The ICON A5 would seem to be a "conventional" (if we stretch the limits of the term) high-wing monoplane.

But what about these things right here: Image of ICON A5 in flight with "seawings(tm)" circled in red

The protrusions from the hull, circled in red, are called "Seawings(tm)." Their declared purpose, according to the POH, is to stabilize the aircraft in water as well as provide pilot and passenger with a means of convenient in- and egress from the cockpit.

I can't find any confirmation or denial as to whether or not they generate any kind of lift, but they do seem to be shaped in a way that could be a manner of airfoil - and certainly if you're designing an aircraft and have lateral protrusions from the hull and you don't shape them to produce lift you've missed an opportunity.

So for the moment, if we assume they do generate some modicum of lift, does that mean the ICON is no longer properly referred to as a monoplane?

My understanding is that "Biplane" would require the wings to be vertically stacked with each other. Some small portion of the seawings does underlie the main wings, but the vast majority of the seawings' structure is well forward of the main wing.

Would that make it a Tandem-Wing aircraft?

Do either of those terms stop having meaning if the seawings - which are declared as intended to provide stability in water and footing for embarking/disembarking occupants - are instead properly though of as structurally part of the hull - and thus the aircraft is at least partially a lifting body?

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    $\begingroup$ It's not a tandem because both "wings" are at roughly the same position lengthwise. The term "sesquiplane" (one and a half wings, so somewhere between monoplane and biplane) exists, but I had never heard of it before googling it just now. But since I'm not sure that is the correct term (if a correct or well-established one even exists), I leave this as a comment and not an answer. $\endgroup$ May 26 at 17:21
  • $\begingroup$ @Raketenolli If you mean the wings are at the same position front-to-rear, they're not. The seawings trailing edge is below the leading edge of the main wings, but the vast bulk of the seawings exists well forward of the main wing. (They wouldn't make good steps otherwise.) $\endgroup$ May 26 at 17:30
  • $\begingroup$ "if you're designing an aircraft and have lateral protrusions from the hull and you don't shape them to produce lift you've missed an opportunity." Brilliant phrasing! $\endgroup$ May 27 at 1:50

1 Answer 1


A famous aircraft with similar "sponsons" (that's what they are normally called) to keep the plane level in the water is the Boeing 314 Clipper. "Sponsons" were also used (and likely originally pioneered) on Dornier flying boats. Examples include the Dornier Wal, Dornier Do X, and Dornier Do 24.

Re a comment: The term "sesquiplane" is normally applied to an airplane with a much larger lower "wing" than we see on the Icon A5-- such as the Nieuport 11.

Consider: should we call the Fokker Dr.1 a "quadruplane", because of the little "wing" on the axle? (No, we should not.)

It would be a stretch to call the Icon A5, or the Boeing 314, or the Dornier flying boats noted above, anything other than high-wing monoplanes.

  • $\begingroup$ Ah - brief, correct and to the point. +1 $\endgroup$ May 26 at 19:30
  • $\begingroup$ @PeterKämpf -- "for once" ? !! : ) $\endgroup$ May 26 at 19:31

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