Holding - why does it happen these days?
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Holding - why does it happen these days?
Folks,
Sitting in the Lambourne hold the other day, me & the FO discussed the unknown quantity of holding and possible solutions and the costs of going round in such circles.
Some of you fine men and women will be able to tell me why holding occurs.
Is it not built into the system to not having swathes of aeroplanes arriving at the same time, or do you folks roll your sleeves up around about the same times every day and get on with it?
I am genuinely curious as to why, in this day and age, we haven't got a system in place that can alleviate the need to hold entirely.
All thoughts much appreciated.
Best regards
KMB01
Sitting in the Lambourne hold the other day, me & the FO discussed the unknown quantity of holding and possible solutions and the costs of going round in such circles.
Some of you fine men and women will be able to tell me why holding occurs.
Is it not built into the system to not having swathes of aeroplanes arriving at the same time, or do you folks roll your sleeves up around about the same times every day and get on with it?
I am genuinely curious as to why, in this day and age, we haven't got a system in place that can alleviate the need to hold entirely.
All thoughts much appreciated.
Best regards
KMB01
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All the airlines choose to arrive at the same time, that's why 
If everything had flow control on to avoid it all arriving at the same time, you would just spend your time delayed on the ground instead.
We try to avoid holding if at all possible. Things are much easier for us if there is no holding, but if we have no choice but to hold due to the number of aircraft inbound at any given time, then it happens unfortunately.
The only way that it can be avoided (except for reasons like fog, severe weather and other such things out of our control) is to reduce the amount of flights to stop them all arriving at the same time.
I do feel sorry having to tell you guys to enter the hold at LAM and tell you the day is 15 to 20 minutes - Wouldn't wish that on anyone!
If everything had flow control on to avoid it all arriving at the same time, you would just spend your time delayed on the ground instead.
We try to avoid holding if at all possible. Things are much easier for us if there is no holding, but if we have no choice but to hold due to the number of aircraft inbound at any given time, then it happens unfortunately.
The only way that it can be avoided (except for reasons like fog, severe weather and other such things out of our control) is to reduce the amount of flights to stop them all arriving at the same time.
I do feel sorry having to tell you guys to enter the hold at LAM and tell you the day is 15 to 20 minutes - Wouldn't wish that on anyone!
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Defruiter
not quite true that we try to avid holding. Flow for heathrow tries to run at 5-10 mins holding - that way they get maximum use of the runway (i.e. always have an aircraft to vector to land just behind another one).
However otherwise holding is obviously avoided if possible. The reason it happens as you state is because airlines all want to fly the same routes at the same times.
Airlines do this because this is what the customer wants.
not quite true that we try to avid holding. Flow for heathrow tries to run at 5-10 mins holding - that way they get maximum use of the runway (i.e. always have an aircraft to vector to land just behind another one).
However otherwise holding is obviously avoided if possible. The reason it happens as you state is because airlines all want to fly the same routes at the same times.
Airlines do this because this is what the customer wants.
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I am genuinely curious as to why, in this day and age, we haven't got a system in place that can alleviate the need to hold entirely.
There is only one reason to hold -- supply exceeds demand. Too many airplanes scheduled in too short a time for a runway.
In America, the airlines are actually allowed to schedule it that way (at many airports.) The kicker (of course) is the weather. A 60-ops-per hour runway can become a 30-ops-per hour runway in rain and wind or a zero-ops-per hour runway during an ice storm.
Weather is still unpredictable. We can't even do a good job of it for a 5 hour flight much less a 90-days-in-advance ticket.
The only way to make it work is to limit the number of scheduled operations to an "average" acceptance rate. On the good days, that equates to a lot of lost productivity, lost tickets sales and lost landing fees. The pressure is always on for the various controlling authorities to allow more aircraft a slot. In a word -- Greed.
I haven't studied the European approach to it all but it *seems* as if they are much more willing to recognize the reality of the situation. In America, the powers that be try to convince folks that technology will somehow cure it all. It won't. Not even the FAA's $20 billion dollar NextGen.
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In theory holding could be eliminated but the bottom line is money. The airport authorities flog as many slots as they think they can cram in and ATC have to work their nuts off to meet that demand.
Some aerodromes have acceptance rates that can only be matched in optimum conditions - perfect weather, correct wind direction and optimum runway configuration. Any less than that and the "capacity" cannot be achieved. The usual solution is to stick on a flow measure but the transition between the old capacity and the new is likely to be absorbed by holding.
The analogy best used to explain it is the checkout queue at the supermarket, the most efficient use of the checkouts is to have a few people waiting at each one.
Some aerodromes have acceptance rates that can only be matched in optimum conditions - perfect weather, correct wind direction and optimum runway configuration. Any less than that and the "capacity" cannot be achieved. The usual solution is to stick on a flow measure but the transition between the old capacity and the new is likely to be absorbed by holding.
