Loss of radio connection on third flight.

[Phil Harman]

Hi Guys. My friend recently purchased the FMS EZ trainer. It flew great on the maiden flight and then again on a new battery a second time. after waiting a while for the motor to cool down again, we put in another new battery. It flew great for about three or four minutes then went completely out of control. None of the controls worked the motor stayed on full throttle. The failsafe had been activated prior to flying so the throttle should have automatically gone to the off position. Instead it circled to the left on full throttle. I was flying at the time and I could do nothing with it. The radio being used was Specktrum DX6 with Orange receiver. This was the second time the radio had failed on this aircraft the first time being with a Specktrum receiver, The first crash we blamed on the receiver, so changed it. fortunately it sustained very little damage the first time. I can only conclude that it is the esc to blame as no power to the radio must have been the problem. When we collected the pieces from the second crash the radio gear looked as though it was working perfectly. Any ideas out there?

[Jon H]

did the first rx survive? if not the bec might be over volting it slightly causing it to fail/overheat after a certain period of time

Edited By Jon Harper - Laser Engines on 09/10/2017 23:50:21

[Piers Bowlan]

I think the significant thing here is your comment, 'after waiting a while for the motor to cool down again'. FMS models are usually OK and this one seems to have plenty of cooling for the motor, (just looking at photos of the model). The stock 1050kv motor turning the stock 10 X 5 prop should only pull 15A static (according to one review), which is well within the 20A ESC fitted to this model. This assumes you fitted the standard 3s LiPo. So why is the motor getting so hot? If you have not fitted a larger prop then the motor should not get excessively hot unless it is faulty, or the ESC is faulty. I agree with Jon, if the ESC is overloaded by the motor pulling excessive amps it will overheat causing the BEC to fail and the loss of control you describe.

First check all the plug connections for poor joints as this can cause overheating. Check the motor turns freely apart from slight 'cogging'. Have any of the motor magnets come lose and are scraping on the windings? Check the correct size prop is fitted. Fit a larger (30A) ESC and see if the motor still overheats. Usually the ESC is to blame I find, but not always. Good luck.

 

Edited By Piers Bowlan on 10/10/2017 04:45:56

[brokenenglish]

I'm not expert enough to comment technically, but I had the same reaction as Piers, above.

I've flown standard electric foamies a lot for the last 5 years, and I've never had to wait for a motor to cool down!

If you're not an expert, better get a PNF model and fly it as supplied. That's all I do and I've never had a problem.

[Chris Bott - Moderator]

If the motor stayed on full throttle and failsafe had been checked beforehand that it cut the motor, then I'd suggest that the Rx continued to receive a signal and that the ESC was working as commanded by the Rx.

This then suggests a Tx fault. As if the stick positions were not getting through to the RF stage but the RF kept transmitting.

[Chris Bott - Moderator]

Another possibility that I can think of is maybe the failsafe had been activated, but had inadvertently been set to full throttle. If so, an RF failure from the Tx would cause the seen symptoms.

[Denis Watkins]

Trying not to start ww3 on the forum Chris

Have earlier sent a PM to Phil suggesting re binding at low throttle

[Tony Kenny]

Just a thought, but on my equipment, the fail safe is built into the Rx and not all of my ESCs have one built in. It works fine, but, I've not tested what happens if I pull the plug on the Rx while power is on. Your post has prompted me to try that just in case throttle sticks on loss of Rx connection - in which case the Rx won't be able to activate its own fail safe.

[Peter Christy]

Chris is right in that had the receiver lost power, the motor would have shut down. All the ESCs I've come across will only provide a "drive" output to the motor when they receive a recognisable signal. This tells me that the receiver was functioning, and providing a throttle signal to the ESC.

This leaves two possibilities. Either: 1) the failsafe was set incorrectly or 2) the transmitter was providing the wrong information. I think we can eliminate the receiver from the equation, as the same issue occurred with two separate receivers.

One final thought - and an easy mistake to make - after the receiver was initially bound with the throttle in the "low" position, was the throttle function reversed at all? That would make the original fail-safe setting incorrect.

--

Pete

[Colin Carpenter]

Phil. You aren't using DSM 2 are you ? Colin

[Simon Chaddock]

Colin's question about DSM2 is valid.

