Taranis X9D+ and X8R lock-out and plane crash

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Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Tue Mar 21, 2017 5:45 pm

Hi,

I have an X9d-plus which has been updated to the LBT firmware v2.1.9 along with the X8R receiver. The radio and RX are about 2yrs old.
The RX was installed in an all carbon F3F with the antennas on the outside of the model at 90deg. It has been flying perfectly like this for 6months. I did however notice a reduction in range when upgraded to the LBT software about 3 months ago.

Today whilst I was flying, my plane was only about 300m away in clear line of sight when I lost all contact with it. The plane slowly spiralled into the ground without me being able to control it.

Looking at the flight log, one can see a strange anomaly and I wondered if someone could please help me interpret what happened. It appears like the signal became weak and the RX either reset itself of just locked-out.

Thanks,

Peter
Attachments
Log 1.png
Log 2.png
Log 3.png
Log 4.png
Log 5.png
Log 6.png
Log 7.png

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bob195558
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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by bob195558 » Wed Mar 22, 2017 10:43 am

Hi peterberetta,
You may have an internal XJT module which has developed a randomly failing problem.
This problem may not show up if you bench test for it,
as I and Aloft Hobbies found out after many hours of bench testing.
Replacing internal XJT module or using an external XJT module may fix your problem.
FrSky did have a problem with a few of there early Taranis-X9D internal XJT modules.

Find more info about this here:
Partial Control Lost with Internal XJT Transmitter: (viewtopic.php?f=95&t=6118&p=86205&hilit ... ing#p86205).

Re: Help troubleshooting "loss of signal" (and crash): (viewtopic.php?f=96&t=6264&p=89270&hilit ... ing#p89270).

I also use erSky9x for Taranis firmware which you can find here: (http://www.er9x.com/).

Bob B.
ErSky9x on Taranis, Sky9x, 9Xtreme, Er9x on 9x with Smartieparts Programmer with TelemetrEZ Board
3D Printing: (http://openrcforums.com/forum/viewforum.php?f=85)

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by andrewju » Wed Mar 22, 2017 3:12 pm

I think I read a few reports of a similar issue with X8R on my local forum. Though, no detailed analysis was done, so the cause of these glitches remains unknown.

Also, a couple of users reported severe range reduction of X8R when working in an area with multiple 433MHz LRS systems in use. The same people also reported that X4R-SB provides much higher range in these conditions (433MHz interference).

Not sure how to track this, as I never faced such issues myself.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Wed Mar 22, 2017 7:16 pm

Thank you Bob. I read the posts about a possible internal XJT failure and am considering purchasing an external XJT module.

What are the benefits of using the erSky9x for Taranis? Will this firmware work with the X9D plus?

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by bob195558 » Wed Mar 22, 2017 7:37 pm

Other Module 2.4GHz Signal Frequency's and antennas info:

9x FlySky 2.4 module / Antenna soldering connection.
(viewtopic.php?f=40&t=8756&p=114627&hili ... r+6G+Combo)

The Fresnel Zone explained (Module 2.4GHz Signal Frequency's and antennas):
(https://www.youtube.com/watch?v=xCVd3QGQhKU&t=1034s).

Two helpful test equipment items,
ImmersionRC RF Power Meter: (https://www.immersionrc.com/downloads/m ... Manual.pdf)
and (https://www.immersionrc.com/fpv-products/rfpowermeter/).
Which can be used to measure a transmitter's output power reading in dBm or mW
and checking the efficiently of antennas by comparing between signal strength of different antennas.
Cost about: $149.99

RF Explorer 6G Combo spectrum analyzer: (http://j3.rf-explorer.com/40-rfe/articl ... cification).
Which can show frequency bands between 15 - 2700 MHz and 4850 - 6100 MHz.
Frequency bands like 72, 433, 933 MHz, 2.4 and 5.8 GHz.
Also GPS 1.228 and 1.575 GHz, and some others like VHF, UHF, FM radio, GPS, WiFi and WiMax, Bluetooth and 2m HAM radio. Cost is about: $365.00.

Bob B.
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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by bob195558 » Wed Mar 22, 2017 9:07 pm

Hi peterberetta,
Yes, Mike B. has erSky9x firmware for both Taranis X9D and X9D-Plus.
Both of opentx and erSky9x are very good opensource firmware's.
Partly it is personal or what you are use to using.
I started with the 9x Radio and flash it with er9x and later upgraded to erSky9x.
Also for me I have had more trouble when using opentx.
ErSky9x can do some things that opentx has not been updated to do.
I have one model where I use two D-Series receivers (D8R-II Plus) using both internal and external modules, which with erSky9x
I can select the external module for (primary module) the Telemetry data being reported to my Taranis.
With opentx, when using both modules at the same time you have to use only the internal module for your telemetry data source.
My testing has shown the external modules maintain a stronger 2.4GHz signal (RSSI / TSSI).
Note: if you flash to erSky9x you will need to use eePSkye on your PC which is made to work with erSky9x.
If there is a bug in the newest test version of erSky9x firmware, Mike B. most of the time is able to fix it in a few day.
This is a big, big plus, which opentx may not be able to be fixed for a much longer time).
As you can see I like erSky9x a lot more. :)

Bob B.
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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Thu Mar 23, 2017 12:45 pm

Thank you Bob. I think I am going to give erSky a try. I just need to make sure my hardware is not faulty. So if I change both the RX and the XJT modules, then I should hopefully be able to reduce the risk of it being a hardware issue.

