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Model Airplane News - April 2013

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Model Airplane News - April 2013

The Fokker Triplane is

The Fokker Triplane is viewed by many as one of the most difficult tail-draggers to land successfully. As it slows down, that small rudder becomes less effective. With practice, however, you can easily master it. Tame Your Tail-dragger Tips to improve your takeoffs and landings Lby Gerry Yarrish | Photos by Hope McCall & Gerry Yarrish Let’s face it, most RC scale aircraft today are tail-draggers; from sport planes and classic civilian aircraft to warbirds and fighters, where the little “steering” wheel is in back behind the main landing gear, the tail-dragger configuration remains very popular. Though the tailwheel has very little effect on the model’s flight performance, the landing gear configuration does make takeoffs and landings much different from planes with tricycle (trike) landing gear. Here are some of the basics to help tame your tail-draggers and improve your takeoffs and landings. Different techniques The major difference between a tail-dragger and a trike-gear model is the relative position of the model’s main landing gear with respect to the position of the center of gravity. With a trike, the CG is forward of the main wheels and, when you land the model, it should touch down on the main wheels. The nose then remains level or tilts slightly downward until the nosewheel comes in contact with the ground. This in turn decreases the wing’s Angle of Attack (AoA) and helps to keep the model Giant-scale WW II warbirds for the most part are tail-draggers. Use those flaps and bring it in straight using short, quick rudder corrections as needed. on the ground. With a tail-dragger, the CG is somewhere behind the main wheels and so after the main gear touches down and the model begins to slow down, the nose slowly tilts upward (the tail comes down) 34 MORE FROM THIS ISSUE AT MODELAIRPLANENEWS.COM

until the tailwheel or tailskid comes in contact with the ground. Another reason for the differing set of challenges is because of the relatively narrow wheel track of the main wheels and the position of the tailwheel so far aft of those wheels. If the tailwheel is allowed to move to one side or the other outboard of the main wheel’s track, inertia then takes over and the tail attempts to circle around to the front end in the classic “ground loop.” With a nosewheel, even on smooth, paved runways, there are no real surprises; but with a tail-dragger, a few eye openers can pop up if you don’t pay attention. Tail-draggers, especially WW I and vintage planes equipped with non-steerable tailskids, behave much better on grass. The drag of the soft, rough sod actually helps keep tail-draggers going straight after landings. But on a hard, smooth runway, you can easily over-control and cause a ground loop. To keep the tail end aft, you have to be quick with your rudder inputs, maintain directional control, and keep the tailwheel between and behind the two main wheels. Generally speaking, a tail-dragger’s turning radius is also larger than a trike’s because the main gear is much farther from the tailwheel, thus producing a bigger radius. To keep the tailwheel down on the ground, you use up-elevator. However, you can tighten your turning radius on the ground by releasing the up elevator, which lightens the tail’s down force. Some WW I planes may even require a bit of down-elevator and a blast of throttle to help swing the tail around. During takeoffs, torque from the engine Here the Top Flite giant-scale F4U Corsair is just about to touch down. Again, use flaps to slow the landing and stay on the rudder until the model comes to a stop. Notice how little up-elevator is being used. Over-correcting during landing can cause a ground loop, or in this case, a nose-over. Keep everything smooth and try always to land into the wind. and propeller forces will tend to make the model veer to the left. Some right-rudder correction is required to keep the model going straight. Trike aircraft have good directional control: both the nosewheel and the rudder maintain directional control. With the tail-dragger, however, since the tailwheel lifts off the ground before the plane becomes airborne, the rudder alone is correcting for heading. With lightly loaded planes like this Hangar 9 Tiger Moth, you can putt around all day long. Vintage biplanes are great for practicing touch-and-gos to help master the tail-dragger. Be sure to always use the rudder. Landing technique There are two types of tail-dragger landings: 3-point (stall landings) and 2-point (wheel landings). The type of model you fly and the wind conditions dictate the best type of landing to use. If you have a highwing, lightly loaded model such as a Piper Cub, you will in most cases be able to flare into a 3-point landing; this type of model is very forgiving and has predictable stall characteristics. In calm weather, the best technique is to come in, maintain straight and level during approach, and then you APRIL 2013 35

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