One of the more common enquiries received at the Sydney Microlight Centre is "do you teach people to fly trikes on floats?" A variation is "I've just bought a float-trike, can you teach me to fly it?" Typically we get these enquiries after someone has seen a trike on floats on The Discovery Chanel or The National Geographic Channel, and their interest is fired by what they have seen.

  The short answer is "No, we don't teach people to fly trikes on floats." Here's why:-

  From bitter experience it has been shown that trikes on floats simply don't work unless the floats are spaced much wider than the normal trike undercarriage. The trike is, by design, very top-heavy. There's about fifty kilos of wing as far above the wheels as possible, and the trike wheelbase is very narrow. If you take the wheels off and put the floats on where the wheels used to be, the whole thing is very unstable.

  Provided nothing causes the trike on floats to start rocking from side to side on the water, things will be fine. But the wake from a passing speedboat, or the chop and swell from a wind-driven sea, can start the trike rocking. The rocking doesn't damp out, and often it becomes greater and greater until the whole trike rolls over and sinks (inverted and by now, very stable)! A picture of a beautiful (and nearly brand-new) Edge XT-912 float-trike being lifted out of Sydney Harbour by a crane comes to mind. Suffice it to say that particular pilot no longer operates float-trikes. "It seemed like a good idea at the time."

  So how do the trikes overseas fly on and off water without sinking? Well, the Canadians have float-trikes using large floats made buy the Krucker company and these are set much wider than the wheels are...making them stable enough not to roll over. They operate of fresh-water lakes (in summer) and in winter they take the floats off and put the skis on to operate off the frozen lakes and snowfields. The Canadians have operated amphibious aircraft with great success for well over fifty years now. They know what works; wide-spaced floats and fresh-water lakes.

  On the continent, the Italian "Ramphos" trike used a fibreglass boat-hull (with small doors for the undercarriage to open through) and seemed moderately successful. However, the wheels were very small, designed for use on immaculately-manicured grass airfields which may be relatively common in Europe but are less so in Australia. I asked the distributor "if the wheels don't come down what do you do?: He replied "Land on the hull!". I formed a mental picture of the beautiful fibreglass hull scraping along on a gravel airstrip and wondered how much the repair bill would be. A few Ramphos trikes made their way here...and at least one sank. They used a lot of stainless-steel in the base rather than aluminium to combat the other great adversity of amphibious aircraft - corrosion.

  Basically, almost all trikes use aluminium tubing in their structure for both the base and wing. Aluminium is both light and strong, and it can be readily alloyed with other metals for reasonable corrosion resistance.

  But on the coast we are operating in a salt-water environment, and even the best aircraft-aluminium alloys have relatively poor resistance to corrosion from salt-water. It isn't just the aluminium bits you can see which is corroding - it's everything! Engine, framework, battens, struts, bolts, nuts, screws, even the stainless-steel wires and copper swages will corrode under the relentless attack of salt-water, and the invisible salt in the air in which we fly around the coast. Aluminium which has been severely corroded by salt-water turns into a white powder. Think of it as the trike beginning to dissolve, because basically that's pretty much what is happening.

 Lastly, there are the dangers inherent in flying, taking off and landing on a surface which can be dangerously deceptive. It is very difficult to accurately judge your altitude over a mirror-calm surface of water. The surface-tension of water adds drag to the trike when taking off and landing, complicating what should be relatively simple manoeuvres. Takeoff distances can be increased, whilst landing distances can be significantly reduced as the hull or floats make contact with the water-surface. If you are drifting sideways at the point of contact, there is a real risk of rolling the trike in an eyeblink.

  In any swell or seaway handling is tricky and as soon as the engine is started the trike begins to move so you need a large area to manoeuvre in whilst you do checks, warm up the engine etc. Get your handling wrong and you are in a lot of trouble, quickly. A trike crashing on water stays afloat for a few seconds once the structural integrity is breached.

 Once on the water the float-trike is now a boat, and in NSW the Roads & Maritime people will have certain requirements for lifesaving apparatus etc which you will need to take into account. You may even require a boat-licence or some sort of certificate to say you have basic boat-handling skills just to fly your trike off water. It's getting complicated, isn't it? None of these complications exist if you are flying off land.

  A common form of float-trike is something like a Zodiac inflatable-boat under a trike base and wing. Twenty years ago or so our former CFI, Paul Haines, flew one which was powered by the Rotax 582 65hp engine. There was so much drag it was barely controllable, and if you mentioned that trike Paul became uncharacteristically worked up about how badly it handled and how frightening it was to try and fly. Later a chap made a float-trike with proper floats and asked Paul to test-fly it for him, on Lake Illawarra. Paul looked it over carefully and decided it was a better aircraft than the first amphibious trike he had flown so he agreed to do the test-flying. He wrote an article about it, so perhaps his own words are best...

         "Here it should be mentioned that there are two modes of taxying. The slow or "plough" taxi is where the floats sit low in the water and a fair bit of water splashes around at less than 5-8 knots. Faster than that and we go into the medium to fast taxi - the hulls climb up "onto the step", the craft begins planing and the speed and manoeuvrability really pick up.

  Having sufficiently explored all the taxi parameters, some mug had to be found to go all the way, and no prizes for guessing who drew the short straw! The first long run was aborted when I felt I was getting slightly out-of-wind (i.e. going sideways), but after that - a long-ish run - planing at high speed (watched by a rather envious jet-skier!) - and the floatplane just stepped off the water and flew. I flew over the Lake, getting used to the slightly different handling (all floats carry a weight and drag penalty), and then decided on a long final powered-approach, directly along the wind streaks on the surface of the water. As you near the surface, the ground effect increases enormously, and you can maintain altitude (about 1 foot AMSL!) with a fair reduction of normal "cruise" power, almost indefinitely. Finally, reducing power to idle, the floats touch down and plane briefly before sinking into the "plough" mode, and excess speed decays rapidly (a bit like driving a 4WD into deep mud!)

  Next it was time for Kevin to fly the machine, and after a perfect take off, he too flew gracefully over the lake, and while flying encountered a friendly passing helicopter who contacted us on the VHF radio and asked if he could fly alongside in formation and take a few pictures, as he had never seen a microlight float-plane before. We requested him to stay on the downwind side, and slightly lower, so we wouldn't get any rotor downwash, and this was accomplished without problem. (Really useful, these VHF airband radios). After the usual professional landing from Kevin (he could see the pelicans were watching critically), we compared notes and had a couple of celebratory lemonades.

  Where do we go from here? Well, there is still a bit of fine-tuning to be done, Kevin is still not quite satisfied with the water rudders, and further improvements are on the way. Also we need to finely adjust the angle of dangle of the floats. At the moment, they hang slightly too nose-high in the air, and it seems likely a more horizontal hang position will be beneficial in reducing drag and increasing performance. How much fun is it? About as much as you can have with your clothes on!!"

  Although Paul managed to fly this trike well enough, it never seemed to progress much further than the prototype. In reality, Kevin's amphibious trike was a bit of a one-off, and none of the various models which have been made by different manufacturers since have been a success in Australia.  To the best of my knowledge there is no-one with an amphibious microlight rating who can teach on them, and then there is the question of registering an amphibious trike you might happen to buy overseas and import into the country. All I can say to that is "Good Luck!".

    And that is why we don't fly, or recommend, trikes on floats.

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