Wind Check on final
Reminds me of landing 10kg over weight in an aircraft with digital fuel gauges. Put analogue gauges in and you can't discern the fuel reading to that precision and don't worry about it.
I was under the impression that for performance calculations tailwinds were factored by 150%.
So if you've planned for a 10 kt reported tailwind the computed data assumes a 15 kt tailwind.
So if you've planned for a 10 kt reported tailwind the computed data assumes a 15 kt tailwind.
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I was under the impression that for performance calculations tailwinds were factored by 150%.
That is very much my point. The performance people use 150% for LDR calculations. That is one thing. The other is the AFM says tailwind limit is 10kts. One is a limit, the other is a buffer included in LDR calculations. The crew on the day are not allowed to use that buffer. They have to use AFM. That is my point: it is an overly restrictive limitation that needs reviewing.
That is very much my point. The performance people use 150% for LDR calculations. That is one thing. The other is the AFM says tailwind limit is 10kts. One is a limit, the other is a buffer included in LDR calculations. The crew on the day are not allowed to use that buffer. They have to use AFM. That is my point: it is an overly restrictive limitation that needs reviewing.
Last edited by RAT 5; 18th Oct 2015 at 19:18.
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The point is I've been in this scenario and diverted. I did not have time to think of all the options, but was driven by 'limitations' and penalties if I infringed them. Afterwards, with time to think, I wondered at the practical options and where they conflicted with the limitations. Was the diversion really necessary with all the consequences? I came to the conclusion that the performance realities and the performance limitations were not equal and caused decisions to be made not on the best data.
Only half a speed-brake
I was told (and shown some clever reading too) to use ATC reported wind. If in doubt, ask for update. Now this is in an area, where the ATC reading can be trusted.
On any runway I operate, we get have 60% more distance comapred to what is required with max braking effort. As mentioned elsewhere, the FMGS reading has a delay of about 4 seconds on the type flown. I would not worry much about 4 more extra knot of tailwind, or 7 (*).
Example:
In the morning the Vapp was 140 kt + 13 tail wind + some temp / compressibility effect: GS = 158 @ 65 tonnes. This is kinetic energy 405,7 MJ, all perfectly by the book as per AFM appendix. Now in the afternoon, sister ship with same brakes comes in, but only limited to AFM -10 kt tail, at 54 tonnes. Vapp 128 kt + 13 tail + TAS effect = GS 146 Kinetic energy = 288 MJ. And this is illegal.
(*) DO NOT FOUL UP THE LANDING!!! Good touchdown needs to be in TDZ, and if on the far edge, max braking is prudent immediately to retain at least some margin from those 60% initially planned. Little Rock, Toronto, Jamaica, Lyon and others did not happen for tailwind, but for touching too deep.
Calculating LDG performance for every landing, adding 15% margin on top of the figures will not prevent an overrun. Going around if ground contact not positively achieved in the TDZ would! (**)
regards,
FD.
(**) that why we never practice this in SIM, do we?
On any runway I operate, we get have 60% more distance comapred to what is required with max braking effort. As mentioned elsewhere, the FMGS reading has a delay of about 4 seconds on the type flown. I would not worry much about 4 more extra knot of tailwind, or 7 (*).
Example:
In the morning the Vapp was 140 kt + 13 tail wind + some temp / compressibility effect: GS = 158 @ 65 tonnes. This is kinetic energy 405,7 MJ, all perfectly by the book as per AFM appendix. Now in the afternoon, sister ship with same brakes comes in, but only limited to AFM -10 kt tail, at 54 tonnes. Vapp 128 kt + 13 tail + TAS effect = GS 146 Kinetic energy = 288 MJ. And this is illegal.
(*) DO NOT FOUL UP THE LANDING!!! Good touchdown needs to be in TDZ, and if on the far edge, max braking is prudent immediately to retain at least some margin from those 60% initially planned. Little Rock, Toronto, Jamaica, Lyon and others did not happen for tailwind, but for touching too deep.
