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### Runway Markings

I know this thread title has been used before, but I couldn't find my answer. Why do some runways have several white arrows leading to the piano keys? PLanes can use this area for takeoff too, so why wouldn't they just make the piano keys start back at the beginning instead of having 1500 ft. of white arrow leading to the piano keys?
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2H4
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### RE: Runway Markings

Displaced thresholds typically exist for obstacle/terrain clearance on final. Another consideration is the load-bearing capability of that concrete or pavement. Runways are reinforced to withstand the weight of a landing aircraft, but not all displaced thresholds are.

2H4
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InnocuousFox
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### RE: Runway Markings

 Quoting 2H4 (Reply 1):Runways are reinforced to withstand the weight of a landing aircraft, but not all displaced thresholds are.

Which is actually the reverse order in effect. They don't bother to reinforce the extension area because they know that no one will be landing there... because of the clearance issue you mentioned.
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Mir
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### RE: Runway Markings

 Quoting C5LOAD (Thread starter):Why do some runways have several white arrows leading to the piano keys? PLanes can use this area for takeoff too

But they can't use it for landing. Thus the white arrows instead of the normal piano keys.

-Mir
7 billion, one nation, imagination...it's a beautiful day

2H4
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### RE: Runway Markings

 Quoting InnocuousFox (Reply 2):They don't bother to reinforce the extension area because they know that no one will be landing there...

KLM is doing their darndest to convince them otherwise, though:

 View Large View MediumPhoto © Trent R Sellers View Large View MediumPhoto © Chris Starnes

View Large View Medium

2H4
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### RE: Runway Markings

Do they use paint, or is it a coating of some kind?
"Slippery when wet?"

I believe that runway marking rules differ between different continents, correct?

Just trying to cover the basics here, please correct me if I´m wrong:

The barcode means start / end of runway, which can be followed by an (overshoot) area, normally not to be used. Then there´s a white line which indicates the middle of the runway, the number is the rough direction of the runway (minus 1 zero) rounded up to 10 degrees and a big cross on the runway would mean "runway not in use"!

Terrible to think about what happened to SQ in Taipei.............

Cheers,

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InnocuousFox
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### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 5):I believe that runway marking rules differ between different continents, correct?

Gotta love Wikipedia
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Mir
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### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 5):I believe that runway marking rules differ between different continents, correct?

Yes, but not much. Some differences I can think of:

- In the US, they won't paint the first number if it's a zero (runway 9, for instance). The same runway in Europe would be painted 09 (and referred to as 'runway zero-nine' in ATC communications)
- The UK has a slightly different 1,000 foot marker than the US.
- Runways in Norway have yellow markings as opposed to white (probably to make visibility easier when there is snow on the runways)

All of them are minor, of course - there is pretty much an international standard.

-Mir
7 billion, one nation, imagination...it's a beautiful day

vikkyvik
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### RE: Runway Markings

 Quoting Mir (Reply 7):- The UK has a slightly different 1,000 foot marker than the US.

...and most of the rest of the world

Also to be noted: the aiming point (the large solid white bar that Mir is talking about) is at 1000 feet in the US. In many other countries, it's somewhere between 1000 and 1500 feet (typically at a metric distance from the threshold, I think...seem to recall seeing 400 meters on several runways).

The rest of the touchdown zone markings also differ somewhat in different countries, although they're always typically located at 500 ft/150 meter increments.

Additionally, the US has historically used 8 large white bars for the threshold marking, while the rest of the world uses the standard 4, 6, 8, 12, or 16 bars (for 50, 75, 100, 150, and 200 foot wide runways respectively). Most new-construction or repainted runways in the US now use this format as well.
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Posts: 132
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### RE: Runway Markings

 Quoting InnocuousFox (Reply 6):Gotta love Wikipedia

Point taken, point taken........
But I think a lot of people post questions here because of the nice personal answers at times and the discussion it may ignite afterwards.
Mir & Vikkyvik for instance.........
Good link by the way, thanks! Good drawings.........

 Quoting Mir (Reply 7):In the US, they won't paint the first number if it's a zero

Interesting, any idea why? Saving paint? Is it really paint, or some other coating?

