Mixed mode at Heathrow?
Join Date: May 2000
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Not an LHR controller myself but have worked at LHR for nearly 5 years. One of the benefits is supposedly an increase in the flow rate, hence more slots available for airlines to use.
One of the major problems Heathrow has is with the lack of stands so if you increase the slots available then you need more stands. Terminal 5 will create more stands but then T2 will be closed while Heathrow East is developed so there might not be too much of an increase.
There are a lot of other issues associated with this which I have seen discussed on here before but I will let an LHR Controller answer that one as I am merely an Airline Ops controller!!!
One of the major problems Heathrow has is with the lack of stands so if you increase the slots available then you need more stands. Terminal 5 will create more stands but then T2 will be closed while Heathrow East is developed so there might not be too much of an increase.
There are a lot of other issues associated with this which I have seen discussed on here before but I will let an LHR Controller answer that one as I am merely an Airline Ops controller!!!
Join Date: Oct 2000
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I shall be very interested in comments from current controllers to see if similar problems exist now as when Mixed Mode was first considered way back in the early-1960s when the 6th floor Approach Control Room was engineered for Mixed Mode with two No. 2 (Final Directors) and 2 PAR (Precision Approach Radar) positions to monitor the approaches. The system was trialled but I do not know the full outcome, other than that it was not put into full operation.
Among the problems then were a) GMC almost unworkable (Maybe that would be surmountable now with split-GMC in operation?) and b) the fact that, in the Approach environment, the offering of traffic for both runways throughout the day was unequal. The concept was to land everything from the north on then 28R/10L and everything from the south on 28L/10R. At particular times most traffic is offering from one direction so one runway was busy whilst the other was quiet - or the radar vectoring got a bit exciting and precise spacing was diffcult to achieve. Nowadays it is possible to stack-swap to provide an even flow from all stacks so maybe that problem has been solved too?
Lastly, of course, the residents out Hounslow-way would probably notice!!
Among the problems then were a) GMC almost unworkable (Maybe that would be surmountable now with split-GMC in operation?) and b) the fact that, in the Approach environment, the offering of traffic for both runways throughout the day was unequal. The concept was to land everything from the north on then 28R/10L and everything from the south on 28L/10R. At particular times most traffic is offering from one direction so one runway was busy whilst the other was quiet - or the radar vectoring got a bit exciting and precise spacing was diffcult to achieve. Nowadays it is possible to stack-swap to provide an even flow from all stacks so maybe that problem has been solved too?
Lastly, of course, the residents out Hounslow-way would probably notice!!
At present, Heathrow can move about 90 aircraft per hour. Gatwick can move 55 per hour. If you run Heathrow like Gatwick you'll shift 110 per hour.
Luckily there's loads of free airspace around Heathrow and lots of free taxiway space so it'll be a doddle to implement
Luckily there's loads of free airspace around Heathrow and lots of free taxiway space so it'll be a doddle to implement
Join Date: Dec 1999
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Mixed Mode benefits....
More runway movements, an extra 15-20 an hour.
Issues:
How do we do it? A/c will have to cross over at some point. Either on the ground (i.e. northbounds of 27R, southbounds off 27L - I sure as heck don't want to do GMC that day, especially on EFPS!!!), or in the air (southbound departs 27R followed by a northbound off 27L). Same for inbounds. Ok, that could be solved at the flight planning stage, in that a flight from Paris to LHR T4 will come in via BIG or OCK for 27L, and a flight from Paris to LHR T1 will be planned to route into LAM for 27R. So you have this neat system set up. however, there will come a time when most of the a/c arriving will be for 27L, and perhaps most of the departures will also be for 27L. What happens then? Do we just lump it and let the delay build up? Or do we land and depart on both runways, disregarding SIDs and NPRs, and then cause carnage on GMC? And what about work in progress? crews flying into LHR currently will know how annoying the WIP is at the moment.
And you can bet that if it does come in, all the slots will be filled, and what happens then if we are precluded from using a runway for departure/arrivals for a particular reason? (WIP). Airlines expect a flow rate of 55-60 per hour, but we can only get 45 on the deck. Massive flow delays, cancellations etc.
I would gladly try and find a way to make it work, but I just don't think one exists for LHR, given the geographical and environmental restrictions.
More runway movements, an extra 15-20 an hour.
Issues:
How do we do it? A/c will have to cross over at some point. Either on the ground (i.e. northbounds of 27R, southbounds off 27L - I sure as heck don't want to do GMC that day, especially on EFPS!!!), or in the air (southbound departs 27R followed by a northbound off 27L). Same for inbounds. Ok, that could be solved at the flight planning stage, in that a flight from Paris to LHR T4 will come in via BIG or OCK for 27L, and a flight from Paris to LHR T1 will be planned to route into LAM for 27R. So you have this neat system set up. however, there will come a time when most of the a/c arriving will be for 27L, and perhaps most of the departures will also be for 27L. What happens then? Do we just lump it and let the delay build up? Or do we land and depart on both runways, disregarding SIDs and NPRs, and then cause carnage on GMC? And what about work in progress? crews flying into LHR currently will know how annoying the WIP is at the moment.
