Boeing 777 FMC Reserve Fuel
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Boeing 777 FMC Reserve Fuel
Dear friends,
What's the figure you enter into PERF INIT Reserve fuel in a flight with a reclearence fix? Should it be alternate fuel +hold? Or alternate + hold + route contingency from reclearence fix to destination?
Happy landings!
What's the figure you enter into PERF INIT Reserve fuel in a flight with a reclearence fix? Should it be alternate fuel +hold? Or alternate + hold + route contingency from reclearence fix to destination?
Happy landings!
FMC reserve fuel
really depends on the operators management and their FOM as to what they wish to apply, however the value would normally be Altn (for Destination) + Hold only. The assumption is that you may use up the variable reserve enroute so it is not expected to be available on arrival.
This is irrespective of being refile or not.
For a refile, the company policy may change details from the basic criteria, but the case will normally be that the flight may not proceed past refile unless it either has suitable weather such as not to require an alternate, and has adequate fuel reserves from that point to destination, being variable, and holding, or has adequate fuel reserves including variable, alternate flight fuel and hold to proceed to a suitable alternate airport. Your fuel policy would provide the information needed. In almost all cases, the onwards (to destination) case will require the higher amount of fuel, and is the value entered into the FMC reserve field. The only real change on the B777 from earlier products is the FMC assumes a descent to the destination, even if there is no arrival loaded, whereas the B744/767 did not. When you add an arrival, do note that the fuel calculation required to complete the arrival as loaded may not reflect the legal criteria of the company policy, dependent on wording, and may give an "insufficient fuel" message that is not really valid in relation to the fuel policy requirements.
Garbage in- garbage out.
expanding on that, there are occasions where the legal fuel is patently inadequate, and where a diversion may occur would result in marginal fuel available; ie a go around from LAX to the west, with an alternate at LAS, will result in not achieving a climb after GA, not achieving cruise altitude, and extended track miles before getting on course. Same case for JFK, dependent on which alternate is selected. (terrain may also result in additional track miles but should be accounted for by the flight navigation department in assessing alternates).
This is irrespective of being refile or not.
For a refile, the company policy may change details from the basic criteria, but the case will normally be that the flight may not proceed past refile unless it either has suitable weather such as not to require an alternate, and has adequate fuel reserves from that point to destination, being variable, and holding, or has adequate fuel reserves including variable, alternate flight fuel and hold to proceed to a suitable alternate airport. Your fuel policy would provide the information needed. In almost all cases, the onwards (to destination) case will require the higher amount of fuel, and is the value entered into the FMC reserve field. The only real change on the B777 from earlier products is the FMC assumes a descent to the destination, even if there is no arrival loaded, whereas the B744/767 did not. When you add an arrival, do note that the fuel calculation required to complete the arrival as loaded may not reflect the legal criteria of the company policy, dependent on wording, and may give an "insufficient fuel" message that is not really valid in relation to the fuel policy requirements.
Garbage in- garbage out.
expanding on that, there are occasions where the legal fuel is patently inadequate, and where a diversion may occur would result in marginal fuel available; ie a go around from LAX to the west, with an alternate at LAS, will result in not achieving a climb after GA, not achieving cruise altitude, and extended track miles before getting on course. Same case for JFK, dependent on which alternate is selected. (terrain may also result in additional track miles but should be accounted for by the flight navigation department in assessing alternates).
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Dear friends,
We are all relatively new to type and we were all taught the we should enter in the reserves field hold + alt, which would represent the minimum fuel over destination (of course we would have headed to the alternate long before
).
But some guys, think that you cannot consume your route contingency before you reach you reclearence fix, so the idea is:
- before reaching the recleareance fix you reserves should read: 10% route contingency (which is 10% of the trip fuel from reclearence fix to destination) + alt + hold. If you have an insufficient fuel message anywhere before the reclearence fix, it would mean that you'll reach the reclearence fix below the minimum fuel required to proceed to destination, so star acting now to save fuel;
- after overflying the reclearence fix your reserves should be changed to alt + hold, for obvious reasons.
I think it is a feasible method, although a good fuel log would alert you very soon as well.
What do you think of that? How do you actually do in your companies?
Thanks a lot for the help and,
Happy landings.
We are all relatively new to type and we were all taught the we should enter in the reserves field hold + alt, which would represent the minimum fuel over destination (of course we would have headed to the alternate long before
).But some guys, think that you cannot consume your route contingency before you reach you reclearence fix, so the idea is:
- before reaching the recleareance fix you reserves should read: 10% route contingency (which is 10% of the trip fuel from reclearence fix to destination) + alt + hold. If you have an insufficient fuel message anywhere before the reclearence fix, it would mean that you'll reach the reclearence fix below the minimum fuel required to proceed to destination, so star acting now to save fuel;
- after overflying the reclearence fix your reserves should be changed to alt + hold, for obvious reasons.
I think it is a feasible method, although a good fuel log would alert you very soon as well.
What do you think of that? How do you actually do in your companies?
Thanks a lot for the help and,
Happy landings.
