Required landing distance available. Does inflight requirement exist?
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safetypee, I'm afraid its applicable to both FAA and EASA
One needs to immerse into materia in order to comprehend the full picture. It's a whole topic with airbus consisting of a whole ebook. If someone wishes to deepen the knowledge that's the way to go. All I wanna say is OLD is a realistic assessment of the landing performance on particular day, runway, aircraft status and landing method. What's the use of some unrealistic figures on a sunny day in TOU, if you're in the grass covered with snow in MAN? Whereas OLD gives you a good idea of where you'll end on that occasion. It's REALISTIC and that's all it matters. 
In-flight assessment operational rules Current FAA and EASA rules make a generic statement regarding the need to assess landing performance in flight: “The commander must satisfy himself/herself that, according to the information available to him/her, the weather at the aerodrome and the condition of the runway intended to be used should not prevent a safe approach and landing”. No guidance is given on the criteria and factors to be taken into account for the determination of a safe landing distance.
Re ‘… its applicable to both FAA and EASA.’ I disagree.
The latest quoted text appears to be taken from the Airbus ‘Safety First’ magazine (Issue 10).
IMHO this does not represent the general view in Europe, and now that the UK CAA has provided leadership with the concept of equivalent safety (link @ #4), it may be difficult for any European Country, Operator, or Captain to choose otherwise. This is the central aspect of this thread.
Reading the two Airbus articles, it is possible that the chosen interpretation is biased towards an ‘engineering’ view of a future requirement to provide operational data. An engineering view is ideal for certification, which deals with actual landing distances, but the industry’s problem with in-flight landing distance assessment is very much an operational issue involving many aspects such as judgement of a poorly reported or unknown runway condition, the variability of the atmosphere, and ever-present weaknesses in human performance.
The concept of OLD is excellent, but the implementation, as with other aspects of TALPA, requires considerable thought.
Where the definition of OLD involves “… the maximum landing performance realistically achievable by a line pilot adhering to standard techniques”, it questions what standard of piloting performance will be acceptable for the tests, and how might this be repeated in operation. Similarly what are ‘standard techniques’; will operators always follow manufacturers’ SOPs.
Add to this the need to improve the accuracy of reported runway braking action or to measure the runway contaminants in order to determine the required landing distance, then there are opportunities for considerable deviation in the objective of achieving a safe landing.
The overall objective of TALPA is to improve all of these aspects, particularly for FAA operators who may not select the same pre-landing safety margins as in Europe.
It would be difficult to argue that Europe should lower its safety standard just to align with the FAA, particularly when FAR operators appear to have an extremely variable interpretation and application of apparently lower standards (SAFO).
The simplistic merits of OLD reduce the safety margin compared with factored distances; this may be justifiable in engineering terms – the technical aspects of landing distance. However, many if not the majority of the landing safety issues are human – operational issues which requires a considerable safety margin.
The operational issues could be further divided into the soft and hard skills; variability in the hard ones is partly offset by the existing distance factors (1.67, 1.92); “This factor accounts for the normal operational variability that can be expected in day to day service such that the chances of a landing overrun are remote.” (AIC 14/2006)
It is more difficult to quantify a safety margin for the soft skills which include assessment, judgement, and decision making; thus the industry continues its safety efforts with CRM, TEM, and ALAR Tool Kit.
If the industry accepts a safety reduction in one area then how is the safety balance to be maintained? It’s very difficult to change the human, but you can improve the conditions of work. Fully factored landing distances provide additional ‘working space’; safe and realistic.
Thus the need to maintain current safety margins, the landing distance factors, and pre-landing assessment.
Safety First 10 (page 8) http://www.ukfsc.co.uk/files/Safety%...ust%202010.pdf
Safety First 12 (page 5) Safety First 12
AIC 14/2006 Large Transport Aeroplanes - Landing Performance NATS | AIS - Home
The latest quoted text appears to be taken from the Airbus ‘Safety First’ magazine (Issue 10).
