Overweight Landing and Field Length
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To all,
I thought I would add a couple of points which I have not seen in the preceding discussion (forgive me if I have overlooked them).
The point has been established that the factoring of the actual landing distance is a dispatch requirement, i.e., a 6000 foot actual landing distance requires a 10000 foot runway under dry conditions. Further we have established that under wet conditions, an additional fifteen percent mist be added, thus requiring 11500 feet.
We have discussed whether this remains a requirement after dispatch. The conventional wisdom is no, it is not a requirement following dispatch. It is a planning requirement only.
In the US, a lesser known requirement resides in Operations Specification C054. This addresses the lower-than-standard minimums case (standard meaning RVR 4000 or 3/4 mile). The relevant text is:
This would seem to suggest that there is an argument to made supporting the use of the dispatch landing distance requirements while in flight.
I was curious to see whether the JARs contained a similar requirement. Perusing through JAR-OPS Part 1, I could not see any such requirement...which, given my lack of familiarity with JAR, isn't saying much. However, I did note the following requirements regarding landing distance in JAR-OPS 1, Subpart G, Paragraph 1.515:
These seem to be two instances which are not consistent with the interpretation that the dispatch requirement goes away after takeoff. Neither directly apply to Haroon's initial scenario, but these things have a way of laying the foundation for the arguments during the hearing. All of which leads us back to John Tullamarine's point that you really need to justify non-compliance with the landing weight by declaring an emergency. Thus, you need justification beyond commercial purposes.
That said, I'll add my two cents regarding the real thing. Based on my very nearly disastrous experience with an overweight 767-300 returning to the departure field, I can state that non-precision approaches at night are probably not the best time to abandon the factoring criteria. Although we had the factored distance for our weight, the maneuvering required after breaking out at five hundred feet and 170 knot Vref put us well past the touchdown zone at an radio altitude of zero (based on the DFDR later reviewed). This necessitated a go-around, which was followed by an immediate failure of the flight directors, which was then followed by a 2000 foot ATC-instructed level off, which directly led to a flap overspeed. Having gotten that sorted out, the ensuing landing, in the touchdown zone this time, led to three of eight main tires failing.
All three of us (I was the non-flying FO) made a remarkably complimentary series of errors that night, which very nearly used up all of the margin that we had. Overweight landings need not be disasters...I've made others that were far less dramatic...but they open the door up to margin-absorbing non-routine irregularities. Although you can and should plan thoroughly and comprehensively, you retain the margins whenever possible because you will never, ever, see the one coming that gets you.
I thought I would add a couple of points which I have not seen in the preceding discussion (forgive me if I have overlooked them).
The point has been established that the factoring of the actual landing distance is a dispatch requirement, i.e., a 6000 foot actual landing distance requires a 10000 foot runway under dry conditions. Further we have established that under wet conditions, an additional fifteen percent mist be added, thus requiring 11500 feet.
We have discussed whether this remains a requirement after dispatch. The conventional wisdom is no, it is not a requirement following dispatch. It is a planning requirement only.
In the US, a lesser known requirement resides in Operations Specification C054. This addresses the lower-than-standard minimums case (standard meaning RVR 4000 or 3/4 mile). The relevant text is:
(2) A pilot-in-command of a turbojet airplane shall not begin an instrument approach procedure when the visibility conditions are reported to be less than ¾ statute mile or RVR 4000, unless the following
conditions exist:
(a) Fifteen percent additional runway length is available over the landing field length specified for the destination airport by the appropriate Sections of the CFR.
Note that this is an operational, inflight requirement. The PIC shall not begin an instrument approach, etc. It turns out that the "appropriate" section of the CFR is 121.195(b), making this requirement identical to that in 121.195(d), which is the 115% requirement. So the requirement is the same, but the threshold criteria and the point in the flight where it is invoked are different.conditions exist:
(a) Fifteen percent additional runway length is available over the landing field length specified for the destination airport by the appropriate Sections of the CFR.
This would seem to suggest that there is an argument to made supporting the use of the dispatch landing distance requirements while in flight.
I was curious to see whether the JARs contained a similar requirement. Perusing through JAR-OPS Part 1, I could not see any such requirement...which, given my lack of familiarity with JAR, isn't saying much. However, I did note the following requirements regarding landing distance in JAR-OPS 1, Subpart G, Paragraph 1.515:
(d) If an operator is unable to comply with subparagraph
(c)(1) above for a destination aerodrome
having a single runway where a landing depends
upon a specified wind component, an aeroplane may
be despatched if 2 alternate aerodromes are
designated which permit full compliance with subparagraphs
(a), (b) and (c). Before commencing an
approach to land at the destination aerodrome the
commander must satisfy himself that a landing can
be made in full compliance with JAR–OPS 1.510
and sub-paragraphs (a) and (b) above.
