at SAN has said anything. Not really sure, but it must be one of the airports with the largest restricted-for-landing zone in the whole wide world. Seen from I-5 it looks like if the threshold was displaced like the half of the complete paved path.

Regards,

Federico in SOUTHAMERICA
 
DLMHT
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RE: Arrows On Runways

Sat Dec 13, 2003 8:49 am

In addition to obstruction clerance, airports can use a displaced threshold on runways that are getting a little worn from all the aircraft landing in the same spot.

Think about it, a number of heavies landing consistently on the same spot would weaken the runway there, and the airport would have to move the touchdown bars just a little further down the runway. Its either that, or they would hae to dig up and replace the pavement at the touchdown point ever couple of years.

Departing aircraft can still taxi over the displaced threshold point, as their weight is more evenly distributed than an aircraft hitting the runway at 180 mph.


DLMHT
 
N243NW
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RE: Arrows On Runways

Sat Dec 13, 2003 10:17 am

Since we're talking about displaced thresholds, what do the yellow chevrons on some runways mean? If I'm not mistaken, those can't be used to take off OR land, correct? If so, what purpose do they really serve?
-N243NW Big grin
B-52s don't take off. They scare the ground away.
 
InnocuousFox
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RE: Arrows On Runways

Sat Dec 13, 2003 10:46 am

"what do the yellow chevrons on some runways mean?"

Same thing, isn't it?
Dave Mark - Intrinsic Algorithm - Reducing the world to mathematical equations!
 
USAFHummer
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RE: Arrows On Runways

Sat Dec 13, 2003 11:02 am

AFAIK The yellow chevrons are not usable for either takeoff or landing...not sure why...

Greg

PS. For future reference this thread should probably be in tech/ops...I've requested that it be moved there...
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flyf15
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RE: Arrows On Runways

Sat Dec 13, 2003 11:03 am

Yellow chevrons are overrun/blast pad. Not suitable for any aircraft operations (takeoff, landing, or taxi).
 
XFSUgimpLB41X
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RE: Arrows On Runways

Sat Dec 13, 2003 3:08 pm

Displaced threshold..like in the picture....cannot land there, but it can be used for takeoff roll and landing rollout...just dont plop the wheels down in that area. You have to wait to touch the wheels down until the threshold bars- but should be aiming toward the usual 1000 foot markers.


Chevrons- don't be caught with your wheels anywhere in that area...not a good thing...unless of course your biscuit's a-burnin'..then anything goes.  Smile

[Edited 2003-12-13 07:15:58]
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SlamClick
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RE: Arrows On Runways

Sat Dec 13, 2003 10:22 pm

Hey Federico

SAN is just like all the others except that the GPWS annunciates:

"Garage! Garage!" on final to 27.


Happiness is not seeing another trite Ste. Maarten photo all week long.
 
USAFHummer
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RE: Arrows On Runways

Sun Dec 14, 2003 1:04 am

I've always wondered what the purpose of yellow-chevroned runway is...since its not legally usable, why is it even there to begin with?

Greg
Chief A.net college football stadium self-pic guru
 
shaun3000
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RE: Arrows On Runways

Sun Dec 14, 2003 4:37 pm

Blast pad - to keep hot exause off the ground. I guess to prevent fire?

Emergency overrun - an added bit of hard runway for an airplane to stop on in an emergency. (Or extra room on the sides of the runway)

In both cases, you don't need the same quality as you do for the runway. It saves money when you don't need useable runway, only concrete for emergencies or as a blast pad.

Or, it could just be old runway that's so beat up it's not suitable for operations, and they didn't want to pay to fix it.
 
SkyGuy11
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Joined: Fri Oct 26, 2001 7:09 am

RE: Arrows On Runways

Mon Dec 15, 2003 3:24 am

Is obstacle clearance the only reason? Because at my "hometown airport" (HAJ), they've got a displaced threshold (is that "threshold" or "threshhold"?) - but the only obstacle that a plane could encounter would be grazing cows...

Sometimes they're there for noise abatement; the greater the displaced threshold, the higher an airplane is at a particular point on approach, and the less 'noise' it makes.

Just take a look at Bakersfield, CA.
.
 
Skymonster
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RE: Arrows On Runways

Thu Dec 18, 2003 11:47 pm

Is obstacle clearance the only reason? Because at my "hometown airport" (HAJ), they've got a displaced threshold (is that "threshold" or "threshhold"?) - but the only obstacle that a plane could encounter would be grazing cows...

Sometimes, when a runway is extended at the approach end, they leave the glideslope and touchdown point where it is if the pre-extension landing distance is already adequate. That saves disruption moving the ILS, PAPIs/VASIs, etc. Seeing as take off is usually more critical for runway length than landing, leaving the approach where it is and having a displaced threshold can make the job of extending the runway much easier and cheaper.

Andy
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