Ground Effect

Most of you know already that ground effect (or WIG, for Wing In Ground effect) is a very important feature of the Coot's design. This is because its effect is strongest at an altitude of one half the wingspan. Not only does the Coot have a long wingspan, but its wings are located closer to the hull bottom than on any other amphibian aircraft. Let's examine the role of ground effect in three aspects of Coot flight: landing, taking off and cross-country flights over large bodies of water.


During the landing flare , the WIG effect, essentially a ‘cushion' of increased air pressure under the wing, increases lift and lowers drag, thereby letting the Coot float down the runway or over the water. This can confuse some pilots, but those who understand it can take advantage of it and consistently make smoother landings at lower speeds.


As I listen to Coot pilots who have had landing difficulties, I get the impression that they were worried about impacting a hard surface. In many cases they eventually admitted that they let the airspeed diminish without realizing it until it was too late. They were moving through the air too slowly to maintain lift. This caused a dramatic impact with the water, reinforcing the pilot's innate fear of a hard water-touchdown.


The secret is to practice on land, where the springy gear legs absorb the results of minor mistakes. Watch the airspeed indicator with your indirect vision throughout the descent. Adjust the throttle to keep your airspeed at 80 mph until you flare over the numbers, and only then let it dissipate. Most runways are long enough to practice this. A Coot must have plenty of airspeed to fly, so be sure to keep this valuable resource working for you until you are right where you want to touch, before you ease off on the throttle from your descent setting.


Once you're comfortable with this approach, maintain the same principles when you flare over the water, even if it looks threatening. The Coot will float over the water just as it did over the runway, and the retracted wheels will let the hull touch down just a second later than the wheels did on the runway.


On takeoff, remember how the Coot got its name. You will be airborne in WIG effect before the wings are flying normally, so level off for a second to let the airspeed build before you raise the nose. Real live Coots do it, and so should you in your mechanical Coot.


Finally, if you should find yourself flying over a fairly large body of water, try flying in ground effect. I know it sounds imprudent at first, but you've already paid the penalty of building and flying an amphibian , so take advantage of its really good point. If the winds are light you can throttle back and use about a third less power while you enjoy the air cushion all the way. If you have a head-wind, use normal power, but use your GPS to prove to yourself that the head-wind is much milder close to the surface, and watch your ETA (estimated time of arrival) change dramatically in your favor. This is a joy unique to pilots of flying boats, and especially Coots, so go out and soak up the pleasure!



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