Before the runway reconfiguration, KORD had two pairs of crosswind runways, but one pair was ditched in favor of four new parallel runways. Why did they decide that reducing the airfield's capabilities in crosswind conditions was a favorable decision? Wikipedia says that the various intersecting runways "were both dangerous and inefficient," but wouldn't removing a pair of crosswind runways make the airfield even more inefficient? Why didn't KORD reconstruct the removed pair of crosswind runways at the northern and southern peripheries of the existing airfield, similar to KDFW?

Someone probably looked at a wind survey and concluded that the new layout is better. I'm making up numbers here, but say for example:

XW layout: 60 planes an hour, any wind direction
Parallel: 100 planes an hour if crosswind component <15 kts

Percentage of time with >15 XWC: 5%

Plan for normal flow of 95/hour and then deal with a bit of chaos periodically.

Non-parallel runways are trickier from an ATC standpoint, which reduces flow rates, so if the scenario was anything like my example, then they made the right play call.

quintol, your question doesn't make much sense.

With regard to the topic headline, "Why does KORD only have 2 crosswind runways?" Well, how many crosswind runways do you think they should have at Chicago O'Hare airport?

Aircraft manufacturers design aircraft with higher crosswind limitations these days which reduces the need for many airports to have crosswind runways.

You asked, "wouldn't removing a pair of crosswind runways make the airfield even more inefficient?" No, it actually makes it more safe and efficient by eliminating intersecting approach paths and deconflicting missed approach procedures. On the ground, parallel runways also reduce the threat of aircraft collision and improve the flow of ground traffic. Of course aircraft operations on parallel runways still generally require the crossing of another runway when aircraft taxi between the runways and a terminal or cargo ramp, but in some cases it is possible to construct a bypass to improve traffic flow (i.e., Taxiway V in Atlanta or Taxiways P/ES/JS at Dallas/Fort Worth).

You also asked, "Why didn't KORD reconstruct the removed pair of crosswind runways at the northern and southern peripheries of the existing airfield . . ." I don't know, but my guess would be limitations of existing land and/or restrictions to departure/arrival corridors.

I have not seen the KORD master plan, but my guess is the end state is to close parallel runways 22R/4L and 22L/4R and operate the airfield with six east/west parallel runways (the 9/27s and the 10/28s) although it might be possible to keep 22L/4R open as well.

Several large airports in the United States operate efficiently without the use of crosswind runways. I don't have time to research all of them at this time but off the top of my head I can think of Atlanta, Los Angeles, Seattle, Orlando, Phoenix.

I fly in and out of O'Hare periodically and it seems to operate fairly well using the parallel runway configuration.

e38

Last master plan I saw called for keeping the 4/22s. The 13/31s have already been shut down.

Not sure if you can realistically have that many parallels and both crosswinds active, though you'd probably only have one active for takeoffs, the other for landings at a time (i.e., if wind is Northeasterly, takeoffs on 4L, landings on 4R, and maybe landings on 10C or 10R closed off temporarily).

e38 wrote:

Aircraft manufacturers design aircraft with higher crosswind limitations these days which reduces the need for many airports to have crosswind runways.

If I remember correctly, none of the manufacturers (at least in "heavy metal" category) specify max crosswind limit.

Instead, they give you maximum demonstrated crosswind.

I think this is to allow landings with higher crosswind than officially presented without any penalties. It's actually quite possible (and safe) to land with crosswinds in excess of 50kts, considering other weather conditions (wind heading/strength, wind stability, clouds and visibility, etc.).

Cheers,
Adam

gloom wrote:

e38 wrote:

Aircraft manufacturers design aircraft with higher crosswind limitations these days which reduces the need for many airports to have crosswind runways.

If I remember correctly, none of the manufacturers (at least in "heavy metal" category) specify max crosswind limit.

Instead, they give you maximum demonstrated crosswind.

I think this is to allow landings with higher crosswind than officially presented without any penalties. It's actually quite possible (and safe) to land with crosswinds in excess of 50kts, considering other weather conditions (wind heading/strength, wind stability, clouds and visibility, etc.).

Cheers,
Adam

While they are called 'maximum demonstrated' no sane line pilot would exceed these limitations nowadays without a very good excuse. You are basically into test pilot territory, which we try to avoid as line pilots. If anything goes wrong the first question the investigators will ask 'why did the pilot exceed the crosswind component that was demonstrated during test flights?'. There was a case a couple of years ago where a Lufthansa A320 had a wing tip strike while landing in a massive crosswind in Hamburg, it was all over the media in Germany. Afterwards the German CAA asked different airlines about their interpretation of 'maximum demonstrated crosswind'. At that time there was no real consensus, but now almost all pilots will consider it as a limitation (i.e. if the last wind check given by the tower before landing is in excess of the maximum demonstrated crosswind a go around would be conducted - the wind indication on the navigation display however is advisory only, the one that 'counts' is the one given by ATC).

I believe Part 121 operators are required to operate within maximum crosswind limits.