IMHO this does not represent the general view in Europe, and now that the UK CAA has provided leadership with the concept of equivalent safety (link @ #4), it may be difficult for any European Country, Operator, or Captain to choose otherwise. This is the central aspect of this thread.
Reading the two Airbus articles, it is possible that the chosen interpretation is biased towards an ‘engineering’ view of a future requirement to provide operational data. An engineering view is ideal for certification, which deals with actual landing distances, but the industry’s problem with in-flight landing distance assessment is very much an operational issue involving many aspects such as judgement of a poorly reported or unknown runway condition, the variability of the atmosphere, and ever-present weaknesses in human performance.
The concept of OLD is excellent, but the implementation, as with other aspects of TALPA, requires considerable thought.
Where the definition of OLD involves “… the maximum landing performance realistically achievable by a line pilot adhering to standard techniques”, it questions what standard of piloting performance will be acceptable for the tests, and how might this be repeated in operation. Similarly what are ‘standard techniques’; will operators always follow manufacturers’ SOPs.
Add to this the need to improve the accuracy of reported runway braking action or to measure the runway contaminants in order to determine the required landing distance, then there are opportunities for considerable deviation in the objective of achieving a safe landing.
The overall objective of TALPA is to improve all of these aspects, particularly for FAA operators who may not select the same pre-landing safety margins as in Europe.
It would be difficult to argue that Europe should lower its safety standard just to align with the FAA, particularly when FAR operators appear to have an extremely variable interpretation and application of apparently lower standards (SAFO).
The simplistic merits of OLD reduce the safety margin compared with factored distances; this may be justifiable in engineering terms – the technical aspects of landing distance. However, many if not the majority of the landing safety issues are human – operational issues which requires a considerable safety margin.
The operational issues could be further divided into the soft and hard skills; variability in the hard ones is partly offset by the existing distance factors (1.67, 1.92); “This factor accounts for the normal operational variability that can be expected in day to day service such that the chances of a landing overrun are remote.” (AIC 14/2006)
It is more difficult to quantify a safety margin for the soft skills which include assessment, judgement, and decision making; thus the industry continues its safety efforts with CRM, TEM, and ALAR Tool Kit.
If the industry accepts a safety reduction in one area then how is the safety balance to be maintained? It’s very difficult to change the human, but you can improve the conditions of work. Fully factored landing distances provide additional ‘working space’; safe and realistic.
Thus the need to maintain current safety margins, the landing distance factors, and pre-landing assessment.
Safety First 10 (page 8) http://www.ukfsc.co.uk/files/Safety%...ust%202010.pdf
Safety First 12 (page 5) Safety First 12
AIC 14/2006 Large Transport Aeroplanes - Landing Performance NATS | AIS - Home
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safetypee, there's numerous explanatory material about landing performance and I don't intent to play a teacher here. However fact is RLD is applicable to dispatch ONLY whereas ALD is for in flight assessment. UK doesn't differ a bit from EU OPS all it says for contaminated RWY at the planning stage RLD is never lower than ALD wet. Application of additional safety margin, typically 15%, is recommended. If you ever used EFB you'd have seen 2 sections for landing performance one is for dispatch stating RLD and the other one for in flight showing ALD and they're shorter by bout 40%. I'll state it again there's NO EU OPS requirement to apply RLD in flight. TALPA rectifies that situation by creating guide line of a realistic ALD assessment thus increasing safety.
9.G, again we appear to be a cross purposes, or at least are intermixing our views.
I may have assumed that it would be self-evident that the use of equivalent safety for contaminated operations would apply equally to normal operations; apologies for the double jump.
Thus why shouldn’t the view promoted by the CAA under the title Operations on Contaminated Runways relate to all normal landing operations?
The CAA’s guidance applies the principles of safety management, which if used more widely could reduce ambiguity in interpreting the need for a pre-landing assessment and the magnitude of the landing distance safety margin.
IMHO this will be a significant benefit to safety in an operational area littered with accidents and close calls.
