Radar ATCO Sequencing
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Prior to the most recent TBS version, which includes Optimised Runway Delivery (i.e. an indicator is presented to Director which is threshold wake separation + expected compression), then the wake separation was delivered to 4DME. so a 4nm H-H separation minima was applied when the leader got to 4DME, with compression reducing that as the leader reduced speed. There was no wake separation applied once leader got to 4DME. Tower would give the caution at 0.5nm compression.
With current TBS we separate to threshold.
With current TBS we separate to threshold.
So what you are saying, Gonzo, is that previously, under commercial pressure, reduction of required safety minima was officially brushed under the carpet with a few weasel words about delivery and compression! :-)
2 s
2 s
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Those procedures had been in place at LHR since well before my time (don’t forget, we used to have LHR-specific separations too (off the top of my head, H-L was 7nm, not 8nm as in rest of UK) and were proven to be safe. LHR did not have any greater rate of wake encounter than anywhere else, as far as I know.
If you take the RECAT EU threshold separations, and add on the compression, it’s striking how similar those distances are to our previous 4DME separation distances.
Introducing RECAT and TBS v2 was a long term goal agreed by UK CAA and NATS to move to separation to threshold.
I prefer to think of it as LHR was running a long term trial of RECAT EU threshold separations.
If you take the RECAT EU threshold separations, and add on the compression, it’s striking how similar those distances are to our previous 4DME separation distances.
Introducing RECAT and TBS v2 was a long term goal agreed by UK CAA and NATS to move to separation to threshold.
I prefer to think of it as LHR was running a long term trial of RECAT EU threshold separations.
Excuse my ignorance, please explain to this long retired 'old fart' what TBS is.
For what it's worth I found that spending 90 minutes as LL/LHR No2 Director, when you might turn 60 or so inbounds onto the ILS LOC', could be absolutely shattering. Having also been a LATCC controller I would say that once you had hacked how to do LL No2 it was easier than TMA, but the concentration required made it a very tiring position.
For what it's worth I found that spending 90 minutes as LL/LHR No2 Director, when you might turn 60 or so inbounds onto the ILS LOC', could be absolutely shattering. Having also been a LATCC controller I would say that once you had hacked how to do LL No2 it was easier than TMA, but the concentration required made it a very tiring position.
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Brian, have a look at NATS.aero/tbs
TBS v1 took the UK 6 category wake separation that you would recognise, and used that distance as a baseline for a headwind of 5kts. This is then translated into time separation, for example 90s for a 4nm separation.
The TBS tool calculates the headwind component on final approach by using the Mode S data downlinked from each aircraft.
It then calculates what distance would result in a 90s gap given current headwinds. So in a 15kt headwind, it might be 3.5nm, in a zero wind day it might be 4.3nm.
An indicator is then depicted on radar 3.5nm or 4.3nm behind the leader of the pair in question for FIN to reference.
Yes, you read that right, if the wind is less than a 5kt headwind, we actually increase separation over the distance based separation.
Only wake separations we’re provided with indicators.
TBS v2 incorporated RECAT (RECATegorisation of wake)....so 757, 767, A300 are what is effectively a ‘lower heavy’ category, and their new separations.
it also incorporates Optimised Runway Delivery, which forecasts the expected compression between the pair of aircraft based on average speed profiles inside 4DME, so FIN sees an indicator which is threshold separation + compression, and Tower sees an indicator at threshold separation only.
TBS v2 is also doing the same in terms of modifying according to headwind component.
TBS v2 also provides indicators for certain pairs where runway occupancy is greater than wake separation, or where wake separation requirement does not exist.
Hope that makes sense!
TBS v1 took the UK 6 category wake separation that you would recognise, and used that distance as a baseline for a headwind of 5kts. This is then translated into time separation, for example 90s for a 4nm separation.
The TBS tool calculates the headwind component on final approach by using the Mode S data downlinked from each aircraft.
It then calculates what distance would result in a 90s gap given current headwinds. So in a 15kt headwind, it might be 3.5nm, in a zero wind day it might be 4.3nm.
