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Guest Paragon

Reserve fuel.

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Guest Paragon

I was wondering what to enter into the FMC where it says reserve. Do I enter the actual reserve + taxi + alternate + holding fuel or just the actual reserve fuel. What difference does it make, if any?-Mikkel

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Guest pierre974

Hi,I think it's Minimum Landing Fuel + Alternate Fuel + a part of Contingency Fuel...Have a look at the FUEL PLANNING METHODOLOGY in the manual (2 - 16), it's very well explained.Regards :-wedge

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Guest Raphouille

Hi !basically, FMC reserve fuel input may be used to avoid a landing "below minimum fuel" at destination and could be the summ of: ALTN fuel+ MIN LEGAL RESERVE (30minutes hold at 1500ft AGL)+ MIN DESIRED LANDING FUEL (see manual P4-6)During cruise, if the "Fuel at destination" calculated by the FMCis below this value, I'm planning to land at any suitable route alternate... Obviously, some real ATP pilots would give you a best advice on this.best regards,Rapha

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Guest Paragon

Excellent, thanks guys. What I can come up with from the manual is:Minimum, which is either 19000 or 24000 depending if it's a domestic route or international. Then the alternate fuel is added plus half of the contingency fuel.Does this seem about right?-Mikkel

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Mikkel-A couple of pointers the help you think "inside the box" on the reserve fuel entry....(We commonly refer to "thinking inside the box" in order to be able to understand what the FMC is saying/doing for us.... catchy, eh?)When you plug a reserver fuel number into this line in the FMC initialization, what you are telling the system is this:"If you predict that I am going to land at my destination with LESS THAN THIS AMOUNT OF FUEL ON THE AIRPLANE- you need to let me know!"This being the case- you want this number to include all the fuel you would need to reach your alternate and land....Think of it as a nagging reminder....On a "good weather day" you would generally be okay just using the MINIMUM LANDING FUEL (19,000lbs) + ALTERNATE FUEL (varies by distance to your alternate- see page 2-12 for an overview)By adding these two figures together- the system will notify you if you are still airborne and have reached the point where it is saying, "hey- you need to get on your way to the alternate NOW."There is a technique to using this figure, however- and it depends on the captain. I generally operate my cockpit to avoid having to make decisions quickly. As such- I always add a buffer.... My thought process works a bit like this:1) Nice clear day at destination: MIN LANDING FUEL + 15 minutes of fuel burn.2) Moderate Weather and flight plan includes an alternate destination: MIN LANDING FUEL + ALTERNATE FUEL + 15 minutes of fuel burn.3) Miserable Weather and flight plan includes an alternate (or two) and traffic can be expected to get stacked into holding: MIN LANDING FUEL + ALTERNATE FUEL + HALF MY HOLDING/CONTINGENCY FUEL + 15 minutes of fuel burn.You see where I'm headed with that process?The airplane will always give me a warning 15 minutes BEFORE I hit a point where I need to make a decision about whethe we are going to continue to the destination or tell ATC "we need to go to XYZ airport."Why 15 minutes? Because I want time to discuss it with my crew, talk to company dispatchers to get their input and concurrance,make arrangements with ATC and familiarize ourselves with the changes to our plan.....Hope that lengthy and verbose explanation helps...OH- I've just been reminded that we have updated the logic on the RESERVES entry so that it gives you the appropriate visual/aural warnings for insufficient fuel.... It's apparently not "quite right" in V1R2, which you have..... In V1R3 it will be....


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Guest Paragon

Thank you for the lengthy reply...I'll print this for use when I plan my fuel load. I am using the 747 fuel planner, I can't remember the name of the author, but it seems very good. One thing about the fuelplanner though, I cannot enter anything less than 100nm for the alternate. Say for example if I'm flying to EGLL, my alternate would probably be EGKK, which is a lot less. I guess I could just subtract manually for this though.Thanks again for the explanation.-Mikkel

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Guest D17S

Great description. I especially liked the analogy to "Thinking inside the box." Just to expand on this theme a bit, let

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>anything less than 100nm for the alternate. Well, talk to the person who created the tool. On the other hand I understand why he thought 100 nm minimum is reasonable. If the weather is bad in EGLL it is also likely to be bad in EGKK. You may have to fly at least 100 nm to get away from the weather. Again, it all depends on the situation. Michael J.http://www.precisionmanuals.com/images/forum/pmdg_747F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

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I thought I knew how to come up with the reserves figure, but this post has taught me better. A must read for everyone, even real drivers. I bet there aren't a lot of 'em who add those 15 extra minutes which could be vital. Thanks for all the info.Best Regards,Victor Limahttp://www.precisionmanuals.com/images/forum/800driver.jpg


Cheers,
Victor M. Lima
 

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Guest dickwu

An exceptional example to show how FMC helps pilots to make decisions and how pilots utilize their resourcesto aid their job. A very good lesson. ThanksDick

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Guest Paragon

Okay I just tried a flight with the new method in mind. It worked as good as can be expected. The trip was 5000+ and my reserve fuel entered into the FMC was 28,5 (24 + 4,5) and I landed with around 21. For around three hours I had some 100+ tailwinds, but that turned around to some 20-30 kt headwind at the end of the trip.The problem was, I never got any messages on the FMC saying that I would land with less fuel than what I entered into the FMC. When would I see a message that I need to figure out a place to land fast?

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