PX4 1.15.4 + IR-LOCK: Precland accuracy/search issues

PX4 Autopilot
1

Setup: PX4 v1.15.4 MC, IR-LOCK (Pixy v1.0.1) on external I2C (0x54), no rangefinder. Autostart irlock + landing_target_estimator. Mission: WP directly over LZ at 10–12 m → LAND (tested Opportunistic and Required).

Works: irlock_report and landing_target_pose (rel_pos_valid=True) are solid; axes correct; vehicle makes small XY corrections.

Problem: Touchdown isn’t as accurate as expected. In Required, if I turn the beacon OFF during LAND, the vehicle doesn’t search—it continues to land/fallback (even with PLD_BTOUT 2–5s, PLD_SRCH_ALT 10m, PLD_SRCH_TOUT 10s, PLD_MAX_SRCH 2, PLD_FAPPR_ALT 1.0m).

Questions:

  1. On 1.15, what exact conditions trigger search in Required during LAND? Does dropping below FAPPR_ALT skip search?

  2. Any proven parameter set without a rangefinder for better final accuracy? (e.g., PLD_HACC_RAD, FAPPR_ALT, LTEST_MEAS_UNC, LTEST_SENS_POS_*/SCALE_*).

  3. Suggested MPC_LAND_ALT1/2/3 for a slower descent earlier, given MPC_LAND_SPEED min is 0.6 m/s?

Happy to share a short log and the .plan. Thanks!