Again the language requires the PIC to make an assessment, before commencing the approach, that the dispatch requirement can be met.(c)(1) above for a destination aerodrome
having a single runway where a landing depends
upon a specified wind component, an aeroplane may
be despatched if 2 alternate aerodromes are
designated which permit full compliance with subparagraphs
(a), (b) and (c). Before commencing an
approach to land at the destination aerodrome the
commander must satisfy himself that a landing can
be made in full compliance with JAR–OPS 1.510
and sub-paragraphs (a) and (b) above.
These seem to be two instances which are not consistent with the interpretation that the dispatch requirement goes away after takeoff. Neither directly apply to Haroon's initial scenario, but these things have a way of laying the foundation for the arguments during the hearing. All of which leads us back to John Tullamarine's point that you really need to justify non-compliance with the landing weight by declaring an emergency. Thus, you need justification beyond commercial purposes.
That said, I'll add my two cents regarding the real thing. Based on my very nearly disastrous experience with an overweight 767-300 returning to the departure field, I can state that non-precision approaches at night are probably not the best time to abandon the factoring criteria. Although we had the factored distance for our weight, the maneuvering required after breaking out at five hundred feet and 170 knot Vref put us well past the touchdown zone at an radio altitude of zero (based on the DFDR later reviewed). This necessitated a go-around, which was followed by an immediate failure of the flight directors, which was then followed by a 2000 foot ATC-instructed level off, which directly led to a flap overspeed. Having gotten that sorted out, the ensuing landing, in the touchdown zone this time, led to three of eight main tires failing.
All three of us (I was the non-flying FO) made a remarkably complimentary series of errors that night, which very nearly used up all of the margin that we had. Overweight landings need not be disasters...I've made others that were far less dramatic...but they open the door up to margin-absorbing non-routine irregularities. Although you can and should plan thoroughly and comprehensively, you retain the margins whenever possible because you will never, ever, see the one coming that gets you.
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I agree, dispatch requirements apply when airborne under JAR.
Nice example of where ATPL courses and training should focus on.
Given the same rwy lenght I would take the side with an upslope even if it is a NON Precision app, check the numbers in the AFM.
As a commander you need to be able to put the acft on the right spot.
There is no need to use max brakes but brake as function of runway lenght.
This is what EK did wrong in Johannesburg.
All this is written down in the FCTM, no secrets.
Nice example of where ATPL courses and training should focus on.
Given the same rwy lenght I would take the side with an upslope even if it is a NON Precision app, check the numbers in the AFM.
As a commander you need to be able to put the acft on the right spot.
There is no need to use max brakes but brake as function of runway lenght.
This is what EK did wrong in Johannesburg.
All this is written down in the FCTM, no secrets.
Mansfield, #61, some interesting items.
For info; JAR is now EU-OPS, but the text is essentially the same.
EU-OPS and FAR 121 are slowly being harmonized; the landing requirements are essentially identical and originate from the same certification requirements CS 25.125 / FAR 25.125. The only significant difference is in contaminated operations where EU-OPS 1.520 requires accountability but FARs do not. However, FAA SAFO 06012 does refer to the difference.
CS 25.1591 ‘Contaminated Runway Certification’ is well worth reading as it provides most of the definitions and assumptions for the operation; one significant point is for operators to determine whether reverse is credited or not.
Pitch Up Authority, re the choice of runway direction, perhaps the head/tailwind – groundspeed might be the dominant consideration. After all it is energy (speed squared), which has to be dissipated within the runway length.
Re There is no need to use max brakes but brake as function of runway length.
Perhaps this is a bold generalisation as it assumes that pilots know what the limiting landing distance is and thus the additional safety margin available from a longer runway.
Unless an operator’s landing performance covers a range of runway distances (usually only the distance of the chosen runway), the crew will only know if they meet the landing requirements or not - yes / no choice.
Landing data is provided for weight (landing mass). A better guide as to how hard to brake can be obtained by comparing the max allowable landing weight (on a given runway) with the actual landing weight, but this too might not consider additional margins on very long runways.
Weight comparison provides some guidance as to the safety margin available, but this still requires experience, and consideration of runway conditions and other variables before choosing a level of braking. Some data (and aircraft systems) provide some of this information, but all, as do humans, have limits of not knowing the precise nature of the conditions, thus rules of thumb such as initially brake harder than you judge might apply.
From your post #60, the reliance on reverse might be foolhardy (cf Midway accident). Normal landing performance rarely credits reverse thrust for good reason. Being ‘independent of the braking system’ is a risky mindset, particularly on slippery runways after cancelling reverse.
Similarly, you may have generalised the phrase ‘the advisory data for slippery runways’, but in EU-land the data required is much more than advisory; see above EU-OPS 1.520, CS 25.1591.
For info; JAR is now EU-OPS, but the text is essentially the same.
