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Could long, aftermarket hydrofoils be added to the water-skids of a plane (like this Cessna with pontoons or smaller)

enter image description here
Cessna 208 Caravan

not designed to have a hydro foil, to increase its ability to land on choppier water?

In theory, the pilot would first enter the water with the skids, clear of the chop, then stall the hydro foil similar to stall landing a plane thus giving the plane a soft or possibly vertical landing.

enter image description here
Grumman JRF-5 with hydrofoils

FreeMan
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Justintimeforfun
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2 Answers2

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It's been done. David Thurston designed a system for the Lake LA-4 that was purported to allow it to land on 5ft waves. It may have been a bit of a handful (the Buccaneer is a demanding airplane on its normal hull). It was crashed by someone who took it for a spin without Thurston's authorization, and that was the end of that.

enter image description here

Chris
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John K
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    Nice find on the plane. I'm looking for something or way to make the work for a much smaller and cheaper aircraft. – Justintimeforfun Aug 03 '20 at 04:39
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    @Justintimeforfun: But where do you find a smaller & cheaper airplane that will float? – jamesqf Aug 03 '20 at 05:42
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    As soon as that hydrofoil touches the water you're going to get a significant pitch down from the moment arm, I can imagine that would make it challenging. – GdD Aug 03 '20 at 09:25
  • @GdD right, especially in a plane with such high center of mass. But I think this technology could be quite promising for electric planes, with batteries in the keel making it more stable. If we can even computer-control the hydrofoils' attitude, better yet. – leftaroundabout Aug 03 '20 at 10:59
  • So you want to add lots of weight on a long moment arm @leftaroundabout? How's that going to help stability? – GdD Aug 03 '20 at 11:24
  • @GdD -- because of the "pendulum effect". See https://aviation.stackexchange.com/questions/53437/does-pendulum-effect-apply-to-hang-gliders-or-any-aircraft/56548#56548 – quiet flyer Aug 03 '20 at 13:54
  • @GdD I think the pendulum effect had been compensated with the Grumman JRF-5 with hydrofoils plural. The forward arms of the picture in the question seems to have an extra set of foils to prevent the nose from tipping forward into the water on landing. With hydrofoil technology being improved such as the wing I think there again there maybe a reason to explore this landing gear again for choppy water landing. – Justintimeforfun Aug 03 '20 at 16:31
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I would make a serious study of this man's work.

Rostislav Alexeyev's "day job" was the design of large hydrofoil ferries, such as the Raketa carrying over 60 people, in the 1950s. This (image from linked article) and its successors are probably the most successful series of hydrofoils in the world.

enter image description here

He went on to design a series of Ekranoplans, ground effect flying vehicles. (pictured, A-90 Orlyonok, from here

enter image description here

These, despite being designed at his Central Hydrofoil Design Bureau, all seem to have used conventional stepped hulls like flying boats or seaplane floats.

He is probably the best person to tell you why.

user_1818839
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  • The most interesting fact are theses plane are more efficient than modern airliners and hydro foils could allow the a ground effect plane to clear swells in the ocean. It is that rouge wave that makes this dangerous in open seas. – Justintimeforfun Aug 03 '20 at 16:49
  • The reason the Ekranoplan uses a conventional hull is pretty simple - a hydrofoil requires a bit of speed to get going and at that point it's already flying. A foil would just be dead weight. – papirtiger Apr 02 '21 at 19:58
  • @papirtiger true for a suitable definition of "a bit of speed" ... hydrofoils can lift a hull clear of the water at sailboat speeds ... like 5 knots https://www.youtube.com/watch?v=UokOO60dsMU – user_1818839 Apr 02 '21 at 20:05