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The Shijiazhuang (now part of AVIC) Y-5B, a Chinese version of the Antonov An-2, has winglets of a particular type:

Y-5B wingtips with winglets
Photo by Linshuo at Airliners.net

Quite a futuristic design for this old biplane of 1958, still in production. Not all version of the Y-5 have such wingtips though:

An-2 wingtips with no winglets
B-50AG. Photo by Weimeng, AirTeamImages

What are the advantages of these winglets in this case, compared to more common ones? Why only one the upper wing? Are they used on other aircraft?

mins
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2 Answers2

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As you said, the Y-5 and Y-5B are Chinese variants of the Antonov AN-2. The Wikipedia page gives this info on the Y-5B:

Shijiazhuang Y-5B-100 – Y-5B aircraft fitted with triple tipsails on the upper wing tips, which reputedly gave 20% higher climb rate and improved L/D ratio by 15%.

Here is a research paper on tipsails which may help a little bit.

There doesn't seem to be a lot of empirical evidence of the performance gains that China claims with the Y-5B. I can't find examples of the triple tipsail design used on any other aircraft.

Just look at the aircraft though, all the struts, wires, hinges, etc hanging out in the wind, and these 3 little tip sails improve L/D by 15% and climb rate by 20%? That's a hard pill to swallow. If it were that simple, it would be a feature of nearly every aircraft.

Ron Beyer
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    I'm perplexed as to why tipsails are not used on a large scale given that "sails fitted to the wing tip can reduce its lift dependent drag by up to 35%", "longitudinal static stability of the wing was significantly improved" and "the wing tip sails showed their ability to break down and reduce the tip vorticity behind the wing". – mins Jan 08 '17 at 11:25
  • I assume because winglets do the same thing for aircraft that don't need to be multi role, but not sure on multi role aircraft, maybe Peter will chime in. – Ron Beyer Jan 08 '17 at 11:46
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    @mins You guys should know by now how sceptical I am of all the claims made in support of winglets. Claiming 15% better L/D with these tiny additions is ridiculous. Same goes for stability claims and especially the nonsense about breaking down tip vorticity. This is simply snake oil, like this. – Peter Kämpf Jan 08 '17 at 20:34
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    @PeterKämpf Dang, Peter, you ruin all the cool new stuff with your silly reality :) – TomMcW Jan 09 '17 at 20:33
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    @TomMcW: Fixed gear, bracing, struts all over the place, and those guys worry about wingtip vortices. Sheesh! – Peter Kämpf Jan 10 '17 at 07:43
  • Your link to the research paper on tipsails has rotten away. Could you replace it, and perhaps include some of its contents inside your answer to prevent this from reoccurring? – AEhere supports Monica Feb 14 '20 at 12:41
  • @AEheresupportsMonica I will try and find it again, but I've forgotten it's contents in the past 3 years so I can't put the contents in here from memory. – Ron Beyer Feb 14 '20 at 12:57
  • @RonBeyer thanks for caring; I am interested in the topic so if I run into anything related I'll put a link in the comments. – AEhere supports Monica Feb 14 '20 at 13:03
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"Tip sails", we all should recognize this feature on soaring birds. Also similar to Fowler flaps. This is a lift enhancing device for slow flight. On the wing tip, it may also serve to reduce the high AOA wing tip vortex, breaking it into smaller vortices.

But notice the birds do not use these at faster speeds, as their drag producing lift is not needed and AOA is lower.

So the tip sail designers may take a cue from birds and airliners, and retract them at higher speeds. The Etrich Taub would lend itself to that type of wing tip. Imagine unfurling them just before landing.

Robert DiGiovanni
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