I like to watch the comings and goings of my local airport using Flightradar24. This is the view I use. In this view I can also see Heathrow and Gatwick. The runways at these airports run mostly east-west. Since the prevailing winds are mostly from the west the landings and take-offs are from east to west. But sometimes (like just within the past half hour) they all switch to going west to east.
So, the questions:
How much delay does switching directions cause a major airport such as LHR?
How much of a tailwind would there have to be to trigger a switch?
When the wind isn’t strong enough to be a factor do airports sometimes switch just for the hell of it, or to give neighbours a break from the noise?
When a scheduled flight takes off from, say, New York to London, do they know the expected runway at the beginning? If not, how far out is the pilot notified?
If a pilot coming into Farnborough is told to land on runway 26 is that enough information to plan the final part of the flight or are they given details.
That’s a great app. Right now, 4:50am to 5:00am, planes are landing in LAX from over the ocean–opposite from normal. I’ve always assumed this switch is because of the early hour of day.
My guess is it would be a land breeze vs sea breeze effect. Those tend to swap over the course of the day as the sun rises and the land heats up.
As to the OP, I recall one of those airport operations videos on Youtube (for Dubai airport, IIRC) saying it took about 15 minutes to switch ALL the planes around when they changed direction of landing due to wind change. But that did not mean that there was a 15 minute overall delay for everyone. Just that some of the planes that were near the front of the line for take off would have delays of near that long. Other planes that were taxiing and were nearer the other end of the runway would take off before the planes from the other end of the runway taxied the length of the runway.
Not sure for the really big places. In the larger Australian ports it is quite seamless.
It depends. I think it is 5 knots here but would have to confirm.
In airports that have noise issues there are preferred routes and runway configurations to try and avoid noise sensitive areas or to “share” the noise.
You find out the runway in use when you get the ATIS, which is a brief weather and information report about the airfield. You can get that anytime but things change so there’s not much point relying on it beyond about 30 minutes from ETA. It can be received by radio or via ACARS.
You are given a STAR and runway. The STAR has the final bit of the route to take you to the runway. Some STARs terminate in vectors, others take you all the way to the start of the relevant instrument approach.
Thanks Richard. This morning all three airports were landing west to east but around noon Farnborough switched directions but the others stayed the same. The wind is low right now so taking off to the west must be the preferred direction for noise. It is much more densely populated east of the airport. I live/work about a mile from the end of the runway and the landing planes are at around 800 feet when they pass over my house.
These are very insightful questions. And Richard has done his usual fine albeit terse job on them. I’ll now add a bunch more noise to the mix. The only thing I know about “terse” is how to spell it.
Delay: The degree of delay depends on how dense the traffic is and how many airports have to be managed as a unit.
In London, LHR, STN, LGW and LCY are all so close together they have to be switched around as a unit. In the US we have a similar situation at New York, where JFK, LGA, EWR, & TEB are so close-by that they’re managed as a unit.
The general idea is the last airplane landing the old way has to be on the ground before the first one landing the other direction gets within about 20 miles = ~6 minutes of the runway. If traffic is sparse that may entail no delay at all for that first arrival the new way. At a place like LHR which is the world champion at squeezing airplanes, they’ll be adjusting the flow of aircraft 500 miles back to try to generate the several minutes of gap necessary to swap airport ends.
The gap needed is larger than the 6 minutes above because of the various routes leading towards the airport. It’s simple when the shortest route leads to the end you’re about to stop using; when you reroute the first airplane onto the other route to the other end of the airport, he just picked up a 20+ mile “long cut” which will help generate delay. The problem comes in when changing in the other direction. The first airplane switched to the new arrival is effectively given a 20-30 mile shortcut to the new runway. You’d better have built in an extra 5-8 minutes of slack ahead of him or he’ll get to the closer end of the runway too soon.
