[Paparazzi-devel] Tuning Suggestions?

[TurboTas]

Hi All.  

I have a funjet with a tiny 2.11 installed.  I’ve been slowly building it over 
the past year or so and have achieved quite a few MANUAL flights, say around 10 
for a total of about an hours flying time.  In all cases I have the ground 
station running so I have the telemetry files.

In MANUAL, the plane flies nice and level when hands off the stick and the 
neutrals have not been tweaked on the radio.  The HSI looks good on the 
telemetry replay.

With that in mind I have made quite a few attempts (at high altitude) at AUTO1 
flight.  The first couple of flights were awful and it transpired that I had 
the orientation of the single axis IR sensor wrong and we had some interesting 
recovery flights after uncommanded rolls and pitches.  Yeuch.

Okay.  Got that problem fixed and the current issue is that each time I attempt 
AUTO1 flight, I get a pretty violent pitching downwards.  Occasionally I get 
perhaps a second of level flight before that happens.  During these breif 
stable spells I see a tiny roll oscillation.  I see this as a good sign that 
the feedback loop is working! I never let the dive get far enough to see if the 
plane does a bunt as I’m quick to grab it back under MANUAL control.  This all 
happens rather fast and the plane reaches an almost vertical dive.

Additionally, under MANUAL control, I find the plane really lively and a joy to 
fly.  Should I be tweaking the control throws so that the plane is more placid 
– maybe the problem is over control?  

In all the AUTO1 test flights, it has always been nose down, rather than nose 
up.  I’ve never been tempted to try invoking AUTO1 when inverted!

My question is more of a cry for help really: Any methodologies for diagnosing 
the problem?  I have the log files and know how to use the graphing tool, but 
am not entirely sure what to look at first!  Does this sound like a tuning 
error or something more critical maybe wrong?  I've been looking at the replays 
on and off for months, but am a bit lost! I could maybe post my airframe file 
and\or the flight logs.

PS, I have not seen this posted in the digests over the last few months, so 
thought it worthy of comment: I recently did a CVS update after about 4 months 
and immediately noticed a huge speed increase in the GUI.  Not sure what has 
changed that may explain the improvement, but thanks!

Kind regards,

Toby.