B777 Flaps setting for dispatch landing distance calculations at alternate airport
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B777 Flaps setting for dispatch landing distance calculations at alternate airport
The following question concerns the B777 flaps setting which is to be considered for dispatch landing distance calculations at the alternate airport, based on the expected landing weight at the alternate airport and therefore on the expected quantity of fuel on board.
It is a matter of regulatory planning for pre-departure and interpretation of regulations, not of in-flight fuel management and what may happen during the flight or what could be the crew options once airborne. This only concerns what it is we have to do before departure in terms of factored required landing distance calculations at the alternate airport.
In summary, calculations of the factored landing distance (60%, 1,15, etc.) are mandatory at dispatch for destination and alternate(s) airports. To perform these calculations we absolutely need a landing weight that is obviously based on the ZFW + remaining fuel. Again not talking about in-flight management, but only planning the flight and interpreting regulations, departing with no extra fuel means landing at alternate airport with only the final reserve fuel on board.
On B772 or B773, the final reserve fuel is less than 4T, thus landing with less than 2T in each main tank. This will trigger the "Fuel Low Qty" non normal C/L which calls for flaps 20 landing...
Dispatch landing distance calculations, however, are based on demonstrated/certified performances/capabilities available only for flaps 25 and 30, the OPT also only displays flaps 25 and 30.
Therefore, what is the flaps setting for the required dispatch (factored) landing distance calculations at alternate airport?...
I know what my airline is doing and why, but for the sake of reflection, I am very interested in knowing what others are doing, how and if it is for the same reason.
Thank's!
Now for the details:
As per IR OPS CAT.POL.A.105 "General" (c) "Due account shall be taken of aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance."
This CAT.POL.A.105 concerns "the mass of the aeroplane: (1) at the start of the take-off; or (2) in the event of in-flight replanning". This is clearly a pre-flight regulatory plan.
CAT.POL.A.225, 230 & 235 all refer to CAT.POL.A.105 for dispatch landing distance calculations at destination and alternate(s).
Fuel regulatory policy is also a matter of pre-flight planning.
CAT.OP.MPA.150 states that "The operator shall ensure that the pre-flight calculation of usable fuel required for a flight includes: taxi fuel; trip fuel; reserve fuel consisting of: contingency fuel; alternate fuel, if a destination alternate aerodrome is required; final reserve fuel; and additional fuel, if required by the type of operation; and extra fuel if required by the commander."
AMC1.CAT.OP.MPA.150(b) gives details of all these quantities, the alternate fuel being calculated for a missed approach from DA at destination to landing at the alternate.
Therefore, without extra fuel required and with contingency fuel being potentially used during the flight, the entire fuel policy regulatory process is based on landing at the alternate airport with only the final reserve fuel.
A crew can and will takeoff with this minimum regulatory fuel for saving the payload (ie Asia-Europe flights with a B773 at MTOW are fairly common).
The crew must verify that the minimum quantity of regulatory fuel is at least on board at the start of the take-off.
During the pre-departure checks, the crew also had to calculate the destination and alternate(s) landing distances with the pre-flight (dispatch) requirements (ie 60% dry factor).
The entire regulatory process "at the start of the take-off" is therefore based on minimum regulatory fuel and the obligation to also comply with dispatch landing distances accounting for "aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance" as per CAT.POL.A.105 c).
Whether the crew then decides to divert and land en-route, or anticipate the diversion to the destination’s alternate without flying down to the (M)DA/H, it is a matter of in-flight fuel management and not of regulatory planning as it was prior to the start of the take-off. In fact, once airborne, the crew will also only have to match the LDA without the factors of 60% or 1,15 and it won’t be based, at least for the B777, on the same landing data as it won’t use the certified landing distances but some more operational values.
Therefore, matching the fuel policy rules with dispatch landing distance calculations rules, as the IR-OPS is written, leads to a calculation of landing distance at the alternate airport on the basis of a landing weight equal to ZFW + final reserve fuel.
(One might wonder if the contingency fuel is assumed to be still on board. This will not be important on a relatively short trip departing with minimum regulatory fuel, and this contingency fuel is anyway meant to be used for unpredictable deviations of an individual aeroplane from the expected fuel consumption data, deviations from forecast meteorological conditions and deviations from planned routings and/or cruising levels/altitudes.)
The fuel quantity on board at the alternate airport will be the final reserve fuel which is about 3.1 tons for a B773.