In general, airline airports will alternate between periods of heavy landing activity, then a lull, then heavy takeoff activity, then a lull, etc. It’s almost never all one or all the other, but it ebbs and flows from 80/20 to 20/80 and back with lulls in between.This is all driven by the published schedules and the air traffic management folks know when things are calm and when things are crazy. By choosing to switch during a calm period they minimize the total delay.
As an example, a week ago I was going to JFK on a sunny afternoon, expecting to arrive at about 4pm. In cruise over Virginia, about an hour from landing, ATC suddenly announced “Kennedy is stopped. Everybody expect holding.” That’s your clue shit’s about to get real. Cue a mad flurry of activity in 40 cockpits checking fuel levels, divert range, making alternate plans, calling or datalinking a message to HQ, etc. Mean time you can hear the controllers’ tension going up too. At that warning order they don’t know why Kennedy stopped or how long it’ll be. But they’ve got to stop the conga line in the small space they own and there’s more jets joining the back of the line every minute. They know their next 30 minutes is gonna be insane hard work; I hope they don’t need to pee.
We all slowed down as much as possible and the first few airplanes in line made one turn in holding. By the time we got to the stop point 20 minutes downtrack from the warning order the Kennedy stop had been lifted and we proceeded normally to a landing at JFK.
Turns out the whole event was just JFK doing their runway change from the mid-day configuration to the evening configuration. Due to a wind shift they had to do it an hour earlier than expected and caught the rest of the system flat-footed. The stop was their way of forcing the gap in traffic needed to “turn the airport into the wind” as we say.
IOW, about 95% false alarm in terms of delay or divert. But for the guy at the front of the line, that could have been 5 or 8 minutes he didn’t have to spare.
2) Wind: At least in the US, 10 knots is the legal maximum tailwind. If the wind is worse than that we can’t land (or takeoff). Plus or minus a little “creative accounting” on ATC’s part. At certain airports with very short runways, or in slippery (ice/snow) conditions, the limits are more restrictive. I believe LCY has a zero-knot tailwind policy.
3) Switching other than wind: Each airport has preferred configurations for noise and for traffic flow. Unless the wind is prohibitive, they’ll align the airport for that goal.
Long haul international airports such as LHR, CDG, JFK, LAX, etc., have very distinct busy & calm times. In New York in late afternoon / early evening they’ll look carefully at the weather forecast for the next 5 hours and try to set things up now while it’s calm before they have 75 777 & 747 & A380s taxiing around. At LHR they expect to receive an insane burst of arrivals from about 0400 local until about 1000 local. They also want to get any changes out of the way early. As we saw above last week.
So you may see them changing ends when the wind is immaterial. If so, that’s to get ready for a rush when it’ll be too busy to change ends, or simply to align for the noise & flow plan for that time of day.
All this stuff is pre-figured out and the control agencies have a playbook on how to make an alignment swap. First you create these traffic gaps using speed control or zigzag vectors, then you close off these routes and open those, then you stop taxiing airplanes *this *way, then … through dozens or even a hundred steps depending on the airspace complexity and how many airports are doing the dance together.
4) Advance notice of runway: Before departure each airplane will be given the weather forecast for their expected arrival time. Which is the first clue. With modern forecasting techniques, this stuff is almost always spot-on. The only exception is if thunderstorms are forecast as possible or probable for the area. They’re inherently unpredictable at the small scale needed. And depending on where a storm is sitting versus the runway, the wind could be blowing in any direction imaginable. Or even all of them at once.
Each airport updates its weather report at least hourly; more frequently in dynamic conditions. Forecasts are updated every 6 hours or if anything unexpected happens. All this info can be downloaded via the airplane’s datalink. On days where the weather is benign we don’t bother following it closely while enroute (but see below). On days when conditions (or fuel load) are dicey, we can set up a subscription to all this data and our printer is chattering out news every few minutes for hours on end.
