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Say a seaplane has ditched onto ocean or a very large lake due to engine failure. Is it possible to sail the plane to the shore using wind alone, similar to sailing a boat?

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Based on Terry's answer, it seems to be a very different process from sailing a sailboat. To sail like a sailboat, you'd have to deal with the surface area of the plane that the wind hits, and also erect a sail of surface area large enough to overcome the effects of the plane's surface area. There also has to be something that does the job that a keel does, and you need a rudder that acts in the water (not an airplane rudder). Finally, you have to have control over the angle of both the rudder and the sail. Those are the minimum elements for a vessel to be a sailed like a sailboat. – Todd Wilcox Mar 28 at 13:51
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@ToddWilcox: Apparently seaplanes do have water rudders, and long narrow floats should provide some lateral drift resistance even without a keel. (That's how catamarans work.) You don't have anything like a proper sail, of course, but the body of the plane should still catch some wind, and the rudder will provide some limited aerodynamic control. So I can believe that something vaguely similar to sailing a sailboat might be possible, at least on some limited range of headings and wind speeds. – Ilmari Karonen Mar 28 at 14:59
up vote 32 down vote accepted

You can sail a seaplane, but there are a lot of considerations. For starters, it makes a big difference as to whether you're talking about a seaplane where the hull is in the water or a floatplane. A floatplane sitting up on its pontoons (floats) is more up in the wind, but it's also more susceptible to rough water because of its higher center of gravity.

My personal experience with sailing a floatplane was with a J-3 cub with an 85 horse engine on rivers and lakes. If we wanted to back onto the shore, we had to sail it since there was no reverse pitch propeller.

For purposes of explanation on how to do it, let's say that there's no wind, but we're on a river with enough current that the movement of the floatplane with the current when the engine is off gives the floatplane a wind relative to the water. Further let's say the river is flowing from east to west, and we want to back onto a beach on the north shore. We land and stop the engine upstream from the beach. As the floatplane drifts it will weathervane into the wind. Thus, with the controls neutralized, we'll be facing west and moving downstream in mid-river with the current, but not as fast the current because of the drag of the wind on the aircraft.

The rule of thumb is that you point the tail towards the shore you wish to get to. We do that by applying left rudder and right aileron. Thus we have increased the drag on the left wing, which will swing the nose left, and the left rudder will also swing the nose left. Thus the nose is now pointed a few degrees toward the left shore (south), the tail toward the right shore (north). The airplane will then sail to the right shore (north) relative to the direction the aircraft nose is pointing because the the aircraft is moving backwards relative to the water.

The trick in this instance is vary the control input to arrive at the downstream point you want. For practice, I used to have students sail to alternate sides of the river on Oregon's Willamette River downstream from the city of Eugene.

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I never had this particular experience, but I once ran out of gas in a boat in the middle of a lake and used my swim fin as an oar to get me to shore. – Howard Miller Mar 28 at 10:43
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After trying and failing to visualize your example, I assume there must be a typo somewhere in your answer, specifically between "we'll be facing west" and "the left shore relative to the aircraft, in other words the north shore." Those two statements surely can't both be correct; if the aircraft is facing west (and is, hopefully, not upside down :), the left shore should be the south shore. Having no personal experience of floatplane handling characteristics, however, I can't tell which part of your answer might need fixing. – Ilmari Karonen Mar 28 at 11:49
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@Blckknght: ... Basically, the key realization, in sailing terms, is that you're not tacking the plane into the wind (without a proper sail, it can't really do that), but rather sailing it with the wind, backwards! That would be a ridiculous way to sail a sailboat (the sails won't catch the wind properly, and the rudder would be unstable), but for a plane with ailerons to provide drag, and with an air rudder to maintain stable heading, it apparently works. – Ilmari Karonen Mar 28 at 15:20
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@Blckknght That's because As the floatplane drifts it will weathervane into the wind. – TomMcW Mar 28 at 19:28
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@Blckknght A good number of the students I instructed for their float plane rating also found that rule counter-intuitive initially. The thing to remember is that you're moving backwards with respect to the water and thus toward the shore the tail is pointing to. – Terry Mar 28 at 19:50

It's been done at least once before.

In 1925 a US Navy PN-9 landed in the Pacific when it ran out of fuel on the way to Hawai'i. The crew then rigged a sail from parts of the canvas wings and sailed their plane over 400 miles (in nine days) to reach the islands.

http://timeandnavigation.si.edu/multimedia-asset/naval-aircraft-factory-pn-9-116-scale

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"Non-Flight of the Navigator"? – smci Mar 29 at 6:08

I know this is not what was asked, but I couldn't resist. There was indeed a seaplane that could be sailed: A sailplane with a seaplane hull. It was a curiosity and built only because none had been built before - or ever since.

DFS Seeadler floating on water

DFS Seeadler floating on water (picture source). First flight was in 1935, and the official reasoning was to create a modern sailplane for clubs without access to a good airfield, but a lake nearby. But I guess the designer Hans Jacobs knew already how flimsy the official reasoning was: Below the keeled fuselage bottom was a wooden skid to allow landing on land.

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