Design, Construction, and Adjustment

AOA sensor construction details are summarized in Figure 12. All drawings are to scale. On the left are a number of views and assembly details. Typical vane movements over the full dynamic range are shown in the middle. Various null-adjustment settings are illustrated on the right.

The sensor element is locked into place with thread wound around it in a couple of places and with CA. Figure 13 provides front and back close-up views of the hall-effect sensor component. The component pins should be trimmed prior to assembly. Apply several coats of nitrate dope over the balsa vane and then add counterweight for balance about the pivot pin. The vane should be free to rotate 360 degrees. Add a drop of oil to pivot pin to reduce friction.

The rivet should be hammered down flat to lock the two brass pieces together with enough friction to prevent inadvertent movement but still allow for sensor null-adjustments. Use a flat screwdriver for prying when making null-adjustments. The two pieces should be permanently locked together with a drop of CA after final test flights have been completed.

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Alignment and Test Flight Preparations

Preparation procedure steps for the first test flight:

1. Program elevator and aileron gains between to 50% and 60% respectively at the transmitter.
2. The hall-effect sensor element may have an inherent output offset which has be adjusted out. With AOA sensor vane pointed forward (the wrong way), null the output of the AOA sensor by adjusting pot R3 to minimize the difference between regulated 2.5V and U1-7 (see schematics).
3. AOA sensor gain should be adjusted to between 1.0 and 1.5 to start. Measure the gain - don’t guess.
4. Prepare for first test flights with a slightly forward CG setting. I recommend a CG setting of ~27% if the final setting is expected to be farther aft. The accuracy of all CG settings is vital. It is recommended that CG calculations be based on the constructed model, not on the design plans. The differences are generally significant. At this time, also prepare for a way to back off to the final CG position in a couple or more increments (remove nose weight incrementally until final trim CG and/or elevon deflection is reached).
5. Align AOA sensor mechanically to produce zero output at trim angle-of-attack. Use your best guess to start.
6. Adjust elevator trim to slightly reflex position (with AOA sensor out of the way - pointed forward) to account for the slightly forward CG at start. A trailing edge rise of about an eight of an inch for a two inch wide elevon is about right.