What is the structural impact on the wing if no fuel is stored in the wings and just in the fuselage and how to counter possible advantages/disadvantages? Has this topic already been researched?
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1$\begingroup$ Please don't re-post your closed question (now deleted)! Wait for it to be re-opened. And please address the points from Federico's comment first... $\endgroup$– BianfableMay 11, 2021 at 10:59
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$\begingroup$ Sorry for that. I already adressed his points. What remains unclear? $\endgroup$– mldmnnMay 11, 2021 at 11:08
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3$\begingroup$ It is unclear to me what exactly you want to know. "What happens if..." isn't really a specific question (like e.g. "How much thinner could wings be if..."). Right now, it sounds like you want to start a discussion about this topic, but this site is not a discussion forum. Have a look at the tour to learn more. $\endgroup$– BianfableMay 11, 2021 at 11:11
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1$\begingroup$ Your question implies that planes currently store hydrogen in their wings. But there are no planes that store hydrogen in their wings (at least that I am aware of), the energy density is way too low. Planes run on jet fuel, which is basically kerosene. Jet fuel is stored in the wings. Are you asking about the impact of not storing jet fuel in the wings? $\endgroup$– Daniel KMay 11, 2021 at 11:36
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1$\begingroup$ I get the impression you're trying to ask "what if we ditch wet wings and also use hydrogen" $\endgroup$– AbdullahMay 11, 2021 at 11:54
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2 Answers
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This has been well-studied, here are the basics.
For the case of fuselage tankage for fuel: The structural loads caused by the weight of the fuel in a fuselage tank must be transmitted between the wings and the fuselage. This means beefing up the wing-to-fuselage attachment points, which is not required if the wings carry the tankage instead. Putting the tankage in the fuselage also means less room for passengers and cargo.
The best place for this fuselage tank would be right at the center of gravity so the CG shift with fuel consumption is minimized- which unfortunately puts the tank right where the passengers sit. And because this places fuel in close proximity to passengers, it creates a risk factor during a crash.
There are more subtleties involved, but these are the primary considerations. I invite the experts here to weigh in with more details.
answered May 11, 2021 at 19:30
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$\begingroup$ An example would be the B-52G using a wet wing, which, "remarkably, had both a lower empty weight and substantially higher takeoff weight" historynet.com. $\endgroup$– user14897May 11, 2021 at 22:54
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$\begingroup$ @ymb1 Previous versions of the B-52 also held their fuel in the wing, albeit in rubber bladders. Those added weight, too. $\endgroup$ May 12, 2021 at 1:49
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$\begingroup$ @PeterKämpf: Thanks for the tip. I checked the fuel capacity, the -F carried 227,000 L, while the -G carried 262,000 L. $\endgroup$– user14897May 12, 2021 at 2:08
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I'm a vibrations guys (although not specifically wing vibration), so let me add one point to complete niels nielsen's answer.
If the mass of the wings is reduced by removing the fuel, but the stiffness of the wings stays the same, then the natural frequencies of the wing will go up. A higher natural frequency would have an effect on flutter margin (probably makes it better). Dynamic loads on the wing (e.g. fan blade out loads) would also be affected, although it would be hard to predict if these would go up or down. Likely for some components, these loads would go up, but for others they would go down. By components here I am referring to things like the engine mounts, pylon, and pylon to wing connections.
On the other hand, if mass is removed, you could keep the natural frequencies the same by reducing the stiffness a comparable amount. This would save weight and likely cost.
I don't have exact numbers for either case, but it should be an appreciable amount.
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$\begingroup$ If mass is removed ... This would save weight and likely cost – not for wings, as that mass helps counter the bending moment from the lift; airplanes without under-wing engines have heavier wings and reduced payload because of that. $\endgroup$– user14897May 12, 2021 at 1:05