A380 upsets A380
My apologies if it's simplistic, but could you point out why it's flawed?
Both flights departed from the same airport, close together, heading in identical directions (diverging very late in the flight). If wake turbulence falls over time (as I understand it does), having the trailing aircraft at a higher flight level should prevent the trailing aircraft being upset by the wake turbulence of the lower, leading aircraft (unless, of course, the second aircraft overtakes the first). Where is the logical fallacy? Genuine question.
Both flights departed from the same airport, close together, heading in identical directions (diverging very late in the flight). If wake turbulence falls over time (as I understand it does), having the trailing aircraft at a higher flight level should prevent the trailing aircraft being upset by the wake turbulence of the lower, leading aircraft (unless, of course, the second aircraft overtakes the first). Where is the logical fallacy? Genuine question.
....not very simple at all.Different types have different cruising speeds, significantly different in some cases, with very little ability to vary the speed greatly from the optimum (especially at altitude).
Same types can be at significantly different weights which means different optimum crusing altitudes, cruise off optimum level and your fuel consumption goes up, sometimes significantly...
Different levels (altitudes) can mean significantly different winds - which effects speed over the ground. You can be sat in a 50 knot tailwind, 2000 Feet below you traffic could have no tailwind at all......
The result of the above is it’s not a simple case of ATC putting the higher aircraft at the back end of the line and expecting it to stay there.
If you take a look at the Organised North Atlantic Track system where there is 1000 foot vertical separation on each track there is a mix of aircraft at different levels and different speeds ..some days you are overtaking other above/below traffic, other days you are being overtaken. The published defence against wake vortex there is to consider offseting one or two miles right of track, dependent on the threat- The aim is to try not to downwind of the aircraft ahead and above you, and you often have to talk to the other traffic on an air to air frequency to coordinate your offsets.
Hope that helps.
Last edited by wiggy; 15th Jun 2018 at 06:17.
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The 380 does appear to have interesting wake characteristics though. Despite the benign sounding event here, I understand that one large EU Boeing operator is looking closely at the number of ASR's generated by upset's in trail of 380's - a recent example being an uncommanded roll left of 42deg followed by a sizable right roll with tens of miles of separation at 1000' below. The startle effect during cruise should not be underestimated.
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There wasn't even any hand-flying, according to the Qantas chief pilot: https://www.nzherald.co.nz/business/...ectid=12071673
But in fairness to any pax who really were upset, negative g can have a very discombobulating effect on some people (like myself). And then, the real beat-ups are in the Murdoch press (= Fox News).
But in fairness to any pax who really were upset, negative g can have a very discombobulating effect on some people (like myself). And then, the real beat-ups are in the Murdoch press (= Fox News).
My apologies if it's simplistic, but could you point out why it's flawed?
Both flights departed from the same airport, close together, heading in identical directions (diverging very late in the flight). If wake turbulence falls over time (as I understand it does), having the trailing aircraft at a higher flight level should prevent the trailing aircraft being upset by the wake turbulence of the lower, leading aircraft (unless, of course, the second aircraft overtakes the first). Where is the logical fallacy? Genuine question.
Both flights departed from the same airport, close together, heading in identical directions (diverging very late in the flight). If wake turbulence falls over time (as I understand it does), having the trailing aircraft at a higher flight level should prevent the trailing aircraft being upset by the wake turbulence of the lower, leading aircraft (unless, of course, the second aircraft overtakes the first). Where is the logical fallacy? Genuine question.
First issue you would have to take into account is getting the 2nd aircraft above the second early on in the flight and then continually reverse step climbing them all the way to their final cruise level. With 2 aircraft this could have a moderate impact on workload.. but scheduling often has 5 or 6 jets departing LA for Oz, or departing SY for the USA in succession. The workload required in order to stack 6 aircraft in the opposite order to which they depart would be too much.
Then you have to take into account weight vs available level. An A380 loaded for 15 hours won’t be able to accept much higher than 30,000 ft initially.. so if #6 is that aircraft then 5 gets 29,000, 4 gets 28,000, 3 gets 27,000.. etc. The first few to depart get penalised heavily, have to mix it with turboprops.. and probably won’t make it across the pacific because of the extra fuel burn at lower levels. Then you have the issue as someone else has mentioned of possibly doing all this work then the last one gets to the highest level, hits some natural turbulence and needs to descend.. so you have to push every back down.