An indicator is then depicted on radar 3.5nm or 4.3nm behind the leader of the pair in question for FIN to reference.
Yes, you read that right, if the wind is less than a 5kt headwind, we actually increase separation over the distance based separation.
Only wake separations we’re provided with indicators.
TBS v2 incorporated RECAT (RECATegorisation of wake)....so 757, 767, A300 are what is effectively a ‘lower heavy’ category, and their new separations.
it also incorporates Optimised Runway Delivery, which forecasts the expected compression between the pair of aircraft based on average speed profiles inside 4DME, so FIN sees an indicator which is threshold separation + compression, and Tower sees an indicator at threshold separation only.
TBS v2 is also doing the same in terms of modifying according to headwind component.
TBS v2 also provides indicators for certain pairs where runway occupancy is greater than wake separation, or where wake separation requirement does not exist.
Hope that makes sense!
All very mind boggling ! I just wonder what used to happen in the days before Wake Turbulence Separation existed. To my recollection; I can't remember vast numbers of aeroplanes hurtling to the ground because they were too close to each other !
Though by then, there had already been fatalities as a result of encountering WT.
Thanks Gonzo
I didn't understand a word of that - perhaps I need a months course at the college on full allowances to get to grips with TBS! Oh, I forgot - no college, no allowances these days!
I didn't understand a word of that - perhaps I need a months course at the college on full allowances to get to grips with TBS! Oh, I forgot - no college, no allowances these days!
I generally accept what you say, Dave; but, I was vectoring plenty of a/c back then in pressurized environments (Aberdeen & Jersey - & others were doing the same at Heathrow & Gatwick) without the benefit of Wake Turbulence Sepn., & the regular separation was 3 nm (no WTS). I can’t remember any WT inspired incidents though. Maybe my memory is failing.
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Brian, have a look at NATS.aero/tbs
TBS v1 took the UK 6 category wake separation that you would recognise, and used that distance as a baseline for a headwind of 5kts. This is then translated into time separation, for example 90s for a 4nm separation.
The TBS tool calculates the headwind component on final approach by using the Mode S data downlinked from each aircraft.
It then calculates what distance would result in a 90s gap given current headwinds. So in a 15kt headwind, it might be 3.5nm, in a zero wind day it might be 4.3nm.
An indicator is then depicted on radar 3.5nm or 4.3nm behind the leader of the pair in question for FIN to reference.
Yes, you read that right, if the wind is less than a 5kt headwind, we actually increase separation over the distance based separation.
Only wake separations we’re provided with indicators.
TBS v2 incorporated RECAT (RECATegorisation of wake)....so 757, 767, A300 are what is effectively a ‘lower heavy’ category, and their new separations.
it also incorporates Optimised Runway Delivery, which forecasts the expected compression between the pair of aircraft based on average speed profiles inside 4DME, so FIN sees an indicator which is threshold separation + compression, and Tower sees an indicator at threshold separation only.
TBS v2 is also doing the same in terms of modifying according to headwind component.
TBS v2 also provides indicators for certain pairs where runway occupancy is greater than wake separation, or where wake separation requirement does not exist.
Hope that makes sense!
TBS v1 took the UK 6 category wake separation that you would recognise, and used that distance as a baseline for a headwind of 5kts. This is then translated into time separation, for example 90s for a 4nm separation.
The TBS tool calculates the headwind component on final approach by using the Mode S data downlinked from each aircraft.
It then calculates what distance would result in a 90s gap given current headwinds. So in a 15kt headwind, it might be 3.5nm, in a zero wind day it might be 4.3nm.
An indicator is then depicted on radar 3.5nm or 4.3nm behind the leader of the pair in question for FIN to reference.
Yes, you read that right, if the wind is less than a 5kt headwind, we actually increase separation over the distance based separation.
Only wake separations we’re provided with indicators.
TBS v2 incorporated RECAT (RECATegorisation of wake)....so 757, 767, A300 are what is effectively a ‘lower heavy’ category, and their new separations.
it also incorporates Optimised Runway Delivery, which forecasts the expected compression between the pair of aircraft based on average speed profiles inside 4DME, so FIN sees an indicator which is threshold separation + compression, and Tower sees an indicator at threshold separation only.