I have not used an EFB, neither do I know what standard of performance such a system is based on, nor any assumptions in use. However, adding a 15% margin to EU contaminated data (perhaps calculated in a manner envisaged by OLD) is not the same level of safety as 15% added to the AFM actual distance in normal operations.
I agree that the UK guidance does not contradict any rule, but it does provide clarity in the use of RLD (in-flight) as a means of establishing a safe approach (1.450). The wording of EU OPS neither prohibits nor promotes RLD as a possible means of maintaining safety; there are no rules for this, but neither is TALPA a rule making concern.
Based on current understandings:-
For contaminated operations FOLD may not improve safety over existing EU OPS, but in the US there will be benefit (after rule-making). Both EU and US operations are likely to continue with the current elevated level of risk, but the EU mitigates this with infrequent exposure, the US currently does not.
For normal operations, FOLD may simplify the pre-landing assessment in EU OPS; similarly in the US, but until the FAA mandates a pre-landing assessment and the use of FOLD, then their normal operations could be exposed to a higher level of risk than in the EU, and even with FOLD the safety margin may be less than the factored distance.
A regulatory complication is the quest for EASA/FAA harmonization. The EU has cert and ops rules for contaminated and normal operations, but not so in the US (only normal ops). It would be unwise to change the EU requirements to accommodate a new US rule (incorporating OLD) if the resultant safety margins are reduced. Also, noting that the current FAA regulatory hold may be commercially driven.
I may have assumed that it would be self-evident that the use of equivalent safety for contaminated operations would apply equally to normal operations; apologies for the double jump.
Thus why shouldn’t the view promoted by the CAA under the title Operations on Contaminated Runways relate to all normal landing operations?
The CAA’s guidance applies the principles of safety management, which if used more widely could reduce ambiguity in interpreting the need for a pre-landing assessment and the magnitude of the landing distance safety margin.
IMHO this will be a significant benefit to safety in an operational area littered with accidents and close calls.
I have not used an EFB, neither do I know what standard of performance such a system is based on, nor any assumptions in use. However, adding a 15% margin to EU contaminated data (perhaps calculated in a manner envisaged by OLD) is not the same level of safety as 15% added to the AFM actual distance in normal operations.
I agree that the UK guidance does not contradict any rule, but it does provide clarity in the use of RLD (in-flight) as a means of establishing a safe approach (1.450). The wording of EU OPS neither prohibits nor promotes RLD as a possible means of maintaining safety; there are no rules for this, but neither is TALPA a rule making concern.
Based on current understandings:-
For contaminated operations FOLD may not improve safety over existing EU OPS, but in the US there will be benefit (after rule-making). Both EU and US operations are likely to continue with the current elevated level of risk, but the EU mitigates this with infrequent exposure, the US currently does not.
For normal operations, FOLD may simplify the pre-landing assessment in EU OPS; similarly in the US, but until the FAA mandates a pre-landing assessment and the use of FOLD, then their normal operations could be exposed to a higher level of risk than in the EU, and even with FOLD the safety margin may be less than the factored distance.
A regulatory complication is the quest for EASA/FAA harmonization. The EU has cert and ops rules for contaminated and normal operations, but not so in the US (only normal ops). It would be unwise to change the EU requirements to accommodate a new US rule (incorporating OLD) if the resultant safety margins are reduced. Also, noting that the current FAA regulatory hold may be commercially driven.
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legal requirement
The title of this thread is plain and clear to me.