The logical way to run this is get #1 as high as they can go, if #2 is too close behind to get the same level they get one below, #1 will take higher once they can, then in turn you can keep climbing #2 and so on..
If the first one hits turbulence at a level it’s easier to return him to where it was smooth.
To put it into perspective, in a TMA we can legally have an A380 following another A380 in the climb 3miles behind. An A330 behind an A380 needs 6miles, a single engine light and you need 8 miles.. these were 2 supers with 20 miles between them.. 6 and a half times further away then you can legally put them at the same level. Having a wake turbulence issue with this kid of spacing is not the norm.. it’s a rare occurrence caused by the perfect weather/atmospheric conditions. You can’t run impractical, workload heavy, penalising procedures to safeguard against something that may happen 1 in a thousand flights.. we put them as close as we can legally and safely to get everyone where they are going as quickly as possible.. if it happens that on the odd chance you’re copping wake turbulence from the aircraft 20 miles ahead and above then the pilot will let ATC know (as they did), they’ll be cleared to deviate a little to the right or change level, and it will all be over in 20 seconds.
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Slightly more understandable if you’re comparing, or discussing different airlines.
However, this incident was the result of; two aircraft from the same carrier (Qantas), departing the same airport (LAX), with (in effect) the same destination (Australia), at very similar departure times for whatever the reason.
Flight Planning and weather/wind forecasting has developed significantly, so much so that it should be possible to accurately predict, based on the actual time of departure, where company aircraft MAY ‘share the same airspace’..that is, cross paths or remain in trail for a period, within +/- 2000 feet. Unfortunately, regardless of aircraft and flight planning capability, two A380 cannot occupy the same space. That 'space' is not limited to the dimensions of the aircraft..
It has been well established that the adverse effects of wake turbulence linger for some time (i.e. minutes), usually sink over time, and can shift due to proximate winds, in this case upper level winds. A380 at close to maximum weight, such as a Qantas aircraft departing LAX for Australia (i.e. Melbourne, Sydney, Brisbane etc.), would create dangerous levels of turbulence. Further, the aircraft in question, during cruise and/or cruise climb are traveling at a speed which results in significant distance across the ground in the same time period (i.e. at 450 knots, 7.5 nm per minute, x 3 mins for 22.5 NM). This would suggest a ‘gap’ of minutes, concurrent to the 'minimum altitude separation' may not be that smart..
In addition, TCAS should assist to maintain SA regarding the proximity of other aircraft, and direct LOS communications could be used to manage the flight path and any possible conflicts.
Sheer luck that no passengers or cabin crew were injured in this incident..
However, this incident was the result of; two aircraft from the same carrier (Qantas), departing the same airport (LAX), with (in effect) the same destination (Australia), at very similar departure times for whatever the reason.
Flight Planning and weather/wind forecasting has developed significantly, so much so that it should be possible to accurately predict, based on the actual time of departure, where company aircraft MAY ‘share the same airspace’..that is, cross paths or remain in trail for a period, within +/- 2000 feet. Unfortunately, regardless of aircraft and flight planning capability, two A380 cannot occupy the same space. That 'space' is not limited to the dimensions of the aircraft..
It has been well established that the adverse effects of wake turbulence linger for some time (i.e. minutes), usually sink over time, and can shift due to proximate winds, in this case upper level winds. A380 at close to maximum weight, such as a Qantas aircraft departing LAX for Australia (i.e. Melbourne, Sydney, Brisbane etc.), would create dangerous levels of turbulence. Further, the aircraft in question, during cruise and/or cruise climb are traveling at a speed which results in significant distance across the ground in the same time period (i.e. at 450 knots, 7.5 nm per minute, x 3 mins for 22.5 NM). This would suggest a ‘gap’ of minutes, concurrent to the 'minimum altitude separation' may not be that smart..
In addition, TCAS should assist to maintain SA regarding the proximity of other aircraft, and direct LOS communications could be used to manage the flight path and any possible conflicts.
Sheer luck that no passengers or cabin crew were injured in this incident..
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It get's even more complicated in the Middle East, where most of these 380s operate. Departures from DXB, AUH and DOH are immediately affected, heading eastbound, by long haul traffic overflying these units and heading into VABB airspace. That means that there are few, decent levels available for these departures during busy spells because of oceanic separation standards applied in VABB and the fact that the overflyers often have priority for the levels unless serious economic penalties are incurred (how do you sort that out in chaotic traffic?).