Calculating LDG performance for every landing, adding 15% margin on top of the figures will not prevent an overrun. Going around if ground contact not positively achieved in the TDZ would! (**)
regards,
FD.
(**) that why we never practice this in SIM, do we?
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Calculating LDG performance for every landing, adding 15% margin on top of the figures will not prevent an overrun. Going around if ground contact not positively achieved in the TDZ would! (**)
regards,
FD.
(**) that why we never practice this in SIM, do we?
I'm not sure I understand what you are trying to say, or meaning. Perhaps there is a typo. Would you please clarify. I do agree that the TDZ point, assuming the correct speed, is more relevant then a couple of kts extra tailwind.
regards,
FD.
(**) that why we never practice this in SIM, do we?
I'm not sure I understand what you are trying to say, or meaning. Perhaps there is a typo. Would you please clarify. I do agree that the TDZ point, assuming the correct speed, is more relevant then a couple of kts extra tailwind.
Several posts imply that because there are safety margins (factors) then these can be ‘used’ before the event. The margins in the pre landing calculation provide an acceptable level of safety; a small additional tailwind beyond that planed will reduce the level of safety, but by how much may not be known.
A crew can elect to accept the increased risk but must be prepared to justify it if there were to be an incident, i.e. justify the risk to yourself before deciding.
Such a decision requires a good understanding of the components and origin of the risk. In the calculation of landing distance the relevancies are difficult to establish because there are many unknowns, inaccuracies, and assumptions. Check the small print in the book values of landing distance; what is assumed in the calculation, what is the reference manual.
RAT makes a good point re AFM limits vs advisory landing data. If you have an incident after deviating from the AFM without good justification, then you are answerable in civil law – including manslaughter.
Deviation from advice could similarly escalate, but hopefully nothing more than a chat with the chief pilot because your justification should have greater validity - economics and passenger comfort are never justifiable after an incident.
FMS wind is historical, it only represents conditions where you have been (often averaging higher altitudes and greater distances); airfield wind is where you are going, or somewhere close, but this is not without error.
The approved safety margin maintains a suitable level of safety for normal daily operational variability (try listing the factors in this), but this margin is insufficient to accommodate simultaneous limiting deviations and must not be planned to be used.
An increasing tailwind is a high risk category as this can interact with several factors; a tendency to stretch the flare distance, a slower reduction in airspeed, a different visual perception, and probably unfamiliarity with landings in the higher wind values; and also remember that the energy to be reduced is proportional to ground speed squared.
https://www.scribd.com/doc/285864189...ind-Operations
http://www.nlr-atsi.nl/downloads/som...f-tailwind.pdf
http://www.nlr-atsi.nl/downloads/run...-of-runway.pdf
A crew can elect to accept the increased risk but must be prepared to justify it if there were to be an incident, i.e. justify the risk to yourself before deciding.
Such a decision requires a good understanding of the components and origin of the risk. In the calculation of landing distance the relevancies are difficult to establish because there are many unknowns, inaccuracies, and assumptions. Check the small print in the book values of landing distance; what is assumed in the calculation, what is the reference manual.
RAT makes a good point re AFM limits vs advisory landing data. If you have an incident after deviating from the AFM without good justification, then you are answerable in civil law – including manslaughter.
Deviation from advice could similarly escalate, but hopefully nothing more than a chat with the chief pilot because your justification should have greater validity - economics and passenger comfort are never justifiable after an incident.
FMS wind is historical, it only represents conditions where you have been (often averaging higher altitudes and greater distances); airfield wind is where you are going, or somewhere close, but this is not without error.
The approved safety margin maintains a suitable level of safety for normal daily operational variability (try listing the factors in this), but this margin is insufficient to accommodate simultaneous limiting deviations and must not be planned to be used.
