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Autorotation thoughts

Posted by gsenroc on May 5, 2014 at 5:58am

Hi,

I've been flying my heli for a while but I came across a problem, which doesn't happen quite often but it may be important for safety. It's the power failure and autorotation.

Recently I had a major failure of my battery during the flight, the battery just suddenly died that my motor has stopped but the servos were still working thanks to the separate battery for servo and PX4. Luckily I was about to land my heli about 4m high so I heard that the motor had stopped.

I changed to stab mode, and tried to do my first autorotation in my life without any experience and I'm glad I was not panic. Although my autorotation was not well performed, the stab mode helped a lot. In the end I just had a slight hard landing, nothing was broken.

After this accident I was thinking, whether it's necessary to have some way (from our PX4/Pixhawk) to perform the autorotation or maybe a warning to the pilot when such failure happens. If I wasn't close enough to my heli I'll have no idea that the motor had failed and the heli will sure lose all its power before I realized what was going on.

If it's a large heli like 600 or 700, it will sure turn out to be a disaster. Afterall for a UAV a lot of things are controlled by the FC, we may not notice it until it's too late, and unlike the 3D pilots, our heli can be far away and we won't feel anything. So yeah, I kind of feel that we may need some safe mechanism through Ardupilot, to protect the heli, and maybe protect other people.

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Replies

  • Rob_Lefebvre May 5, 2014 at 11:59am

    I almost forgot, somebody has already done auto-autorotation with Arducopter:

    Unfortunately they are not yet sharing back to the project.  They are not required to unless they were to distribute the program.  I believe they were just using Arducopter as a basis to develop this feature for their thesis.

  • gsenroc May 5, 2014 at 11:30am

    Hi David, yea I feel quite lucky it just happened in such low altitude. It will probably crash hard if it happened higher.

    What's the common pitch range people using for Stab? I have a range from about -8 to +10 at the moment and it seems working pretty well though. The only thing is that the "throttle mid" is about 65%, the pitch is around +5 degree I guess, so there would be a little jump when I switch to Alt-Hold. A bit annoying with this jump and I need to raise throttle (pitch) stick before switching back to Stab, but since landing with Alt-hold works very well for me, I don't use Stab as often as before.

    BTW, I don't know much about autorotation, how much negative pitch is needed for a normal RC heli, for example a 450 and 500 class?

    • Eli Cohen > gsenroc May 5, 2014 at 11:37am

      This would be awesome if you could get it working! I came across this project at Stanford a few years ago... it's pretty relevant!

      https://www.youtube.com/watch?v=3wI4dwqfIdc

      http://heli.stanford.edu/papers/AbbeelCoatesHunterNg_aaoarch_iser20...

      • David Boulanger > Eli Cohen May 5, 2014 at 12:06pm

        Rob, I practice on my simulator a lot.  Its fun. There is a target you try and land on. Of course if you screw up you just try again.  I don't know if 3 or 4 degrees will be enough.  By the time you realize you have a problem your headspeed has probably slowed a lot and is 4 degrees going to get it crank up enough to flare out for landing.  I have never done one in real life.  It would be to expensive to practice.  I also have about 4 degrees negative in STAB.  Next time I am practicing on the simulator I will pay more attention.

        Wait a minute.  I am installing a C.C. Phoenix Edge on my 550 this evening.  It has a autorotation bail out feature that can be programmed with the castle link. Anyway, sooner or later everyone who flies a heli's will need to attempt an auto.

        Regards,

        David R. Boulanger

        • Rob_Lefebvre > David Boulanger May 5, 2014 at 2:05pm

          I am looking to buy a simulator, but keep on getting caught up on the question of "which one".  Obviously Real Flight seems to be the most common, but I've also heard it's not that good, from a technical standpoint.

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