With less than 2 tons in a main tank, therefore less than 4 tons of fuel on board, the non normal checklist "Fuel Low Qty" will display and call for a flaps 20 landing.
Knowing from dispatch that if you have the "aeroplane configuration" flaps 20 at the alternate it will thus have "adverse effect on performance", obviously increasing landing distance compared to a flaps 30 landing, do you take flaps 20 or flaps 25/30 for alternate airport dispatch landing distance calculations and why?
Do flaps 20 have to be taken in consideration because it is the only flaps setting that corresponds to the planned fuel remaining on board without voluntarily deviating from the FCOM/FCTM/QRH?
If you're thinking of considering flaps 20, how do you do that since we don’t have dispatch datas for flaps 20 landing?… Dispatch landing distance calculations are based on demonstrated/certified performances/capabilities only available for flaps 25 and 30, and the OPT only displays flaps 25 and 30...
It is a matter of regulatory planning for pre-departure and interpretation of regulations, not of in-flight fuel management and what may happen during the flight or what could be the crew options once airborne. This only concerns what it is we have to do before departure in terms of factored required landing distance calculations at the alternate airport.
In summary, calculations of the factored landing distance (60%, 1,15, etc.) are mandatory at dispatch for destination and alternate(s) airports. To perform these calculations we absolutely need a landing weight that is obviously based on the ZFW + remaining fuel. Again not talking about in-flight management, but only planning the flight and interpreting regulations, departing with no extra fuel means landing at alternate airport with only the final reserve fuel on board.
On B772 or B773, the final reserve fuel is less than 4T, thus landing with less than 2T in each main tank. This will trigger the "Fuel Low Qty" non normal C/L which calls for flaps 20 landing...
Dispatch landing distance calculations, however, are based on demonstrated/certified performances/capabilities available only for flaps 25 and 30, the OPT also only displays flaps 25 and 30.
Therefore, what is the flaps setting for the required dispatch (factored) landing distance calculations at alternate airport?...
I know what my airline is doing and why, but for the sake of reflection, I am very interested in knowing what others are doing, how and if it is for the same reason.
Thank's!
Now for the details:
As per IR OPS CAT.POL.A.105 "General" (c) "Due account shall be taken of aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance."
This CAT.POL.A.105 concerns "the mass of the aeroplane: (1) at the start of the take-off; or (2) in the event of in-flight replanning". This is clearly a pre-flight regulatory plan.
CAT.POL.A.225, 230 & 235 all refer to CAT.POL.A.105 for dispatch landing distance calculations at destination and alternate(s).
Fuel regulatory policy is also a matter of pre-flight planning.
CAT.OP.MPA.150 states that "The operator shall ensure that the pre-flight calculation of usable fuel required for a flight includes: taxi fuel; trip fuel; reserve fuel consisting of: contingency fuel; alternate fuel, if a destination alternate aerodrome is required; final reserve fuel; and additional fuel, if required by the type of operation; and extra fuel if required by the commander."
AMC1.CAT.OP.MPA.150(b) gives details of all these quantities, the alternate fuel being calculated for a missed approach from DA at destination to landing at the alternate.
Therefore, without extra fuel required and with contingency fuel being potentially used during the flight, the entire fuel policy regulatory process is based on landing at the alternate airport with only the final reserve fuel.
A crew can and will takeoff with this minimum regulatory fuel for saving the payload (ie Asia-Europe flights with a B773 at MTOW are fairly common).
The crew must verify that the minimum quantity of regulatory fuel is at least on board at the start of the take-off.
During the pre-departure checks, the crew also had to calculate the destination and alternate(s) landing distances with the pre-flight (dispatch) requirements (ie 60% dry factor).
The entire regulatory process "at the start of the take-off" is therefore based on minimum regulatory fuel and the obligation to also comply with dispatch landing distances accounting for "aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance" as per CAT.POL.A.105 c).
Whether the crew then decides to divert and land en-route, or anticipate the diversion to the destination’s alternate without flying down to the (M)DA/H, it is a matter of in-flight fuel management and not of regulatory planning as it was prior to the start of the take-off. In fact, once airborne, the crew will also only have to match the LDA without the factors of 60% or 1,15 and it won’t be based, at least for the B777, on the same landing data as it won’t use the certified landing distances but some more operational values.