5) How much information to plan a landing: As **Richard **mentioned, airline airports publish something called ATIS Automatic terminal information service - Wikipedia . This is available both as a voice recording over the communications radio and as a datalink message. In addition to up to the minute weather it includes which runway(s) are in use and which approach procedures are being used to each of them. As well as an abbreviated list of special considerations like closed exit taxiways, slippery runways, etc., that bear directly on takeoffs or landings. Complex airports often have 2 separate ATIS, one for takeoff / departure and a separate one for arrival / landing.
We always obtain the ATIS before leaving cruise, roughly 30 minutes before touchdown. Most often we’ll have gotten the previous one too. That info, coupled with your assigned route to the local area, and familiarity with how they typically operate the airport, will give you all the info you need to set up the avionics, arrange your paper or iPad nav charts, conduct your briefings, etc.
In some cases the arrival routing will take you seamlessly to a runway. That’s certainly the wave of the future. But in most of the US, the future isn’t here yet.
Instead the common case today is that the arrival routing dumps you off 15-30 flight miles from the airport at 5,000 to 10,000 feet above the field. ATC uses radar and verbal vectoring to merge the several arrival flows from different directions into one properly spaced-out stream aimed more or less at the runway. Then at 5-15 miles from touchdown they’ll turn it over to us to either execute the published approach procedure or find the airport the old-fashioned way: look out the window.
It’s not uncommon that runway or approach procedure assignments will change close-in versus what you’d planned in cruise. If so, there’s a 1-2 minute flurry of activity to reconfigure everything, rebrief, and get back to business as usual. If ATC gets too aggressive trying to shoe-horn in a change when there isn’t time or space to do it right, the solution is simple: stick with the original plan or go around and use the extra time and space to get prepped for what you’ll be doing instead.
[QUOTE=LSLGuy]
Long haul international airports such as LHR, CDG, JFK, LAX, etc., have very distinct busy & calm times. In New York in late afternoon / early evening they’ll look carefully at the weather forecast for the next 5 hours and try to set things up now while it’s calm before they have 75 777 & 747 & A380s taxiing around. At LHR they expect to receive an insane burst of arrivals from about 0400 local until about 1000 local. They also want to get any changes out of the way early. As we saw above last week.
[/QUOTE]
Bit of a sidetrack, but most of the international arrival and departure times standards were set back in the 1970’s and 1980’s, in order to be convenient to European and North American airports. Which is why you see 2am arrival and departure times at Asian and ME Airports. With the world economic center of gravity shifting, just how much longer is this arrangement feasible?
And, how does the above work for megahubs like Dubai, Singapore and increasingly Istanbul? Those places are either busy or very busy, 24 hrs a day. Dubai can be crazy.
A few thoughts that don’t add up to a coherent essay. …
Ultimately, individual airlines schedule their ops to make sense for their customers. The sum total of that at any given hub/gateway is whatever it happens to be.
The size of the Atlantic ocean is fixed. Which means that as long as aircraft speeds don’t change much, neither will transit times. The time zone difference between eastern North America and Western Europe is also fixed. As is the human physiological reaction to time zone shifts aka “jet lag”.
A consequence is that there will “always” (see below) be demand to leave North America in the local evening to arrive in Western Europe in the local dawn hours. And demand to go the other way leaving at local noon arriving at local mid-afternoon.
What will change with changing global traffic patterns is how large a percentage of total trans-Atlantic flying fits this mold. In the 1960s & '70s it was all of it. Now it’s maybe 2/3rds of it.
Places like Dubai and Singapore are pure hubs, not much destinations. That is to say only a tiny fraction of the passengers have that as a destination. It’s simply a place to change planes on the way to someplace else. Which means those plane changes happens at whatever local time of day produces the commercially viable arrival and departure times at the other ends, e.g. in London & Sydney or wherever. The fact Dubai has a full blast hub operation going from 0100 to 0500 local says nothing about Dubai except that nearly nobody actually wants to go there.
