just wondering why do some airports have two types surfaces on the same runway? Noticed in satellite pics some asphault runways have about first 500m of concrete like light brown portion before the main asphault surface. Is there any advantage of such design?In the pic the end section has pcn 84/R/W/T, rest asphault section has 90/F/B/W/T. what I can figure out so far is the end is rigid and slightly weak.

The concrete can take more of a pounding compared to the asphalt. Some times they also extend the runway and make the extensions out of concrete.

Construction also changes depending on the type of aircraft that can use an airport, construction can extend deeper into the ground for more support in the landing areas for heavy weights.. Painted markings show where the main touchdown contact should be and that is a beefier area most times.

Interesting;) I

I always wondered the same thing. Having never actually seen it in real life, I assumed that the light brown stuff was similar to the 'rumble-strip' you see on some roads, and would be grippier for aircraft to land on.But the concrete taking more of an impact seems to make more sense... haha

I always wondered the same thing. Having never actually seen it in real life, I assumed that the light brown stuff was similar to the 'rumble-strip' you see on some roads, and would be grippier for aircraft to land on.But the concrete taking more of an impact seems to make more sense... haha

Those grooves they cut into the runway gives the water a place to go and run off so there is not much left to cause aircraft to hydroplane. Airport crews will go out and remove built up rubber at busy airports so that the needed rough textures will not get smooth and have less friction.

Airport crews will go out and remove built up rubber at busy airports so that the needed rough textures will not get smooth and have less friction.

Doesn't the rubber on the runway increase friction? I say that based on my knowledge of auto racing, esp in F-1...the fact that you must follow the racing line with the laid rubber to get maximum grip.

Doesn't the rubber on the runway increase friction? I say that based on my knowledge of auto racing, esp in F-1...the fact that you must follow the racing line with the laid rubber to get maximum grip.

Don't forget, auto racing is not done on concrete for the most part.I believe it's because it fills in the rain grooves and causes the water to pool etc. However, for as little as I know about the process, they may only dig out the rain grooves :( I'll ask my airport manager friend the next time I see him for more info.EDIT; well what do you know, the Internet truely does have just about every subject on it.... couldn't believe it :(http://en.wikipedia.org/wiki/Airfield_rubber_removal

Doesn't the rubber on the runway increase friction? I say that based on my knowledge of auto racing, esp in F-1...the fact that you must follow the racing line with the laid rubber to get maximum grip.

Remember that in racing, the tires are already moving and are hot when they get to the built up areas. One has to wonder why they use asphault for runways when concrete has better strength, last longer and has better friction properties compared to asphault. Yes, I know asphault is cheaper, but you have to make the runway thicker than concrete and does not last as long hence needing replacement sooner rather than later, thus negating any savings.

Doesn't the rubber on the runway increase friction? I say that based on my knowledge of auto racing, esp in F-1...the fact that you must follow the racing line with the laid rubber to get maximum grip.

I

All one has to do is look at the side of a racecar to see that the rubber goes somewhere. Crumbs do break off and are swept out of the groove, no matter which type of racing, F-1, Indy or Sprint Cup. I would suspect it be even worse adding water to the mix in the F-1 and Indy Car series should cars get out of the groove.

Remember that in racing, the tires are already moving and are hot when they get to the built up areas. One has to wonder why they use asphault for runways when concrete has better strength, last longer and has better friction properties compared to asphault. Yes, I know asphault is cheaper, but you have to make the runway thicker than concrete and does not last as long hence needing replacement sooner rather than later, thus negating any savings.

my guess is it might be easier and quicker to do patchwork on cracks and broken asphault surfaces than on concrete thus resuming runway operations without much delaybtw, anybody knows what exactly flexible runway surface in PCN values is?

Don't forget, auto racing is not done on concrete for the most part.I believe it's because it fills in the rain grooves and causes the water to pool etc. However, for as little as I know about the process, they may only dig out the rain grooves :( I'll ask my airport manager friend the next time I see him for more info.EDIT; well what do you know, the Internet truely does have just about every subject on it.... couldn't believe it :(http://en.wikipedia.org/wiki/Airfield_rubber_removal

Staggerwing- Re your Wiki reference and the line therein referring to "Tires not spinning on contact----".Many years ago I read about a new airplane tire design that had flaps built into the sidewalls. When the gear dropped, airflow caught these flaps and started the wheels spinning- well before touchdown. There was even a photo, so the scheme was not simply theory.Wonder what happened to that idea? Patent perhaps locked up by the tire manufacturers?Alex Reid

Staggerwing- Re your Wiki reference and the line therein referring to "Tires not spinning on contact----".Many years ago I read about a new airplane tire design that had flaps built into the sidewalls. When the gear dropped, airflow caught these flaps and started the wheels spinning- well before touchdown. There was even a photo, so the scheme was not simply theory.Wonder what happened to that idea? Patent perhaps locked up by the tire manufacturers?Alex Reid

I would imagine the idea was dropped. Why, because if the wheels are spinning as they make contact with the ground there is a great change of skidding. I absolutely would not want my wheels spinning if have to land on a wet rwy.Vololiberista

I would imagine the idea was dropped. Why, because if the wheels are spinning as they make contact with the ground there is a great change of skidding. I absolutely would not want my wheels spinning if have to land on a wet rwy.Vololiberista

But with no pre spin, the tires are stopped and initially skidding/sliding for a distance before they are able to spin up to say 160 Kts. Strikes me that a sliding, stopped tire is more dangerous than one spinning at aircraft speed. That's why you avoid wheel lockup in your car or even have anti skid brakes to prevent lockup and consequential accidents!Alex Reid