China's transport, tanker & heavy lift aircraft - esp. Y-20/YY-20

TerraN_EmpirE said:

Winglets are on a few military transport. C130 have been retrofit. Some C295 and C17 have them. They reduce wing vortex effect, said Vortex’s increase drag. So they improve fuel efficiency at the cost of increased costs and width.

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There is no question that winglets have positive effect on aerodynamics at certain speed and altitude. However, you can achieve the same range benefit with a larger wing. Air forces aren't exactly concerned about squeezing every little bit of CASM that airlines are. For the US Air Force transports, maybe they are doing it because productions have stopped and they are trying to find ways to give it more range. We are not at that part of development cycle for Y20 project yet.

A PLAAF spokesman has confirmed that a Y-20 has taken off for Europe (for the Airpower22 show).

More Y-20 photos from Changchun.

Y-20 transporting disaster relief supplies to Pakistan.

tphuang said:

There is no question that winglets have positive effect on aerodynamics at certain speed and altitude. However, you can achieve the same range benefit with a larger wing. Air forces aren't exactly concerned about squeezing every little bit of CASM that airlines are. For the US Air Force transports, maybe they are doing it because productions have stopped and they are trying to find ways to give it more range. We are not at that part of development cycle for Y20 project yet.

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First, yes you can to a degree. However that again creates issues of manufacturing an exceptionally long wing which adds weight and cost.
next it was added to C130s. C17 came from the factory. From the factory as part of the design not aftermarket. C295 isn’t American it’s European.
father alternative include features like rakes or fences.

TerraN_EmpirE said:

First, yes you can to a degree. However that again creates issues of manufacturing an exceptionally long wing which adds weight and cost.
next it was added to C130s. C17 came from the factory. From the factory as part of the design not aftermarket. C295 isn’t American it’s European.
father alternative include features like rakes or fences.

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hmm, winglets also add weight and complexity. Keep in mind that you have another part now that you have to produce and maintain. That's another supplier in your supply chain that you need to worry about. Making a wing slightly larger doesn't create that problem at all.

Airlines have done experiments of retrofitting winglets onto existing airliners. In many cases, it hasn't even made financial sense for them. I will give you an example. A few years ago, JetBlue was looking into adding sharklets to its A320CEO fleet. They added it to less than 10% of the fleet. It ended up abandoning the project because the fuel savings from adding sharklets was not worth the additional complexity of retrofitting and maintaining it. And that's for an airline that runs extremely high cycle in terms of utilization, so has the most to gain from squeezing every single ounce of fuel efficiency. Given that PLAAF does not have similar requirements in terms of wingspan for category 3 gates, what is the rationale to add something that will make wing construction more complicated when they can achieve the same objective from just a larger wing? Maybe there will come a time when it makes sense to add winglet to Y20, but there are more pressing goals to this project like fitting WS20 and getting tanker/transport version into mass production.

tphuang said:

hmm, winglets also add weight and complexity. Keep in mind that you have another part now that you have to produce and maintain. That's another supplier in your supply chain that you need to worry about. Making a wing slightly larger doesn't create that problem at all.

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well, having a longer wing also adds weight and complexity to the overall structure, as you now have more lift on the wing to deal with.

tphuang said:

Airlines have done experiments of retrofitting winglets onto existing airliners. In many cases, it hasn't even made financial sense for them. I will give you an example. A few years ago, JetBlue was looking into adding sharklets to its A320CEO fleet. They added it to less than 10% of the fleet. It ended up abandoning the project because the fuel savings from adding sharklets was not worth the additional complexity of retrofitting and maintaining it. And that's for an airline that runs extremely high cycle in terms of utilization, so has the most to gain from squeezing every single ounce of fuel efficiency.

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The A320CEO already had a small triangular winglet, so perhaps the change to the larger sharklet didn't make enough sense. None the less, I believe there should be a good amount of improvement in fuel efficiency (and therefore range) from no winglet to winglet. Chinese aerospace industry has experience with winglets from various other projects (C919, drones, etc.) Therefore I think @by78's explanation - the connection to Antonov and the experience they bring - to be the most likely reason.

T-U-P said:

well, having a longer wing also adds weight and complexity to the overall structure, as you now have more lift on the wing to deal with.


The A320CEO already had a small triangular winglet, so perhaps the change to the larger sharklet didn't make enough sense. None the less, I believe there should be a good amount of improvement in fuel efficiency (and therefore range) from no winglet to winglet. Chinese aerospace industry has experience with winglets from various other projects (C919, drones, etc.) Therefore I think @by78's explanation - the connection to Antonov and the experience they bring - to be the most likely reason.

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hmm, every wing has its own weight and complexity. If you design it to be larger from the beginning to achieve certain fuel tank, I don't see why it would be more complicated than a slightly smaller wing. As we've seen in civil aviation, the more complicated winglet you add, the efficiency you could squeeze out at certain speed and altitude. So, there is normally incentives for airliners to incorporate more complicated winglets to squeeze out efficiency. For military transport/tanker, you are more concerned about range.

Basically, you have a B757 vs A321NEO situation. The former had longer range despite using older engine, because it just had larger wing that carried more fuel. But in the end, 757 didn't sell well because it needed a 767 sized gate. If Y-20 doesn't have the same limitation, I don't understand why you need to add more complexity to its design when your goal is to just get as many of them into service as possible.

C919 has to conform to category 3 gates. That's why it makes sense to add winglets on there.

As one of my professors once said, as a rule of thumb, to get the same effect of making the wing longer by 1 metre/foot, you a winglet that is 2 metre/feet. Boeing and Airbus sales people make it seem like winglets are magical, but in reality like @tphuang said, they only have a small positive impact over a narrow operating range, their benefit need to over come their own added weight, drag and cost.