Therefore, matching the fuel policy rules with dispatch landing distance calculations rules, as the IR-OPS is written, leads to a calculation of landing distance at the alternate airport on the basis of a landing weight equal to ZFW + final reserve fuel.
(One might wonder if the contingency fuel is assumed to be still on board. This will not be important on a relatively short trip departing with minimum regulatory fuel, and this contingency fuel is anyway meant to be used for unpredictable deviations of an individual aeroplane from the expected fuel consumption data, deviations from forecast meteorological conditions and deviations from planned routings and/or cruising levels/altitudes.)
The fuel quantity on board at the alternate airport will be the final reserve fuel which is about 3.1 tons for a B773.
With less than 2 tons in a main tank, therefore less than 4 tons of fuel on board, the non normal checklist "Fuel Low Qty" will display and call for a flaps 20 landing.
Knowing from dispatch that if you have the "aeroplane configuration" flaps 20 at the alternate it will thus have "adverse effect on performance", obviously increasing landing distance compared to a flaps 30 landing, do you take flaps 20 or flaps 25/30 for alternate airport dispatch landing distance calculations and why?
Do flaps 20 have to be taken in consideration because it is the only flaps setting that corresponds to the planned fuel remaining on board without voluntarily deviating from the FCOM/FCTM/QRH?
If you're thinking of considering flaps 20, how do you do that since we don’t have dispatch datas for flaps 20 landing?… Dispatch landing distance calculations are based on demonstrated/certified performances/capabilities only available for flaps 25 and 30, and the OPT only displays flaps 25 and 30...
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Given the lack of an answer it might be the way I asked, not to mention that it is not an exhilarating subject. I try rephrasing anyway:
On B777, the calculation of the required landing distance (RLD) at the alternate airport is made on the OPT with the choice of flaps 25 or 30 only.
This calculation, known as "landing-dispatch", gives the maxi performance landing limit weight at any airport (destination or alternate) taking into account the regulatory requirements at the flight preparation stage (factors 0.6, 1.15, etc.) and based on the following conditions: RWY, Missed Approach gradient, RWY condition, wind, OAT, QNH, Reversers, Autoland or Manual, A/C config, A/I config, MEL, CDL, NOTAM and FLAPS.
Before the flight, the crew must verify that the landing weight will be lower than this maxi performance landing limit weight in order to be able to retain the airport as an alternate.
The regulatory provisions, which I referred to in my previous post, make it necessary to take into account the "aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance."
The regulatory flight profile, departing with the minimum regulatory fuel, leads to land at the alternate airport with only the final reserve fuel on board.
This final reserve fuel is less than 4 tons on B777.
With less than 4 tons of fuel on board, Boeing's procedures (QRH NNC "Fuel Low Qty") impose on the crew to land flaps 20.
Again, it is a matter of regulatory planning and of interpretation of regulations, not of in-flight fuel management and what may happen during the flight or what will do the crew once airborne.
Therefore, you already know at preflight that you're supposed to land flaps 20 at the alternate airport but you can only check the flaps 25 or 30 RLD.
According to the "Dispatch" requirements, regulatory accessibility of the alternate airport is thus verified with flaps 25 or 30, whereas the regulatory flight sequence is based on landing at the alternate with only the final reserve fuel on board and consequently with a mandatory Flaps 20 configuration.
So, what (and how) do you do, and why?
Thank's!
On B777, the calculation of the required landing distance (RLD) at the alternate airport is made on the OPT with the choice of flaps 25 or 30 only.
This calculation, known as "landing-dispatch", gives the maxi performance landing limit weight at any airport (destination or alternate) taking into account the regulatory requirements at the flight preparation stage (factors 0.6, 1.15, etc.) and based on the following conditions: RWY, Missed Approach gradient, RWY condition, wind, OAT, QNH, Reversers, Autoland or Manual, A/C config, A/I config, MEL, CDL, NOTAM and FLAPS.
Before the flight, the crew must verify that the landing weight will be lower than this maxi performance landing limit weight in order to be able to retain the airport as an alternate.
The regulatory provisions, which I referred to in my previous post, make it necessary to take into account the "aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance."
The regulatory flight profile, departing with the minimum regulatory fuel, leads to land at the alternate airport with only the final reserve fuel on board.
This final reserve fuel is less than 4 tons on B777.
