The pedestal has in its upper compartment two panels, offering the following features:
- Left Panel:
- Calibration of the flight controls for rudder, aileron, elevator and brakes (left and right)
- Flight director ON/OFF switch
- Rudder auto-coordination ON/OFF switch
- Right Panel:
- Calibration of the engine controls
However, the two calibration procedures of the controls can only be performed, when the aircraft is on ground - safety first !
To allow for dawn-dusk and night flight, the two panels are illuminated by an LED bar, which is located close above the two panels. This bar holds six warm white 3 mm LEDs. As for all other panel and gauge illuminations, also these can be dimmed.
Left Panel: Flight Control Calibration
Pressing the START / NEXT button will initialise the calibration procedure of the flight controls, which is indicated by the illumination of the yellow elevator LED. Then three procedures have to be performed:
- The elevator, hence the yoke, has to be placed to the minimum position by pushing it to the most down position. Then the MIN button on the panel shall be pressed. The controller will now read the associated elevator potentiometer value.
- Then the elevator has to be placed to the neutral position and then the MID button shall be pressed.
- The same has to be performed for the maximum position, where the elevator shall be pulled to it maximum position, followed by pressing the MAX button on the panel.
Having defined these three calibration positions, the controller computes a new control function and will save the resulting three elevator calibration coefficients a, b and c into the EEMEM area of the micro-processor.
When this procedure has been completed, the START / NEXT button has to be pressed again, which then lights up the aileron LED, indicating, that the same procedure has to be performed for the aileron control, i.e. the MIN, MID and MAX position has to be defined. The procedure has to be repeated for the rudder, the left and right brake. When the calibration procedure is completed, then all LEDs are shut off. In case of an handling error during these procedures, one can press the START / NEXT button to terminate the calibration procedure and the old control function will further be used. Even if nonsensical inputs are made, e.g. the minimum position is greater than the maximum position, the process is interrupted and the corresponding LED flashes.
The consequence is, that we have for each control three defined fixpoints, from which the control function can be computed by solving a quadratic equation. This control function converts the read digital counts of the potentiometer to an FSX event parameter. As shown in the right picture, the left control function is for the rudder, aileron and the elevator (range -16383 to +16383), while the right one is for the brakes (range 0 to +16383). To solve the quadratic equation based on the three float fixpoint values, the micro-processor only needs 0.8 ms to calculate the resulting calibration coefficients a, b and c.
When loading a new firmware into the micro-processor, the controller defines a control function along the 'Default Calibration Function', which is simply a linear function, hence a straight line, as shown in the right picture.
This procedure works very satisfactorily and allows to re-calibrate the controls in a very easy manner, without updating the firmware of the controller in case the controls have been modified.
In addition, it ensures that the center position can be set exactly to the physical mid position of the control, which is very important for the elevator and aileron control of the yoke.
Left Panel: Flight Director and Rudder Auto-Coordination Switch
These two switches are straight forward. One switches the Flight Director on or off and the other one switches the rudder auto-coordination function on or off. When switching to ON, the rudder is automatically controlled by the aileron control of the yoke and not by the pedals.
The indicator for the Flight Director is typically an integral part of the Attitude Indicator, the upper mid one of the six-pack. How to implement this in the still to be developed Attitude Indicator is so far not clear for me, because this would require two additional mechanisms in this rather complex gauge, one for the pitch and one for the bank information. An alternative solution would be to develop a dedicated gauge, which only shows the Flight Director pitch and bank information. This gauge could be placed at the position of the 'Instrument Air' gauge, which I do not intend to implement.
The complete panel itself has been 3D printed and sprayed with black dull paint. Also the push buttons are printed in 3D. The electronics board behind the panel holds the switches, the LEDs and the push buttons, see right picture.
Right Panel: Engine Control Calibration
With this panel the engine controls in terms of throttle, propeller pitch and mixture can be calibrated. The calibration procedure is very simple. Pressing the START button will light up the yellow calibration LED and the procedure is as follows:
- All levers of the engine control shall be placed to the minimum position. Then the small calibration switch shall be put to the MIN position, followed by pressing the SET button.
- Then all levers of the engine control shall be placed to the maximum position. Set the small calibration switch to the MAX position, followed by pressing the SET button.
This already completes the calibration procedure, the yellow LED shuts down and the controller computes the new calibration coefficients and stores them into the EEMEM area of the micro-processor. Having only two fixpoints (MIN, MAX) the control function is of course a linear one.
The physical and electrical design of this panel is nearly identical with the left one.