It isn't rocket science - or is it?
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Join Date: Nov 2001
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It isn't rocket science - or is it?
Heavy delays at Heathrow this morning due to wind.
I am tired of crusty old Captains, mainly of a certain mainline airline, aggressively questioning the nature of the delay on a Sunday morning.
When confronted with the reply that it was due to wind (for brevity due to workload), the general ignorant response was that it ''wasn't that strong'', with the aggravating implication that it must be the fault of ATC.
So for the ignorant - the rocket science reply:
The wind at 3A was westerly at >65kt whereas, at surface level, it was 265/16. Groundspeeds of individual aircraft, supposedly flying at 160kts, were generally in the order of 112 KT at 10DME, increasing to around 130KT at 6 DME and as high as 145 KT at around 300ft.
We were positioning aircraft the minimum 2.5 miles apart at around 12DME only to see, due to the wind gradient, the preceding aircraft pull away and, by touchdown, gain almost a mile on the succeeding aircraft.
The result - a lower than scheduled for landing rate of around 34 movements per hour.
The solution - place aircraft an illegal 1.5 miles apart at 12 DME and see how
A. The CAA SRG and
B. The crusty old captain, respond.
Add to this scenario the fact that vortex wake spacing minima are the same in any wind condition, it shouldn't be beyond the wit of any pilot flying into any busy international airfield to deduce that, although the surface wind ''isn't particularly strong,'' it does influence the landing rate and consequent delays, particularly if no flow restrictions are in place.
So, although the surface wind is a mere 16 kts and ''not that strong'' it does in fact reduce the landing rate significantly.
I am tired of crusty old Captains, mainly of a certain mainline airline, aggressively questioning the nature of the delay on a Sunday morning.
When confronted with the reply that it was due to wind (for brevity due to workload), the general ignorant response was that it ''wasn't that strong'', with the aggravating implication that it must be the fault of ATC.
So for the ignorant - the rocket science reply:
The wind at 3A was westerly at >65kt whereas, at surface level, it was 265/16. Groundspeeds of individual aircraft, supposedly flying at 160kts, were generally in the order of 112 KT at 10DME, increasing to around 130KT at 6 DME and as high as 145 KT at around 300ft.
We were positioning aircraft the minimum 2.5 miles apart at around 12DME only to see, due to the wind gradient, the preceding aircraft pull away and, by touchdown, gain almost a mile on the succeeding aircraft.
The result - a lower than scheduled for landing rate of around 34 movements per hour.
The solution - place aircraft an illegal 1.5 miles apart at 12 DME and see how
A. The CAA SRG and
B. The crusty old captain, respond.
Add to this scenario the fact that vortex wake spacing minima are the same in any wind condition, it shouldn't be beyond the wit of any pilot flying into any busy international airfield to deduce that, although the surface wind ''isn't particularly strong,'' it does influence the landing rate and consequent delays, particularly if no flow restrictions are in place.
So, although the surface wind is a mere 16 kts and ''not that strong'' it does in fact reduce the landing rate significantly.
Join Date: Jul 2001
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Whilst it is frustrating getting questions from the crews, why do you seem so cross? Did you mention it's due to the strong wind at 3000 feet? In days gone by when I worked approach (another bat time another bat channel) we would have included that type of thing on the ATIS to reduce discussions over the air...
Whilst I appreciate the difficulty associated with strong winds on long final as opposed to short final, this circumstance does sound like a perfect case for mixed ops on both runways... Would that up the rate?
Whilst I appreciate the difficulty associated with strong winds on long final as opposed to short final, this circumstance does sound like a perfect case for mixed ops on both runways... Would that up the rate?
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Got to be worth looking at. Going back to before runway 2, EGCC frequently did high 50s, given reasonable headwinds and VMC. Not bad considering the taxi-way structure and links available at the time. I appreciate EGLL may have tighter noise constraints, but do they not date from the days of B707s and DC8s?
Just out of curiosity what is the declared runway capacity at EGLL these days, assuming everything is serviceable?
Just out of curiosity what is the declared runway capacity at EGLL these days, assuming everything is serviceable?
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Yes, but the Government wouldn't allow it...
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Dual runway trial finishes Feb 29. Can be used when a/c face a 10 minute wait to land or take-off and if 30% of all flights are delayed by more than 15 minutes. ["travel weekly"]
I'm puzzled by the explanation given that if aircraft are passing DME 12 at 2.5 nm intervals at 112 kts GS there can only be 34 landings an hour.
If one divides 112 by 2.5 nm then that is 44.8 aircraft an hour passing 12 DME. As they descend and their GS increases then at 300', and 145 kts, there will still be 44.8 aircraft an hour passing that point - however their spacing will have increased to 3.2 nm. (145/44.8).