An increasing tailwind is a high risk category as this can interact with several factors; a tendency to stretch the flare distance, a slower reduction in airspeed, a different visual perception, and probably unfamiliarity with landings in the higher wind values; and also remember that the energy to be reduced is proportional to ground speed squared.
https://www.scribd.com/doc/285864189...ind-Operations
http://www.nlr-atsi.nl/downloads/som...f-tailwind.pdf
http://www.nlr-atsi.nl/downloads/run...-of-runway.pdf
Only half a speed-brake
I mean to say that to avoid RWY excursions all we need to do is go missed when touchdown is too far. And for this, a little sim excercise would be nice; just like we do with (no)visual contact at DH. Because classroom knowledge will not be enough at that moment once we will find ourselves for the first time on a far side of an high energy touchdown. A time-honored drill of discontinuing a long landing could make a lot of difference.
B: The in-flight calculations are nice, but apart from consumig valuable (thinking of 4 sectors MUC-AMS with deice and no APU) time, especially when needing to use side mounted EFB, they will not prevent anything. What you find is that the LDA < LDR, that's all. Like I said, a rant.
take care, FD.
Several posts imply that because there are safety margins (factors) then these can be ‘used’ before the event.
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Originally Posted by safetypee
A crew can elect to accept the increased risk but must be prepared to justify it if there were to be an incident.
Let's assume that I would have landed with a tower reported tailwind of 12 kts on this 3305m long rwy 25 (with ILS). There's no doubt in my mind that landing was the best and safest option. Still I elected to go around to come back for the VOR 07 approach. Sure, when needed, a go around is nothing dangerous, but going around unnecessarily, will scare the pax, submit the engines to an extra high temperature peak, burn 400 kg of reserve fuel, give extra workload to crew and atc and might delay other traffic. In the situation in Rhodos I described doing all this added nothing to safety! The contrary is true!
So then why did I go around? Well, I can imagine the twr controller writing a report that I landed with a 12 kts tailwind or a kid taping the conversations with twr, filming the landing and putting it on Youtube.
I regret that is has come to a point where decisions are not always being made in the best interest of safety, but just to make sure nobody can sue or fire you.
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Sabenaboy: I empathise with you and agree with your concerns. I doubt ATC can do anything because they do to know the limitations of the a/c. A sly sneaky F/O is another matter. Now imagine if you'd screwed up the NPA and had an incident. The AAIB/NTSB etc might investigate and ask, "why did they G.A. and not land ILS RW25?" You just can not win.
So let's go further: the cloud base is between ILS & NPA minima, perhaps and/or the visibility too. You decided to GA due to the ILS tailwind being 3kts >10. There is then an effective approach ban onto the NPA. You hold for 30 mins and the wind increases and the approach ban remains. You divert to another Greek island in the middle of the night. Imagine the chaos and cost caused. Eventually you return to mission control and are summoned to CP's office after he has read your report of GA + Diversion. Would you expect a pat on the back? If you had landed on ILS, and somehow a rumour reached the ears of said CP, would you expect to hear anything further?
Damned if you do, damned if you don't. 1000' on finals, as ATC give landing clearance with wind, is not the time to go into a long winded CRM committee meeting. It's also not a time to continue with lingering doubts swimming around your brain when you should be concentrating on what's in front of you. It is a moment for clear reasoned judgement and decision making. And there-in lies the rub; hence this discussion. Being a commander and knowing what is the best and safest thing to do, but having a written limitation with a new shiny know it all 'advocating their opionion' RHS jockey.
I always thought that the job of a commander was to do what was best & safest for their pax and the operation. There were the days when 'rules were for the obedience of......... and the guidance of wise men.' Shame that was abused and the book of limitations became thicker.
Sometimes the Mediterranean ATC's were not too bad and could be useful; if you knew the rules. I once was arriving at MXP. CAT 3 was out and the RVR was 550m. Passing FL100 we checked again and they asked what we needed. "600m". Passing IAF for the ILS we were given the wind, landing clearance and 600m. After that everyone kept quiet. It had been a long night over the N.Atlantic and we were very grateful. Perhaps it was true, perhaps not. I didn't ask.The difference is, could I have landed if they had reported 500m? No. Would I have landed with 13kts tailwind & 600m..................
