Color Schemes:

The Yak is one of the best designs for precision aerobatics.

The most obvious proof of this is to simply look at pattern planes. Pattern planes are not scale planes. Pattern planes are simply the best shape of an airplane to fly at the very highest level of precision. Pattern planes have been tweaked and tweaked for decades. The shape of the rudder, the placement of the rudder, the placement of the stabs, the placement of the wing towards the centerline of the plane, the use of double tapered wings, the thrust line of the engine, all have been massaged to make the ultimate flying machines. Is it true that no pattern plane has a round cowl or fuselage like a Yak, however this fuselage design is not too bad, and the rest of the characteristics are as good as then can get!

Design

Three important design factors of a great flying aircraft follow. The Aviation Models Extra 260 is well designed in all of these areas.

1) Low pitch coupling - when the rudder is applied, most aerobatic planes pitch to the belly. Reducing this is extremely difficult to do. The relationship between the thrustline, wing location, stab location and rudder shape are critical. Typically the stab is located on the thrustline, the wing is just a little low, and the rudder area above and below the thrustline is as even as possible. If incorrectly designed, serious flying problems result. When you are flying straight and level and you use the rudder to adjust the flight path, or if you are flying knife edge, or if you are simply flying a loop and you are using rudder to stay on track, the last thing you want is the plane to pitch down with the application of rudder. This can be controlled with mixing in a computer radio, but cannot be eliminated in all aspects of flying. If the plane isn't designed for low pitch coupling, then it will be a real handful to fly precisely.

2) Low roll coupling - when the rudder is applied the plane may roll. This is due to the dihedral in the wing and the shape and position of the rudder. The more the dihedral the more the plane will roll with rudder (called proverse roll coupling), however, too little dihedral will make the plane roll the other way (called adverse roll coupling). This must be designed in during the prototype stage so that there is none. This can be designed into any aerobatic plane. Just the same as above, when you apply rudder, you want yaw only, no pitching, no rolling. This really shows up in slow rolls. You will noticeably see the roll rate of the plane speed up and slow down when you use the rudder. This makes you look like a bad pilot.

3) Wing Loading - the relationship between the weight of the plane and the size of the wing. When you get a plane, starting off with a plane which comes out light is the first step. Starting with a heavy airframe is difficult (and expensive) to overcome. Keeping weight to a minimum is critical to many aspects of performance. This is something that the designer has control over - but the pilot can have a large influence on this as well. When we recommend parts to the pilot we suggest the lightest parts possible.