The poster wants to now if such legally binding requirement exists? The answer is NO, there's NO such requirement in the EU OPS. However operator might elect to include such as a requirement in it's relevant documentation. Think logically of it. Why would EASA or FAA bother with TALPA spending time, manpower and money if there was a requirement for RLD in flight? In that case all one needs to do is simply check if RLD is less than LDA and that's it. Why to bother with ALD? In this case we wouldn't be able to complete the landing on quite a number of occasions. RLD is used in the assessment of suitability of airdrome for dispatch purposes at the planning stage and regulator applied their a safety margin for unforeseen circumstances. ALD is relevant after airborne to be able to assess a real landing performance. How else do you wanna know if you'll be able to stop within LDA on a diversion conducting overweight landing for medical emergency with dying pax in the back? Are you not gonna divert coz your RLD isn't equal to LDA but more than ALD? The only problem is, as we're well aware of, it's basically inadequate. To make it somewhat adequate FAA applies 15% margin. However fundamental problem lies with the determination method of ALD. It's nothing but a test pilot landing and doesn't reflect daily business. That's the conclusion, after several overruns, FAA and EASA came to and started to work on a new concept TALPA. Well, nuff of academical BS. I don't disagree with your common sense but regulations are clear. It's also very much a commander's decision regardless of applied margins regs or anything else. If I'm not happy bout the way the situation unfolds it's a no go, no matter what the numbers are saying. Experience sometimes overrules.
Required landing distance available. Does inflight requirement exist?
Last edited by 9.G; 15th Dec 2011 at 21:36. Reason: spelling and editing
Legality was the question, and as explained above the ‘legality’ is with the interpretation of the rules, particularly 1.450.
The UK CAA has provided an interpretation such that any other Authority, Operator, or Commander might be challenged to justify an alternative so that in the event of an accident, the lawyers would not be knocking at their door; now that is ‘legality’.
I prefer to think that the guidance material provides a basis for a Commander to judge a safety margin for landing and thus be comfortable with his/her responsibilities within the rule – but s/he still has to complete the ‘plan’, and that activity also requires experience.
The UK CAA has provided an interpretation such that any other Authority, Operator, or Commander might be challenged to justify an alternative so that in the event of an accident, the lawyers would not be knocking at their door; now that is ‘legality’.
I prefer to think that the guidance material provides a basis for a Commander to judge a safety margin for landing and thus be comfortable with his/her responsibilities within the rule – but s/he still has to complete the ‘plan’, and that activity also requires experience.
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EASA isn't UK CAA to start with and certainly UK CAA won't preach anything contrary to the common understanding of legal foundation in the industry. Do you really think airbus and Boeing would release the EFB with those modules and let the pilots assess landing performance with ALD if it wasn't legal? Come on mate, reading something into context and understanding it are different things.
Let's see a practical example:
you are flying to a RWY limited field landing performance wise. The forecast is for dry RWY conditions. RLD is 1670 M for dry conditions. LDA is 1700 M. Now you're getting ATIS and it's says RA thus RWY is wet. Your ALD as per QRH or EFB is 1150 M including the margin of 15% for wet and RLD logically would be 1930 m My only question is are you gonna land or divert?
Let's see a practical example:
you are flying to a RWY limited field landing performance wise. The forecast is for dry RWY conditions. RLD is 1670 M for dry conditions. LDA is 1700 M. Now you're getting ATIS and it's says RA thus RWY is wet. Your ALD as per QRH or EFB is 1150 M including the margin of 15% for wet and RLD logically would be 1930 m My only question is are you gonna land or divert?
EASA isn’t UK CAA, or the other way round, but each EU State has responsibility for safety oversight and promotion. EU makes the law; EASA generates rules / specs, etc; EASA / State National Authorities implement the safety activities.
Most aircraft manufacturers publish ‘actual’ landing distance; there are several views of what ‘actual’ includes. The AFM certification distances are the theoretical ‘unachievable’ minimum. Boeing provides their version of ‘actual’ in the QRH which makes many assumptions, adjustments, and additions, this distance probably is the absolute minimum that a pilot could achieve, but for some operators the QRH includes a further 15% margin. The FAA refers to something similar in SAFO. I am not familiar with what Airbus publishes.
The numerical example is a classic ‘can we do this’ question, as opposed the primary, and overriding safety question, “should we be doing this”.
The answer depends on the situation; in abnormal / emergency situations some additional risk can be tolerated – you have to know what the risk is and what the acceptable limits are.
In normal operation, the risks of landing should be minimized with good planning and practice – the process of safety; the UK CAA guidance provides an acceptable method of achieving that objective, which can be applied to a range of landing operations.