Further more, the aiming point is about 350 meters (roughly 1000 feet) down the runway? Really, interesting! I mean I knew that they don´t use the 1st meters like they do on aircraft carriers............but skipping 350 meters seems quite a lot! I don´t think they skip that much at UIO / GYE where I live, but that´s maybe because of short runways to start off with.

Cheers,

A lot of people need to be offended on a regular basis I always felt, and IÃ?Â´m the very boy to do it! - Billy Connolly

vikkyvik
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### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 9):Further more, the aiming point is about 350 meters (roughly 1000 feet) down the runway? Really, interesting! I mean I knew that they don´t use the 1st meters like they do on aircraft carriers............but skipping 350 meters seems quite a lot! I don´t think they skip that much at UIO / GYE where I live, but that´s maybe because of short runways to start off with.

Well, a typical 3-degree approach has the aircraft crossing the threshold at a height of 50 feet. At a 3-degree descent (meaning little to no flare), the airplane will touch down just about 950 feet down the runway.

This allows a margin of error on both sides of the touchdown point. If your landing point is right at the threshold, and you land short, you could be in deep trouble

Also, 1000 feet is better estimated as 300 meters than 350 (it's actually about 305 meters).
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InnocuousFox
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### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 9):Quoting InnocuousFox (Reply 6): Gotta love Wikipedia Point taken, point taken........ But I think a lot of people post questions here because of the nice personal answers at times and the discussion it may ignite afterwards.

I think you missed my intent entirely. I was looking there for my own benefit on a few things. I found that it answered some of the questions here, so I simply posted it for others.
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Faro
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### RE: Runway Markings

 Quoting 2H4 (Reply 1):Displaced thresholds typically exist for obstacle/terrain clearance on final. Another consideration is the load-bearing capability of that concrete or pavement. Runways are reinforced to withstand the weight of a landing aircraft, but not all displaced thresholds are.

I may be mistaken, but I believe a departing aircraft at MTOW exerts a greater load on the runway pavement than a landing aircraft at MLW and nominal flare.

Faro
The chalice not my son

2H4
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### RE: Runway Markings

 Quoting Faro (Reply 12):I may be mistaken, but I believe a departing aircraft at MTOW exerts a greater load on the runway pavement than a landing aircraft at MLW and nominal flare.

I'm not sure about that, either. But wouldn't they have to plan (and build) for landing impacts above and beyond that of a normal flare? We wouldn't want a hard landing to damage the runway, after all.

So if a normal flare/landing is X g's, I wonder how much of a margin must be built into runway surfaces. X + 10%? 20%? It would be interesting to learn.

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Faro
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### RE: Runway Markings

 Quoting 2H4 (Reply 13):So if a normal flare/landing is X g's, I wonder how much of a margin must be built into runway surfaces. X + 10%? 20%? It would be interesting to learn.

It would indeed, given also that one would perhaps incorporate another additional margin into the displaced threshold pavement area: pilots sometimes undershoot as is graphically demonstrated by your 747 pix in SXM above. I have a sneaking suspicion that the displaced threshold is built to the same load bearing standards as the nominal landing area...

Faro
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FredT
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### RE: Runway Markings

I'd be very, very cautious with that assumption if I was you! Wikipedia is very often way, way off.

The source to be trusted on runway markings is ICAO Annex XIV. Member states who wish to deviate from this should include this in their list of exceptions.
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MSNDC9
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### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 5):Do they use paint, or is it a coating of some kind? "Slippery when wet?"

They use reflective beads in the paint at most airports.

FAA Standards are here:

http://www.faa.gov/airports/resource.../media/150-5340-1J/150_5340_1j.pdf

[Edited 2009-07-21 09:40:15]

Mir
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### RE: Runway Markings

Because that's the way the runway is referred to. What would be "runway zero-nine" in other countries is just "runway nine" in the US.

I suspect, though, that your real question is why the runways are referred to that way in the US. And unfortunately, I can't be of any help there - I have no idea.

-Mir
7 billion, one nation, imagination...it's a beautiful day

vikkyvik
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### RE: Runway Markings

 Quoting Faro (Reply 12):I may be mistaken, but I believe a departing aircraft at MTOW exerts a greater load on the runway pavement than a landing aircraft at MLW and nominal flare.

At nominal flare, maybe. But as 2H4 stated, they have to allow for hard landings and such.