This experience has shaken my confidence in FrSky's products and I was wondering if I should move back to Futaba or some other brand.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by bob195558 » Thu Mar 23, 2017 5:54 pm

Futaba is good, but also cost is a lot more with its difficulty programming and less capabilities.
A lot of people use FrSky TX and RX systems with its lower cost telemetry and have no to very little troubles.
The very few FrSky troubles seem to have been mostly with the early X-Series.
It is a reliable 2.4GHz system.

Bob B.
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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Thu Mar 23, 2017 6:18 pm

bob195558 wrote:
Thu Mar 23, 2017 5:54 pm
The very few FrSky troubles seem to have been mostly with the early X-Series.
It is a reliable 2.4GHz system.

Bob B.
Obviously not only the early ones :) :D

I can only share my experience with frsky. I have been using the older Frsky "D" series without issues whatsoever for about 7 years now and never had the slightest problem, but to be honest I don't really want to move to the X series.

Since the X series came out (2 or 3 years ago?? ), I have read about many more problems with it than About problems with the D series in 7 years. Actually,as far as I remember, there were only a couple issues with the D series that were immediately fixed. One of them was a bad batch of antennas on the DJT and DHT modules. Never heard or read about a D receiver failing like I did with the X series. I have burnt one myself though :(

My advice is that you try to find out what the problem was.. What really caused the crash. Does the receiver work normally again? If so, can you repeat the problem on the ground? Testing is very important..
Do you know if it was the rx or the radio?

João
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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by mmilan » Thu Mar 23, 2017 7:39 pm

I have an observation with two X8Rs. Both units lost signal (manifest by loss of control) at about 200 meters when making a fairly steep turn from downwind to base. I ordered and changed both antennas from the paddle pcb to Frsky's linear unipolar antennas. The problem was solved. I have since used both receivers without issue. For me then it was not the Rx but the antennas.
Mike

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Thu Mar 23, 2017 8:08 pm

It is very possible. I never liked those antennas, and I'm not the only one. If you want a bit more safety, you could probably replace them with some dipoles.. That is what I use on the DIY receivers I build based on Midelic's project.

https://www.rcgroups.com/forums/showthr ... RX-Modules

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Fri Mar 24, 2017 9:31 am

Hi João,

Thanks for your advice.

I was actually using dipole antennas with the 60cm extension so that I could run them a fair distance down the fuselage to try prevent the wing from shielding the signal. The plane is all carbon and I am well aware of the problems this could cause. At the point where I lost control the plane was flying away from me and climbing steeply so the wing could not have shielded the signal. What does puzzle me is that the logs show the RSSI dropping rapidly to below 45dBi which I would not have expected at the distance the plane was away from me (less than 300m with no obstructions or radio masts anywhere nearby).

Last night I left the TX and RX on for over 1hr with servos connected and twiddled the sticks every few minutes. The RX did not heat up. I just noted that as the TX and RX battery levels dropped, the RSSI dropped slightly.

I see that FrSky have released an RX4R receiver now to act as a redundant RX. I am thinking of ordering one of these to use with my expensive glass ships. I also ordered the new M9 Hall Sensor Gimbals for my Taranis X9D plus and am about to order the external XJT module. I will however keep trying to figure out ways of testing, but I know it can be difficult to simulate this kind of failure because there are so many unknown parameters.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 9:57 am

How are you powering the servos? If using a BEC, is it powerful enough? If a servo shorts, the voltage could drop to a level that could cause a receiver brown out.
You need to start looking for that. If there is such a problem you will have the same with every single receiver you install..

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by Carbo » Fri Mar 24, 2017 11:44 am

Locking at the screenshots the flight started at 11:09:40. The crash was 11:10:24, 44s later. Before the crash there was more and more elevator applied, at the end 100%, the RX was working at that time. Is there a chance, that the elevator servo did not work or there was something wrong with the linkage? I see a possibility, that RX ant TX worked until the final impact.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Fri Mar 24, 2017 11:45 am

Hi,

I have a new 4cell eneloop NiMh battery and the voltage hardly drops under load according to the logs. The log shows that the voltage remained above 5v under load during this flight. The battery was fully charged and this was my first flight on this charge. I was in the air for approx 4,5minutes when the lockout occurred.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 11:53 am

Carbo wrote:
Fri Mar 24, 2017 11:44 am
Before the crash there was more and more elevator applied, at the end 100%, the RX was working at that time.
This could lead the model to a stall and falling to the ground.

