Tsaord From , joined Dec 1969, posts, RR: Posted (9 years 2 months 3 weeks 6 days 12 hours ago) and read 2757 times:
I can't help but wonder why MDW has little or no delays/cancellation when a storm or something else happens.
I know MDW is a smaller airport with less flights then ORD. But I heard on AM 780 that ORD cancelled north of 500 flights while during the same snow storm we had just last week MDW was no where near that at all. Do the planes at MDW take off into a different sky than the planes at ORD?
Just curious. Can any insider with better knowledge of airport operations educate me about this?
Apodino From United States of America, joined Apr 2005, 4500 posts, RR: 5
Reply 1, posted (9 years 2 months 3 weeks 6 days 11 hours ago) and read 2709 times:
Even though the airports are separated by only 20 miles or so, there is a big difference in the operations of both airports.
At ORD you have the huge hubs of both UA and CO, plus a lot of other airline traffic as well. Demand is obviously very high in this airport, at times approaching 90 aircraft per hour. On a good day weatherwise, ORD will run either Plan X (East config) or Plan Wierd (West config). I believe X allows an Airport Acceptance rate (the number of planes per hour that an airport can land) of 100, and Wierd about 92. (Wierd is slightly less due to the fact that it relies on LAHSO on 22R). However, several things can affect this, and when you lose three landing runways at ORD, your Arrival rate takes a hit, then also add into that increased separation for IFR (Not so much an issue at ORD since visual approaches are rarely used in a non trip config). Today for example, the TStorms had enough of an impact to force a 60 rate. If you go down to a single landing runway, which can happen, your Rate will be in the high 30's. And the rule of thumb is this, when Airport Acceptance Rate is less than the demand in a given hour, flights have to be delayed somehow. If its not a lot of excess demand, the TRACONS can usually manage with miles in trail, and sometimes airborne holding. But if you get in a situation with a lot of excess demand over a period, thats when you see the ground delay programs.
At midway, the AAR rarely changes since they can typically only take one landing airplane at a time with the two main air carrier runways crossing each other. While IFR conditions can knock out a runway in ORD reducing the AAR, they can't affect MDW since they are typically only using one runway anyways. Thus weather does not have the impact on MDW that it can on LGA. That is why bad weather rarely affects DCA as well, because although the airport has three runways, it basically is run as a single runway airport. Single runway airports are rarely affected by weather because of this.
For the record, I will list some airports where delays are common and what can bring the arrival rate down at each airport.
EWR: Any sort of gusty wind or ifr will cause them to lose the Overflow runway (11-29) which is an automatic program there with all the demand in that place.
LGA: Wind can cause the airport to go single runway, which means you have to intertwine departures which will slow the AAR down, additionally IFR conditions can create problems:
JFK: I haven't quite figured this airport out yet, but I do know their best config is ILS 22L while running VOR 13L at the same time. Winds and IFR will bring rates down since they can lose parallel approaches this way.
PHL: Any sort of wet runway makes 17-35 unusable to most carriers, forcing everyone to use the long runway, bring the AAR from either 52 or 48 (Depending on east or west ops), to 36. Also there are ceiling restrictions, but not as restrictive as some other places.
PHX: Even in VFR conditions if the CIG is 5000 feet this place will have problems.
LAS: If winds force any config other than 25's (i.e. 1's and 7's) this airport can be slowed down.
ORD: Lots of things. Weather that forces anything other than X or Wierd is bad. X is least vulnerable to delays due to no crossing landing or takeoff runways while in config.
ORDPIA From United States of America, joined Jan 2006, 140 posts, RR: 1
Reply 2, posted (9 years 2 months 3 weeks 6 days 11 hours ago) and read 2709 times:
While I don't have that great a knowledge on airport ops from what I do know I can tell you is that ORD handles near max loads for a clear day, everyday. So having to deal with that on a less than perfect day leads to delays, while MDW is also very busy the arrival/departure rate is not as near the max as it is at ORD. Secondly the weather between these two airports can differ greatly, For instance last Thursday, I believe, MDW had problems with fog however ORD did not, as I'm sure you know the weather here can change greatly between the loop, ORD, MDW, and the other suburbs. Combine both of these and you can see two entirely different situations just 15 miles apart.
Apodino From United States of America, joined Apr 2005, 4500 posts, RR: 5
Reply 3, posted (9 years 2 months 3 weeks 6 days 11 hours ago) and read 2686 times:
And a further explaination of ORD plans. With so much traffic in ord, and the odd runway config, they have several plans that they run for different configs, which I will explain breifly.
Plan X (Also the calm wind config): Usually winds winds are light or out of the east or northeast. Typically in this config Northeast and Northwest arrivals are brought in on 9R, with Southeast and Southwest brought in on 4R, with 9L available for overflows. 4R is used for departures to the east and some north, 9L is used for some east and all departures to the south. 32L from T10 is used for departues to the west and north, with a lot of the european flights using 32R. Flights to ASIA often use the full length of 32L, which slows down 9R arrivals, otherwise there is very little crossing runways in this config.
