I have a friend that is considering putting his Navion on floats. A huge challenge. I recall having seen a photo of a Navion on floats, an old black and white photo, but I can no longer find it. If we can find it, it would be very helpful as he might be able to look up the N number and get FAA records on the engineering, etc.

Can anyone help in find information on Navion float conversions? Any thoughts on a Navion on floats?

  • $\begingroup$ I've seen photos of a DC-3 on floats. Getting the work done by an appropriately qualified shop and getting the FAA inspector to sign off are the main things involved. $\endgroup$ – Zeiss Ikon May 7 '19 at 13:13
  • $\begingroup$ I edited you post, please confirm if I got the right A/C type, as I was unfamiliar with it, and would expect others to have the same issue. $\endgroup$ – AEhere supports Monica May 7 '19 at 13:20
  • $\begingroup$ As for thoughts... looks difficult to pull off, unless the gear fittings are overdesigned and will tolerate the torque of a float system. Also, the low wing would give me some pause due to the small wingtip clearances; ground (water) loops are not enjoyable. $\endgroup$ – AEhere supports Monica May 7 '19 at 13:26
  • $\begingroup$ Yes, I am discussing a Navion. First made by North American (P-51, etc.), then Ryan (Spirit of St. Louis, etc.) and then a couple of others who bought the type certificate. $\endgroup$ – Bob Pinizzotto May 7 '19 at 20:13

It can be done in theory, as can most airplanes if you develop the attachment fittings and the airplane has a reasonably slow takeoff and landing speed. The Beech 18 has long been used on floats in the bush.

Notwithstanding the fact that it was done once upon a time on a Navion, in the absence of a pre-existing STC, and access to the particular floats covered by it, the costs would be staggering unless you put the airplane into the Experimental category and even there it would be only slightly less than staggering.

I don't see any signs of a float kit that was ever developed for the Navion for Edo or Wipline, and I assume it's a certfied category aircraft, so I'm going with starting from scratch, which means staggering, which means "fuggeddaboudit".

As an ex bush pilot, as far as doing well as a float plane, several comments:

As a thing, in general, low wing float planes suck. The wings get in the way of docks.

The takeoff and landing speed needs to be reasonably low, ideally below 50 kt. There is a bit of a hydrodynamic "wall" you hit around that speed while aquaplaning and if you can't lift off before that speed you zoom along seemingly forever building that last few knots, not to mention the concrete like character the water starts to take on.

To have good utility, unless you base it at a lake and only fly to other lakes, the floats should be amphibious, but amphibs on a 4 place airplane leave you with a 2 place airplane (even though you've removed the landing gear). Straight floats have only a minimal effect on useful load (because credit is taken for the lift generated by the floats plus the removal of the ldg gear), but amphibs are brutal because the weight of landing gear and pumps is ballast. In the bush you don't see that many working airplanes with amphibs for that reason unless they really need it.

Hull insurance on a straight floatplane is somewhat higher than wheels, but on an amphib, the premium will melt your eyeballs. Because, maybe sooner or maybe later, just about every single amphib out there will get landed wheels down on water, eventually.

The floats are destabilizing in yaw, and the Navion has a rather smallish rudder/fin, so it will almost certainly need a ventral fin. Expect to add it to the STC development work. Only a few sea planes have gotten away with not adding extra fin area.

So, bottom line is, unless you can find an installation STC, and can locate a set of floats covered by the STC, making it just bolt it all together, rig, make a log entry, and fly, it's a gargantuan task that will quickly bring your friend down to earth unless money is no object.

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    $\begingroup$ "The floats are destabilizing in yaw" pitch as well, unless I'm missing something? Never mind the larger control authority to contract that effect in pitch. $\endgroup$ – AEhere supports Monica May 7 '19 at 14:01
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    $\begingroup$ The floats create a nose-down pitching moment, but the lift force generated by the floats moves the pitching neutral point forward and offsets that to a sufficient extent that no additional band-aids are required on seaplanes. When you fly a seaplane the existence of the floats below only becomes obvious when doing things like stalls where the pendulous effects can be felt. The yaw mode is the big one. I used to train ppl in a little floatplane called a Fleet Canuck, which didn't have any xtra fin on floats. It was like a glider in yaw, slithering everywhere if you weren't fast on your feet. $\endgroup$ – John K May 7 '19 at 16:45
  • $\begingroup$ John: Thank you for your answer. I agree with the entire thing, if that means anything. $\endgroup$ – Bob Pinizzotto May 7 '19 at 20:12
  • $\begingroup$ "...will get landed wheels down on water, eventually" - I was thinking wheels up on land would be the greater evil. :-\ $\endgroup$ – pr1268 May 12 '19 at 1:19
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    $\begingroup$ No, wheels down on water is over on your back every time. Wheels up on land is grind off a bit of the skeg if on pavement, and no damage at all if on grass. You can't have a normal gear warning system with amphibs because how is it to know whether the gear should be up or down for a given landing. Thats one reason the hull insurance premium on an amphib is up there in piston helicopter territory. $\endgroup$ – John K May 12 '19 at 2:31

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