To calculate some (very) rough numbers for a 737-800 (data taken from Boeing's website):

MTOW: 174,200 lbs
MLW: 146,300 lbs

At a forward approach speed of 150 mph (220 ft/s), and 3 degree glideslope, vertical speed will be around 690 ft/min (11.5 ft/s). Assume that the flare arrests the vertical speed to 300 ft/min (5 ft/s) (I have no idea how good this approximation is for flare). Assume that it takes one second for the vertical speed to be arrested upon contact with the ground.

Based on those simple numbers (and not knowing much about airplane shock absorbers), it'll take about 22,715 lbs of force to arrest the airplane's descent. Add that to the max landing weight, and you get 169,015 lbs of force.

That obviously discounts any lift the wings may still be producing, though the spoilers will do a good job of cutting that down.

Say the aircraft lands hard, assuming no flare at all, and keeping everything else the same, it'll take about 52,245 lbs of force to arrest the descent. Add MLW and you get 198,545 lbs - significantly more than MTOW.

Again, these are extremely simplified approximations done mostly for my own interest
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tb727
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### RE: Runway Markings

 Quoting MSNDC9 (Reply 16):They use reflective beads in the paint at most airports.

And the paint is slippery when wet, especially if there is a coating of snow you can really tell if you hit a paint line if you have some brake pressure being applied.
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Starlionblue
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### RE: Runway Markings

I seem to recall that only runways over a certain length have piano keys. Is this correct?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

2H4
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### RE: Runway Markings

 Quoting Starlionblue (Reply 20):I seem to recall that only runways over a certain length have piano keys. Is this correct?

Upon reading this, my mind inexplicably went to this photo:

View Large View Medium

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Mir
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### RE: Runway Markings

 Quoting 2H4 (Reply 21):Upon reading this, my mind inexplicably went to this photo:

My question would be: why even bother?

-Mir
7 billion, one nation, imagination...it's a beautiful day

Leej
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### RE: Runway Markings

Got me thinking now (must be lunchtime!)
If an aircraft is at MLW, does it mean that it lands with that full weight thumping down, or is it much less because of course the aircraft is still generating lift at the point of touchdown? The aircraft is still in effect flying when the tyres smoke, with the weight bearing down slowly (to it's gross weight) once all lift has been cancelled. This would verify Faro's belief that an aircraft at MTOW would indeed place more stress on the pavement during the initial take-off roll.
Just a thought....

Mir
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### RE: Runway Markings

 Quoting Leej (Reply 23):Got me thinking now (must be lunchtime!) If an aircraft is at MLW, does it mean that it lands with that full weight thumping down, or is it much less because of course the aircraft is still generating lift at the point of touchdown? The aircraft is still in effect flying when the tyres smoke, with the weight bearing down slowly (to it's gross weight) once all lift has been cancelled. This would verify Faro's belief that an aircraft at MTOW would indeed place more stress on the pavement during the initial take-off roll. Just a thought....

But all the lift is cancelled out pretty quickly due to the spoilers coming out. And on takeoff, the wings do start generating lift and taking some weight off the wheels before the nose actually lifts off. So it works both ways.

-Mir
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danvs
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### RE: Runway Markings

 Quoting Faro (Reply 12):I may be mistaken, but I believe a departing aircraft at MTOW exerts a greater load on the runway pavement than a landing aircraft at MLW and nominal flare.

I don't have any numbers, but I believe it's more or less like you said.
In many airports, the ends of the runways are paved in concrete (more resistant than asphalt). I've always assumed this was due to the effect of airplanes taking off on the pavement being more severe than the one exerted by an airplane landing.
Examples:

By Balix photography

By Nick Onkow

[Edited 2009-07-22 10:25:35]

Scooter01
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### RE: Runway Markings

 Quoting Mir (Reply 22): My question would be: why even bother?

So that you can go back and remember...

We've got something like tthis at FBU too...

(Not my pic., but one done by P.A. Viking at Scanair Forum .no)

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Leej
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### RE: Runway Markings

Sorry I am still not convinced. If one looks at the A330 videos at MAN on Youtube, where touchdowns are so graceful - is it correct that the complete aircraft weight is on the runway at the moment of touchdown?
Or, is it a much smaller amount, with a progressive increase of the whole aircraft weight once it is at taxi speed?
I guess my confusion lays with th issues of aircraft landing at maximum weight - for example an emergency, and the real weight at the moment of touchdown

vikkyvik
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### RE: Runway Markings

 Quoting Starlionblue (Reply 20):I seem to recall that only runways over a certain length have piano keys. Is this correct?

