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Reserves Question

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Hi,Can someone briefly explain reserves, mostly how do you know what number to put in the FMC. I have a private pilot's knowledge of reserve fuel and how much should be carried, but not much more. For example if I am carrying 5k reserve fuel, what number would I enter in the FMC?Thanks,Jeff


Jeff

Commercial | Instrument | Multi-Engine Land

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I'm not quite sure what to put there. All I ever put in there is 5.2, as I believe that is just over an extra hour of fuel.If you know your alternate airport, you can look in the fuel burn charts in the manuals to figure out how much fuel you need.Good luck.-stefan


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Hi Jeff,I'm not sure if this is what you're looking for but if you carry 5k or 5,000lbs of fuel, you would enter 5.0 into the FMC. I've heard that 5,200lbs or 5.2 entered into the FMC would give you about an hour of reserve fuel. Ken.

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Guest frankathl

Hi Jeff,This is a complex question, as far as I

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Guest Shalomar

Donny AKA ShalomarFly 2 ROCKS!!!I don't consider myself more experienced, but I have been looking over the manual for my PMDG 777. If you properly prepare for all contingencies and they do not occur, you might arrive at your destination at an overweight situation for the runway. It doesn't make it any easier, but in that case it is recomended to either offload payload (not looked upom favorably by airlines I assume), make an extra fuel stop at a place so you can carry the contingency fuel or not carry fuel for certain contingencies that in your pilot's discretion can be safely eliminated on your particular flight. Or reduce certain contingency quantities. It might also be an isue with weight on departure depending on runway length.Best Regards, Donny:-wave

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Guest frankathl

Hi Donny,You do need to take into account both structurally limiting and performance related aircraft weights(runway length and condition, winds, temperature, etc) for departure and destination when calculating fuel load and plan accordingly. So, yes, a compromise may be necessary, but, as I mentioned before, you do not always need to carry maximum reserve fuel, anyway. It comes down to experience as well as running the numbers.BR,Frank

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Guest PittsburghII

Hi Frank, That was an excellent description of how to plan fuel :-) When I read the original question, I guess the question is how much to put in the reserve field in the FMC. My understanding is that what you put in that field during preflight determines the level at which the INSUFFICIENT FUEL message will trigger. Hope that answers the original question, and, when combined with Frank's excellent post, sheds a little light on how this field is used.Thanks,BoazKSEA (previously EKCH)

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Guest tmetzinger

>Hi Frank,>> That was an excellent description of how to plan fuel :-)>When I read the original question, I guess the question is how>much to put in the reserve field in the FMC. My understanding>is that what you put in that field during preflight determines>the level at which the INSUFFICIENT FUEL message will trigger.>Hope that answers the original question, and, when combined>with Frank's excellent post, sheds a little light on how this>field is used.>>Thanks,>Boaz>KSEA (previously EKCH) BOAZ is correct, the RESERVE field in the PERF INIT page is used to trigger the insufficient fuel alert. What you put in there is up to you.I tend to put the fuel I need for my US 45 min reserve, my alternate, and any contingency fuel into that field. That way if I'm assigned a hold somewhere I know I can hold until I get the light, and them I'm eating into my "spare" fuel.The insufficient fuel warning is a very good reminder for you - and what it tells you is "You need to change what you're doing NOW, or you may put your flight at risk".Note to FSBuild users - you can specify your holding fuel and taxi fuel and such in FSBuild both in quantity (i.e. 300 Lbs for taxi) or in time (i.e. :30 for holding), and it will convert time to quantity for you in the dispatch nav log.

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Guest frankathl

Hi Boaz and Tim,Yes, I see I shouldn't have made a direct connection between the amount of reserve fuel actually carried and the amount of fuel you enter into the RESERVES field in the FMC. As both of you pointed out, the amount entered in that field depends upon the quantity you want to have remaining in your tanks when the INSUFFICIENT FUEL warning is generated, and this could be other than the total amount of reserve fuel on board.With regard to fuel reserves in general, the amount carried on top of legal minimums seems very much to depend on the individual airline and the part of the world you are flying in. Asking for a definitive answer here is like asking for a definitive set of checklists or procedures. The answer you receive will depend to a large extent on whom you ask(which goes for most questions, I suppose? :-))BR,Frank

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Guest tmetzinger

As both of>you pointed out, the amount entered in that field depends upon>the quantity you want to have remaining in your tanks when the>INSUFFICIENT FUEL warning is generated, and this could be>other than the total amount of reserve fuel on board.One nit to pick... the alert doesn't come on when you actually nibble into the reserve, the alert comes on when the FMC predicts you'll have less than the reserve at the completion of your flight.

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Hi,SAS uses the following data:Taxi Fuel: Normally 200kg, 300kg for long taxi ways (Schiphol)Trip Fuel: Speaks for itselfContingency Fuel: 5% of trip fuel, min 500kgAlternate Fuel: Fuel to alternate airportCompany Fuel: Extra added fuel decided by airlineExtra Fuel: Extra fuel decided by captainFinal Reserves: Fuel to fly for 30min at 1.500ft over alternate (ex 1.000kg for 737)So in the FMC for reserves you fill in:Total Fuel - Trip fuel - Taxi Fuel


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System: P3D V4 - 80386 DX2 - 4MB RAM - 3dfx Voodoo5 - Windows 3.11

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Guest frankathl

Hi Tim,Oh yes, of course, I forgot it's predictive! That's why you can sometimes get INSUFFICIENT FUEL warnings early on in a flight.Thanks,Frank

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Guest frankathl

Thanks, Egbert!Just the kind of information I was looking for.BR,Frank

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Thanks for the help everyone!Jeff


Jeff

Commercial | Instrument | Multi-Engine Land

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