RTL does not ensure it's actually getting closer to home.

[GoogleCodeExporter]

Please see the video :http://youtu.be/gD1JAz4oEDI  
at position 5:15 - you can see the RTL fails to get any closer to home - 
because headwind is making it stand still.

While PositionHold (Loiter) could easily gain from such behavior, - an AP 
destination , and *especially* emergency RTH should ensure that the plane is 
actually getting closer to home. (use throttle to gain groundspeed)  - 
otherwise it could waste battery floating at the same place, or - if only 
flying by airspeed, even be taken to a greater distance.

This aircraft does have a pilot tube - I do not know if that's what makes it 
behave like this.

Original issue reported on code.google.com by andre.kj...@gmail.com on 22 Feb 2012 at 9:09

[GoogleCodeExporter]

I suspect that cruise speed controls throttle.

the logic may look like: 
if airspeed =< cruise speed increase_throttle

and should be like

if airspeed =< cruisespeed or groundspeed < cruisespeed then increase_throttle

Original comment by andre.kj...@gmail.com on 5 Mar 2012 at 9:29

[GoogleCodeExporter]

Just set min_gndspd_cm and make sure your max airspeed ("fbw max" is within 
your airplane's capabilities.

Original comment by Mr.Challinger@gmail.com on 20 Mar 2012 at 6:05

[GoogleCodeExporter]

ARSPD_FBW_MAX=16  - I think it's higher than the windspeed.
Please note that the AP does not apply/increase throttle - at 5:15 in the video 
- it should apply throttle.  

Also I did not knew FBW_MAX was used for other purposes than FBW ?
- how is it used ? - should it be set like an maximum airframe speed ? (well 
above level flight at max throttle ?)

Original comment by andre.kj...@gmail.com on 20 Mar 2012 at 6:18