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rennman

Landing Fuel Weight?

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Greetings. What should be the ideal fuel weight range when my wheels hit the runway? The plane flys very different if I'm too heavy or too light.

Thanks.

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What should be the ideal fuel weight range when my wheels hit the runway?

 

The manual says 24,000 pounds/10,886 kilograms as a minimum. I would recommend a flight planner such as PFPX, FSBuild, or Flight Operations Center to plan flights for routes and fuel calculations.

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It's not just fuel weight you're concerned about, it would actually be the gross weight. If you're flying a Boeing 747-400F and you're at maximum payload, you are going to be significantly heavier on landing than if you were flying a Boeing 747-400 that was only carrying passengers and their bags.

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Thanks for responding.

Yes I should be thinking of gross weight. Should the ideal landing weight always be as light as possible, or is there a such thing as too light ?  Thanks again.

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Well, when you're doing your fuel planning, you also plan for reserves. You want to land with at least your reserves on board. Other than that, it's hard to give exact numbers since even with the same fuel load, your zero fuel weight may be different, therefore affecting your gross weight and subsequently your approach speeds.

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I think what I am really trying to find out is...what is the optimum gross landing weight?...this should be only one figure regardless of all variables. Once I know that, then it's up to me to do the right calculations to be at that weight on landing.

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The optimum value would be as close to 0kg as possible (with enough fuel to taxi to gate). There is legal value for minimum landing fuel on alternate, but it differs from CAA to CAA. It should be around 6 tones for 747. Then you have SOP minimum landing fuel at alternate which is more restrictive.

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I think what I am really trying to find out is...what is the optimum gross landing weight?...this should be only one figure regardless of all variables. Once I know that, then it's up to me to do the right calculations to be at that weight on landing.

Never heard of a term such as optimum gross landing weight. On landing, you'd want to go as slow as you could go, so naturally, it would be closer to zero. Problem is, the airplane alone weighs at least 394,000 pounds before you even start loading passengers, cargo, and fuel. And on a typical flight, you aren't going to try to get as close to a specific landing weight as possible. As long as you're below the maximum landing weight and you are within runway performance limitations, you're good to go. So if your maximum landing weight is 630,000 and the runway is only 5,000 feet long at sea level, according to the charts here, you're limited to 628,900 pounds at flaps 30 in order to be able to stop on the runway. As long as you are below that weight, you're good to go. You're not going to start throwing passengers and cargo off just because you couldn't get your landing weight down to 400,000 pounds.

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That answers my question very well. If you want to be as light as possible on landing, then the goal is to be just above minimums. The reason I ask is that landing speeds and trim vary alot if I'm really light to really heavy. This plane is the best add on I've ever flown. IMO. Thanks for helping me fly it!

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Just keep in mind that's absolute minimum fuel in case you spent all contingency fuel, perform a missed approach, fly to the most distant alternate you planned, hold there for 45min, and land (I'm sure I forgot something to add, but anyway, you should see the logic). In other words, you do not want to land at your main destination with that minimum fuel on board.

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That answers my question very well. If you want to be as light as possible on landing, then the goal is to be just above minimums. The reason I ask is that landing speeds and trim vary alot if I'm really light to really heavy. This plane is the best add on I've ever flown. IMO. Thanks for helping me fly it!

Yes, it is true that landing speeds and trim vary based on weight, but you really shouldn't be trying to land with as little weight as possible, otherwise you might as well be flying the plane empty with no passengers or cargo. Airlines don't make money that way. If anything, they would try to pack as much passengers and cargo as they possibly can to try to maximize profits. In most airports where you would fly a 747, the runways would be long enough that you don't have to worry much about not being able to stop in time. But up to you how you want to fly, I suppose.

 

Just keep in mind that's absolute minimum fuel in case you spent all contingency fuel, perform a missed approach, fly to the most distant alternate you planned, hold there for 45min, and land (I'm sure I forgot something to add, but anyway, you should see the logic). In other words, you do not want to land at your main destination with that minimum fuel on board.

You pretty much nailed it. For FAA purposes, looking at my notes, for domestic fuel, it's trip fuel, fuel to the most distant alternate if required, 45 minutes at normal cruise speed. For flag, it's trip fuel, fuel to most distant alternate if required, 10% trip time, 30 minutes holding at 1500 AGL.

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On boeing FMCs:

 

Look at the PROG page and see the predicted fuel at your destination. Take this number, write it down. 

 

Look at your PERF page, which should show your Zero Fuel Weight (ZFW). Ad the first number to this. It will be your landing weight!

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 I see the logic. You want to be as light as possible on landing as all the needs of the flight will allow. Pass, cargo and resereve fuel will remain the same in a perfect scenario, but trip fuel weight will always change during the flight. So when I land, my fuel weight should not be much more than fuel to the most distant alternate if required, 45 minutes at normal cruise speed. For flag, it's trip fuel, fuel to most distant alternate if required, 10% trip time, 30 minutes holding at 1500 AGL.

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 I see the logic. You want to be as light as possible on landing as all the needs of the flight will allow. Pass, cargo and resereve fuel will remain the same in a perfect scenario, but trip fuel weight will always change during the flight. So when I land, my fuel weight should not be much more than fuel to the most distant alternate if required, 45 minutes at normal cruise speed. For flag, it's trip fuel, fuel to most distant alternate if required, 10% trip time, 30 minutes holding at 1500 AGL.

Basically. Don't go too crazy about getting exact weights down since that can vary from flight to flight. Obviously, on a longer flight, your trip fuel will be much greater than it would be on a shorter flight. Your fuel to the most distant alternate is also going to change as well, depending on how far it is from your destination. On one flight, your alternate might only be 50 miles away, but on another flight, it might be 500 miles away. That's a huge difference. And you might have a flight that has weather that's good enough that you might not even need an alternate. As for trip time, you might have one flight that's an hour long versus one that's 16 hours long. 10% of that is 6 minutes and 96 minutes respectively. That's a huge difference. Even 30 minutes holding at 1500 feet AGL could be different. One day, you might land at JFK where 1,500 AGL is 1,500 MSL. Another day, you might land at Denver where 1,500 AGL is 7,000 feet MSL.

 

The point I'm trying to get across here is you want to land as light as practical, but you don't want to go too crazy with exact numbers. As long as your weight is low enough to allow you to stop on the runway, you're good.

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I think I'm getting it. My calculations show about 25,000 pounds of fuel remaining without any diverts to alternate. This is a big difference from my last flight where I landed with 125,000 pounds remaining. It was a good landing but my angle of attack on approach was too high because I was so heavy. It so great that this a/c simulates it. Thanks again for your help!

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I think I'm getting it. My calculations show about 25,000 pounds of fuel remaining without any diverts to alternate. This is a big difference from my last flight where I landed with 125,000 pounds remaining. It was a good landing but my angle of attack on approach was too high because I was so heavy. It so great that this a/c simulates it. Thanks again for your help!

Yeah, 125,000 pounds is way too much on landing....but if your angle of attack was high, you might have also been going too slow, or a combination of both too heavy and too slow.

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Couldn't go faster without exceeding flap speed. AOA was too high at max flap 30  speed because I was just way too heavy...I'm glad im learning these things in the safety of a sim!

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Couldn't go faster without exceeding flap speed. AOA was too high at max flap 30  speed because I was just way too heavy...I'm glad im learning these things in the safety of a sim!

Then you may have to shoot for a flaps 25 landing. If you're too heavy for even that, probably time to enter a holding pattern and dump fuel. In any case, you probably exceeded the maximum landing weight if the approach speeds were that high.

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