Questions about Automatic Takeoff

ArduPlane
1

Hi guys,

I really need help on this. I’m beginner with planes and I’m fighting with automatic takeoff using a bungee launcher.
If there is wind the automatic take off works fine, I upload the mission, take some distance and release the plane.
When there is no wind or little wind, I really cannot takeoff. I tried a lot, change the stretched chord, change TKOFF_THR_MINACC, TKOFF_THR_DELAY and TKOFF_THR_MINSPD, but nothing appear to work.
I discover the TKOFF_FLAP_PCNT, I tried 15, 30, 50 but I can’t see the flap been used, in the works scenario or in the scenario not working, the flap is always at 0 - the difference is the wind (in my point of view).

I really don’t know much about plane and if can someone point me a direction about what I’m must search I will appreciate.
This is a log from a crash - the takeoff didn’t work -
https://drive.google.com/open?id=0B1omx8hPUswTeC1xcTZQSjVsdmM

This is a log from a correct flight https://drive.google.com/open?id=0B1omx8hPUswTdFU1c0RoMGxvWWs

Thanks a lot guys.

2

You don’t seem to have flap or flapersons enabled. Did you read this?
http://ardupilot.org/plane/docs/flaperons-on-plane.html

3

I think you’re problem is the takeoff is much too steep and you are stalling. The plane is at 43 degrees pitch up on takeoff, and goes to 56 degrees briefly. That is way too steep. I don’t know how you are launching it, but whatever system you are using you should change it to be no more than 20 degrees nose up.
You should also raise PTCH2SRV_P to 1.0 and PTCH2SRV_I to 0.3.
Cheers, Tridge

1 Like
4

Thanks a lot @tridge,

was my mistake about elevon and flaperon, really sorry for that and thanks for all your help.
Btw I’m using a bungee launcher.

5

Hi @tridge, sorry I was sending in gitter messages and forgot this thread.
I changed the parameters and I was trying a new flight today with a new wing(the other has to be replaced after a severe crash).
I was with same result, when I launch the wing, instead to gain altitude, the wing has hit the ground with a moderate speed - I had to glue some parts.
Any clue what I can do or analyze? This are the logs from this flyght: https://drive.google.com/open?id=0B1omx8hPUswTZ3FIM2NoQlBNTnM

6

I chatted with @juvinski on gitter today. I looked at these logs and some new ones he posted:

  • there’s a CG problem
  • Pitch PID.P is set too high (2), the lower autotune values are better
  • TKOFF_THR_MINACC=6 is a saftey problem. Log shows accel is hitting 30s, I suggest 12-15.
  • The auto land mission is generally all wrong.
  • TKOFF_THR_MINSPD=6 is not reccommend. The description says _MIN_ACC is prefered
  • TKOFF_THR_DELAY=16 (1.6 second delay) is waaaaay too long. Default is 2, I suggest a number closer to that
  • LIM_PITCH_MIN/MAX of -4000/+4000 (+/-40deg) is extreme. Default is 20, I suggest a number closer to that
  • TECS_PITCH_MIN/MAX of 0/0 means to not do anythign special during takeoff, use the global limits. If you’re having takeoff problems, I suggest looking at every takeoff related param

In general, it looks like you’re touched too many params. Save params, Reset to defaults, and compare. The defaults should be pretty good, change what you need for your aircraft type and launch method but don’t go too crazy on the other params. Also, I highly suggest flying v3.8beta.