The analogy best used to explain it is the checkout queue at the supermarket, the most efficient use of the checkouts is to have a few people waiting at each one.
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People in checkout queues are not using x kilos of a rapidly dwindling resource every minute though.
At one airport in the UK I believe it often happens because one of the runways closes just as the inbound rush arrives
.
Flowman is spot on stating that the bottom line is money. There is shedloads of capacity in the UK ATC system, but we just don't use it effectively, (strangely enough) for 'economic reasons'.
No matter how many new runways you build, we can't all fly at the same time.
At an exhibition held in our town a few years ago, a government talking head gushed enthusiastically about multiple airport expansion plans and the benefits this would bring to the travelling public and local communities. When someone asked him how all these extra planes would fly around safely the answer was "well ATC will sort it out, we have just opened a new centre at Swanwick". At an airport many years ago, the boss of a UK airline would schedule 6 of his aircraft to take off at 0700, and complained repeatedly that the last one was always 10-15 minutes late getting airborne. Allegedly, he never visited ATC to find out why.
Looking at it from a slightly different angle, basic systems theory states that every system, (whether it be a biological, physical, or a transport system), has a defined, quantifiable 'carrying capacity'.
When the carrying capacity is exceeded, the system starts to break down. In a hydrological system, (say a river valley), when the carrying capacity is exceeded, you get flooding. In a transport system, (say ATC), you get holding, either on the ground or in the air.
If you want to witness a system repeatedly breaking down in spectacular fashion, listen to Sally Boazman's hourly traffic reports on BBC Radio2.
Theoretically, the UK ATC system will only reach its own carrying capacity when all area sectors/aerodrome/approach control positions are manned H24. I suspect we are a long way from this scenario.
Apart from the unforeseen and relatively short-term effects of WX, incidents, equipment failures and runway closures, the holding requirement could be reduced significantly if we are prepared to change our travelling times, and smooth out the 'peaks'. Unfortunately, due to the above-mentioned factors such as 'customer demand', greed, and the bottom line, this is something that aerodrome and airline managers are reluctant to address. The common sense 'O' Level is notable for its absence.
It's not a new problem either. In the early 70s, I remember watching 17 aircraft queueing for T/O on 28R (EGLL). Half of them were BEA Tridents
.
At one airport in the UK I believe it often happens because one of the runways closes just as the inbound rush arrives
. Flowman is spot on stating that the bottom line is money. There is shedloads of capacity in the UK ATC system, but we just don't use it effectively, (strangely enough) for 'economic reasons'.
No matter how many new runways you build, we can't all fly at the same time.
At an exhibition held in our town a few years ago, a government talking head gushed enthusiastically about multiple airport expansion plans and the benefits this would bring to the travelling public and local communities. When someone asked him how all these extra planes would fly around safely the answer was "well ATC will sort it out, we have just opened a new centre at Swanwick". At an airport many years ago, the boss of a UK airline would schedule 6 of his aircraft to take off at 0700, and complained repeatedly that the last one was always 10-15 minutes late getting airborne. Allegedly, he never visited ATC to find out why.
Looking at it from a slightly different angle, basic systems theory states that every system, (whether it be a biological, physical, or a transport system), has a defined, quantifiable 'carrying capacity'.
When the carrying capacity is exceeded, the system starts to break down. In a hydrological system, (say a river valley), when the carrying capacity is exceeded, you get flooding. In a transport system, (say ATC), you get holding, either on the ground or in the air.
If you want to witness a system repeatedly breaking down in spectacular fashion, listen to Sally Boazman's hourly traffic reports on BBC Radio2.
Theoretically, the UK ATC system will only reach its own carrying capacity when all area sectors/aerodrome/approach control positions are manned H24. I suspect we are a long way from this scenario.
Apart from the unforeseen and relatively short-term effects of WX, incidents, equipment failures and runway closures, the holding requirement could be reduced significantly if we are prepared to change our travelling times, and smooth out the 'peaks'. Unfortunately, due to the above-mentioned factors such as 'customer demand', greed, and the bottom line, this is something that aerodrome and airline managers are reluctant to address. The common sense 'O' Level is notable for its absence.
It's not a new problem either. In the early 70s, I remember watching 17 aircraft queueing for T/O on 28R (EGLL). Half of them were BEA Tridents
.
Last edited by ZOOKER; 16th Aug 2008 at 11:15. Reason: spelling error detected
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kemblejet01
As controllers, we just work here as the saying goes. BAA policy is the short answer......too many slots allocated at peak demand times. This is known as a "full stack" policy whereby there is always a continuous flow of inbound traffic to facilitate picking the optimum mix for maximum runway utilisation. 25 years ago NATS told the government that extra concrete was urgently needed.....now there is twice the demand and to be quite blunt, it is only through excellent ATC by London Terminal and Approach that Heathrow can operate at a scratch under 100% efficiency. I just sit and watch in amazement from my tube next door in Area.....I don't know how the hell they do it!!!
