Working through flight data of small 2kg foam plane that had undesirable porpoising after flight using default arduplane 4.1.7 values. Was concerned about integral or proportional values causing the pitching oscillations but after extensive reading was considering that with FLTE set to zero this effectively disables the error correction that can be applied by the PID loop as shown in the PID Controller Flow Diagram Roll, Pitch and Yaw Controller Tuning — Plane documentation
Not sure how the default could be 0 when the allowable range is documented as 2-50. But I do see that AC_PID_EFILT_HZ_DEFAULT is 0.0f.
The error could have come in on my side when loading some other parameters , However also just pulled down arduplane 4.3 SITL and these are the default parameters under 4.3 so it does appear that the default value is zero ? question is would this disable the PID loop. I suspect it is intended to be zero for the first flight since documentation suggests getting feedforward gain correct first and then bringing in P and D terms " Now vehicle can be flown again to start trimming P and D. Starting with D and P at 0:" Roll, Pitch and Yaw Controller Tuning — Plane documentation
Values from 4.3 SITL download under plane . I believe these to be the downloaded values as I deleted the following files eeprom.bin plane.parm from my HDD before running the SITL download. If I have this wrong please correct this statement
Someone can correct me if I am wrong but _FLTE = 0 I believe disables the lowpass filtering on the error term. The alpha term (smoothing factor) of the LPF is set to 1.0 when the cutoff frequency is zero, meaning no smoothing is occurring.