TBS v2 is also doing the same in terms of modifying according to headwind component.
TBS v2 also provides indicators for certain pairs where runway occupancy is greater than wake separation, or where wake separation requirement does not exist.
Hope that makes sense!
That's an extremely helpful explanation of TBS - many thanks!
Is TBS yet operational at LGW, and are there any further complexities involved with TBS on a mixed mode runway?
Best regards
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Hi,
Basic idea in our region is to reduce the speed 210 on first contact (about 25nm to go / or downwind abeam the airport), then 190 on base, 180 to 10 dme and finally 160 to 4 dme.
Cheers
Basic idea in our region is to reduce the speed 210 on first contact (about 25nm to go / or downwind abeam the airport), then 190 on base, 180 to 10 dme and finally 160 to 4 dme.
Cheers
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TBS linked to some sort of departure manager would be the daddy - imagine providing spacing to suit the departure order (ie heavy and medium haul narrowbodies departures get bigger gaps, short haul gets slightly smaller gaps). Maximum runway utilisation. But at what £ ?
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Packer27L What you describe is already achieved by air controllers at busy airports so I don't see the benefit of more gadgets. I'd far rather know that the air men have their eyes out the windows than having to spend more time on electronic gizmos.
HD, think of busy single runway airports where the departure order could be fed into Time Based Separation software.
Presently, departure gaps are about 6 Miles, sometimes less in a strong wing and sometimes more after heavy arrivals. What if the TBS indicators were tailor made for each departure? You could have 90 seconds for a 737, 110 for a heavy, you could even have the aircraft weight included in the equation so each departure gap was individually calculated for each departure.
All the radar director would see was an indicator precisely calculated for the next departure and all the air controller needs to know is the next gap is custom made for their next departure.
you could increase the hourly movement rate at busy, single runway airfields by 10-20%.
And no electronic gizmos to distract anyone.
Presently, departure gaps are about 6 Miles, sometimes less in a strong wing and sometimes more after heavy arrivals. What if the TBS indicators were tailor made for each departure? You could have 90 seconds for a 737, 110 for a heavy, you could even have the aircraft weight included in the equation so each departure gap was individually calculated for each departure.
All the radar director would see was an indicator precisely calculated for the next departure and all the air controller needs to know is the next gap is custom made for their next departure.
you could increase the hourly movement rate at busy, single runway airfields by 10-20%.
And no electronic gizmos to distract anyone.
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Del Prado, not sure you could get another 10-20% out of Gatwick. Essentially, when busy, the gaps are already tailor made to get 2 away or whatever the plan is that FIN and DEPS have come up with.
I disagree.
A gap is usually 6 to get one away.
If you have a 777 following a 777 with a 747 to depart in between the gap required is 6.
if you have a 738 followed by a 319 with a 738 to go in between the gap is still 6.
Defaulting to the lowest common denominator spacing (which is based on the worst case traffic mix) does not lead to an efficient system.
There are savings to be had by having tailor made gaps calculated to suit each aircraft type rather than default to 6 miles, which is enough to get a heavy away between two heavies.
Also 737s could do 170kts to 5 and A319/320 could do 160 to 5, increasing stable approaches and reducing go arounds.
Wouldn’t it be better to have a systematic spacing delivery where landing clearance is consistently given at, say 200’ than varying between 50’ and 500’ ?
A gap is usually 6 to get one away.
If you have a 777 following a 777 with a 747 to depart in between the gap required is 6.
if you have a 738 followed by a 319 with a 738 to go in between the gap is still 6.
Defaulting to the lowest common denominator spacing (which is based on the worst case traffic mix) does not lead to an efficient system.
There are savings to be had by having tailor made gaps calculated to suit each aircraft type rather than default to 6 miles, which is enough to get a heavy away between two heavies.
Also 737s could do 170kts to 5 and A319/320 could do 160 to 5, increasing stable approaches and reducing go arounds.
Wouldn’t it be better to have a systematic spacing delivery where landing clearance is consistently given at, say 200’ than varying between 50’ and 500’ ?