With less than 4 tons of fuel on board, Boeing's procedures (QRH NNC "Fuel Low Qty") impose on the crew to land flaps 20.
Again, it is a matter of regulatory planning and of interpretation of regulations, not of in-flight fuel management and what may happen during the flight or what will do the crew once airborne.
Therefore, you already know at preflight that you're supposed to land flaps 20 at the alternate airport but you can only check the flaps 25 or 30 RLD.
According to the "Dispatch" requirements, regulatory accessibility of the alternate airport is thus verified with flaps 25 or 30, whereas the regulatory flight sequence is based on landing at the alternate with only the final reserve fuel on board and consequently with a mandatory Flaps 20 configuration.
So, what (and how) do you do, and why?
Thank's!
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Final reserve fuel is 30 minutes.
(as per EASA IR-OPS AMC1 CAT.OP.MPA.150(b) (5) (ii) - Fuel policy: "for aeroplanes with turbine engines, fuel to fly for 30 minutes at holding speed at 1500ft (450m) above aerodrome elevation in standard conditions, calculated with the estimated mass on arrival at the destination alternate aerodrome or the destination aerodrome, when no destination alternate aerodrome is required.")
This is approximately 3.1 tons for a B773 and 2.6 tons for a B772.
(as per EASA IR-OPS AMC1 CAT.OP.MPA.150(b) (5) (ii) - Fuel policy: "for aeroplanes with turbine engines, fuel to fly for 30 minutes at holding speed at 1500ft (450m) above aerodrome elevation in standard conditions, calculated with the estimated mass on arrival at the destination alternate aerodrome or the destination aerodrome, when no destination alternate aerodrome is required.")
This is approximately 3.1 tons for a B773 and 2.6 tons for a B772.
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At my airline (European legacy) we only have dispatch landing tables for a flaps 30 landing. We add additional fuel if landing with flaps 20, as required by the low fuel qty procedure, would cause us to exceed the available ldg distance according to the Performance Inflight tables.
Maybe the reasoning is that the use of contingency fuel occurs only after dispatch.
We have tons of lawyers and guys with slide rules in service, so I can only assume that this method has the blessing of the regulators.
Maybe the reasoning is that the use of contingency fuel occurs only after dispatch.
We have tons of lawyers and guys with slide rules in service, so I can only assume that this method has the blessing of the regulators.
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Thank's Long Haul for the reply. It is an interesting solution.
How is it written in your Sops?
In order to "add additional fuel" as you wrote, it looks like you're checking before departure with the Flaps 20 inflight tables to make sure you can dispatch...
Checking dispatch requirements with inflight tables due to the lack of dispatch tables for the specific configuration, isn't there something a little unnatural?
If this Flaps 20 question was not of concern at dispatch you obviously would not have to check the flaps 20 inflight tables and possibly "add additional fuel"?
It looks like your airline is trying to mitigate.
However, I understand that if you don't exceed the LDA with the Flaps 20 inflight tables then you're not adding fuel, is that correct? Which means it is then acceptable and obviously planned to land Flaps 20 at the alternate airport even though the Flaps 20 landing distance you checked is only satisfying the LDA and not the RLD (0.6, 1.15 factors)?
It comes down to knowing you'll land Flaps 20 and not checking the RLD but only the LDA. What if 1.667 x (uncertified) Flaps 20 landing distance exceeds the LDA?
It may have the blessing of the regulators but it may also be a loophole... Which is what I'm trying to figure out since we don't do anything (European legacy as well) and also have the same blessing... It is then a variable-geometry blessing!
Not to mention that for a short trip like US east coast to western Europe, you'll have a 3% contingency fuel of less than 1 ton and a final reserve fuel of about 2.6 tons on a B772. Occurring or not after dispatch, the use of contingency fuel is here irrelevant since you'll end up anyway with less than 4 tons at the alternate even if you don't use that contingency fuel...
Do you mind asking one of these guys, just to check that there is a deliberate blessing?
How is it written in your Sops?
In order to "add additional fuel" as you wrote, it looks like you're checking before departure with the Flaps 20 inflight tables to make sure you can dispatch...
Checking dispatch requirements with inflight tables due to the lack of dispatch tables for the specific configuration, isn't there something a little unnatural?
If this Flaps 20 question was not of concern at dispatch you obviously would not have to check the flaps 20 inflight tables and possibly "add additional fuel"?
It looks like your airline is trying to mitigate.
