Lessons Learned from our Aircraft First Flight Tests: Overcoming Challenges. Part 2
- Elena Karpovich
- Jul 6, 2025
- 2 min read
QSTAB Mode: In this minimally stabilized mode, our aircraft has a strong tendency to slide to one side (due to lift), making controlled flight difficult. For this reason, as well as due to my poor piloting capabilities, I always tried to fly in more automated modes.
Problem 3: Unstable Behavior in QHOVER Mode
Problem:
The drone suffered from strong motor oscillations and continued sliding unpredictably. At one point, it drifted toward the runway, forcing a manual landing. Unfortunately, upon touchdown, the drone flipped over due to inertia.
Possible Causes:
Overly Aggressive PID Tuning:
The P (Proportional) and I (Integral) gains in the altitude/attitude controllers were likely too high for our drone’s weight and motor response.
Excessive gains can cause oscillations and instability, especially in hover modes where fine adjustments are critical.
Vibration or IMU Issues:
If the flight controller was receiving noisy accelerometer/gyro data, it could have led to erratic corrections.
Center of Gravity (CoG) Imbalance:
A slight weight imbalance could have contributed to the sliding behavior.
Solutions & Lessons Learned:
Reduce PID Gains:
A systematic reduction in P and I terms (especially for altitude and attitude control) could have stabilized flight.
Incremental tuning in a controlled environment (e.g., tethered tests) would have been safer.
Check Vibration Damping:
Ensure proper soft-mounting of the flight controller to minimize vibration interference.
Final Takeaway: PID tuning is a delicate balance—too little, and the drone drifts; too much, and it oscillates or becomes unstable. Unfortunately, I didn’t get a chance to fully diagnose this issue, but the experience reinforced the importance of gradual tuning and pre-flight checks to prevent unexpected behavior.
And finally, here are some data from the logs:
Comments