X8 take-off using catapult

Hi Folks,

Does someone have experience and good results launching X8 wing with a catapult in Auto take-off mode? I would like to have your feedback and parameters / values used for that aim.

Regards AA

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  • Antonio,

    We made several tests this morning with our EZ Star "testbed" plane.  This uses the same (APM 2.75) firmware but does not have the size risk of the X-8.

    Prior to starting, I ensured that we were using the same parameters you listed earlier.  The only difference is that we have THR_SUPP_MAN = 0.  We do not want the prop to spin at all until commanded by the APM.  Our procedure is to put the plane on the bungee stand in MANUAL mode.  Once ready, we switch to AUTO and release the bungee.

    The first test was with the throttle set to "zero".  The throttle channel stayed at zero and the motor did not spin up.  When it was clear that the plane was starting to descend, we changed to MANUAL and landed the plane with pilot-controlled throttle.  The AutoTakeoff instruction did not do anything with the throttle.

    The second test was with the throttle set to 50%, just a little above cruise.  This time the APM did advance the throttle to max and did climb to the target altitude.  You can see the same data presentation in the two log graph pictures attached here.

    So we were able to use Paul's suggested parameters but the throttle position seems to be important too.

    AutoTakeoff with Throttle at Zero.jpg

    AutoTakeoff with Throttle at 50%.jpg

  • I have been trying this with a X8 and something appears to have changed in the recent firmware.  AutoTakeoff was working earlier this year, arounf the March timeframe.  It stopped working reliably when the firmware was updated to ArduPlane Ver 2.74.  The motor did not start and the X8 landed straight ahead when we tried autotakeoff with 2.74.  The motor used to start when the plane crossed over the bungee stake, about 100 feet from the launch point. 

    Since then I have been using an EasyStar as the testbed to avoid any damage to the X8.  The flightplan stays the same, it has an autotakeoff straight out to 350 feet followed by a loiter unlimited.  So far we haven't seen two attempts in a row that do the same thing.  Most of the time, the plane lands straight ahead.  Sometimes the motor starts.  The flight path is never the same.  Every attempt ends in a switch to manual mode for recovery and landing.

    This feature has been worked on by the developers but the documentation has not been updated in a very long time.

    I will be updating one APM with the new 2.75 firmware and will test this again next week.

  • I know I have seen lots of folks doing it on video so it should be pretty easy. Antonio what are you setup for on that X8? What is your motor combo?

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