If you power the model from 4 eneloops, how do you fly the glider to the desired altitude when you start? Towed by another model? winch?
Electric motor powered by another battery?

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 11:56 am

Carbo wrote:
Fri Mar 24, 2017 11:44 am
I see a possibility, that RX ant TX worked until the final impact.
But then, the RSSI value dropped very quickly..

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by Carbo » Fri Mar 24, 2017 12:06 pm

Usually when the plane hits the ground. Maybe Peter can publish the complete logfile. It has 0,1s resolution, we can see exactly how fast the RSSI dropped at the end.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Fri Mar 24, 2017 12:10 pm

Hi Carbo, yes I agree with your interpretation of the log in that I applied more and more elevator as well as more and more aileron. The plane had gone into a spiral dive.

I realize now that the the start of the log recording was when I switched on the plane, tested the servo movement, then walked to the front of the slope to launch, this was just over 3min. So the flight as you say was not 4min but only 44 seconds.

It is quite possible that the RX - TX worked until the moment of impact. That in some sense would be a relief.

The first thing that I said to my fellow pilot on the slope was "I think the elevator jammed or I have experienced a lock-out"

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Fri Mar 24, 2017 12:11 pm

I was flying on a slope in England (Ivinghoe Beacon) - wind was about 25knots, very strong lift. No motor or winch needed.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Fri Mar 24, 2017 12:15 pm

Trying to figure out how I attach the log file

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by Carbo » Fri Mar 24, 2017 12:17 pm

peterberetta wrote:
Fri Mar 24, 2017 11:45 am
Hi,

I have a new 4cell eneloop NiMh battery and the voltage hardly drops under load according to the logs. The log shows that the voltage remained above 5v under load during this flight. The battery was fully charged and this was my first flight on this charge. I was in the air for approx 4,5minutes when the lockout occurred.
I only try to interprete the logfile. If there is no issue in logging, it seems that there was a short ruddertest at the beginning of the record. The plane received no input for some minutes (lying on the ground?). RSSI changed at high level (pilot moved with the TX?). From the start of pilot input (rudder/aileron/elevator) to the impact it is only a timespan of about 44s.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 12:19 pm

Put the log file inside a zip file and attach it to your post.
Below, just beside the "submit" button, there is another one that says "Full Editor & Preview". Click it. Then drag and drop your file to the post window.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 12:20 pm

But what about the loss of RSSI?

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by peterberetta » Fri Mar 24, 2017 12:23 pm

Zip of log file attached
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Miraj-2017-03-21 2.csv.zip
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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by Carbo » Fri Mar 24, 2017 12:23 pm

I need some minutes to translate, you are much to fast for me.

@ jhsa: If the plane hits the ground in a crash, there is usually a short RSSI loss near ground and immediately some damage to the battery/connectors/equipment, killing the RX side and telemetry.

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 12:45 pm

Just looked at the file. It looks like you didn't lose signal..
After the plane crashed, it looks like you had a constant value of 42.

This starts looking like you've stalled the model while flying quite low, and it crashed.

It could also be that you had the feeling you had no elevator because the model was already too slow.. Then you pulled the elevator a bit further causing the model to lose lift and stall..

We would know for sure if we had logged indicated airspeed and/or angle of attack. like this we are just guessing.. :)

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by Carbo » Fri Mar 24, 2017 12:46 pm

The picture shows the last 12s of the flight (it makes me sad to see a beautiful glider crashing, even in the log).
Miraij.png
We see full elevator, the strong RSSI loss, when the plane approaches the ground. The constant telemetry values after the impact. Overall there is a good chance that a non working elevator caused the crash. The RC equipment worked to the bitter end.

Edit: FYI: OpenTX keeps the last recorded telemetry values

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 12:51 pm

Carbo wrote:
Fri Mar 24, 2017 12:23 pm

@ jhsa: If the plane hits the ground in a crash, there is usually a short RSSI loss near ground and immediately some damage to the battery/connectors/equipment, killing the RX side and telemetry.
Yes, the RSSI seemed to stay at 42. I don't know how OpenTX handle the RSSI in case of link loss. Does it force it to zero, or does it remain with the last known value?
In the Ersky9x log files we have a "Valid" field where we can see if telemetry is being received at all..


Also, am I looking in the wrong place in the log file? :o

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Re: Taranis X9D+ and X8R lock-out and plane crash

Post by jhsa » Fri Mar 24, 2017 12:55 pm

Carbo wrote:
Fri Mar 24, 2017 12:46 pm

Edit: FYI: OpenTX keeps the last recorded telemetry values
Ok, then the rx might have lost the link after hitting the ground..
Question, was the model still powered ON when recovered? or was the battery disconnected?

João

EDIT: You really don't want the radio to keep displaying and logging the last received RSSI. It makes it difficult to find out what really happened. You won't know if you lost link or not.
That is why this was changed in Ersky9x. But this is not about Ersky9x :) so, it doesn't matter.
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