P.S. pop down and sit in for a while.....always welcome.
P.P.S. "full stack" was a severe embarrassment in the recent fuel price hike, and this led to the introduction of the universally-loathed 270 knot descent trial......we hardly ever refused a prefered speed request without the need for a draconian office-numpty directive.
P.S. pop down and sit in for a while.....always welcome.
P.P.S. "full stack" was a severe embarrassment in the recent fuel price hike, and this led to the introduction of the universally-loathed 270 knot descent trial......we hardly ever refused a prefered speed request without the need for a draconian office-numpty directive.
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DefruiterI might have been slightly wrong - only being a lowly TC controller and not a traffic manager... I think I over egged it when I said they look to flow for a 5-10 min delay to keep optimum runway use.It might actually be that they flow for a handful of aircraft over the expecetd hourly landing rate. Either way, it is done to ensure that EGLL App are not sitting twiddling their thumbs if it can be avoided.055166K - despite the regular bitching between AC and TC (we still have a lot to learn about each others operation) the whole team AC/TC/APP and Twr work well together to make the incredibly busy and complicated airspace work
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The analogy best used to explain it is the checkout queue at the supermarket, the most efficient use of the checkouts is to have a few people waiting at each one.
Statements about the oversubscription of certain times of the day are valid, runway slot compliance is important to the integrity of the system.
There is shedloads of capacity in the UK ATC system, but we just don't use it effectively,
(strangely enough) for 'economic reasons'.
Perhaps we could try and force people to go on holiday in the small hours, but I don't believe the charter airlines or local residents would be onboard with it. An extra runway somewhere in the south east that could move another 900 planes would alleviate holding. In theory. In reality if that extra capacity is at Heathrow (or indeed Gatwick) it will be filled in no time and we'll be back to where we started only with even more movements. Supply and demand.
The truth of the matter is that so long as it is still economically viable for aircraft to be holding and burning x kilos of fuel they will. Sensible or not. Only when the accountants start telling those in charge that they have to change to survive will they.
Last edited by hangten; 17th Aug 2008 at 13:23. Reason: Syntax error!
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Nice arguments, hangten.
'Economical reasons' - now there's a mixed bag.
When one buys a plane ticket it isn't necessarily because one can afford it - it's largely because one has a piece or three of plastic labelled 'never never'.
One may buy a plane ticket even if one is behind with their mortgage payments if one wants or dares or just does what one wants.
I think the crux of the question has to do more with exploitation of various systems than with what emanates from the dull accountants' domain.
It is far more a question of what a customer/a company/a regulator/a government wants, will tolerate, decides is their rule-set or gets away with in this world.
If one wants green, one doesn't push aircraft round and round in circles at low level as a means of dispersing commercial pressure on the system.
If one wants to show one is a safe ATC service one doesn't constantly work on the limits set by the regulator.
If one wants to service a fair slice of the business, one doesn't continually blame other industry partners for failing to push their limits.
If one wanted to be safer in one's seat down the back one might choose a rearward facing seat and a better harness.
All these things are in fact said to be wanted from time to time but what does one actually have?
One might therefore say it isn't 'economical reasons', but 'industry culture', 'national cuture', personal standards or a combination of one with the others that dictates what one does or does not do.
One or the other(s) has a lot to answer for
(and not just why holding still happens to one thesedays ).
'Economical reasons' - now there's a mixed bag.
When one buys a plane ticket it isn't necessarily because one can afford it - it's largely because one has a piece or three of plastic labelled 'never never'.
One may buy a plane ticket even if one is behind with their mortgage payments if one wants or dares or just does what one wants.
I think the crux of the question has to do more with exploitation of various systems than with what emanates from the dull accountants' domain.
It is far more a question of what a customer/a company/a regulator/a government wants, will tolerate, decides is their rule-set or gets away with in this world.
If one wants green, one doesn't push aircraft round and round in circles at low level as a means of dispersing commercial pressure on the system.
If one wants to show one is a safe ATC service one doesn't constantly work on the limits set by the regulator.
If one wants to service a fair slice of the business, one doesn't continually blame other industry partners for failing to push their limits.
If one wanted to be safer in one's seat down the back one might choose a rearward facing seat and a better harness.
All these things are in fact said to be wanted from time to time but what does one actually have?
One might therefore say it isn't 'economical reasons', but 'industry culture', 'national cuture', personal standards or a combination of one with the others that dictates what one does or does not do.
One or the other(s) has a lot to answer for
(and not just why holding still happens to one thesedays ).
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Of course all holding can be eliminated. It means taking the delay enroute or before the flight departs (the most efficient way- in every sense).
