Picking the Right Aircraft
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There are few modern pattern designs I have seen that are not decent fliers. If you have a pattern-only plane, you can skip this discussion and move on to the next section.

The rest of us are stuck flying scale models and are forced to accept the limitations given to us by our full scale counterparts. The problem is that all full scale civilian aircraft are built to have high static and dynamic stability. What that means to us is - if you roll the plane 90 degrees and let go of everything, the plane will roll itself back to level. Also, if you push the nose down 45 degrees, it will raise its nose right back up. This is required by the FAA to keep civil pilots from killing themselves. This is bad for us, though, because the plane does not always want to stay in the orientation it is placed.

The following is a list of aircraft configurations that are desirable for a pattern plane. They are listed in order of greatest importance to least important. Armed with this basic knowledge, you will be able to look at a plane and have a good idea how it will perform.

Wing airfoil. You must use a plane with a symmetrical airfoil. Period. This means the top and bottom of the wing have the same shape. This will give us similar upright and inverted performance.

Dihedral. There must be little or no dihedral in the wing and tail. Dihedral is an aerodynamic bandaide for tendencies we do not want. If the plane has more than 1 degree, it is not acceptable for our use. Excess dihedral hurts knife edge and inverted stability.

Wing placement. The wing should be vertically mounted as close as possible to the mass center of the fuselage. Simply put, the wing should be near the middle of the fuselage. For a biplane, consider the wing to be mounted mid way between the two wings. A high wing mounting hurts inverted performance, and a low wing hurts upright performance - unless you add dihedral.

Engine location. The engine should be vertically located as close as possible to the mass center of the fuselage. Any variance in engine location will affect your vertical up-lines.

Horizontal stabilizer (elevator). Should be vertically located close to the mass center of the fuselage. Once again, a stab that is far off center is an aerodynamic bandaide for tendencies we do not want.

Wing sweep. Aft sweep is excellent for pattern because it stabilizes BOTH upright and inverted flight. No sweep is good. Forward sweep generally hurts smooth control response for pattern, but that may be a benefit for 3D performance. Currently the only forward swept scale aerobatic plane I am familiar with is the Edge 540.

Once you have a plane that does not deviate to much from the above optimum characteristics, give it a good look over. Be certain the wings and tail are not mounted crooked.

Make sure the wing and tail have the same incidence, unless they are supposed to be different (like the Ultimate, which has +2 degrees of tail incidence). Make sure both wings have the same incidence, and that the incidence remains the same for the length of each wing.

Make certain the control surfaces are not twisted or warped - this is a common ARF abnormality. Incidences do not have to be checked with fancy gadgets. Simply walk behind the plane and orient yourself so you can see both sides on edge, and visually compare the angles of the wings and tail. What the angles actually are is not nearly as important as having the angles all match each other. There is only one word for a warped competition plane…EBAY.

The final consideration is the length of the nose versus the tail. An airplane with a short nose will likely be difficult to balance - the Edge 540, Cap 232, and Katana come to mind. If you have to add nose weight to balance a plane, you are handicapping yourself from the start.

Aircraft weight discussion

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