rethinking wings?

[IAHM-COL]

Rethinking wings?

[KL-666]

This development to minimize to the max worries me a bit. When things were made overly strong, a 707 survived loosing the wing part outboard of the outer engine. A quarter of the wing length? But now making everything just strong enough, we see with engine manufacturers already problems arising.

Kind regards, Vincent

[IAHM-COL]

A very similar wondering Jwocky has had.

[jwocky]

Actually, I did in the meantime a little bit math on this, based on the wing seen in that video. Under the assumption, we talk about 777-200 size here, which seems to be what the video implies, we have roughly wing area of 214sqm per wing at a lever of 30.5m from the fuselage middle line. Which gives us on average a width of 7m, give or take. Just to get some estimations together here.
So, 30m without any spars, in this thirty meters, we store about 85,000l of fuel, that is 68,000kg. So, if all the tanks in this wing are full, the wing is heavy, but it is by volume also literally full. Nothing really moves because, well, all tanks are full, which means, the tanks also have no tendency to bulge too much under any outside force.
However, once the tanks are not full anymore, liquid can move in them. Thus, we have the force of the wind on the leading edge of the wing and we have dynamic forces of liquid in the tanks. At half full, that means, we have a load pressing on the wing edge in regular leveled wing flights that forces this wing to actually deform by up to some centimeters. The profile changes. And in this wing, we have 34000kg happily moving at least over a distance of some meters. Now, if that plane changes it motion status in any way, 34,000kg go on the move. They do it in a conventional wing as well, that is why big planes have not one big, but several tanks in the wings. So, in a turn, nothing we wouldn't see with a conventional wing happens. But, when the pitch changes, when the plane descends, when the plane accelerates, it means, the fuel flows to the back of the tanks. Opposite to a wing with spars, hard connected to the upper and lower side of the wings, this wing can deform over the whole length. It is already working due to the pressure on the leading edge during flight, now this effect adds up. Technically the wing bulges out in the area where the backside of the tanks is. Which leads to two effects: First, the lift profile changes. Because nothing actually gives the spar-less wing stability in the z-axis and since metal can't become spontaneously more, the wing gets shorter by about the same amount in the x-axis. The second thing is, exactly when you take the nose up to flare in the end approach, your wing will lose lift while the tank bulge is maximized and reduces the air flow over the flaps behind them. If you have a good headwind, exactly from your course direction, mother nature will probably save your ass, but if you have no wind, or God beware are forced to try a tail wind landing, you will just drop the last few meters. It will behave like a built-in wind shear.
Of course, partially you can compensate for this effects by reducing the maximal landing weight. Well, and the maximal TOW as well, because at take-off, you have your nose up as well, and for MTOW flights, you have usually not max fuel on board.
Now, lets look at this from the economical side. We can save 2.5% (actually, I come up slightly higher savings) fuel consumption. But we pay for this with a lower weight capacity and the chance on some quite hairy flight behavior at take-offs and landings. So, we have less seats on a plane the same size, which actually results in even bigger fuel savings, but the fix costs per seat and light mile increase. So, you can buy a 777-200ER for aboutish 250 million USD new. This means, 45,000 cycles without and lifetime expanding measures. So, 45,000 flights * 313 seats, that is basically your income calculation base with that plane. Now imagine, the plane is only half of those flights booked fully. Then a weight reduction by 10% means, you end up with half of the flights at max at 22500*282 and the rest, whatever you can fill. Over all, you save a little more than 2.5% fuel costs but for the price of on average 5% the income.
The real killer is, that the wing works, as described above. The wear is higher than on a wing with spars because of the lack of vertical stability. Which means, the plane will not make the full 45,000 cycles. Maybe 30,000, maybe 35,000, it is hard to say, it also depends on the materials used to make each part of the wing. Can be as well, wheel well area needs replacing after only 15,000 cycles. So, your plane has at best a limited lifetime at increased maintenance costs. In the worst case scenario, everyone thinks it is a good idea and after the first 10,000 flights, those things fall out of the sky because the wings break off from metal fatigue. And that doesn't even include the cases, Vincent spoke about, when a crew has to treat the plane a bit rougher, be it in a crosswind landing, or actually touches something. This wing has almost no stability against any force working along the x-axis and a very limited stability on the z-axis. A sudden updraft for example produces a z-force with 30m leverage. You may survive a good wind shear landing, but after that, you need to exchange both wings because they are probably structurally compromised. No way, you pay that from 2.5 (or even 2.8% as I calculated) fuel savings.
So, I am not a fan of building wings that are in two directions just strong enough for surviving exclusively nice weather flights at a reduces lifetime.

[HJ1an]

I am fascinated by the computer tech. But... yikes!

[jwocky]

The computer tech works, one has only to go and feed the program with the right parameters, I guess.

[KL-666]

Fine if the computers work. But there is another factor. What if the materials do not meet the strength as advertised? Then i would like a safety margin in the design.

https://www.nytimes.com/2017/10/10/business/kobe-steel-japan.html

I wonder if engine manufacturers have used Kobe Steel. There is a trail of falsifying steel documentation for over 10 years. The last few years engines started to disintegrate inexplicably. Is there some relation?

Kind regards, Vincent

[IAHM-COL]

oh no! That's outrageous!

[HJ1an]

https://www.nytimes.com/2017/10/10/business/kobe-steel-japan.html
I wonder if engine manufacturers have used Kobe Steel. There is a trail of falsifying steel documentation for over 10 years. The last few years engines started to disintegrate inexplicably. Is there some relation?

Ouch.

I would expect the engine manufacturers themselves scrutinize their raw materials when it comes to building gigantic blades of engineering marvels spinning at 3500 rpm, rather than - say a alloy part that acts as a chassis of a car but.. what do I know, right?

[jwocky]

I am not sure, can you even test steel a 100% after it is produced? The way as I imagine it it,s they get for example bars, roll them out flat and punch the basic parts, for example turbine blades, out of it. Even if you x-ray every piece then, it would be very hard to find microscopic inclusions for example, but that is where the cracks start.