But having spoken to airline reps, they all say they will take the delay in the air. Why? Customer perception. If the punter takes his delay in the airport lounge he is pissed off and blames the airline. If the competition next door depart their flight on time, then hold at the destination, guess which airline gets the business next time. The stupid punter doesnt arrive any earlier, but he has the perception of it being the airline's fault if he departs late.
Plus as long as hub-and-spoke theory exists, we'll all have jobs. It's great if your airline has 6 planes, but when you get to 60, carry the holding fuel.
But having spoken to airline reps, they all say they will take the delay in the air. Why? Customer perception. If the punter takes his delay in the airport lounge he is pissed off and blames the airline. If the competition next door depart their flight on time, then hold at the destination, guess which airline gets the business next time. The stupid punter doesnt arrive any earlier, but he has the perception of it being the airline's fault if he departs late.
Plus as long as hub-and-spoke theory exists, we'll all have jobs. It's great if your airline has 6 planes, but when you get to 60, carry the holding fuel.
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Holding
If you have ever flown into Heathrow at 6am, you will undoubtedly have had to hold waiting for the night curfew to end. Most airlines request that they land at 0601 or 0602 in order that they do not cross noise monitoring points before 0600. We all appreciate that the first wave/rotation of traffic is vital to ensure the days schedules run smoothly.
Witness then the rush of all those who would wish to land first at 0601. (VIR 744 running into BNN some time ago "our box says that if you give us a heading off BNN, we will land at 0601" response "would love to help you, unfortunately you are number 8 in the sequence, take up the hold"). Have also sat on BA back from VHHH (3rd of the 3 services, which unlike the earlier two doesn't qualify for a night slot). All the way back from VHHH the IFE was indicating that we would arrive at 0605, indeed that is what the crew were also telling us. Arrive at LAM, 10 mins + holding due to volume of traffic. Surprise!!!!
99% of the time, Heathrow will be holding at 0600. If, however, we aren't and/or delays are minimal, this is usually due to late arrival of trans Atlantic traffic due winds,tracks etc., this in turn will lead to higher loadings of traffic and therefore holding during the morning.
Capacity figures are calculated to ideal scenarios, airlines will schedule to slots allocated accordingly. Mix in a little bad weather or an emergency necessitating runway inspections etc and delays build. Surface wind speed also effects landing rates, stronger wind = lower ground speed = lower movement rate.
Demand does exceed capacity at times for any number of reasons. The system runs at its most efficient as described by anotherthing. We need demand at the stacks to sustain good landing rates. Some argue that the system runs best with 20mins + holding, since we can use both runways for arrivals (6 per hour on the nominated departure runway Tactically Enhanced Arrival Mode).
All airports have limiting factors. Regrettably, with so many variables, limitations and constraints, holding becomes inevitable.
Witness then the rush of all those who would wish to land first at 0601. (VIR 744 running into BNN some time ago "our box says that if you give us a heading off BNN, we will land at 0601" response "would love to help you, unfortunately you are number 8 in the sequence, take up the hold"). Have also sat on BA back from VHHH (3rd of the 3 services, which unlike the earlier two doesn't qualify for a night slot). All the way back from VHHH the IFE was indicating that we would arrive at 0605, indeed that is what the crew were also telling us. Arrive at LAM, 10 mins + holding due to volume of traffic. Surprise!!!!
99% of the time, Heathrow will be holding at 0600. If, however, we aren't and/or delays are minimal, this is usually due to late arrival of trans Atlantic traffic due winds,tracks etc., this in turn will lead to higher loadings of traffic and therefore holding during the morning.
Capacity figures are calculated to ideal scenarios, airlines will schedule to slots allocated accordingly. Mix in a little bad weather or an emergency necessitating runway inspections etc and delays build. Surface wind speed also effects landing rates, stronger wind = lower ground speed = lower movement rate.
Demand does exceed capacity at times for any number of reasons. The system runs at its most efficient as described by anotherthing. We need demand at the stacks to sustain good landing rates. Some argue that the system runs best with 20mins + holding, since we can use both runways for arrivals (6 per hour on the nominated departure runway Tactically Enhanced Arrival Mode).
All airports have limiting factors. Regrettably, with so many variables, limitations and constraints, holding becomes inevitable.
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Some argue that the system runs best with 20mins + holding, since we can use both runways for arrivals (6 per hour on the nominated departure runway Tactically Enhanced Arrival Mode).
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Interesting to note that a significant number of slots are being, or are in the process of being, transferred from M/S vortex categories to H.
I'm sure whoever it is that decides the hourly capacity figures is taking into account the fact there are more and more heavies operating into the airport than ever before...
I'm sure whoever it is that decides the hourly capacity figures is taking into account the fact there are more and more heavies operating into the airport than ever before...