Trouble with these topics is in the bar, for a social chat, there will be many diverse opinions from the old and new pilots, the thinkers and the rule abiders. Ask the XAA's for an official answer and there be only the rule book with no discretion. Sometimes it's a cruel world we have to tolerate, but I understand the reasoning. There will be too many guys who 'give them a yard and they'll take a mile.' Sad but true, and so the discretion has to be removed. However, the wroth of the CP & the pax might be for real.
Anyway it's been a fun chat and I'm glad I am no longer in the discretion-less no thinking allowed LHS. It is a shame that aspects of our job as commanders has fallen into that of a 'jobs worth'. Sadly, in the case of a 13t tailwind, and if the CP did want to see the back of you, if might become just that....'jobs worth'.
So let's go further: the cloud base is between ILS & NPA minima, perhaps and/or the visibility too. You decided to GA due to the ILS tailwind being 3kts >10. There is then an effective approach ban onto the NPA. You hold for 30 mins and the wind increases and the approach ban remains. You divert to another Greek island in the middle of the night. Imagine the chaos and cost caused. Eventually you return to mission control and are summoned to CP's office after he has read your report of GA + Diversion. Would you expect a pat on the back? If you had landed on ILS, and somehow a rumour reached the ears of said CP, would you expect to hear anything further?
Damned if you do, damned if you don't. 1000' on finals, as ATC give landing clearance with wind, is not the time to go into a long winded CRM committee meeting. It's also not a time to continue with lingering doubts swimming around your brain when you should be concentrating on what's in front of you. It is a moment for clear reasoned judgement and decision making. And there-in lies the rub; hence this discussion. Being a commander and knowing what is the best and safest thing to do, but having a written limitation with a new shiny know it all 'advocating their opionion' RHS jockey.
I always thought that the job of a commander was to do what was best & safest for their pax and the operation. There were the days when 'rules were for the obedience of......... and the guidance of wise men.' Shame that was abused and the book of limitations became thicker.
Sometimes the Mediterranean ATC's were not too bad and could be useful; if you knew the rules. I once was arriving at MXP. CAT 3 was out and the RVR was 550m. Passing FL100 we checked again and they asked what we needed. "600m". Passing IAF for the ILS we were given the wind, landing clearance and 600m. After that everyone kept quiet. It had been a long night over the N.Atlantic and we were very grateful. Perhaps it was true, perhaps not. I didn't ask.The difference is, could I have landed if they had reported 500m? No. Would I have landed with 13kts tailwind & 600m..................
Trouble with these topics is in the bar, for a social chat, there will be many diverse opinions from the old and new pilots, the thinkers and the rule abiders. Ask the XAA's for an official answer and there be only the rule book with no discretion. Sometimes it's a cruel world we have to tolerate, but I understand the reasoning. There will be too many guys who 'give them a yard and they'll take a mile.' Sad but true, and so the discretion has to be removed. However, the wroth of the CP & the pax might be for real.
Anyway it's been a fun chat and I'm glad I am no longer in the discretion-less no thinking allowed LHS. It is a shame that aspects of our job as commanders has fallen into that of a 'jobs worth'. Sadly, in the case of a 13t tailwind, and if the CP did want to see the back of you, if might become just that....'jobs worth'.
Last edited by RAT 5; 20th Oct 2015 at 17:06.
There will always be a need for airmanship – judgement, but in modern high-reliability and complex operating environments the opportunity to apply this is reducing. The views of modern operations in previous posts illustrate the reducing margins between the required standard of operation and established safety limits, i.e. there is less room for the human to experiment and develop judgement, yet human judgement is still required in ‘unforeseen’ circumstances.
I detest the constraining legalist approach, encouraged by the layout modern regulations, commercial pressures, and litigious public culture, but this is today’s environment and we have to learn to manage operations within it.
It is important to evaluate the previous example situations over time. Responsibility in making a justifiable decision in operation is not the same as justifying the decision afterwards - being responsible after the fact. Unfortunately not all areas of the industry realise or accept this difference, also as regulations drift towards ‘law’ (EU) there is a tendency to apply legal interpretations to all events opposed to human-system views required to maintain safety.
