Radio or Receiver fatal fail

[Richrfl]

Hi, gents, I have been flying My Tandem TX18 and SR10+ for a few months without a glitch, however, last week after a three-minute flight without any trouble, however, at two minutes into the second flight, the "thing" hit the fan.
I lost control of the airplane and trashed a $500 bucks plane. To make the end of the story short, I found that the RX indicated very low RSSI, although the VFR was excellent. I would not be wasting time in reaching this forum if the plane was at that time 1 mile from me, but as it can be seen from the attached log, the distance was not more than 600ft, up in the air, without trees between me and the plane.
For more information, the plane is an EPO, therefore there is no chance of loss of signal because of the build-up, nor RF interference, otherwise, my RSSI should have been very high.
Although I did not check the range after the crash, I verified that TX and RX were talking with each other. I would like to have some advice on which should be the next step to avoid another destroyed plane.

 

[HENNY]

Hi, gents, I have been flying My Tandem TX18 and SR10+ for a few months without a glitch, however, last week after a three-minute flight without any trouble, however, at two minutes into the second flight, the "thing" hit the fan.
I lost control of the airplane and trashed a $500 bucks plane. To make the end of the story short, I found that the RX indicated very low RSSI, although the VFR was excellent. I would not be wasting time in reaching this forum if the plane was at that time 1 mile from me, but as it can be seen from the attached log, the distance was not more than 600ft, up in the air, without trees between me and the plane.
For more information, the plane is an EPO, therefore there is no chance of loss of signal because of the build-up, nor RF interference, otherwise, my RSSI should have been very high.
Although I did not check the range after the crash, I verified that TX and RX were talking with each other. I would like to have some advice on which should be the next step to avoid another destroyed plane.

You did not indicate what your model was made of IE Carbon fiber? or how you mounted the RX in the model and the position of your RX antennas. How were you powering your receiver, a separate battery or powered from a speed controller.

Very low RSSI is an indication you are about to loose connection with your model and indicates an RF connection issue. Had you set the fail safe to assist in making a graceful landing in such loss of RSSI.

 

[Richrfl]

Thank you for your response Henny. As I indicated the model was EPO, meaning, foam. The antennas were one vertical, the other horizontal parallel to the fuselage's longitudinal axis. The receiver was powered by the ESC. Please, keep in mind that I was flying this very model for over six months without a glitch. I Verified the operation of the ESC and it works as expected, as the last thing I expected to fail was the FrSky part. Also, as you can see from the log, the battery voltage was nominal. Maybe, if you take a look at it you will find a few questions answered. Also, Just for the sake of comaprison, I can upload some more Logs. One last question that I expect to be asked is if I change the flying field, and the answer is no. Here is a view of the field https://forums.realflight.com/index.php?resources/pbrca_snhfe-test_pi.30562/

 

[HENNY]

Thank you for your response Henny. As I indicated the model was EPO, meaning, foam. The antennas were one vertical, the other horizontal parallel to the fuselage's longitudinal axis. The receiver was powered by the ESC. Please, keep in mind that I was flying this very model for over six months without a glitch. I Verified the operation of the ESC and it works as expected, as the last thing I expected to fail was the FrSky part. Also, as you can see from the log, the battery voltage was nominal. Maybe, if you take a look at it you will find a few questions answered. Also, Just for the sake of comaprison, I can upload some more Logs. One last question that I expect to be asked is if I change the flying field, and the answer is no. Here is a view of the field https://forums.realflight.com/index.php?resources/pbrca_snhfe-test_pi.30562/

I would perform a range check to confirm the hardware is operating correctly first.

With regards to antenna orientation the theory says one horizontal and one vertical however my practice says place one antenna either side of the fuz in a horizonal orientation away from batteries servos etc. Insert the antennas in a drinking straw or heat shrink so they are not locked in place as this can damage the PCB connector or even pop them off the PCB connector if the receiver moves and strains the antenna cable.