Oooo, that's a tough one....

I've definitely seen runways as short as 4000-odd feet with piano keys....

Gonna have to try and research that.

 Quoting Mir (Reply 24):But all the lift is cancelled out pretty quickly due to the spoilers coming out.

Not all the lift. But certainly a significant amount of it.

 Quoting Leej (Reply 27):Sorry I am still not convinced. If one looks at the A330 videos at MAN on Youtube, where touchdowns are so graceful - is it correct that the complete aircraft weight is on the runway at the moment of touchdown?

Once the spoilers are out, quite a significant portion of the aircraft's weight is going to be on the wheels. I don't know how much, but the spoilers plus the reduced AOA of the wings (once the nose gear is lowered) will kill quite a bit of lift.

Without the lift from the wings, there's no place for the aircraft weight to go but to the ground through the landing gear.

 Quoting Leej (Reply 27):I guess my confusion lays with th issues of aircraft landing at maximum weight - for example an emergency, and the real weight at the moment of touchdown

Runways have to support aircraft at MTOW, which is greater than MLW. The added force at landing comes from the vertical speed of the airplane descending. The ground has to stop the airplane from descending. An airplane's flare arrests quite a bit of the vertical speed, allowing it to touch down more gently, resulting in less stress on the landing gear, airframe, and runway.
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2H4
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### RE: Runway Markings

 Quoting Leej (Reply 27):is it correct that the complete aircraft weight is on the runway at the moment of touchdown?

I don't think anyone is arguing that this is the case. I think the discussion (at least at first) suggested that a hard landing can drive the mains into the ground and produce a force that exceeds that which is applied to the pavement at MTOW.

And I personally questioned whether the runway is stressed to pressures above and beyond the pressures applied by a taxiing aircraft at MTOW, and if so, what percentage above and beyond those pressures.

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danvs
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### RE: Runway Markings

 Quoting Starlionblue (Reply 20):I seem to recall that only runways over a certain length have piano keys. Is this correct?

I've found a description of ICAO recommended airport signs and runway markings. It's on the introduction section of an old set of Jeppesen charts I bought a long time ago (around 1995):

Threshold markings:
Threshold markings consist of longitudinal stripes of uniform dimensions disposed symmetrically about the centerline of the runway. The number of stripes shall be in accordance with the runway width as follows:

RUNWAY WIDTH-----NUMBER OF STRIPES
18m----------------------------- 4
23m----------------------------- 6
30m----------------------------- 8
45m----------------------------- 12
60m----------------------------- 16

Length of the runway has more to do with touchdown zone markings:

RUNWAY LENGTH-----PAIR(S) OF MARKINGS
Less than 900m-----------------------1
Between 900m and 1200m--------2
Between 1200m and 1500m------3
Between 1500m and 2100m------4
2100m or more-------------------------6

Faro
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### RE: Runway Markings

 Quoting Vikkyvik (Reply 28):Runways have to support aircraft at MTOW, which is greater than MLW. The added force at landing comes from the vertical speed of the airplane descending. The ground has to stop the airplane from descending. An airplane's flare arrests quite a bit of the vertical speed, allowing it to touch down more gently, resulting in less stress on the landing gear, airframe, and runway.

I imagine runways are stressed to greater loads than MTOW or MLW aircraft landing at very high rates of descent: conceivably you should also accommodate a crash landing like with UA 232 and not have to immobilise your runway for prolonged, major structural repairs. The original question stemming from reply 1 was whether all displaced thresholds are stressed in a like manner to the nominal runway area or not:

 Quoting 2H4 (Reply 1):Runways are reinforced to withstand the weight of a landing aircraft, but not all displaced thresholds are.

My opinion is that they probably are.

Faro
The chalice not my son

swiftski
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### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 5):The barcode means start / end of runway, which can be followed by an (overshoot) area, normally not to be used

The start of the runway is actually at the holding point.

You then have TODA, TORA, LDA, etc

 Quoting EcuadorianMD11 (Reply 5):Then there´s a white line which indicates the middle of the runway

Centreline

 Quoting EcuadorianMD11 (Reply 5):the number is the rough direction of the runway (minus 1 zero) rounded up to 10 degrees

In some cases, an airport with 020/200 will use 03/21 so as not to get easily confused.

