Discussions

I did my best to tune my New 2013 Skywalker but never got to the point where I could get all the feedback from the plane that was described in the tuning guide. Nonetheless, I found that it was flying very accurately in Auto, so I prepared a long mission along the coastline. I have several questions about what happened along the way.

1)  During the Auto takeoff, the APM never pitches the nose up enough. I have the takeoff angle set to 15* but she lets the nose drop to the point that I have to quickly pull back on the stick to keep from hitting the ground. After that, it still doesn't ever pull the nose up to the 20* pitch max, and the airspeed accelerates up to 53 mph (24 m/s) despite my ARSPD_FBW_MAX being set to 43 mph (19 m/s).

EDIT: I have the TECS Climb Max set to 6.0 m/s. and I hit that a few times in the takeoff which may explain why she wouldn't pitch up any higher despite the high airspeed. It looks like I need to increase the Max Climb rate, or reduce the Max Throttle. Strange logic that it would give priority to TECS Max Climb over the Max airspeed.

Request: There should be a Takeoff Power parameter to allow 100% throttle for takeoff only and still limit the max throttle for normal autopilot use as currently done.

2) After reaching the Takeoff altitude of 150ft, the plane turns to WP2 but it does not climb up to 400ft as expected. Instead it throttles way back and levels out at 230ft, then starts a dive to 170ft and levels out. Then she starts climbing back up to 200ft and levels out. Finally I switch to manual. As I get closer to WP2 I switch back to Auto and she promptly gets right on track and the programmed 400ft altitude. Altitude control is very accurate for the rest of the flight, until the airspeed failure (forshadowing :) I included several waypoint turns in the video to see. I think they are a bit too aggressive and I should increase the L1 Period from 10. I see some oveshoot.

3) During the flight to WP2, I tried adjusting the the throttle stick, but it made no changes to the airspeed. I have THROTTLE_NUDGE enabled.

4) At ~4:00 in the video you can see that things go seriously wrong! Airspeed drops to zero, throttle goes to 100%, and the plane pitches over. We have had some good discussions on these forums about airpeed sensor failures and the remote possibility of clogged pitot tubes. I couldn't believe this was actually happening to me on my first mission! Even stranger is that my altimiter went haywire too. Did I suffer a total pitot/static failure? I was very impressed with how well the new TECS controller handled this potentially catastrophic situation. Although the autopilot got very busy, it was not about to crash the plane, and gave me plenty of time to react.

SOLVED:

Upon landing I noticed that my altitude was -380ft. When the failure occured I was at +380ft. That's when I figured out what had happened. My copilot who was looking through Mission Planner inadvertantly clicked on Do Action, and I had left the menu on PREFLIGHT_CALIBRATION. He reset the airspeed and baro sensors in mid flight.

Maybe there should be a safety feature that automatically un-selects the these Preflight options from the dropdown box, or perhaps a secondary prompt for confirmation.

Here is the FPV video:

Here is the flight plan file and screenshot:

2nd%20kailua%20beach%20with%20autoland.txt

Here's my log:

The takeoff doesn't occur until 54%.

2013-09-09%2009-52-45%20KaiBeach2.tlog

Here are the PIDs I had during this mission:

2013-09-09%2009-52-45%20KaiBeach2.param

 The PTCH2SRV_P looks really high to me, so I stopped increasing it before I hit any oscillations. Maybe I need to keep increasing it? Should I be increasing the Nav Pitch Alt PID, I left it stock because I don't know what it does or how to set it?

Perhaps the APM doesn't have enough pitch authority on initial takeoff with low air flow over the elevator to counteract the downforce from the high mounted pusher prop. I can live with this if the Pitch PIDs look otherwise adequately tuned. Please provide some recommendations. Thank you!