 

[Richrfl]

Thank you for your suggestions Henny. Considering that there are several potential reasons for this crash according to the log data my first step was to perform a range check as you also suggested, but this time using a different receiver (X8R), which of course checked OK. Beyond that, I flew a suicide plane for a couple of minutes without a hitch. However, to eliminate any possibility that the transmitter fails after several flights with a short time between flights, I will keep flying the same plane and receiver for a couple of days (weather permits). The next step will be to repeat the whole process with the receiver used in the crash event. At this point, I am afraid, again, based on the data log, that the transmitter suffered a hiccup and dropped its power for no apparent reason. The only difference between this flight and all previous flights I had for the last two years is that in this case, the time between flights was no more than 2 minutes. Even I have flown this TX/RX in Florida summer for years, I also had a TX hang up a couple of times, one of them while flying. Being an Electrical Engineer and having burnt my fingers touching hot chips, I learned not to assume that electronics never fail or have unexpected behaviour. However, progressive testing is the only way to find the possible origin of the problem. I will also consider your suggestion of sticking the antennas out of the fuse. This is a practice that seems it's almost mandatory for Spektrum users.

 

[HENNY]

One more thing to check on your X18 TX is ensure the RF module has the latest firmware. Long press the sys button and advance to Info. It will indicate your RF firmware version. The latest version is V2.2.6

It can be found here. https://www.frsky-rc.com/tandem-x18s-x18se/

 

[Richrfl]

Well, Henny. This is interesting. If I am not wrong, the last time I hooked up the TX to the Suite was last Tuesday and all versions were up to date. Your suggestion of checking the Rev. was very positive, as when I hooked up the TX now, I found most of the SW and FW were outdated. Good deal. Although I did not find the improvements with the 2.2.6, I hope this issue has been resolved. I am updating the TX now and will continue with my test protocol. I hope one way or another I find no further issues. Also, I will check for any FW update for the SR10+, just in case.

 

[HENNY]

Well, Henny. This is interesting. If I am not wrong, the last time I hooked up the TX to the Suite was last Tuesday and all versions were up to date. Your suggestion of checking the Rev. was very positive, as when I hooked up the TX now, I found most of the SW and FW were outdated. Good deal. Although I did not find the improvements with the 2.2.6, I hope this issue has been resolved. I am updating the TX now and will continue with my test protocol. I hope one way or another I find no further issues. Also, I will check for any FW update for the SR10+, just in case.

OK so just to be clear, RF version 2.2.6 has nothing to do with Ethos firmware. There are two micro controllers in your FRsky radio. The Ethos powered controller looks at all the hardware such as sticks, pots, switches etc and the RF transmission controller which controls the signal transmission only.

Hope this helps.

 

[Richrfl]

Thank you for the detailed information. I tend to put everything in the same package, which confuses the other party. My fault.

 

[microwaves]

Hi, gents, I have been flying My Tandem TX18 and SR10+ for a few months without a glitch, however, last week after a three-minute flight without any trouble, however, at two minutes into the second flight, the "thing" hit the fan.
I lost control of the airplane and trashed a $500 bucks plane. To make the end of the story short, I found that the RX indicated very low RSSI, although the VFR was excellent. I would not be wasting time in reaching this forum if the plane was at that time 1 mile from me, but as it can be seen from the attached log, the distance was not more than 600ft, up in the air, without trees between me and the plane.
For more information, the plane is an EPO, therefore there is no chance of loss of signal because of the build-up, nor RF interference, otherwise, my RSSI should have been very high.
Although I did not check the range after the crash, I verified that TX and RX were talking with each other. I would like to have some advice on which should be the next step to avoid another destroyed plane.

At long distances, correct antenna coupling is critical. Check attachement.

 

[Richrfl]

Very interesting diagram Micro. I noticed though that in this case the antennas are located in an horizontal plane, rather than vertical. I will take the time to think what would happen when the plane flights in a vertical climbing or any aerobatic maneuver. Thank you for your input.

 

[microwaves]

Very interesting diagram Micro. I noticed though that in this case the antennas are located in an horizontal plane, rather than vertical. I will take the time to think what would happen when the plane flights in a vertical climbing or any aerobatic maneuver. Thank you for your input.

Optimum antenna positions.
The table plot estimates the power level received at the receiver versus range.
Also cell phone towers operate in the 2.4 GHz range with power outputs of many watts.
Check to see if a cell phone tower is in the area where you lost your plane.

The link will explain how your 2.4 GHz equipment operates.

https://r.search.yahoo.com/_ylt=AwrNOIvEWutlpoUZZAEPxQt.;_ylu=Y29sbwNiZjEEcG9zAzIEdnRpZAMEc2VjA3Ny/RV=2/RE=1709951813/RO=10/RU=https%3a%2f%2fwww.modelaviation.com%2frc-spread-spectrum-demystified/RK=2/RS=8YizENKBiEBNmyw_MPlm5bsUMro-

 

[microwaves]

One more thing! Single antenna dead zones.