Most aircraft manufacturers publish ‘actual’ landing distance; there are several views of what ‘actual’ includes. The AFM certification distances are the theoretical ‘unachievable’ minimum. Boeing provides their version of ‘actual’ in the QRH which makes many assumptions, adjustments, and additions, this distance probably is the absolute minimum that a pilot could achieve, but for some operators the QRH includes a further 15% margin. The FAA refers to something similar in SAFO. I am not familiar with what Airbus publishes.
The numerical example is a classic ‘can we do this’ question, as opposed the primary, and overriding safety question, “should we be doing this”.
The answer depends on the situation; in abnormal / emergency situations some additional risk can be tolerated – you have to know what the risk is and what the acceptable limits are.
In normal operation, the risks of landing should be minimized with good planning and practice – the process of safety; the UK CAA guidance provides an acceptable method of achieving that objective, which can be applied to a range of landing operations.
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I take it you've never been to DTM with LDA 1300 m in normal operation and yet there're numerous flights on both airbus and Boeing daily. Go figure! Nice rethoric on your side alas far fetched from reality!
I like the ‘should we be doing this’ as opposed to ‘can we do this’ attitude.
The limited field landing example appears to be a simple question of comparing RLD and RLA, then agree / disagree with the discussions above.
The exact content of the RLD may not be known. Does it depend on reverse, max brake, accurate threshold crossing height / speed / touchdown position? What airborne distance is assumed? Are all of these aspects achievable, all at the same time?
If the details are not known then at least 15% margin is required, possibly more.
There are other important aspects required for a decision – what is the wind, how wet is the runway (reporting accuracies); is the runway grooved, are there rubber deposits; is there an overrun area?
For a safety assessment before landing, all of these are aspects must be known. If there is variability, or areas of inaccuracy, then additional safety margins should be added, these could very quickly add up to the same factors as used for dispatch, thus this might be a good minimum if a more accurate pre-landing assessment cannot be made.
I suppose that the simple answer is if the aircraft was scheduled to operate to this airport, and if the legal dispatch requirements were met with full factored distances, then a landing at the planned landing weight would have a good safety factor – at or near full dispatch factors plus/minus wind, and the advantage of thrust reverse. So why in the example is the ALD / RLD ‘so tight”?
The limited field landing example appears to be a simple question of comparing RLD and RLA, then agree / disagree with the discussions above.
The exact content of the RLD may not be known. Does it depend on reverse, max brake, accurate threshold crossing height / speed / touchdown position? What airborne distance is assumed? Are all of these aspects achievable, all at the same time?
If the details are not known then at least 15% margin is required, possibly more.
There are other important aspects required for a decision – what is the wind, how wet is the runway (reporting accuracies); is the runway grooved, are there rubber deposits; is there an overrun area?
For a safety assessment before landing, all of these are aspects must be known. If there is variability, or areas of inaccuracy, then additional safety margins should be added, these could very quickly add up to the same factors as used for dispatch, thus this might be a good minimum if a more accurate pre-landing assessment cannot be made.
I suppose that the simple answer is if the aircraft was scheduled to operate to this airport, and if the legal dispatch requirements were met with full factored distances, then a landing at the planned landing weight would have a good safety factor – at or near full dispatch factors plus/minus wind, and the advantage of thrust reverse. So why in the example is the ALD / RLD ‘so tight”?
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It appears to be legal. However company regulations differ greatly between companies and some take a more conservative approach to that. For example we can not use any inflight calculated landing distance that is less than the dispatch landing distance in my outfit. Our operational factor is 20% (or greater on commanders discretion) instead of 15% and it is on top of any factor that might be used within the OEM data.
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Hello,
I'm just checking my 737-800 information and here comes a strange conclusion:
-'Dispatch' required landing distance for a landing weight of 65T, F40, 0 ft pressure altitude, dry runway is: 1625m.
-QRH Performance Inflight advisory information 65T, dry runway, F40, sea level, no slope, no tailwind, no isa deviation, 5kts above Vref, 2 reversers max manual braking: 950m, to be multiplied by 1,15 (Thats what we are required to factor in in my company, I'm not sure if this is a general legal requirement?), so its 1093m.