In the Gulf, where most of these behemoths operate, we've found that more and more of our R/T time is spent answering queries about aircraft types flying above smaller aircraft. There are significantly more off sets given to such aircraft to avoid wake turbulence and often, we'll see aircraft inbound from oceanic airspace taking an unapproved offset to ensure they stay away from unwanted bumps from planes they can see on TCAS and they're unaware of aircraft type. It seems that newer types can use mode S to improve situational awareness, which may help in sorting some of these issues out because we can't always give advisories to affected aircraft due to the heavy volumes of traffic we get here. We still routinely have 25-30 aircraft on a sector frequency which only gives us enough time to do the basic stuff. Good luck.
In the Gulf, where most of these behemoths operate, we've found that more and more of our R/T time is spent answering queries about aircraft types flying above smaller aircraft. There are significantly more off sets given to such aircraft to avoid wake turbulence and often, we'll see aircraft inbound from oceanic airspace taking an unapproved offset to ensure they stay away from unwanted bumps from planes they can see on TCAS and they're unaware of aircraft type. It seems that newer types can use mode S to improve situational awareness, which may help in sorting some of these issues out because we can't always give advisories to affected aircraft due to the heavy volumes of traffic we get here. We still routinely have 25-30 aircraft on a sector frequency which only gives us enough time to do the basic stuff. Good luck.
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For any journalists reading this thread but whom might be completely flummoxed about how to cover this death defying terror in the skies story... here's a very useful resource for you:
The Lazy Journalists Plane Story Generator
The Lazy Journalists Plane Story Generator
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Not much mention of OFFSET,in this thread! Thought that was why the button was there.
Im often a little surprised about crews who sit exactly underneath other crews,for quite long periods,in the cruise.
Whilst it is a fact that,as in Hertford,Hereford & Hampshire,hurricanes hardly do happen...I wouldn't want a depressurised aircraft bowling down on me!
Call me a pessimist!
Im often a little surprised about crews who sit exactly underneath other crews,for quite long periods,in the cruise.
Whilst it is a fact that,as in Hertford,Hereford & Hampshire,hurricanes hardly do happen...I wouldn't want a depressurised aircraft bowling down on me!
Call me a pessimist!
Not much mention of OFFSET,in this thread! Thought that was why the button was there.
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Not simple at all. You may not understand that aircraft type and weight play a role in what initial altitude an aircraft can climb to and sometimes the preferred level is not available due other traffic.
........Hundreds of horrified travelers held hands *believing they were about to die as the aircraft suddenly dropped over the Pacific Ocean on Sunday.
...........
QF94 passenger Janelle Wilson told The Australian the “three-quarters-full” plane suddenly entered a “free fall nosedive … a direct decline towards the ocean” for about 10 seconds.
...........
QF94 passenger Janelle Wilson told The Australian the “three-quarters-full” plane suddenly entered a “free fall nosedive … a direct decline towards the ocean” for about 10 seconds.
...........
The total lack of awareness and understanding of the average passenger never ceases to amaze me. I recently watched a succession of apparently functional human beings fail to work out how to open the toilet door, despite fiddling with ash tray for ages. Some came back repeatedly for increasingly urgent fiddles with the the ash tray. I guess they were checking all the other ash trays on all the other toilets too. Others cheerfully get up and open overhead lockers as soon as the wheels hit the ground.
So we should not be too surprised by bizarre comments such as this.
But I often wonder when everyone smiles and nods when given the safety brief in the emergency exit row, thank God there is no ash-tay on that door.
Thread Starter
One thing I have noticed on the NATS. A380’s overtaking slower traffic above do not properly offset as the pass the lower traffic. If you are above another flight and overtaking it you are expected to change your offset so you don’t match lower traffic. In practice A380’s don’t do it often if at all.
Thank you to those who explained why my simplistic concept isn't simple to implement - particularly whysprSYD.
I had also expressed myself poorly, instead of calling it a "default" position, it should have been "starting point" as I realise the trailing aircraft may overtake the aircraft that departed earlier. In such a case I expect lateral separation would be used to effect the overtake, and then the vertical positions rearranged, but I see that is not so easy.
