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Futaba Frame Error Rate

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Old 08-19-2019, 12:44 PM
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Default Futaba Frame Error Rate

Hello,

I would like to know if frame error metrics are captured by radio system during flight and if so how can I review them.

I am using the 18MZ transmitter and the R7014SB receiver.

Thanks!
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Old 08-19-2019, 08:44 PM
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Not that I am aware of. Are you having an issue?
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Old 08-20-2019, 07:16 AM
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Thanks Bill,

We fly a 64lb LMA-1 class aircraft at several airshows every year. Safety is our paramount concern! At an airshow up in Canada last week the pilot reported a temporary loss of control of the aircraft. Trying to find the cause of that incident is critical to us. It could have been several things but having the ability to monitor the Frame Error Rate during the flight would be a huge diagnostic help. I know other radio manufacturers offer this type of information. I was surprised to learn my flagship Futaba system does not. Are there any tools available to capture and report this information to us on the Futaba system?
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Old 08-20-2019, 08:34 AM
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There was a guy in Europe who sold a aftermarket mAh counter =, sort of electric fuel gauge device. It could count frame loss. A couple of the aftermarket power distribution devices also can do a frame count I think. Thing is there was no real methodology to relate frame loss to holds, etc.

I know at least a couple of Team Futaba guys like Brian O'Meara and Bill Hempel are also flying LMA'a. Not sure what, if any, issues they have had.

If the aircraft has lots of carbon or other RF blocking materials it is critical to get the antennas out and away from that material.

What plane is it?
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Old 08-20-2019, 09:11 AM
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Bill,

The airframe is a COMP ARF P47. We have the receiver's diversity antenna held in a holder at 90 degrees from each other and at 45 degrees down & back with reference to the horizon. The airframe is basically fiberglass composite. The airplane was flying directly at the transmitter when the incident occured. I suppose the Moki 250 radial could have blocked the signal for a moment........ that is the kind of information having this ability would provide. It's also possible the pilot just got the airframe too slow and it began to stall or that there was a rotor of wind through the trees just below the aircraft that caused the issue. It's the not knowing that causes the largest concern. I realize that even if this capability existed it would not guarantee that we could diagnose it with certainty but if for example, we could prove that there were not any significant number of discarded frames during the flight it would help point us in another direction.

While there are many systems to externally monitor Rx voltage and current It seems only the receiver knows when a transmitted frame is rejected and thus only the Futaba receiver could count these occurrences and provide them to the user. If that ability is not available via the Futaba Rx I fear it just isn't available at all with this system.

I guess I was hoping there was some embedded firmware in the RX that would output that frame error data if some special conditions were met.

Sigh......

Tom
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Old 08-20-2019, 09:25 AM
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OK WAIT!!!!!

I just ran across this post on another forum. Can you verify this for me?Originally Posted by tomsdk
Actually, there is a way to get receiver RSSI back to your TX. The SBUS.2 serial stream offers the recever RSSI (as frame error rate). So you can make a virual sensor that uplinks the RSSI to the transmitter. I did this, and can monitor the RSSI on my T14SG, and even set an alarm if the received signal gets below a certain level. Name:  popcorn.gif
Views: 75
Size:  2.4 KB Ofcourse this should happen very rarely due to the very good Futaba link - but its a nice safety feature.

Cheers
Thomas

Thanks for the tip.
I don't know how many times I've read "Futaba doesn't do that" in regards to this subject.
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Old 08-20-2019, 01:45 PM
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Brian O'Meara is flying that airframe as well I think.

The device you found is the one I was talking about. There is no math to determine the value of the frame count it gives. So you are getting data, but there is no reliable means to know what the data mean.

Since 2.4 is digital it is sort of there or not. Fluctuations may, or may not. be meaningful. As long as the radio receives sufficient signal it keeps working. I suppose you could set a super conservative alarm, but not sure that will help.

Out of curiosity, what RX are you using??
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Old 08-20-2019, 06:48 PM
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Bill,
I was using the R6014HS receiver when the event occured and have ordered the R7014SB to replace it and provide telemetry information.

Is the R7014SB receiver capable of outputting the RSSI information and is that information stored or streamed during the flight back to the TX then discarded for new data? That is to say would we have to monitor it on the Tx screen during in real time or can we evaluate it later?

Thanks

Tom
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Old 08-20-2019, 07:25 PM
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No Futaba RX streams RSSI that can be read real time. Some aftermarket devices, like the one you found, read something, they call it RSSI, but I cannot say for certain. Again, the issue is with the data some of these devices provide there is no clear path to interpreting it.

Having said that, if you log your telemetry you can view it using the converter and there is a column that gives an indication of the telemetry signal strength back.

I always suggest using a preset failsafe so you can know for sure if you had a hold. I prefer this instead of holding last good command. Failsafe places my controls in a known position, usually neutral.

How many times did you have an issue? Any commonalities between the times it happened?
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Old 08-21-2019, 01:05 PM
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Thanks Bill!

Understood.

The event just happened one time never any glitches on the past 20+ flights

Not overly concerned just want to make sure we are doing everything we can to maintain safety! I also use neutral flight surfaces and engine to idle for my failsafe. We didn't hear the engine drop RPM so that sure points away from a significant signal receive issue.

Thanks again for all your time and information

Tom
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Old 08-21-2019, 01:33 PM
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No failsafe to me means something else happened unrelated to a signal issue, otherwise you would have had a failsafe event..

It can be an internal cause. I've seen everything from plugs, extensions, ignition noise, servos, etc. cause what looks to be a radio issue. None of those is going to result in a failsafe since that is triggered by loss of RF signal.

If you like I can reach out to Brian O'Meara who also has a large P-47 to see if he can shed any light.
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