So if I understand correctly, the current interpretation of the rules say that if I'm in flight, I can happily land a B737-800 on a 1100m runway because the 'Dipatch required landing distance does not apply in flight'?
I think you better have a very good reason to make an attempt on such a short runway (uncontained fire/smoke...). But according to my company, that should be ok!!!
Any thoughts on this?
Best regards,
Alpagueur
I'm just checking my 737-800 information and here comes a strange conclusion:
-'Dispatch' required landing distance for a landing weight of 65T, F40, 0 ft pressure altitude, dry runway is: 1625m.
-QRH Performance Inflight advisory information 65T, dry runway, F40, sea level, no slope, no tailwind, no isa deviation, 5kts above Vref, 2 reversers max manual braking: 950m, to be multiplied by 1,15 (Thats what we are required to factor in in my company, I'm not sure if this is a general legal requirement?), so its 1093m.
So if I understand correctly, the current interpretation of the rules say that if I'm in flight, I can happily land a B737-800 on a 1100m runway because the 'Dipatch required landing distance does not apply in flight'?
I think you better have a very good reason to make an attempt on such a short runway (uncontained fire/smoke...). But according to my company, that should be ok!!!
Any thoughts on this?
Best regards,
Alpagueur
If you dispatched to a runway which was 1.67 times your unfactored landing distance why are you now considering landing somewhere else?
If you have re-planned in flight you need the dispatch requirements at the time of re-planning. If you have a abnormality or emergency that requires immediate landing you will be applying the appropriate abnormal landing factor.
The only reason you would have a reduced margin in normal ops would be poor planning. Either an unexpected rain shower made the dry runway wet or incorrect fuel planning (could be due to winds or routing) makes you arrive heavier than planned. You aren’t suddenly going to lose all your margin without a reason.
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It is extremely simple. If the legal margins required for dispatch did not exist 80% of the flights would end up in the grass. Same reasoning for in flight. Boeing QRH gives you the actual distance no factoring except 15% in case of slippery. You use it to plan where you ill leave the RWY for taxi AND you have to factor yourself.
In case of a non normal it’s a different story
In case of a non normal it’s a different story
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imagine some of us do fly LAHSO ops which is pretty much standard at busy airports over in the US. You can have 13000 ft RWY it's irrelevant coz in LAHSO you ought to stop within declared LDA for LAHSO. Guess what, it's ALD you go with not RLD to assess your suitability for LAHSO. Sorry I forgot we shouldn't be doing all that non sense in commercial aviation.
Most of this thread has been about the legal aspects, and many pilots appear to have a need to hide behind a legal statement.
For dispatch, the ‘law’ is explicit – an operator “shall” – as per Hoppy #8. This applies to destination and alternate aerodrome, and at the point from which the revised operational flight plan applies, i.e. between those two it includes the other runway.
Before landing, a commander “must” satisfy … ... will be safe (EU-OPS 400); again the ‘law’ is explicit. The only judgement is in what is safe; for views of that, read the ICAO Safety Management Manual, and then look for the legal trail to the State law re flying safely.
A QRH contains data and recommendations (no law), these have to be understood and applied – by adding your own justifiable safety margin, as per Pitch Up #36.
There is no hiding behind a legal statement, there’s no need to. Pilots, commanders have to bear responsibility for their decisions; choices of action have to be justified, first to ourselves then everyone else.
For dispatch, the ‘law’ is explicit – an operator “shall” – as per Hoppy #8. This applies to destination and alternate aerodrome, and at the point from which the revised operational flight plan applies, i.e. between those two it includes the other runway.
Before landing, a commander “must” satisfy … ... will be safe (EU-OPS 400); again the ‘law’ is explicit. The only judgement is in what is safe; for views of that, read the ICAO Safety Management Manual, and then look for the legal trail to the State law re flying safely.
A QRH contains data and recommendations (no law), these have to be understood and applied – by adding your own justifiable safety margin, as per Pitch Up #36.
