Electric Models
With correct settings, you can expect very good results. The value for 100% can be obtained from the manual or calculated using a propeller calculator. 0% is also straightforward; it corresponds to the idle current draw and has a minimal impact on the overall result.
The value at 50% is crucial, as it is highly dependent on the ESC (Electronic Speed Controller) characteristic. In this example of a Parkmaster, it corresponds to approximately one-quarter of the maximum current. Whenever possible, throttle positions at 25% and 75% should also be measured and entered to ensure accurate settings.
Measurement Method
Currently, I use a clamp ammeter to measure the currents while the model is on the ground in a stationary position. For the intermediate values at 25%, 50%, and 75%, I precisely set the throttle stick to the required value (displaying the percentage of the stick position in the display) with the safety switch turned on, then turn off the safety switch, and record the value. It goes without saying that extreme caution is necessary during these measurements, especially since the motor often spins up quite aggressively at 75%.
The essential aspect is to determine a “throttle curve” through these measurements that corresponds to the ESC’s characteristic. The absolute values are less important than their ratios to each other.
In the end, approximately 15% is subtracted from all the values because the currents during flight are significantly lower. These adjusted values are then entered into the CalCa program.
Fine-Tuning
After the initial flights, I recharge the batteries fully and compare the recharged capacity with the consumed capacity using an Excel table. Based on this comparison, I adjust all the values by the corresponding percentage, either upward or downward. If done correctly, it should be possible to set the main alarm at around 25% and thereby land at slightly over 3.7 volts per cell voltage.
Jet Engines
In most cases, the settings for jet engines can be taken directly from the manual. For instance, my JetCat P140-RX consumes 510mL at full throttle (100% throttle) and 115mL at idle (0% throttle). If you leave the preset throttle curve, the values in between are linear. Therefore, set 25%, 50%, and 75% to “-1” so that the program calculates a straight line between 0% and 100%.
Gasoline Engines and other IC Engines
Determining consumption values for gasoline engines can be challenging. One could use a temporarily installed flow meter, but even those struggle to provide an exact value at idle. Currently, I use approximately 100mL for 100% throttle on a 2-stroke engine with a 200cc displacement and about 15mL at idle, with linear values (“-1”) in between. Since I only fly jet engines apart from IC engines, I have limited experience with this. However, a colleague of mine has used it and finds that calca-Gas still provides a reasonably good overview of the approximate state.