Auto-Landing Glide Slope

Hi Everyone.

Apologies if this has already been asked before, but I have been trying to attempt an autonomous landing with an APM 2.5 in a Skywalker.  The aircraft navigates perfectly fine all the way up until the aircraft aims for the landing waypoint.  At this point it seems that the aircraft has a lot of trouble losing altitude.

I've attached a screen shot of the tuning window below. During regular waypoint navigation, the aircraft has no problem dropping 100 ft over 10 seconds.  However, as shown below, when navigating to the landing waypoint, the aircraft only drops six ft over a period of 10 seconds.  The blue line on the graph below shows altitude with the red line showing the target altitude. The graph ends about 3 seconds out from the landing point.


I also tried approaching the landing point from the opposite direction but still had the same results.  Is there any parameter controlling the descent rate during an autonomous landing.  Any help would be really appreciated.

Thanks guys,


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  • I am experiencing the same behavior. Have been successful with auto landings previously (APM2.5+ArduPlane2.70), however after switching to new airframe and ArduPlane 2.72, I am unable to land the aircraft automatically, even when applying full flaps manually during the approach - the autopilot adjusts the throttle accordingly not to lose airspeed/altitude. Otherwise the setup is the same (airspeed sensor enabled, GPS, etc).

    PS: Just got an idea - there is the Minimum altitude for FBWB mode (ArduPlane:ALT_HOLD_FBWCM) parameter ... what if it kicks in during the auto landing, preventing the airframe to descent below this value? (I haven´t changed the value since my successful auto landings, however the new ArduPlane version might treat the parameter differently? Just an idea. Have to check on the airfield.)

  • Developer

    What is the motor doing during this time?  Are you maybe just expecting it to come down faster than the airframes sink rate? There is no way my SkyWalker will drop 100 feet in 10 seconds at normal gliding airspeed unless I deploy flaps.  If the motor is off during the final approach and you are not coming down as fast as you like, you need to (1) change the speed to a slower speed to get on the back side of the L/D curve so the sink rate will be higher, (2) employ flaps or some other drag device and/or (3) plan for a longer final approach.

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