Design Improvements for the Zenith 601 HDS: Aileron Trim

Aileron Trim

The simple aileron trim system relies on the fact that, barring presence of an unusually heavy passenger, any adjustment is always for lifting the left wing. This is due to the following facts. First, the torque from the Rotax 912 wants to drop the left wing. Second, in the pilot-only mode, the left hand seating of the pilot also wants to lower the left wing. That second force is neutralized in the pilot-plus-passenger mode by the passenger. Fuel is always symmetrically loaded and used, so it has no impact on wing balance.

Aileron trim is achieved by a propeller control cable from Aircraft Spruce mounted between the two seats. To lift the left wing, either the control button is depressed and the knob is pulled forward, or the knob is turned counterclockwise. Thus, the turning corresponds intuitively to the notion that the counterclockwise turning of the knob lifts the left wing.

The propeller control cable makes a 270 deg turn in the tail cone and connects via three soft springs to the aileron cable. The next two photos show details.

On long flights it becomes tiring to hold the center control stick without elbow support. The remedy is a small block made up from styrofoam and covered with seat material. In cruise we set the block on the center armrest and use it to support the arm. This has solved the fatigue problem.

The block has a non-slip rubber surface so that it does not move on the armrest. For takeoff and landing, the block is put into the baggage compartment, since we do not like the restriction imposed by the block on the arm during these operations.