I have had two occasions where I have had complete loss of control with a Spektrum DX6i and Orange rx DSM2 but both instances were at a very busy site 'open days' with many planes in the air..

I normally fly alone and never had similar over a period of several years.

Orange DSMX was not effected.

[Phil Harman]

Thanks for your replies guys. Failsafe checked several times and is working with about two second or so delay. Using a 3 cell lipo as recommended, 2900. Rx used in another aircraft without problem. Tx used with other aircraft without problem. Rx rebound carried out on both receivers on low throttle. Not using DSM2

[Phil Harman]

Im not sure wether the motor was hot, but since flying electric it seemed a good idea to allow five or ten minutes between flights just to be on the safe side.

[Phil Harman]

The prop etc is as standard supplied and not been altered in any way.

[Phil Harman]

We have several other BNF models and this is the first one to cause a problem. Previously flown ic models without this kind of problem. Still flying Mk lX spitfire, Hanger 9 Cherokee and Flair SE5a with four strokes. Electric is just less to carry to the field.

[Phil Harman]

The receiver wouldn't have stayed on to operate safe mode if the power supply to the receiver had been temporarily interrupted due to a problem with the Esc and the throttle would have remained in the same position . Thats why I tend to think that its the Esc that is the problem.

[Peter Christy]

Posted by Phil Harman on 10/10/2017 16:42:29:

The receiver wouldn't have stayed on to operate safe mode if the power supply to the receiver had been temporarily interrupted due to a problem with the Esc and the throttle would have remained in the same position . Thats why I tend to think that its the Esc that is the problem.

I'm not sure why you think that. ESC's rely on a valid input from the receiver to operate. If they are not receiving a valid input, then the motor will stop. The ESC will only receive a valid input if the receiver is providing it.

Its not like the servo throttle on an IC engine which may freeze in the last position. If the receiver stops spitting out pulses, the motor will shut down. If the motor did not shut down, the the ESC was getting a valid signal from the receiver for whatever reason.

The only type of ESC that could keep a motor running in the absence of a signal is the old type for DC brushed motors. In these, if the output transistor fails short circuit, the motor will keep running. Brushless motors are essentially 3-phase AC motors, and will not run unless fed correctly phased switched current.

--

Pete

[Phil Harman]

If it wasn't a problem with the Esc then what else could have caused it. the aircraft wasn't out of range. In fact it was only about 200 yards when I lost control. The previous two flights were great. It flew really well. I doubt that both receivers were faulty. I have been corrected by my friend who's aircraft it was that the first receiver was Orange and after the first crash he replaced it with Lemon receiver. The DX6 Transmitter is a DSMX transmitter so it couldn't have been on DSM2 by mistake besides witch fact the aircraft had two good flight each time before crashing on the third flight. We've put the Esc away marked suspect along with both receivers.

[Piers Bowlan]

If it is not the receiver, ESC or motor, then that just leaves the servos and Transmitter. I have heard of a faulty servo causing strange behaviour on other channels, in fact there was a thread about that on this forum somewhere. More likely is an intermittent transmitter fault perhaps? You could always get the transmitter checked out by Mike Ridley, here if you wanted to be sure.

[onetenor]

What about the connections to the Rx (servos etc)? Battery ?

[Phil Harman]

We've flown other aircraft since with the same transmitter so I don't think its that. All of the servos being faulty is hardly likely since I tried all movements prior to the crash. Nothing worked. The only other thing is radio signal interference like we used to get with 35mhz if someone else was on your frequency. Question is, is that possible on 2.4ghz

[Phil Harman]

All connections were good and all were working after the crash.

[Frank Skilbeck]

Phil, it is not possible to get interference on 2.4 that makes the Rx do strange things, if the link is interfered with then the Rx should go to failsafe.

The only thing I could think of is a corrupted model memory, which causes the transmitter to stop acting on the stick inputs, but I must admit I've never come across this.

[Denis Watkins]

Have PM you Phil, but to add, some of your quoted receiver makes are really parkfly, were 200 yards would be 100 yards too far out.

They work nearby and on range test, but some single antenna are parkfly, and don't go much over 300 feet range

[Phil Harman]

Hey Guys thanks for all your comments. The EZ flyer has now gone to the great aircraft hanger in the sky and is resigned to be put down to experience.