Plan Wierd : Used when winds are Westerly. In this config, Southeast and Southwest arrivals are usually brought in on 27L, Northeast and Northwest arrivals on 22R, with 27R as an overflow. Because of this, 22R is often run as LAHSO of 27L so that you can use both runways at the same time, but the runways have to be dry and some carriers, noteably AA, won't take such a clearance. 22L is used for departures to the East and some South, 27L is used for departures to the West and South, and again 32L T10 is used for departures to the north, with 32R and 32L full length being used as before.
The other big plan is plan B: This is typicaly used in southerly wind directions, and they have to be blowing quite a bit. In this config 14R is used for landing by planes from the Northwest and Southwest, 22R is used by planes from the Northeast and Southeast, and 22L is often used as an overflow runway. Departure delays are common in this config because they are lacking in this config. Typically 22L is used for easterly departures, and 27L is used for westerly departures, with some departures using 14L.
Csturdiv From Australia, joined Aug 2005, 1891 posts, RR: 3
Reply 4, posted (9 years 2 months 3 weeks 6 days 11 hours ago) and read 2656 times:
I am glad that you asked that. A few weeks ago when we got that nasty snow storm/blizzard, I wondered the same thing when I heard the flight cancellations at both ORD and MDW, but I forgot to ask. Then tonight when I was driving home from work, on the radio they were talking about over 400 flights canceled today at ORD and something like 20-40 flights at MDW were canceled. I was going to ask the same thing.
An American expat from the ORD area living and working in Australia
Mir From United States of America, joined Jan 2004, 22854 posts, RR: 53
Reply 6, posted (9 years 2 months 3 weeks 6 days 10 hours ago) and read 2575 times:
Quoting Apodino (Reply 1): JFK: I haven't quite figured this airport out yet, but I do know their best config is ILS 22L while running VOR 13L at the same time. Winds and IFR will bring rates down since they can lose parallel approaches this way.
JFK does like to use 22L and 13L at the same time, but they're generally both VOR approaches. The only other config they have with two landing runways is 31L and 31R, but you have to work departures in on 31L, which slows people down getting out.
If winds force operations down to just the 4s or the 22s during heavy traffic periods, things can get slow.
7 billion, one nation, imagination...it's a beautiful day
Boeing7E7 From , joined Dec 1969, posts, RR:
Reply 7, posted (9 years 2 months 3 weeks 6 days 9 hours ago) and read 2539 times:
Quoting Tsaord (Thread starter): I can't help but wonder why MDW has little or no delays/cancellation when a storm or something else happens.
Maybe the TSA has something to do with it....
Actually it has to do with peak hour handling capacity of the facility. An airport builds out its gate capacity based on VFR conditions. For O'Hare, this is based on the airports ability to handle 190 flights per hour (Arrivals and Departures, not just arrival rates as Apodino is refering too) during those conditions. When the weather takes a dump, this handling rate is reduced to 136 flights per hour, a net 28% reduction in handling capacity. Basically, you have more gates then your airfield can support and by extension more operations than your airfield can support when the weather is not optimum. Add to that de-icing and well, you get the picture..... Enter the O'Hare Modernization Program. When complete, O'Hare will be able to handle about 300 an hour in VFR and 240 in IFR conditions. It's still a 20% reduction, but the gates will effectively be limited by land mass (not enough room to build out gates to 300 operations per hour). In a nut shell, today you end up with more planes on the ground and in the air due to gate scheduling than the runway system can handle. In the future, it will be more balanced between gate and runway capacity significantly reducing the problem.
SLCUT2777 From United States of America, joined Dec 2005, 4212 posts, RR: 9
Reply 9, posted (9 years 2 months 3 weeks 6 days 3 hours ago) and read 2417 times:
Quoting Jetdeltamsy (Reply 8): When did CO start hubbing at ORD????? That's pretty good for the 3 or 4 gates they have.
I'm quite certain AA was meant. They started hubbing @ORD back in 1982. I can't help but also think WN controlling most of the flights and gates by a considerable margin is a contributing factor to this as well.
DELTA Air Lines; The Only Way To Fly from Salt Lake City; Let the Western Heritage always be with Delta!
Kalvado From United States of America, joined Feb 2006, 600 posts, RR: 0
Reply 10, posted (9 years 2 months 3 weeks 6 days ago) and read 2312 times:
I'm afraid with all those technical discussions, root cause of the problem is not mentioned:
Airlines make money by attracting many pax to flights, which will end up being canceled. Yield of remaining flights goes up, canceled tickets end up as a free credit from pax to airline - and airline cannot be held responsible for weather caused delays....