E-flite 440h Motor Failure

Hello all,

I'm part of a team that's been working on a Multiplex EasyStar, and the motor we've been using is an E-flite 400h 4200Kv brushless. Today, while going through our pre-flight checklist, we found that the motor cut off just before full throttle. We were able to throttle up again once the buzzer on the motor played a few tones. We decided to fly around 90% throttle and see how long we could go. We had about 10-15 seconds of powered flight before the motor failed again. We thought it might be the battery, since we were running with a 2S lipo, so we switched to a 3S. This time, 100% throttle was attained, but it lasted for only about 15 seconds again before dying. During each flight, control of the throttle wasn't regained after it became unresponsive, but the control surfaces remained responsive.

Following the flight with the 3S battery, the tones played quite a while after the landing, signaling a ready motor. We then pushed it to full throttle while we held in place, and the motor lasted for 5 seconds. When the tones sounded again, we opened up full throttle with a duration of 3 seconds. Since the control surfaces can respond even while the motor is out of commission, we think our problem isn't loss of communication with the transmitter. Instead, it seems to be linked to exceeding a max temperature parameter. We would appreciate some tips on troubleshooting this problem.

Kind Regards,

Jake Green

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  • T3

    Hi Jake, it sounds like you are overloading the system...lets try and fix it!

    Do you know what amps your motor is pulling at full throttle? Should be below 25A for the 440h.

    What speed controller are you using?

    And what is the prop diameter and pitch? 

    • Hi Dawid, thanks for your reply! We're using an Ares 18-amp ESC and a 7" diameter, 6" pitch prop. Maybe the ESC has too much current going through it and it cuts off? I can't tell how many amps the motor is using, since I still have to buy a multimeter that can handle more than 10A (all of ours are limited to 10A right now).

      • T3

        Jake, I would say that you are using too large a prop for that motor. You are probably drawing close to 30amps on that setup and therefore the ESC is overheating and cutting power to the motor. The problem here is that that motor is a fast one and is designed to spin a very small prop very fast.

        There are a couple of options:

        1) Try using a smaller prop say a 6x4 with a 2S lipo (3S is too much), but even this prop might be too much

        2) Use a ESC with a 25Amp continious rating and a 6x4 prop with 2S lipo

        3) Use the existing prop and ESC but with a new motor, something like the Turnigy D2836/8 1100KV

        If it was me I would pick option 3, it is the closest thing to the recommended setup for your model.

        Found this pdf that has information on selecting the right power for the EasyStar, might help you out a bit


        Hope this helps, let me know how it goes!

        • Hi Dawid,

          Our group was able to solve the problem, thanks to your recommendations! We ended up using a 25A ESC with the existing prop and a Rimfire 400 motor. Saturday we took out the EasyStar and had it in the air for around 20 minutes. Everything works like a charm! Thanks again for your help.

          God bless,

          Jake Green

        • Hi Dawid, thanks for your continued help. I may have made a big mistake in my initial post. I think the motor we flew was actually a 420h 3800KV with the 18A esc and prop as stated. Sorry for the confusion! I'll read that PDF and try to see what else I can come up with.

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