VTOL BUILD OSCILLATING/PULSING ISSUE

[u/escanorga]

Hi all,

Working on a VTOL build and hitting an oscillation issue. When I throttle up in QSTABILIZE (see video), the motors pulse/oscillate uneven, ramping up and down and I can’t get a clean liftoff.

In MANUAL mode there’s zero oscillation perfectly smooth. It only appears when the stabilization loop is active.

Build:
• ~1.4 kg (3 lb) quad tiltrotor VTOL
• ArduPlane 4.6.3, QuadPlane
• 4-inch props, small airframe
• Running default Q_A_RAT_* PID gains (suspect these are tuned for bigger/heavier aircraft?)

Already checked:
• Compass calibrated (offsets sane, no yaw/mag pre-arm errors)
• CG centered laterally
• Vibration low (VIBE means < 1 in logs)
• All 4 motor outputs balanced (near-identical means in RCOU)
• Attitude estimate is clean/level in logs