However, I understand that if you don't exceed the LDA with the Flaps 20 inflight tables then you're not adding fuel, is that correct? Which means it is then acceptable and obviously planned to land Flaps 20 at the alternate airport even though the Flaps 20 landing distance you checked is only satisfying the LDA and not the RLD (0.6, 1.15 factors)?
It comes down to knowing you'll land Flaps 20 and not checking the RLD but only the LDA. What if 1.667 x (uncertified) Flaps 20 landing distance exceeds the LDA?
It may have the blessing of the regulators but it may also be a loophole... Which is what I'm trying to figure out since we don't do anything (European legacy as well) and also have the same blessing... It is then a variable-geometry blessing!
Not to mention that for a short trip like US east coast to western Europe, you'll have a 3% contingency fuel of less than 1 ton and a final reserve fuel of about 2.6 tons on a B772. Occurring or not after dispatch, the use of contingency fuel is here irrelevant since you'll end up anyway with less than 4 tons at the alternate even if you don't use that contingency fuel...
Do you mind asking one of these guys, just to check that there is a deliberate blessing?
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Thank's Nike.
Of course I know the QRH note. I also know the FCTM explanation Low Fuel in 8.24.
Of course "In some situations, at the captain’s discretion, deviation from a checklist may be needed".
As I said it is not a matter of in-flight management. It is a matter of regulations interpretation. The whole point is to check a RLD based on the planned conditions. You're entering wind and contaminated Rwy condition although you're not sure you'll face these conditions once airborne if diverting to this alternate or even to another airport...
Regulations call for RLD check with expected conditions that you'll enter in the OPT.
Landing with 30 mins in the tanks at the alternate is a normal condition for regulations.
It is obviously a "non normal" condition for Boeing since it will trigger a "non normal" C/L!
Whatever is the explanation for the NNC, there will still be a NNC that you may disregard, or not, based on captain's discretion.
Usually captain's discretion applies when it will improve safety. May I say that one could consider that choosing a better alternate or making sure RLD provisions are met with Flaps 20, providing you have the tools, might more improve safety than deciding to disregard a NNC at planning stage?
Is it normal to plan on landing with a NNC, to only check a Flaps 30 RLD at planning stage and to already decide to disregard the NNC requirements? It comes down to considering this non normal C/L as normal and to systematically disregard the call for FLAPS 20.
I'm not sure it is intellectually satisfying.
Based on Long Haul post, it looks like it is not that normal since his legacy airline is calling for additional fuel based on the result of "inflight" FLAPS 20 LDA calculations...
I would also prefer the answer to be as simple and practical as saying captain's good judgment. I'm not sure that good judgment is standardised and I don't think regulations point in that direction.
Thank's for the input anyway since it comes close to what we are doing, although is it entirely satisfying?
Of course I know the QRH note. I also know the FCTM explanation Low Fuel in 8.24.
Of course "In some situations, at the captain’s discretion, deviation from a checklist may be needed".
As I said it is not a matter of in-flight management. It is a matter of regulations interpretation. The whole point is to check a RLD based on the planned conditions. You're entering wind and contaminated Rwy condition although you're not sure you'll face these conditions once airborne if diverting to this alternate or even to another airport...
Regulations call for RLD check with expected conditions that you'll enter in the OPT.
Landing with 30 mins in the tanks at the alternate is a normal condition for regulations.
It is obviously a "non normal" condition for Boeing since it will trigger a "non normal" C/L!
Whatever is the explanation for the NNC, there will still be a NNC that you may disregard, or not, based on captain's discretion.
Usually captain's discretion applies when it will improve safety. May I say that one could consider that choosing a better alternate or making sure RLD provisions are met with Flaps 20, providing you have the tools, might more improve safety than deciding to disregard a NNC at planning stage?
Is it normal to plan on landing with a NNC, to only check a Flaps 30 RLD at planning stage and to already decide to disregard the NNC requirements? It comes down to considering this non normal C/L as normal and to systematically disregard the call for FLAPS 20.
I'm not sure it is intellectually satisfying.
Based on Long Haul post, it looks like it is not that normal since his legacy airline is calling for additional fuel based on the result of "inflight" FLAPS 20 LDA calculations...
I would also prefer the answer to be as simple and practical as saying captain's good judgment. I'm not sure that good judgment is standardised and I don't think regulations point in that direction.