There is no hiding behind a legal statement, there’s no need to. Pilots, commanders have to bear responsibility for their decisions; choices of action have to be justified, first to ourselves then everyone else.
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talking of legal aspects I should mention RTFQ principle. Bus drivers among us should be familiar with the QRH content of chapter 4 Landing distance without autobrake. I really wonder why airbus puts a little note there saying The above distances are given for use in flight. Before departure refer to FCOM. Damn you airbus how dare you being illegal some of us cry out loud. RTFQ would be airbuses builders reply, I can imagine. Mind you airbus, unlike boeing, is written by lawyers not pilots and not for pilots. A very nice little brochure called getting to grips with performance will shed some light for those interested.
Last edited by 9.G; 20th Dec 2011 at 07:18.
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Mind you airbus, unlike boeing, is written by lawyers not pilots and not for pilots.
The relevant QRH chapter is called "inflight performance", at least in our 737 QRH.
Imagine an airport with 2 runways... On arrival, the crosswind is out of limits for the main, long runway and instead you are given a shorter, less used, lets say 1000m runway perpendicular to the main one... This is a possible scenario I would think, no? Well I'm not gonna land there with a 737-800 at 65 tons...
No problem for your 1000m landing, then. 
Fair enough, but what's the abnormal landing factor for a 'low fuel' situation. There is none of course...
You are, of course, now in the regime of using your command authority to ignore ANY rule prudent in an emergency.
as you start the flight/diversion to that (new) airfield, you can "throw away" your Dispatch distance as you only need QRH distance in flight...?? Which defeats the whole idea of having a Dispatch distance!
The 67% (or 92%) margin for despatch on runway length is exactly the same. If is rains or you are a bit heavier - you aren't required to divert, as this was a despatch safety margin. The fact that it has reduced a bit in flight is what it was there for.
Of course, if that margin has reduced to the point where the commander no longer considers it safe to land (given their inflight calculation of the minimum the aircraft requires, and safety factors the commander thinks prudent due crew experience or whatever) then you don't land. Welcome to the command decision process!
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moreover the actual decision to land is made on short final dependable on how situation unfolds. Having said that TALPA will account for RWY conditions, like residual rubber, among others which could be detrimental factor in some places even in light drizzle. I'd rather land in moderate rain in DTM with 1350 M LDA than in BOM in damp conditions coz boy you just go skating on a hydro pillow. How often did one see a airdrome been hammered with snow where ATC still reports BA medium till few minutes later it switches to unreliable. Experience and knowledge of local shortcomings as well as your aircraft influence the decision as much as regulatory aspects. Having said that I concur with the statement from check board: welcome to commander's decision making process.
Last edited by 9.G; 21st Dec 2011 at 12:41.
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Commanders Decision
I remember the day that we had 40 kts headwind. Besides the wind there are of course the gusts.
Now there are two issues here:
1. Accurate landing: very difficult
2. Passengers comfort: several idiots tried to land and the result was. Two pax suffered a heart attack and a couple wetted their pants.
I never even tried the approach.
From the post above I can only conclude that to be 100% sure, the only way I will board an aircraft when the wx is marginal is when I am flying myself.
Checkboard:Contingency is there to cater for inaccurate planning. You need it before starting the flight. Factoring is there for inaccurate landing, deviations from planned braking action. As with contingency, you need it BEFORE starting the flare.
Now there are two issues here:
1. Accurate landing: very difficult
2. Passengers comfort: several idiots tried to land and the result was. Two pax suffered a heart attack and a couple wetted their pants.
I never even tried the approach.
From the post above I can only conclude that to be 100% sure, the only way I will board an aircraft when the wx is marginal is when I am flying myself.
Checkboard:Contingency is there to cater for inaccurate planning. You need it before starting the flight. Factoring is there for inaccurate landing, deviations from planned braking action. As with contingency, you need it BEFORE starting the flare.
Last edited by Pitch Up Authority; 21st Dec 2011 at 14:25.