Unusual OS MAX engine behavior with APM 2.5

I have:


3825-750 OS MAX motor (specifically recommended by OS MAX)

APM 2.5 with full updates as of 2/16/2013

JP1 is REMOVED so I can power the servos separately

There is NO BEC with my ESC, power comes from a 5v BEC that can carry 5A continuously

Futaba 7C TX

Using the new power module to power the board, provide current sensing and power all peripherals such as GPS, air speed sensor and telemetry radio.

This bird uses 2 digital servos for the elevons.

This bird CRASHED for unknown reasons at 68mph.  The engine bearing is rattling and I will replace it, but just in case this problem has nothing to do with it, I'm posting it because I'm stumped.  The APM 2.5 passes all tests I can throw at it, except it does this.

This ESC has a cut off feature when it does not receive a signal from my Futaba TX within 1.5 seconds.  Instead of cutting off though, it idles the engine at around 2000 RPM.  Its steady and very consistent.  It should shut the motor off.  It will not shut the motor off while in stabilize mode either.

So I put it in manual, put throttle at half.  Engine fires up fine.  Turn off TX, engine should shut off but instead idles.

So I put it in stabilize, put throttle at half.  Engine fires up fine.  Plane stabilize works fine.  TX shuts off, engine idles instead of shutting off.

In manual or stabilize the throttle is not consistent, I strongly suspect its due to imminent bearing failure but a bad bearing should not be causing the no cut off issue(?).

It seems like its getting another signal from the APM 2.5.

Why is it doing this?

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  • It's an x8 platform.

    These are the logs from the crash, I cant see anything obvious.  The trouble started when I put it into stabilize mode.  I never put it into RTL myself so I think that's the failsafes?

    I installed a new motor, the garbled sound is gone...old motor is toast.

    2013-02-03 16-44-10.rlog

    2013-02-03 16-44-10.tlog

  • I'll do this proper, gimme a bit to make video and upload the telemetry logs.

  • You have much information on your system set up but what was occuring leading up to the crash?

    Did motor rpm/speed lead to the crash? Was it a loss of control (flying surfaces)? You mentioned elevons, is this a flying wing (I think so)? Is this a home brew aircraft or a commercial unit?


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