A normal aeroplane is fitted with doors on the bottom like bomb doors on a bomber. The doors open, and an inflatable flotation/planing hull pops out and is inflated by high pressure gas supplies. Now the aeroplane can land on water. After it takes off, the inflatable pontoony thing is sucked empty and reeled back into the storage space behind the now-closing doors. Then the wheels can be deployed as usual and the aeroplane can land on tarmac.-- pocmloc, Sep 04 2014 rumblenackery https://www.google....IVM3iA_DH8ge0o4LYCQ [pocmloc, Sep 04 2014] I wonder if instead of using a stored pressurized gas to inflate this, you could simply use air from the high pressure zone at the front of the plane?-- ytk, Sep 04 2014 Excellent idea, I was deliberately vague about the nature of the //high pressure gas supplies//.-- pocmloc, Sep 04 2014 The pressure on the leading edge of a 'plane travelling at 150miles/hour is only a few per cent higher than that of the atmosphere, and probably wouldn't be enough to even unfurl the pontoons. You could use engine offtake air though.-- EnochLives, Sep 04 2014 There's YT vids of floatplanes and flying boats landing in water. You can hear that it's not a smooth thing. I don't think rubber is going to stand up to that kind of force.-- FlyingToaster, Sep 04 2014 It will - at least, fabric reinforced polymer composites will - but the problem is that a structure strong enough to contain the pressure and handle the shock is not going to "fold" easily when deflated.
For this idea to work, the float needs to resemble the thin, highly flexible material of a survival raft, which can be packed into a very small space. But that material won't have the necessary mechanical properties.
And there's the issue of wing profile. A wing that can generate sufficient lift at the low speeds attainable in a water takeoff is going to exhibit very poor performance at high altitudes and high cruise speeds, without some complex variable geometry, which adds a lot of weight. Seaplanes can't "rotate" the way land-based planes can; they have to "fly off the water" before they can adopt a nose- up attitude for the climb out of the ground effect.
The inflatable would have to be of a multi- celled design to prevent a minor tear causing a catastrophic failure.
Plenty of high-pressure air from the interstage compressors of a gas turbine, though.-- 8th of 7, Sep 04 2014 Well. might as well have a plane that carries its own airstrip. big balloons not known for keeping shape well at speed. Probably bamboo covered with graphene, unrolls from the nose of the plane.-- not_morrison_rm, Sep 04 2014 Put it on a helicopter?-- 4and20, Sep 05 2014 random, halfbakery