That said, just how often is ORD really in such a bad crosswind situation that they would need to switch? It makes much more sense to emphasize the prevailing winds.

SAN is another airport that doesn't have a crosswind runway (anymore).

The days of 32L takeoffs from the T-1 intersection are gone. CO used to request takeoffs on 32L from T-1 and sometimes got into the air in under 5 minutes (CO only flew west in past years). That was run under the standard landings on old 27R and 27L and departures on 32R and 22R. Under that configuration,the only conflict was 27R and 32R crossed each other and aircraft taxiing to 22L crossed the 27L approach.

SAN closed the crosswind runway maybe 20 years ago and was maybe never used by jets due to length. The area is used by cargo carriers for parking and staging/loading. SAN has other problems as it doesn't have an ILS on the runway used 97% of the time (RW27). Under low visibility situations RW9 is mandated for arrivals - many times this puts departures on RW9 if they can get off with taller hills on the east side have to wait for a hole on arrival path to use RW27. Under some situation only head to head operations are used where a a few aircraft arrive, then a few depart. SAN is already the busiest single runway in the USA and is projected to max out at 290,000 annual operations within 10 years. There are a substantial number of missed approaches due to the non-precision approach and runway ocupancy of arrivals and/or departures.
SAN is proposing a huge expansion that would tear down Terminal 1 and other buildings to build a new Terminal 1 and parallel taxiway south of the runway. A Part 150 Study is underway and projections actually project noise contours increases for the first time since 1972 due to the projection of additional flights being forced into hours with operations receiving noise penalty calculations that increase perceived noise that create the contours.

Oops
The 32L Intersrction departure was from T3.

calpsafltskeds wrote:

Oops
The 32L Intersrction departure was from T3.

It could have been T1 or T3, the runway intersections have been renamed so many times over the lifetime of the runway. It was 32L at T10 the last time I used 32L.

It seems like every time I come back to ORD these days, the same taxiway I've been using for years has another new name.

N1120A wrote:

I believe Part 121 operators are required to operate within maximum crosswind limits.

I've never been able to find this specified in the FARs but what they are definitely required to do is submit both flight manuals and company operating manuals to the FAA for approval, and all of these that I've seen have maximum crosswinds listed. For example, the max crosswind for takeoff and landing at my company in the A320 is 38 knots. That is also the Airbus max demonstrated crosswind, but in the FAA-approved flight manual it is just the max crosswind, so you cannot land in normal operations with higher crosswinds than that. The max crosswind at another airline could be lower than max demonstrated, but I'd be shocked if it could ever be higher.

The reason it's good to know that max demonstrated isn't the same as max "capable" is in case of emergencies. If you've got some kind of emergency where you need to get down quickly, and all the runways in range have 40 knot crosswinds, it's still going to be less risky to land on one of those than putting it in a field just to avoid being over max crosswind.

38 knots is a pretty stiff wind, though, and that's probably as good an answer to the original question here as any. Even KORD isn't getting direct crosswinds of 38 knots all that often. (It's not the speed of the wind overall that matters to crosswind calculations; only the crosswind component.) Runway headings are determined by wind surveys and "wind coverage", which is basically the percentage of service time a runway can offer for the types of aircraft intending to use it. The FAA specifies the "desirable" wind coverage at 95% or greater, and there'd be no point redesigning KORD's runways if they weren't actually improving on that. So the answer about modern airliners not really needing a lot of crossing runways is right, and since they don't, it's better to not have them. Pretty much everything in both the air and on the ground gets easier and safer with only parallel runways.

Different jurisdictions, I suppose. Our manuals only have max landing crosswind as "demonstrated". However, the max takeoff crosswind is "certified", noted as being an engine limitation. And the autoland crosswind is "maximum", not "demonstrated".

As Flow2706 says, just because it is "demonstrated", doesn't mean good airmanship doesn't dictate seeing it as a limitation. I think you'd have to be a pretty brave pilot to try landing with reported crosswind beyond the max demonstrated unless you're on fire or something. If anything happened you'd receive an invite for tea and biscuits with the chief pilot. Without the biscuits. Or the tea.

It was T3 when I worked there in the 1980s.

The greatest current difference between runway direction is 130 degrees (Runways 9 and 22 or Runway 27 and 4). According to a calculator of cross winds to get a 38 knot cross wind if the wind direction was from 155 degrees or 335 degrees the worst case would be a 42 knot wind to equal a 38 knot crosswind. 10 degrees to the left or right from the critical point would allow a 46 knot wind to equal a 38 knot cross wind.
Calculations must have been made to see both critical points are from directions ORD wouldn't expect exact wind directions with 40 knots and over.

Quoting Starlionblue (Reply # 12), " . . . you'd receive an invite for tea and biscuits with the chief pilot. Without the biscuits. Or the tea."

Yes, that is true; although in the United States that would be " . . . an invite for coffee and doughnuts with the chief pilot. Without the doughnuts. Or the coffee!"

e38