 Quoting Mir (Reply 22):My question would be: why even bother?

Easier VFR identification?

Posts: 132
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### RE: Runway Markings

 Quoting Swiftski (Reply 32):Quoting EcuadorianMD11 (Reply 5): Then there´s a white line which indicates the middle of the runway Centreline

Thanks, you´re right!
I put that wrong...........I meant "centre" as in longtitudonal..........so for instance: at 2000 meters on a 4000 meter runway.

Cheers,

A lot of people need to be offended on a regular basis I always felt, and IÃ?Â´m the very boy to do it! - Billy Connolly

vikkyvik
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### RE: Runway Markings

 Quoting Swiftski (Reply 32):The start of the runway is actually at the holding point.

You mean, the holding point on a taxiway?

Not saying you're wrong, but wouldn't that be described as the runway environment or runway clear area or something? I was under the impression that runway referred only to the strip of asphalt between thresholds (or including displaced thresholds).
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swiftski
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### RE: Runway Markings

 Quoting Vikkyvik (Reply 34): Quoting Swiftski (Reply 32): The start of the runway is actually at the holding point. You mean, the holding point on a taxiway? Not saying you're wrong, but wouldn't that be described as the runway environment or runway clear area or something? I was under the impression that runway referred only to the strip of asphalt between thresholds (or including displaced thresholds).

If you pass the holding point, then you are "on the runway" even if you have not turned onto it. If you pass a holidng point without clearance, it is a runway incursion and is as serious as taxing as far as, say, the numbers.

It can get quite complicated - eg take off distance including distance to 50ft (60m). I guess it depends how much info the OP desires.

Posts: 132
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### RE: Runway Markings

I guess you meant 50 yards............

Now a different question, though slightly off topic: could big jets (A380-330-40 / B777-747) land on semi-paved runways? What I mean with semi-paved is: a hard lower layer and loose gravel (or lumps of asphalt) on top.
That is what we use for Ultra Lights you see.........

I know, I know.........not a situation to try in real life, but in case of an emergency landing in a rural area for instance.........
I guess it all depends on what weight the surface can carry........
The loose gravel would make a pig´s breakfast of the fan blades I imagine!

Comments anyone? Has it been done succesfully in emergencies?

A lot of people need to be offended on a regular basis I always felt, and IÃ?Â´m the very boy to do it! - Billy Connolly

Starlionblue
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### RE: Runway Markings

I don't think they "should" land on a semi-paved runway. I mean in an emergency anything should be tried, but it probably isn't good either for the plane or the runway.

Of course, nothing says that an aircraft that size can't. An-124, C-5, C-17, 737 with gravel kit all land on semi-paved runways. But they are specially adapted or designed for it.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

vikkyvik
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### RE: Runway Markings

 Quoting Starlionblue (Reply 37):I don't think they "should" land on a semi-paved runway. I mean in an emergency anything should be tried, but it probably isn't good either for the plane or the runway.

Not to mention, airplanes have even sunk into asphalt when they taxied onto a taxiway they weren't supposed to....I think there are photos in the database, but I'm currently too tired to find them
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### RE: Runway Markings

 Quoting Starlionblue (Reply 37): 737 with gravel kit all land on semi-paved runways. But they are specially adapted or designed for it.

Interesting...........and what does a gravel kit consist of please?
I´m imagining: higher ground clearance / some kind of protection behind the landing gear to prevent loose gravel from "going places" / different suspension at the landing gear / better filters against dust / tougher tires.............am I warm?
Additional seat cushions for the pax perhaps?

 Quoting Vikkyvik (Reply 38):I'm currently too tired to find them

Sweet dreamzzzzzzzzzz...........

A lot of people need to be offended on a regular basis I always felt, and IÃ?Â´m the very boy to do it! - Billy Connolly

Starlionblue
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### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 39):Interesting...........and what does a gravel kit consist of please? I´m imagining: higher ground clearance / some kind of protection behind the landing gear to prevent loose gravel from "going places" / different suspension at the landing gear / better filters against dust / tougher tires.............am I warm?