It was convenient that in the early jet age the speed of aircraft and the distance from NY to London & Paris coincidentally made for a nice 2x/day one-way *en masse *slosh of people and planes to and fro. Most other areas of the world don’t share this happy coincidence, so schedule planning, even in the absence of slot constraints, amounts to picking the least-bad combo of departure and arrival times. And means traffic is much more bi-directional at any given time of day than it is over the North Atlantic.
A final comment about aircraft speed. When Concorde was operating between London / Paris and New York / Washington DC they did not stick to the traditional eastbound overnight / westbound afternoon flow. Why? because with their much quicker transits, it made more sense to leave North America first thing in the morning and again in early afternoon, arriving in Europe just a 4 clock-hours later, not 10-12. As and when we have higher-speed airplanes in quantity, that’ll shake everything up.
Get your point about megahubs. However, Dubai is now one of the centers of world trade; many people do go there (you will get me to go there for longer than three days at the point of a gun though), unlike the 1980’ and 1990’s. How would a carrier like Emirates schedule its flights based on who stays in Dubai and who travels on? Is this one of the reasons for why a lot of traffic has gone on to other regional hubs like Abu Dhabi or Doha; that its no longer feasible to be a mega-hub once you are a destination in your own right?
As to your second point, IME the best time to arrive is local afternoon, ensure you can get full nights sleep quickly if sleepy and a few hours awake if not (though of course YMMV). As you say, distances are fixed. Do you think this might increase the demand for SST especially long range commercial SST, to get the ability to have decent arrival and departure times? Unlike W Europe and the Eastern US seaboard, lots of Eurasian and Far Eastern flight routes are either over water or over sparsely populated land.
First paragraph: It’s an interesting tradeoff. I certainly don’t have hard data to back up my conjectures. But I have been reading the trade press in depth for decades as the industry has developed and evolved.
In the domestic US experience we’ve found that you can’t put a big hub in a small city. Non-stop flights can be sold at a premium vs. connecting flights. If 100% of your traffic is connecting through your hub in Podunk you lose too much money vs. your competitors who’re connecting only 60% of their traffic through their hub in Atlanta, Chicago, or wherever. Having or lacking that extra 40% of so called Origin and Destination or “O&D” high yield traffic makes or breaks your total economics.
The fact that the Gulf Big Three are no more commercial airlines than was Soviet-era Aeroflot complicates any discussion of the Mideast hubs. They would all shut down within a week or two if their governments stopped writing subsidy checks.
Second paragraph: Long range SST for transpacific or Europe to South / Southeast Asia would be a huge game changer. Baby steps are going that way now. The engineering problem is fuel efficiency. If we assume somewhat higher fuel prices over the 20-30 year lifetime of such aircraft, the required SST ticket price becomes hugely higher than slower conventional aircraft. A few tycoons will pay that much. But lots of ordinary corporate warriors whose travel budget is decided by their boss won’t be allowed to, no matter how much they might prefer faster travel at better times of day.
It’s the vicious cycle of high cost drives small demand drives higher cost drives smaller demand … . If there’s a step-change someplace the cycle can become virtuous, where low cost drives large demand drives lower cost drives larger demand. …
Third factor we’ve not mentioned: Aircraft range. We are approaching the era where we can build airplanes of moderate size (~200 pax) with anywhere-to-anywhere range. Once that happens the economics shift again. Right now the way to make a “long thin” route work, e.g. Manchester UK to Perth, is to hub it in the middle, so you combine all Manchester to Points East traffic onto a single flight to, say, Doha, and in turn consolidate all Points West to Perth traffic onto a single flight from Doha. At the expense from the customer POV of time wasted in the hub, and hassle spent changing planes at 0 mph when they’d rather be sleeping at 600 mph.