Thank's for the input anyway since it comes close to what we are doing, although is it entirely satisfying?
Another large legacy carrier here.
We take DDG items into account but assume F30 landings for Dispatch Landing Weight Checks.
Maybe our perf/regulatory guys have agreed that the much more conservative margins for DLW would allow a “safe" landing with variant flap using IFLD calcs, should you need to?
We take DDG items into account but assume F30 landings for Dispatch Landing Weight Checks.
Maybe our perf/regulatory guys have agreed that the much more conservative margins for DLW would allow a “safe" landing with variant flap using IFLD calcs, should you need to?
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For about 45% of our flights we use an alternate close to our home base that has one 2000m runway. It is written in our route documentation that when planning to arrive at this particular airport when the runway is wet and the ZFW is above a certain amount, dispatch will add additional fuel because a flaps 20 landing could cause the estimated landing distance from the inflight table to exceed what is available. So we don't actually check the inflight tables before dispatch for every flight as a matter of policy, which would be, as you suggest, a bit unnatural, but we do know that at this one place it could be an issue. Even if I wanted to check the dispatch tables for a flaps 20 landing though, I couldn't, because I don't have them. There really aren't any other alternates in our system that would preclude a flaps 20 landing according to either the dispatch or inflight tables, but if there were any doubt in my mind I would be able to adjust the fuel load accordingly, no questions asked. I understand your point about the fact that, on some flights, we plan to arrive at the alternate in a flaps 20 situation even if we use zero contingency fuel, and that it then logically follows that one should be dispatched according to the dispatch requirements. I have to say, however, that don't lose any sleep over it though. I trust that the guys in charge have thought about this sort of thing, and as long as they let me do my job of getting pax from A to B safely, I let them do their job of making sure that the ops manual pleases the regulator. I see it as my right and responsibility to reject any alternate where a safe landing cannot be made according to the expected conditions at my time of arrival there, but with respect to compliance with regulations my obligations stop where the airline's begin.
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@Zlin77 Thank's for the reply!
Aeroplane is not only deemed serviceable on departure, it is serviceable! Otherwise it would not depart...
But being "serviceable" does mean it will operate normally and will therefore trigger a non normal C/L calling for F20 whenever it will reach less than 4 tons of fuel on board, as should any serviceable B777.
Reaching this quantity at the alternate is a perfectly normal situation complying with fuel policy regulations for a "serviceable" airplane departing with the minimum required fuel.
Whatever happens after take off is indeed a matter of in-flight management and I thought I made clear this was not the question, emphasising that the crew could deal with the fuel as he sees fit.
But at planning stage, since you can only consider using the taxi fuel during taxi, the trip fuel for the trip and the alternate fuel to divert to the alternate, what quantity of fuel is then supposed to remain on board when reaching the alternate? The answer is simple : the final reserve fuel and possibly the contingency fuel, for a total of possibly less than 4 tons. This is how a "deemed serviceable" airplane can only be considered having to land F20 and this being already known at planning stage. Thus the logical question that Long Haul perfectly summarised : "one should be dispatched according to the dispatch requirements" when planning to arrive at the alternate in a F20 situation.
Why planning a F30 landing at planning stage if you know you should land F20 (unless discarding the NNC) due to the fuel quantity you're choosing at planning stage?
I sincerely wish the answer could be as simple as having a serviceable airplane thus planning F30, but I doubt it. Otherwise, what would be the reason for this Legacy to add additional fuel at planning stage to prevent landing F20 in some situations?
Departing with minimum fuel only leaves one option to avoid landing at the alternate with more than 4 tons : not using the contingency fuel and deciding an early diversion without performing the approach at destination in order to use less trip fuel and less alternate fuel. I'm pretty sure you'll agree this is not the normal planning stage fuel policy, although it is definitely what could "happen after takeoff". What WILL "happen after takeoff" is having to deal with LDA and not anymore with RLD.
This is all why my question is about RLD at planning stage. Why is it that you have to take in consideration all expected factors (MEL, CDL, TAF, even a possibly wet or contaminated runway condition, etc.) BUT NOT the fact that the fuel quantity you have on board WILL have you land F20 if you don't take more fuel (or if you disregard the NNC)? Why neglecting only that expected factor which is the normal consequence of landing with less than 4 tons when departing with a fuel quantity that is supposed to have you land with less than 4 tons when simply following the flight plan?