EU-OPS and FAR 121 are slowly being harmonized; the landing requirements are essentially identical and originate from the same certification requirements CS 25.125 / FAR 25.125. The only significant difference is in contaminated operations where EU-OPS 1.520 requires accountability but FARs do not. However, FAA SAFO 06012 does refer to the difference.
CS 25.1591 ‘Contaminated Runway Certification’ is well worth reading as it provides most of the definitions and assumptions for the operation; one significant point is for operators to determine whether reverse is credited or not.
Pitch Up Authority, re the choice of runway direction, perhaps the head/tailwind – groundspeed might be the dominant consideration. After all it is energy (speed squared), which has to be dissipated within the runway length.
Re There is no need to use max brakes but brake as function of runway length.
Perhaps this is a bold generalisation as it assumes that pilots know what the limiting landing distance is and thus the additional safety margin available from a longer runway.
Unless an operator’s landing performance covers a range of runway distances (usually only the distance of the chosen runway), the crew will only know if they meet the landing requirements or not - yes / no choice.
Landing data is provided for weight (landing mass). A better guide as to how hard to brake can be obtained by comparing the max allowable landing weight (on a given runway) with the actual landing weight, but this too might not consider additional margins on very long runways.
Weight comparison provides some guidance as to the safety margin available, but this still requires experience, and consideration of runway conditions and other variables before choosing a level of braking. Some data (and aircraft systems) provide some of this information, but all, as do humans, have limits of not knowing the precise nature of the conditions, thus rules of thumb such as initially brake harder than you judge might apply.
From your post #60, the reliance on reverse might be foolhardy (cf Midway accident). Normal landing performance rarely credits reverse thrust for good reason. Being ‘independent of the braking system’ is a risky mindset, particularly on slippery runways after cancelling reverse.
Similarly, you may have generalised the phrase ‘the advisory data for slippery runways’, but in EU-land the data required is much more than advisory; see above EU-OPS 1.520, CS 25.1591.
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Safetypee: I agree with your statements and I do not see where I stated anything in contradiction.
I you land on a 3000 m runway with a 737 using rev only you take no risk at all. At 120 kts you need 1600 m and at 140 kts about 2000 m to get the speed down to 80 Kts. Nice to know that you have some brakes on top of that if they perform as predicted. Crosswind and directional control are crucial as you may have to stow the rev but all that is part of your assessment.
JAR OPS as opposed to FAR did go one step further by requesting data for slippery rwy with a 15% factor. The problem is the reliability of the friction measurement. See briefing from Boeing on that subject.
I made myself a table based on the AFM with landing data for various overweight conditions including Vmbe limitations. If you look at them on a regular basis you develop a good feeling what is possible.
Groundspeed is a key factor as I had stated before. If rwy is slippery, slope becomes significant.
When driving a car you know how to decelerate as stop before a traffic light. With an aeroplane it just takes a while to get the same feeling but it takes some effort. You need to take some time after each landing to reflect a bit on what happened. After a while it becomes second nature.
A useful exercise on a very long runway is also: Idle rev and no braking and see how she decelerates by herself, you will be surprised.
I you land on a 3000 m runway with a 737 using rev only you take no risk at all. At 120 kts you need 1600 m and at 140 kts about 2000 m to get the speed down to 80 Kts. Nice to know that you have some brakes on top of that if they perform as predicted. Crosswind and directional control are crucial as you may have to stow the rev but all that is part of your assessment.
JAR OPS as opposed to FAR did go one step further by requesting data for slippery rwy with a 15% factor. The problem is the reliability of the friction measurement. See briefing from Boeing on that subject.
I made myself a table based on the AFM with landing data for various overweight conditions including Vmbe limitations. If you look at them on a regular basis you develop a good feeling what is possible.
Groundspeed is a key factor as I had stated before. If rwy is slippery, slope becomes significant.
When driving a car you know how to decelerate as stop before a traffic light. With an aeroplane it just takes a while to get the same feeling but it takes some effort. You need to take some time after each landing to reflect a bit on what happened. After a while it becomes second nature.
A useful exercise on a very long runway is also: Idle rev and no braking and see how she decelerates by herself, you will be surprised.
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Thankyou all for your inputs
According to " JAR / EU-OPS 1.475 ", 1.67 factor for dry runways remains valid for inflight replanning.
Is there a FAR reference like this?
According to " JAR / EU-OPS 1.475 ", 1.67 factor for dry runways remains valid for inflight replanning.
Is there a FAR reference like this?
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Returning for an overweight landing is not 'inflight replanning' as I understand it. That is a defined procedure usually for medium/long haul flights to re-plan a destination if you are struggling for fuel at the initial planning stage.
In any event in my very large EU Ops airline the requirement is not the same once airborne.
In any event in my very large EU Ops airline the requirement is not the same once airborne.
