Today's autolanding attempt with my Skywalker 1880 was a failure. I attempted to insert some Do_Change_Speed commands to incrementally slow down from cruise speed to landing speed. On the base to final turn the plane continued its roll to 80 degrees. I suspect I got too slow and the inside wing tip stalled. However it appears the airspeed was adequate at that point, although it dropped way below stall speed during to recovery. Perhaps there is a lag time in the data? Could this be an accelerated stall? Is there any way to see how many G's I was pulling?

The graph below shows a large divergence between Servo_Roll and Nav_Roll & Roll. I need help understanding this.

Roll shows an 80 deg left bank, that's obvious.

Nav_Roll shows the identical thing, we would this be exactly the same?

Servo_Roll, I presume is showing what the servos were trying to do to correct the excessive bank angle, which probably stalled the wing tip more.

Roll_Sensor is the pink line that is very hard to see. I have no idea what this is telling me.

3691067448?profile=original

 

Here is a short video http://youtu.be/p6kayKtrg9I

 tomorrow.

Here is my flight plan:

3691067461?profile=original

 

Here is a Google Earth view, I just figured out how to display the "Planes", that is so cool!

3691067370?profile=original

 

Here is the .log file, sorry my computer crashed so no tlog.

2013-10-07%2013-59%203.log

 

There were some other odd things you'll see if you watch the video. The plane really dived hard to get down to 175ft at WP20 where it was to do 2 turns in Loiter but the profile was too steep and it crossed the point too high at about 220ft and too fast. Why at this point does the APM add 50%+ throttle in the turn?

 

 

 

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  • 100KM

    What is your min pitch angle parameter.  Your WPs call for a steep descent as you approach your landing site.  Your plane is diving to reach the next WP and reaching 55 mph - which is probably entering the danger zone for a SW if it tries to abruptly pull up.  From WP19 to WP20, MP is predicting a -90% grade (-42° descent angle).

    Bring up the Elevation Graph in MP.  I am not 100% sure I know what APM does with the Do_Speed_Change commands, but I'd be curious to see what MP shows in the Elevation Graph.

    You have the Google Earth track.  Pull up the elevation profile and compare to the Elevation Graph in MP.  I would like to see what you find.

    In general, I think your approach flight path is too steep, with a final turn that is too sharp.  I try to err on the side of very shallow descents and shallow bank angles.  Are you able to play back the log on the Flight Data screen with the flight path overlaid on the waypoints?  What I do for autoland is design the approach such that the path roughly matches the glideslope of my SW.  This makes for a very long, but uneventful approach.  I should admit that I had flaps under manual control on my SW1680 to really scrub off speed on final.

  • Can't help you but gotta ask how you got the aircraft icon to display in GE.

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