In still air with aircraft passing 12 DME with a GS of 160 kts and the same 2.5 nm spacing that would be 64 aircraft an hour so clearly the strong wind does reduce capacity - I just don't know where 34 came from.
What don't I understand?
If one divides 112 by 2.5 nm then that is 44.8 aircraft an hour passing 12 DME. As they descend and their GS increases then at 300', and 145 kts, there will still be 44.8 aircraft an hour passing that point - however their spacing will have increased to 3.2 nm. (145/44.8).
In still air with aircraft passing 12 DME with a GS of 160 kts and the same 2.5 nm spacing that would be 64 aircraft an hour so clearly the strong wind does reduce capacity - I just don't know where 34 came from.
What don't I understand?
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Throw a few Heavy aircraft into the mix (and Heathrow gets a lot!), where the minimum spacing behind them is AT LEAST 4nm, you will soon get to that figure. They don't all fly 2.5nm apart.
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A quick back-of-a-fag-pack calculation, using a ratio of 65:35 M:H (I seem to recall LL was the reverse of Hong Kong) shows that almost 23% of pairs would need 5nm for wake turb, over 12% need 4nm and the rest can be 2.5.
That then works out at 34.4 per hour.
The numbers don't lie. Trust your times, as the old Flows used to say.
That then works out at 34.4 per hour.
The numbers don't lie. Trust your times, as the old Flows used to say.
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According to
Heathrow noise: Operational trial
the four triggers are :
Trigger 1: “The anticipated arrival delay or departure delay is 10 minutes or more”
Trigger 2: “The headwind component on approach to Heathrow is forecast to be greater than 20 knots at 3000ft”
Trigger 3: “The arrival or departure flight schedule is anticipated to run later than 30 minutes or 30% of flights are running outside of the 15 minutes punctuality target”
Trigger 4: “Following a period of disruption to recover the operation such as snow”
although the daily reports at heathrowtrial.com show a fair amount of TEAM (under current conditions - whatever they are) in addition to the TEAM allowed by the operational freedom triggers.
After this lot of trials (four months), there is supposed to be a second trial in the summer (including the Olympics period) which may have similar or different triggers.
It may be that they'll give a few more dual take-offs using 09L/09R then as well.
Heathrow noise: Operational trial
the four triggers are :
Trigger 1: “The anticipated arrival delay or departure delay is 10 minutes or more”
Trigger 2: “The headwind component on approach to Heathrow is forecast to be greater than 20 knots at 3000ft”
Trigger 3: “The arrival or departure flight schedule is anticipated to run later than 30 minutes or 30% of flights are running outside of the 15 minutes punctuality target”
Trigger 4: “Following a period of disruption to recover the operation such as snow”
although the daily reports at heathrowtrial.com show a fair amount of TEAM (under current conditions - whatever they are) in addition to the TEAM allowed by the operational freedom triggers.
After this lot of trials (four months), there is supposed to be a second trial in the summer (including the Olympics period) which may have similar or different triggers.
It may be that they'll give a few more dual take-offs using 09L/09R then as well.
the four triggers are :
Trigger 1: “The anticipated arrival delay or departure delay is 10 minutes or more”
Trigger 2: “The headwind component on approach to Heathrow is forecast to be greater than 20 knots at 3000ft”
Trigger 3: “The arrival or departure flight schedule is anticipated to run later than 30 minutes or 30% of flights are running outside of the 15 minutes punctuality target”
Trigger 4: “Following a period of disruption to recover the operation such as snow”
although the daily reports at heathrowtrial.com show a fair amount of TEAM (under current conditions - whatever they are) in addition to the TEAM allowed by the operational freedom triggers.
Trigger 1: “The anticipated arrival delay or departure delay is 10 minutes or more”
Trigger 2: “The headwind component on approach to Heathrow is forecast to be greater than 20 knots at 3000ft”
Trigger 3: “The arrival or departure flight schedule is anticipated to run later than 30 minutes or 30% of flights are running outside of the 15 minutes punctuality target”
Trigger 4: “Following a period of disruption to recover the operation such as snow”
although the daily reports at heathrowtrial.com show a fair amount of TEAM (under current conditions - whatever they are) in addition to the TEAM allowed by the operational freedom triggers.
TEAM (under Operational Freedoms criteria) is the same concept, but activated instead by one of the 4 triggers listed by the OP, although of course the two sets of criteria aren't mutually exclusive.
So if you see arrivals on both runways after 0700, it could be either "old" TEAM or "new" TEAM depending on the extent of actual or anticipated delays, and how severe "severe" is, although common sense would suggest that the whole point of deploying Operational Freedoms is to prevent delays reaching the "severe" level that would have triggered "old" TEAM.
Simple, innit ?