In addition, modern management style tends to move responsibility downwards leaving the difficult grey areas to the crew to resolve in real time.
Safety defences involve greater constraint via rules or advisory procedures (often interpreted as rules after the event). However, the industry often overlooks the need for everyone (regulator, operator, and crew) to draw their safety boundary, understanding and setting personal standards, - exercising airmanship before the event.
Thus views such as “knowing what is the best and safest thing to do” should not be interpreted as passenger comfort, minimising disruption or maintenance cost, which are often covertly promoted by management before the event, then overridden with “safety first” after an event. These are strategic management problems, not those for the crew to judge on short final.
If a decision and action was safe who cares what others think or say (of course we do), but the experience gained from debriefing (crew or self) knowing that a correct, although not perfect course of action was chosen is invaluable – this is how we learn.
A simplistic view of the required thinking process is like having the ability to join-up the dots in a situation, but this requires the overriding ability (airmanship, expertise) of being able to determine what constitutes a dot in that situation.
The differences in many of the posts can be identified by what is assumed in reaching a decision; assumptions are rooted in knowledge and bias, thus the control of these, and particularly a review of the assumptions beforehand could provide a more balanced view of safety.
Anyway back to reality; the opening scenario (#1) is a question after the event.
During an approach use the reported tower wind. The landing decision at the time should not be based on ‘can officially land’, the decision is yours. Consider if you can land safely bearing in mind the circumstances of the situation; employ airmanship and judgement vs book flying.
… And why are you looking at the FMS on short final opposed to conducting other tasks such as handling and monitoring the aircraft/systems; what are the safety priories, assumptions, knowledge – what are the dots in this situation.
… and before the windshear replies are drafted, consider strategic decision making (thinking ahead), pre landing brief – speed additives or not making the approach at all.
I detest the constraining legalist approach, encouraged by the layout modern regulations, commercial pressures, and litigious public culture, but this is today’s environment and we have to learn to manage operations within it.
It is important to evaluate the previous example situations over time. Responsibility in making a justifiable decision in operation is not the same as justifying the decision afterwards - being responsible after the fact. Unfortunately not all areas of the industry realise or accept this difference, also as regulations drift towards ‘law’ (EU) there is a tendency to apply legal interpretations to all events opposed to human-system views required to maintain safety.
In addition, modern management style tends to move responsibility downwards leaving the difficult grey areas to the crew to resolve in real time.
Safety defences involve greater constraint via rules or advisory procedures (often interpreted as rules after the event). However, the industry often overlooks the need for everyone (regulator, operator, and crew) to draw their safety boundary, understanding and setting personal standards, - exercising airmanship before the event.
Thus views such as “knowing what is the best and safest thing to do” should not be interpreted as passenger comfort, minimising disruption or maintenance cost, which are often covertly promoted by management before the event, then overridden with “safety first” after an event. These are strategic management problems, not those for the crew to judge on short final.
If a decision and action was safe who cares what others think or say (of course we do), but the experience gained from debriefing (crew or self) knowing that a correct, although not perfect course of action was chosen is invaluable – this is how we learn.
A simplistic view of the required thinking process is like having the ability to join-up the dots in a situation, but this requires the overriding ability (airmanship, expertise) of being able to determine what constitutes a dot in that situation.
The differences in many of the posts can be identified by what is assumed in reaching a decision; assumptions are rooted in knowledge and bias, thus the control of these, and particularly a review of the assumptions beforehand could provide a more balanced view of safety.
Anyway back to reality; the opening scenario (#1) is a question after the event.
During an approach use the reported tower wind. The landing decision at the time should not be based on ‘can officially land’, the decision is yours. Consider if you can land safely bearing in mind the circumstances of the situation; employ airmanship and judgement vs book flying.
… And why are you looking at the FMS on short final opposed to conducting other tasks such as handling and monitoring the aircraft/systems; what are the safety priories, assumptions, knowledge – what are the dots in this situation.
… and before the windshear replies are drafted, consider strategic decision making (thinking ahead), pre landing brief – speed additives or not making the approach at all.