I hardly think it is a matter of being deemed serviceable. But I don't have a monopoly on the truth, I'm looking for it as everyone is, thus my question...
It might comply with regulations, but why?
And how can it be in compliance since the regulations say "Due account shall be taken of aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance."?
Isn't it an aeroplane configuration? Isn't operation of systems including performing the NNC? isn't landing F20 having an adverse effect on performance compared to a F30 landing?
I'm only looking for an explanation.
@Long Haul, thank you very much for taking the time to explain in detail your process. This is a clever option since no one has the F20 landing dispatch tables. Thus my question, trying to figure out what other operators are doing, from nothing (as we do) to something more clever. I take good note of this idea because compliance with regulations is the airline obligation (as it is also the commander's IMHO...) and that is part of why I ask the question... Hopefully I don't and won't lose any sleep over it, thank's for the wise advice. May I furthermore ask what is the ZFW amount? And are you operating both the B772 and the B773?
Aeroplane is not only deemed serviceable on departure, it is serviceable! Otherwise it would not depart...
But being "serviceable" does mean it will operate normally and will therefore trigger a non normal C/L calling for F20 whenever it will reach less than 4 tons of fuel on board, as should any serviceable B777.
Reaching this quantity at the alternate is a perfectly normal situation complying with fuel policy regulations for a "serviceable" airplane departing with the minimum required fuel.
Whatever happens after take off is indeed a matter of in-flight management and I thought I made clear this was not the question, emphasising that the crew could deal with the fuel as he sees fit.
But at planning stage, since you can only consider using the taxi fuel during taxi, the trip fuel for the trip and the alternate fuel to divert to the alternate, what quantity of fuel is then supposed to remain on board when reaching the alternate? The answer is simple : the final reserve fuel and possibly the contingency fuel, for a total of possibly less than 4 tons. This is how a "deemed serviceable" airplane can only be considered having to land F20 and this being already known at planning stage. Thus the logical question that Long Haul perfectly summarised : "one should be dispatched according to the dispatch requirements" when planning to arrive at the alternate in a F20 situation.
Why planning a F30 landing at planning stage if you know you should land F20 (unless discarding the NNC) due to the fuel quantity you're choosing at planning stage?
I sincerely wish the answer could be as simple as having a serviceable airplane thus planning F30, but I doubt it. Otherwise, what would be the reason for this Legacy to add additional fuel at planning stage to prevent landing F20 in some situations?
Departing with minimum fuel only leaves one option to avoid landing at the alternate with more than 4 tons : not using the contingency fuel and deciding an early diversion without performing the approach at destination in order to use less trip fuel and less alternate fuel. I'm pretty sure you'll agree this is not the normal planning stage fuel policy, although it is definitely what could "happen after takeoff". What WILL "happen after takeoff" is having to deal with LDA and not anymore with RLD.
This is all why my question is about RLD at planning stage. Why is it that you have to take in consideration all expected factors (MEL, CDL, TAF, even a possibly wet or contaminated runway condition, etc.) BUT NOT the fact that the fuel quantity you have on board WILL have you land F20 if you don't take more fuel (or if you disregard the NNC)? Why neglecting only that expected factor which is the normal consequence of landing with less than 4 tons when departing with a fuel quantity that is supposed to have you land with less than 4 tons when simply following the flight plan?
I hardly think it is a matter of being deemed serviceable. But I don't have a monopoly on the truth, I'm looking for it as everyone is, thus my question...
It might comply with regulations, but why?
And how can it be in compliance since the regulations say "Due account shall be taken of aeroplane configuration, environmental conditions and the operation of systems that have an adverse effect on performance."?
Isn't it an aeroplane configuration? Isn't operation of systems including performing the NNC? isn't landing F20 having an adverse effect on performance compared to a F30 landing?
I'm only looking for an explanation.
@Long Haul, thank you very much for taking the time to explain in detail your process. This is a clever option since no one has the F20 landing dispatch tables. Thus my question, trying to figure out what other operators are doing, from nothing (as we do) to something more clever. I take good note of this idea because compliance with regulations is the airline obligation (as it is also the commander's IMHO...) and that is part of why I ask the question... Hopefully I don't and won't lose any sleep over it, thank's for the wise advice. May I furthermore ask what is the ZFW amount? And are you operating both the B772 and the B773?
Last edited by Diogene; 11th Aug 2017 at 09:53.
