Tail Design - ZODIAC CH 640: New Four Seat Kit Aircraft from Chris Heintz

CH 640 Tail

The empennage (tail) of the new ZODIAC CH 640 demonstrates the design and construction efficiency of aeronautical engineer Chris Heintz. The tail is comprised of a single horizontal tail (stabilator) and a single vertical tail (rudder).
The stabilator is dynamically balanced and mounted to the fuselage with two large steel bearings. Operation of the stabilator is through the push-pull movement of the control wheel yoke control. The "flying tail" stabilator is equipped with dual trim tabs (interconnected) mounted on the trailing edge. The trim tab is actuated by an electric trim motor (standard) or a push-pull control cable (optional), which is activated by the pilot by moving a manual trim wheel, similar to conventional aircraft. Maximum push-pull yoke force at full trim deflection and at the worst limits of the center of gravity is under 35 Lbs.

The stabilator construction is a conventional semi-monocoque structure. Individual aluminum ribs riveted to a large box type spar enclosed in aluminum skins make up the stabilator. The one piece control surface does not have any moving parts other than the dual trim tabs which are piano hinged at the trailing edge. The stabilator control cables are adjustable through the large access panel under the rear fuselage bottom.

Like all Zodiac models, the CH 640 features an all-flying vertical tail (rudder) section for excellent effectiveness and control, especially at low speeds. The all-flying rudder provides responsive rudder control, while also minimizing weight and complexity (there’s only one vertical tail section). Two rudder bearings bolt to the rear fuselage to fix the rudder to the fuselage.

The rudder is dynamically balanced by a small weight installed in the leading edge. Operation of the rudder is through the movement of the rudder pedals. The rudder is "self centering" in flight through the nose wheel strut bearing.

Construction of the rudder is a conventional semi-monocoque structure. Individual aluminum ribs riveted to a simple "U" channel spar enclosed in aluminum skins make up the rudder. The one piece rudder control cables are connected with turnbuckles to the rudder which can be adjusted from the outside of the aircraft. The "self centering" and easy to adjust cables eliminate the need for a fixed rudder trim tab.

Building the tail sections...

Made up of only two primary structures, the ZODIAC CH 640 tail sections demonstrate Heintz' design and construction philosophy of keeping the aircraft simple, and quick and easy to build. Most aircraft tail sections are made up of an elevator, stabilizer, vertical fin and a rudder - which obviously means more parts to assemble and a longer construction time...