QuadPlane 4.6.3: Q_LAND_FINAL_SPD Applied From High Altitude, Q_WP_SPEED_DN Ignored During Q_LAND/Q_RTL #32155
Description
In ArduPlane firmware 4.6.3 (QuadPlane), the parameter Q_LAND_SPEED is no longer available. Previously, this parameter allowed control of the vertical descent speed during the main VTOL descent phase, before the vehicle reached the final landing altitude defined by Q_LAND_FINAL_ALT.
Current behavior observed:
Vehicle starts Q_LAND / Q_RTL from ~100 meters altitude
Parameters set:
Q_LAND_FINAL_SPD = 0.5 m/s
Q_LAND_FINAL_ALT = 7 m
Expected behavior (based on earlier firmware logic):
Descend from 100 m → 7 m at 1 m/s (Q_LAND_SPEED)
Below 7 m descend at 0.5 m/s (Q_LAND_FINAL_SPD)
However, in 4.6.3:
The vehicle descends at 0.5 m/s from the full 100 m altitude
Q_WP_SPEED_DN (which appears to replace Q_LAND_SPEED) does not affect descent rate during Q_LAND/Q_RTL
The aircraft appears to use only Q_LAND_FINAL_SPD for the entire landing profile
Operational impact
For heavy QuadPlanes:
Very long descent time (~200 seconds from 100 m)
Excessive battery drain
Voltage sag risk
Possibility of brownout or crash before touchdown
This creates a serious safety risk, especially for:
Logistics drones
Agricultural VTOLs
Heavy-lift QuadPlanes
The absence of a parameter to control pre-final descent speed removes an important safety and endurance control previously available.
Suspected issue
Landing logic may be entering final descent mode prematurely, or the firmware may not be properly using Q_WP_SPEED_DN during Q_LAND/Q_RTL vertical descent.
Version
ArduPlane 4.6.3
Platform
[ ] All
[ ] AntennaTracker
[ ] Copter
[✔] Plane
[ ] Rover
[ ] Submarine
Airframe type
QuadPlane VTOL (multirotor + fixed wing hybrid)
Hardware type
Pixhawk-class flight controller
Logs
Logs showing descent from ~100 m at constant 0.5 m/s despite Q_WP_SPEED_DN changes can be provided upon request.
Contributor
SUNDAR C