Why do so many airports have intersecting runways instead of parallel runways?

Question

It seems like parallel runways would be the best for safety and air traffic control.

I'm getting responses regarding wind direction. What about all the airports that have only or mostly parallel runways? Are they dangerous? Atlanta has 4 parallel runways, and perhaps one perpendicular. Some of your answers imply that Atlanta has a dangerous setup.

Answer 1

Parallel does work best for getting the maximum number of aircraft landed for a given period of time (all else being equal). Intersecting runways are more common at older airports, and at smaller airports. Both were designed to serve aircraft that were more affected by crosswinds than modern jet airliners.

My airplane is designed to cross the runway threshold when landing at 63 knots. So you can see that a 30-knot crosswind is a big deal for me. So on windy days, all else being equal, I like flying to places with intersecting runways, because it's more likely that I can find a runway pointed into the wind.

A 767 doesn't really have that problem to the same degree.

There is nothing unsafe about the layout at Hartsfield.

Answer 2

ive heard that when an airport is in the design stage, they do a study of the winds.. if the results say that the wind is going to blow from the west 90 percent of the time (just a number i come up with) then they build runways to accommodate that.. but say they only blow from the west 50 percent of the time, then they would wanna build runways in different directions.. but since space is limited then they have intersecting runways.. its not really unsafe unless its an uncontrolled airport, meaning there isnt a tower controller.. parallel runways are more dangerous in my opinion cuz you can be so close to another airplane even though he is landing on another runway.. normally at controlled airports, intersecting runways are not used at the same time

Answer 3

Intersecting runways allow aircraft to take off into the prevailing headwinds and also save fuel by not having to make a turn towards the right direction. With air traffic control, they make sure there are no runway collisions. Aircraft do land on parallel runways. Which parallel runways are assigned for incoming flights depends on which way the wind is blowing on any given day. I'm not sure but take SFO for example. The east/west runways are for incoming aircraft, and the north/south runways are for takeoffs.

Answer 4

For parallel runways to be operated at the same time, they must have a certain distance between them, and that takes alot of space. That's like asking why LaGuardia doesn't have 10,000' runways. Old airports typically have only a limited amount of space to work with because of land use restrictions, and parallel runways my not fit on airport property.

Most medium sized airports prefer to have a smaller "crosswind" runway for seasonal wind changes for the smaller aircraft that are more effected by strong winds. You can take close to the same number of landings and departures as you could with a close parallel by using one runway for departures and one for landings... and use a lot less space. Look at Teterboro or Burbank. But, yes there are drawbacks and the potential for an increase (albeit small) in runway incursions is one of them.

Answer 5

Reminds me of a funny story a friend once told me. He was captain of a small commuter plane and had a brand new copilot with him. They had been given a land and hold short clearance and told to advise if unable. It was one busy day and the tower wanted to get one departure off the crossing runway if he could. Dan had the copilot tell the tower to stand by, he'd take a look. He did and the tower came back with something like "Need all the help you can give me today thanks."

The copilot was way behind in his duties one of which was to brief the passengers, no flight attendant on this small aircraft, over the PA system to fasten their seat belts and raise their tray tables and such. Most were buckled in anyway with all the turbulence on descent and there were some very white knuckles gripping the arm rests back there in the tiny cabin.

Dan said "You take care of the briefing while I look at the chart and check this out. Not much time and we need to move along here."

This poor guy was already so far behind the aircraft that if they crashed he wouldn't get hurt. He turned his microphone transmit selector nob to PA, keyed his mic and began to read his pax briefing card and his less than assuring voice filled the cabin but way to slowly for Dan's comfort. He was one real busy commuter captain now in this high work load environment, especially with what little help he was getting from the right seat, and he did not like what he saw about the land and hold short instructions so he tapped the copilot on the arm and said, "Forget the briefing. Tell the tower we're not going to be able to make it."

Our hero keyed his mike again and in his already excited voice nearly screamed, "We're not going to make it!" His microphone transmit nob was still selected to the passenger PA.

Answer 6

Sometimes in windy cities, airports will be built like this so that palnes coming in for a landing can come in against the wind and not have a cross wind. This actually makes it a lot safer than having parallel runways.

Answer 7

the more runways the better chance you can take off - land to a favoring wind direction, they dont actually use all the runways everyday mainly one or two that favor the prevailing wind, you cant control weather so its the best you can do, wind gusts and wind shear can flip over aircraft even the big jumbos or stall them its always important to fly into the wind

Answer 8

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Answer 9

Your question requires a short-"winded" answer...the wind blows any direction, if you limit the runway direction(s), you decrease safety, so they have 2 or 3 different directional runways to allow for wind changes. that's the reason.

the gremlin guy

Answer 10

To take advantage of different wind directions for take-offs and landings.