Re: [Paparazzi-devel] Reply to "How to descent faster? ( Famille Chateauvieux-Hellwig)"

[David Carlson]

If you do have a powered glider, the best way to lose a lot of altitude 
in a hurry without getting too much airspeed is to side-slip your 
airframe.  This is actually really easy to do if you have a rudder 
(which most powered gliders do).  Simply go into a loiter circle  at a 
decent roll angle (> 30 degrees) and apply full opposite rudder.  This 
is normally how I lose altitude if I don't have spoilers on my powered 
gliders and it works like a charm without the danger of snapping the wings.

Buzz

Famille Chateauvieux-Hellwig wrote:
> Le dimanche 30 août 2009 18:12:29 Pascal Brisset, vous avez écrit :
>   
> > Hi,
> >
> > this kind of procedure is available in
> > conf/flight_plans/grosslobke_demo.xml (from Martin):
> >
> >     <block NAME="down" strip_button="Down">
> >      <set var="lateral_mode" value="LATERAL_MODE_ROLL"/>
> >      <set var="v_ctl_mode" value="V_CTL_MODE_MANUAL"/>
> >      <set value="TRUE" var="h_ctl_disabled"/>
> >      <set value="(-0.6*MAX_PPRZ)" var="h_ctl_aileron_setpoint"/>
> >      <set value="(0.9*MAX_PPRZ)" var="h_ctl_elevator_setpoint"/>
> >      <while cond="estimator_z > ground_alt + 220"/>
> >      <set value="0" var="h_ctl_aileron_setpoint"/>
> >      <set value="0" var="h_ctl_elevator_setpoint"/>
> >      <!--deroute block="down_end"/-->
> >     </block>
> >     <block NAME="down_end" strip_button="DownEnd">
> >      <set value="0" var="h_ctl_aileron_setpoint"/>
> >      <set value="0" var="h_ctl_elevator_setpoint"/>
> >      <while cond="1.> stage_time"/>
> >      <set value="FALSE" var="h_ctl_disabled"/>
> >      <deroute block="wait"/>
> >     </block>
> >
> > The trick is to set the h_ctl_disabled variable to disable
> > stabilization, put the aircraft in a spiral ... and
> > restart the autopilot high enough from the ground. Of course, your
> > airframe has to handle it (it was the cause of one of the first crash
> > with Paparazzi: switching from a manual dive to auto1; Twinstar's wings
> > did not support the strong resulting pull)
> >
> > --Pascal
> >
> >     
> Hi Pascal,
>
> I'm not sure what the paparazzi command are. You probably do not need the 
> ailerons. Is 0.9*max_pprz pushing or pulling ?
> I would put the rudder to 100% right or left, and elevator up 100%. I mean 
> 100% of the servo range, not just the max pprz... a twinstar definitely stands 
> this treatment, but you really want to have the "sticks in the corner"
> Martial
>
>
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