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

From: David Carlson
Subject: Re: [Paparazzi-devel] Reply to "How to descent faster? ( Famille Chateauvieux-Hellwig)"
Date: Mon, 31 Aug 2009 09:50:42 +0300
User-agent: Thunderbird (X11/20090817)

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.


Famille Chateauvieux-Hellwig wrote:
Le dimanche 30 août 2009 18:12:29 Pascal Brisset, vous avez écrit :

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 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"/>

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)


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"

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