Fixed gear amphibian?

Hi all, very busy with Uni lately and so haven't been around much.

Just pondering some thoughts and was considering a fixed landing gear on amphibian hull. Does anyone know of any aircraft that used this? I've tried a few searches but can't find anything. For a single seater so a retracting gear would probably be a considerable weight penalty.

thanks

 

There have been some amphibian aircraft that used wheels protruding permanently through the hull or floats, but it doesn't seem to be a popular solution.

 

What about balloon tires with enough bouyancy to support the plane at a standstill?

(Yes, I know they would be HUGE!) :gig:

 

A hover cushion would be the other option for both land and water.

 

The only "fixed gear" amphibians made I know of are a Lake Buccaneer prototype and the Russian Dingo. Both used hovercraft style air cushion hulls.

If the airplane is only to land on grass runways a skid will make do. Search and you will find videos off floatplanes landing and taking off from grass fields.

 

grass field is least likely...asphalt runway or water in my case. maybe grass strips if i feel like a detour. I think i'll have a look around for some inspiration on landing gear designs that are lightweight and simple.

 

Then have a look at sailplanes. A single retractable wheel like on a sailplane is probably the lightest possible and should suffice on a light one seat airplane. Do also look at amphibious floats, I do think you will find that not all have wheel well doors. That makes the design simpler and lighter.

If you want two wheels, have a look at other light amphibian airplanes and maybe the gear on the KR-2. On amphibians the undercarriage does not always retract, it is rather rotated up for landing on water and down for landing on hard surfaces.

 

as it did on the original Europa two-seater. Neatly coupled to the flaps, too, making it harder to forget lowering/retracting.

 

Fascinating, I've never heard of that before. Here's a video of the Lake.

[video=youtube;pGNqRKv4zbc]https://www.youtube.com/watch?v=pGNqRKv4zbc[/video]

 

Maybe a main wheel (or in line wheels or bogey) beginning just aft of the step and just proud of the keel line, and in line wheels on the forward keel line at the contact point. Motorglider wing tip tip wheels on wing floats.

Dino

 

I have an ultralight that has floats (and wheel gear that needs replacing), and was wondering if I could do that. Perhaps add a layer of Kevlar or a high-density plastic skid? Both? My field is grass; I suppose I would need to vary landing spots to prevent bare areas, or do the floats not cause much wear and tear on the sod? How about just skis ("skid")? Seems the brake system on the wheel gear could be eliminated.

 

You've mentioned it before in your unorthodox hull thread, but I never followed up on it. Watching the video that skier posted, the hovercraft fuse does add a lot of versatility, fascinating!

 

From what I could find on YouTube I do believe I best have a couple wheels sticking out of the floats a bit. Interesting thought, briefly.

 

One of the most common float-plane accidents is forgetting to retract the nose-wheel(s) before setting down on water. The nose-wheel digs in and you do the world's smallest front loop!

The simplest way to prevent nosing-over in the lake is to never install a nosewheel.

You could probably get away with a fixed tail-wheel undercarriage if it only extended a little below the keel. That would restrict you to landing on only the smoothest asphalt runways. You would have to "pitch" the airplane precisely to avoid scraping the keel.
The tail-wheel would be so far aft and produce so little drag that it would make little difference on landing.

Burt Rutan hinted at a similar concept last year, but Burt refuses to publish drawings or pictures until after he has test-flown his retirement project.

Another way would entail installing a fixed main wheel just aft of the step. Then install a retractable ski/step just ahead of the main-wheel. If you inflated an air-bag to extend the ski/step, it would auto-retract is you forgot to retract the step when landing on asphalt.

Something as important as lowering/raising wheels really should include two or three ways of confirmation during the pre-landing check-list. Hard-wired retraction handle (e.g. solid control rods linked directly) Many float-planes jus flop their nose-wheels on top of their bows when they retract. The pilot can visually confirm that at least one nose-wheel is up-and-locked. Speaking of visual confirmation, have you noticed the little, convex mirrors hanging from wing struts on lots of floatplanes. Those mirrors allow pilots to see under their floats to confirm wheel position.
Fancier amphibians sport a variety of instruments or warning lights across the top of the instrument panel. The fanciest amphibians have "*****ing Betty" horns that nag about wheel position an time you retard the throttle to flight idle before the wheels are locked.

 

On my ultralight when the floats are fitted the nose-wheel is removed. Sounds like I may as well forget the floats on grass. Devising even simple wheel retract mechanicals is more than my interest level in that project.

 

Have you searched for and looked at videos of the use and abuse of Full Lotus floats?
On an ultralight airplane some kind of plastic skid may work on a grass field. I would think the biggest catch is insufficient power to get the airplane moving, especially if the grass field is dry.

Old gliders used to only have a skid undercarriage and they where even towed aloft from the hillside by the other glider club members waiting on their turn to fly, so it might not be impossible. Some plastic with a low friction coefficient and good wear properties may fit the bill as the skid sole.

 

Correction if I may: The Buc XA had gear repositioned by reaching outside the cockpit. The Buc SX (single seater) and Buc II (two seater) and all Aventura aircraft are retracted from inside the cockpit. I worked for the Buc company and was a demo pilot, and then helped to design the Aventura and worked their for 3 yrs before branching out on my own.

 

Bury a bunch of roller blade wheels in a couple of retractable skids?

 

Very narrow (1" wide) fixed wheels should work for water and paved runways.
The narrow wheels slip through the water like a sailboat daggerboard.
I guy named Reynolds built RC models with fixed wheels on floats made from clear plexiglass.

I will be doing this when I get around to building floats.