Paradoxically, with present tech it can save fuel to stop in the middle to refuel. You waste some in the descent, landing, takeoff & climb, but you’re not lugging nearly half of the total burn across the first of the two legs. If the stopover point isn’t too far off the least-distance nonstop route it all works. But the more efficient the aircraft gets, the less true that is. Right now efficient hemispheric range requires 777-300 or larger aircraft = ~300 seats. Next gen or next gen + 1 will shift that number down a bunch.
Hubs will always be necessary as consolidation points for cities with small O&D demand. But as air travel demand over any given city pair grows, eventually it supports a few non-stops in addition to the many one-stop-via-hub flights. If demand is dense enough and there’re no regulatory or logistical obstacles, eventually almost all traffic is carried nonstop.
Fourth factor: Regulatory obstacles. The domestic US or intra-European market is pretty fully deregulated. Any carrier can connect any two cities how and when they choose. The rest of the planet is not that way. Not even close. The vast majority of non-stop service between Country A and Country B must be carried by airlines based in A or B, not in C through Z. There are various regional agreements (so-called Open Skies) chipping away at this system.
Airport slots are the other major regulatory/logistical obstacle to schedules being optimized for customer convenience. Most gateway airports are full. Most neighborhoods don’t want more airplane noise. Traffic outside Asia is still growing faster than the economy, and traffic within Asia is just exploding. Something has to give.
Even if we waved a magic wand and doubled Heathrow’s or CDG’s capacity overnight that still would not meet demand for the ideal timeslots. Though it would at least leave a couple hours a day where there was capacity in excess of demand.
Back in the 80s, there was a nifty computer simulation game of this (based off of actual simulation software for traffic controllers) called TRACON. I had many a wonderful hour spent trying to configure the approaches (and takeoffs) of planes into the Los Angeles and San Francisco areas. Sadly, the game had a limitation on the number of planes you could introduce in the 90 min. max runtime, a limitation that was a bare fraction of the actual number of planes that arrive in those areas. Of course, since there was only one controller being simulated, that made sense. But I would love to have seen the actual radar view of what it looks like trying to shoehorn all the arrivals to LAX, ONT, SNA, et al. down the “slot” between the San Bernardino and San Jacinto peaks. :eek:
Sites like the OP’s flightradar24 or flightaware.com can show you that in real time now. If you get the subscription version of some of these you can replay recordings taken during peak times or weird winds or whatever.
I don’t know of any site that collects radar/ADS-B data and also voice comm so as to let you eavesdrop on the flow from the POV of any given controller. It might well exist, but I’ve never looked for something like that. There are certainly rafts of online “planespotters” who’re enthused by this stuff who’d know about all this if it exists. I know there are folks who have aviation band radio scanners at home and stream it out onto the 'net. Finding one of those for a busy approach control then configuring flightaware or whoever to show you the same airspace would be sorta fun that way.
Back to the OP.
Try replying to an SDMB thread sometime during a 30 minute turn-around, you’ll get terse sorted pretty quick ;).
Depending on local weather phenomenon such as a sea breeze, this can result in one or two of the airfields having a non-optimum runway configuration, such as tailwind landings at one airport to fit in with the headwind landings of another airport.
That wouldn’t surprise me, it is short (1500m), and has a steeper than normal approach. It’s bread and butter for a BAe146 but not really suitable for most types.
It’s worth noting Singapore is a very popular destination for people from Australia/NZ elsewhere in southeast Asia. Great food, good shopping, super clean and first world. It’s not just a giant airport - although Changi is awesome, with its own butterfly garden.
My understanding is flights are generally configured to arrived at their destinations in daylight hours, but obviously that depends on a variety of factors - I’ve come back into Australia from several overseas airports and arrived at varying times of day. Generally flights from the US (Los Angeles) seem to get into Brisbane in the early morning, however.
IME, whatever direction of travel; arrive early in the morning or late at night, days of jet lag. Arrive mid-afternoon; get good nights sleep; fine next day.
