Intersecting runway vs parallel runway

[ssangyongs]

Newer airports seldom (or none) built intersecting runways which crisscross each other. AFAIK, if 1 is active, the other one has to be deactivated for t/o and landing. So it's just as bad as having only 1 active runway.

Crosswind limitation on aircraft types nowadays far exceeding what we have in the 1970's. That's one of the reason for them to build intersecting runways. But it's fast become obsolete for an airport to have 2 runways intersect with each other.

From the guys in the tower, what do you think?

[JustaFew]

Having worked both runway layouts, each has benefits and disadvantages. In the UK, many airfields were built by the miltary with intersecting runways. This reduces the max crosswind component to 30 degrees. The main disadvantage with more than runway one is the cost of lighting and approach systems. To reduce costs, several airfields change the status of a runway which is not often used to a taxiway.
In terms of use from an ATC point of view, you simply use what is available and get on with it.

[niknak]

Our cross runway (22/04) was withdrawn some 2 years ago now, largely due to the fact that to keep it up to standard and in active service would have cost far more than the income it generated, (at 1400m, it was around 500m shorter than the main runway (27/09)).
There's no doubt that when we could use it, it was a very useful facility to have, larely because the landing distance in one direction before the intersection with the main runway, was more than adequate to accomodate a landing turboprop (Shorts 360 etc) - we weren't allowed to use the "land and hold short of" procedure that ICAO sometimes permit, but it allowed you to push the envelope just that little bit more.

Ironically, since it was withdrawn, there's no doubt that the prevailing wind has become significantly more SW/NE, as opposed to W/E, whether that's down to global warming or dear departed colleagues having undue influence from above, I don't know.;)

[HEATHROW DIRECTOR]

<<AFAIK, if 1 is active, the other one has to be deactivated for t/o and landing. >>

Presumably a new rule? At Heathrow we used to land on 05 and depart 10R, and land 23L and 28L which were crossing runways.. but that was loooong ago.

[FinDir]

EGLL 10R and 28L! How long ago was that exactly?

[HEATHROW DIRECTOR]

Well, I did say loooong ago. Perhaps I should have said looooooooong ago!!

[Spitoon]

Newer airports seldom (or none) built intersecting runways which crisscross each other. AFAIK, if 1 is active, the other one has to be deactivated for t/o and landing. So it's just as bad as having only 1 active runway.It's mainly economics - if you can justify building a new airport/runway you will want to get the maximum return from the investment. Crossing runways can be operated at the same time - there are plenty of well established procedures that ensure separation of movements (and a few iffy ones like LAHSO/HIRO) but all are 'dependent', i.e. some things cannot be permitted while aircraft are in certain positions or relative positions. This means that you always lose some capacity when compared to two runways that can be operated independently, i.e. without having to worry about what's going on on the other runway. To get independent operations the runways have to be a specific distance apart - offset thresholds and parallel is the optimum for most types of operations (can't remember all the distances offhand).

[sr562]

The distance that spitoon refers is 750m. Provided you have 750m between parallel runways this provides adequate wake vortex separation and so each runway can be used independantly of the other. Not sure bout offset thresholds but would assume that provided there is the above distance between them the same will apply.