In any case, while sharing the frustration about pathetic reporting (I am a yachtsman and they can't get anything right reporting about that either), I think wake turbulence is a danger to aircraft and causes significant discomfort (and fear) to passengers, so should be addressed as comprehensively as possible to reduce incidences as much as possible. I have experienced it, but had seen the other plane and knew it was a possibility - it was still a surprise as to how "sharp-edged" the effect was (a sudden bump and lurch, not a gentle yaw/roll) - very disconcerting).
I had also expressed myself poorly, instead of calling it a "default" position, it should have been "starting point" as I realise the trailing aircraft may overtake the aircraft that departed earlier. In such a case I expect lateral separation would be used to effect the overtake, and then the vertical positions rearranged, but I see that is not so easy.
In any case, while sharing the frustration about pathetic reporting (I am a yachtsman and they can't get anything right reporting about that either), I think wake turbulence is a danger to aircraft and causes significant discomfort (and fear) to passengers, so should be addressed as comprehensively as possible to reduce incidences as much as possible. I have experienced it, but had seen the other plane and knew it was a possibility - it was still a surprise as to how "sharp-edged" the effect was (a sudden bump and lurch, not a gentle yaw/roll) - very disconcerting).
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Not much mention of OFFSET,in this thread! Thought that was why the button was there.
Im often a little surprised about crews who sit exactly underneath other crews,for quite long periods,in the cruise.
Whilst it is a fact that,as in Hertford,Hereford & Hampshire,hurricanes hardly do happen...I wouldn't want a depressurised aircraft bowling down on me!
Call me a pessimist!
Im often a little surprised about crews who sit exactly underneath other crews,for quite long periods,in the cruise.
Whilst it is a fact that,as in Hertford,Hereford & Hampshire,hurricanes hardly do happen...I wouldn't want a depressurised aircraft bowling down on me!
Call me a pessimist!
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Wakey wakey
It get's even more complicated in the Middle East, where most of these 380s operate. Departures from DXB, AUH and DOH are immediately affected, heading eastbound, by long haul traffic overflying these units and heading into VABB airspace. That means that there are few, decent levels available for these departures during busy spells because of oceanic separation standards applied in VABB and the fact that the overflyers often have priority for the levels unless serious economic penalties are incurred (how do you sort that out in chaotic traffic?).
In the Gulf, where most of these behemoths operate, we've found that more and more of our R/T time is spent answering queries about aircraft types flying above smaller aircraft. There are significantly more off sets given to such aircraft to avoid wake turbulence and often, we'll see aircraft inbound from oceanic airspace taking an unapproved offset to ensure they stay away from unwanted bumps from planes they can see on TCAS and they're unaware of aircraft type. It seems that newer types can use mode S to improve situational awareness, which may help in sorting some of these issues out because we can't always give advisories to affected aircraft due to the heavy volumes of traffic we get here. We still routinely have 25-30 aircraft on a sector frequency which only gives us enough time to do the basic stuff. Good luck.
In the Gulf, where most of these behemoths operate, we've found that more and more of our R/T time is spent answering queries about aircraft types flying above smaller aircraft. There are significantly more off sets given to such aircraft to avoid wake turbulence and often, we'll see aircraft inbound from oceanic airspace taking an unapproved offset to ensure they stay away from unwanted bumps from planes they can see on TCAS and they're unaware of aircraft type. It seems that newer types can use mode S to improve situational awareness, which may help in sorting some of these issues out because we can't always give advisories to affected aircraft due to the heavy volumes of traffic we get here. We still routinely have 25-30 aircraft on a sector frequency which only gives us enough time to do the basic stuff. Good luck.
It’s become SOP now to offset and query ATC , we know you’re busy but with no Mode S in our aircraft and winds favourable for likely turbulence , no one wants to take a chance.
What could be done IMHO is ATC should be given upper air wind data so that they get a better SA of likely wake turbulence for aircraft 1000 feet below, maybe they already have that 👍
I’m sure most here are aware but the German challenger accident due EK 380 wake in Jan2017 makes for a sobering read.
https://www.flightglobal.com/news/ar...on-rou-437303/
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It sounds as though what's needed is a standard procedure for ATC to include a recommended offset due to other traffic when assigning route/height. I don't know if that would result in a greater or smaller workload; more up-front but if it results in less requests later then it might be easier.