And you can bet that if it does come in, all the slots will be filled, and what happens then if we are precluded from using a runway for departure/arrivals for a particular reason? (WIP). Airlines expect a flow rate of 55-60 per hour, but we can only get 45 on the deck. Massive flow delays, cancellations etc.
I would gladly try and find a way to make it work, but I just don't think one exists for LHR, given the geographical and environmental restrictions.
Join Date: Mar 2002
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There are a number of ways of doing MM, departing on either existing SIDs or preferrably new ones and operating either independent or radar separated (staggared) arrivals. NATS was initially instructed to work out what "maximum" capacity mixed-mode was, and then work back from that as necessary to reach an all-round acceptable solution.
Either way, a few of the ESSENTIAL operational points are:
1. With a few exceptions departures will depart in Compass mode, i.e. in the direction of intended flight. Crossing departures are an accident waiting to happen. The "toast racking" of the airport will significantly assist GMC in that regard; it still won't be easy but it has been demonstrated that theoretically at least the traffic will flow satisfactorily around te central area.
2. To balance that essential, arrivals will be crossed using Strategic flight planning, and tactical manoeuvre pre-stack to deliver arrivals into an appropriate stack for their landing runway.
3. As a general rule, T1 will use the northern runway, T2 & 4 the southern runway and T3 & 5 will balance between the two.
4. As has been pointed out, traffic rarely falls perfectly in balance and so each runway needs to be flexible enough to cater for surges in arrivals and departures. This requirement strongly favours Independent parallel mixed mode but that causes other problems.
5. Indpendent mixed-mode denies the possiblity of full CDAs using the current TMA/holding arrangements. In the current political climate that is difficult to swallow and VERY REGRETABLY in my opinion, the government are therefore going to consult on a lesser form of arrival system where a single final director is used to vector two streams of traffic onto the approaches in staggered formation so that, theoretically at least, vertical separation is not required.
6. I believe this to be a significant safety risk: The most difficult part of the Final director's job is timing of turns; the bussier the r/t the more difficult that is. It is already and issue, adding another 15 % will make it significantly worse. There are also other issues; e.g. wake vortex (in the event of going through the centreline) and the implications of strong crosswinds, where one turn will be tight and the other wide. If one final is longer than the other then one base leg will point straight across the front of traffic on the other final, WITHOUT VERTICAL! It is asking for trouble, in my view. Blocked r/t anyone?
7. Finally, it is inflexible. One side cannot "pack" arrivals or departures because of operations on the other side and this means that unless the traffic offers in perfect balance between arrivals and departures and between individual SID demand capacity is immediately lost.
Hope that helps
.4
Either way, a few of the ESSENTIAL operational points are:
1. With a few exceptions departures will depart in Compass mode, i.e. in the direction of intended flight. Crossing departures are an accident waiting to happen. The "toast racking" of the airport will significantly assist GMC in that regard; it still won't be easy but it has been demonstrated that theoretically at least the traffic will flow satisfactorily around te central area.
2. To balance that essential, arrivals will be crossed using Strategic flight planning, and tactical manoeuvre pre-stack to deliver arrivals into an appropriate stack for their landing runway.
3. As a general rule, T1 will use the northern runway, T2 & 4 the southern runway and T3 & 5 will balance between the two.
4. As has been pointed out, traffic rarely falls perfectly in balance and so each runway needs to be flexible enough to cater for surges in arrivals and departures. This requirement strongly favours Independent parallel mixed mode but that causes other problems.
5. Indpendent mixed-mode denies the possiblity of full CDAs using the current TMA/holding arrangements. In the current political climate that is difficult to swallow and VERY REGRETABLY in my opinion, the government are therefore going to consult on a lesser form of arrival system where a single final director is used to vector two streams of traffic onto the approaches in staggered formation so that, theoretically at least, vertical separation is not required.
6. I believe this to be a significant safety risk: The most difficult part of the Final director's job is timing of turns; the bussier the r/t the more difficult that is. It is already and issue, adding another 15 % will make it significantly worse. There are also other issues; e.g. wake vortex (in the event of going through the centreline) and the implications of strong crosswinds, where one turn will be tight and the other wide. If one final is longer than the other then one base leg will point straight across the front of traffic on the other final, WITHOUT VERTICAL! It is asking for trouble, in my view. Blocked r/t anyone?
7. Finally, it is inflexible. One side cannot "pack" arrivals or departures because of operations on the other side and this means that unless the traffic offers in perfect balance between arrivals and departures and between individual SID demand capacity is immediately lost.
Hope that helps
.4