Higher ground clearance: No
Protection behind landing gear: Yes. A skid on the front. The front gear doors are altered to allow more space. This leads to extra drag.
Filter against dust: Sort of. Blowers ahead of the engines mess with vortices to prevent FOD ingestion.
Tougher tires: Don't know.

Pics. Note the front skid with gear door alteration, and the vortex thingies on the engines:

 View Large View MediumPhoto © Teemu Tuuri - FAP View Large View MediumPhoto © Timo Harsch

"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

FredT
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### RE: Runway Markings

 Quoting Swiftski (Reply 35):If you pass the holding point, then you are "on the runway" even if you have not turned onto it.

But is the 'start of the runway' the same as 'the point where you enter the runway'? I'd say no, or things would be getting interesting.

Stick with 'threshold' instead of 'start of the runway' and we avoid the confusion altogether.

No, but he meant 15 meters.

Regarding gravel kit, hardening of the flaps is another Good Thing, which I've seen in some gravel kits. Kicked up gravel kan 'modify' them in ways not quite desirable otherwise.

You can also add high flotation gear to some types, giving a lower tyre pressure which is better on soft surfaces.
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HAWK21M
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### RE: Runway Markings

 Quoting FredT (Reply 41):You can also add high flotation gear to some types, giving a lower tyre pressure which is better on soft surfaces.

Any Examples?
regds
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FredT
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### RE: Runway Markings

The King Air 200 is one type I know of which has high flotation gear available as a retrofit.
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tdscanuck
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### RE: Runway Markings

 Quoting FredT (Reply 41): But is the 'start of the runway' the same as 'the point where you enter the runway'? I'd say no, or things would be getting interesting.

It's not the same. You're supposed to include an allowance for the distance you use between entering the runway and starting the takeoff roll.

 Quoting HAWK21M (Reply 42): Quoting FredT (Reply 41): You can also add high flotation gear to some types, giving a lower tyre pressure which is better on soft surfaces. Any Examples?

The Indian A320's with double-axle bogies.

Tom.

2H4
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### RE: Runway Markings

Here are some fun ones:

 View Large View MediumPhoto © Matt Cairns View Large View MediumPhoto © Fredrik Bull

2H4
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### RE: Runway Markings

 Quoting Starlionblue (Reply 40):Pics. Note the front skid with gear door alteration, and the vortex thingies on the engines:

Interesting pics..........that skid is amazing.......no diversion to an asphalt runway though, I suppose!!
What ´s that vortex thingy for exactly?
Is it supposed to keep gravel out of the engine?

 Quoting FredT (Reply 43):high flotation gear available as a retrofit.

 Quoting 2H4 (Reply 45):Here are some fun ones:

Is "High Flotation gear" a hoity toity phrase for "extra big wheels" or am I being too simplistic now? Just asking............
Cool pics just the same...........

Cheers,

A lot of people need to be offended on a regular basis I always felt, and IÃ?Â´m the very boy to do it! - Billy Connolly

Starlionblue
Posts: 17578
Joined: Fri Feb 27, 2004 9:54 pm

### RE: Runway Markings

 Quoting EcuadorianMD11 (Reply 46): Interesting pics..........that skid is amazing.......no diversion to an asphalt runway though, I suppose!!

Oh it works fine on an asphalt/concrete runway. The wheels actually extend a bit below the skid.

 Quoting EcuadorianMD11 (Reply 46):What ´s that vortex thingy for exactly? Is it supposed to keep gravel out of the engine?

As I understand it (and I could be wrong), it disrupts vortices which form around the intake, preventing gravel from entering the engine. If you look at a 737 on a humid day, there's a vortex that forms when the engines are close to the ground, sucking air in from below.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

### RE: Runway Markings

 Quoting Starlionblue (Reply 47):there's a vortex that forms when the engines are close to the ground, sucking air in from below.

Allow me

 View Large View MediumPhoto © Paul Markman View Large View MediumPhoto © Darren Wilson

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2H4
Intentionally Left Blank

Starlionblue
Posts: 17578
Joined: Fri Feb 27, 2004 9:54 pm

### RE: Runway Markings

 Quoting 2H4 (Reply 48):Quoting Starlionblue (Reply 47): there's a vortex that forms when the engines are close to the ground, sucking air in from below. Allow me Smile

Thanks. I knew I could count on you!
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

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