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Old 06-07-2021, 10:36 AM   #1
toonieroll
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Kraken 580 - Flight 105 - 4651T issue


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Yesterday. I was flying my Kraken 580. It was the first flight of the day for the 580, but I had done a dozen flights on other models. At 109 seconds into the flight, I was quite far out. Not out of sight far out, but probably about as far as I ever fly. The motor cut out. The bird went into free fall to the ground. I tried to do an autorotation but nothing was responding. Fortunately, the helicopter landed on the skids, but hard. I started the walk of shame towards the helicopter, and it started a chicken dance. After a couple of seconds, I hit throttle hold (I should have hit it earlier I guess...but thought it was dead).

Broken blades, servo horns, and a couple of other small things. The side panels have some cracks and a chunk is out of the tail boom from a blade strike. I got away lucky I think.

Here is where it gets interesting. I am using an MSH Brain 2/Ikon 2 flybarless system with 2 remote satellites. One is a standard dsmx satellite and the other a 4651T SRXL2 Telemetry satellite. In the logs I had a 150 RX Fail Safe event. I had some Frame losses (4) but according to the transmitter zero holds. This thread describes the exact same issue. https://www.helifreak.com/showthread.php?t=885009. In layman's terms, it is possible for the 4651T to send an errored packet causing failsafe and soft start even if the other satellite has zero issues. Redundancy nullified. A firmware release for the satellite came out a couple weeks back that might address the issue. firmware 2.43.2 I think.

I have a DX8G2 running firmware 2.05. It probably should be updated and could be part of the issue.

I have 4 machines with 4651T satellites. Do I reflash them with the latest firmware or unplug them and add non-telemetry satellites?

I don't need the help of software/firmware issues to crash my helicopters. It is much more satisfying to do it myself.
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Old 06-07-2021, 12:49 PM   #2
TheSteve
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Re: Kraken 580 - Flight 105 - 4651T issue

That sucks, sorry to hear of the crash. I would update the firmware on the SPM4651T's and keep flying your fleet. I was the one that found the bad packets the receiver would send out and reported them to Spektrum. I have seen no issues with the updated firmware. The firmware in your TX probably should be updated but had nothing to do with the problem, it is 100% an SPM4650/SPM4651 problem.
For the problem to occur your SPM4651 did go into fail safe, so it thought there was complete signal loss for quite a few frames. It may be worth reviewing the antenna location. It is also possible there was a brief burst of interference. I also have some other theories related to the SPM4650/SPM4651 receivers but will keep them to myself pending further testing.
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Old 06-07-2021, 01:53 PM   #3
toonieroll
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Re: Kraken 580 - Flight 105 - 4651T issue

Thanks for your input, Steve. I did see your analysis on Helifreak. Good work! The spm4651T is mounted on the top of the boom with an antenna wire sticking out of each side. I have a grounding wire to the tail so I don't think it is static. I verified the grounding wire is good with a meter. The other satellite is on the bottom of the helicopter.

A fail-safe of the single receiver, the SPM4651T is possible. Under normal circumstances shouldn't this be fine? Isn't that the purpose of the 2 receivers? I do occasionally check the lost frames on the receivers. The A/B numbers on the transmitter. It is usually quite low (single digits). I did notice on this flight they were a lot higher than normal. I think they were around 30 and 50. There were 4 complete frame loses (the big number) and 0 holds reported by the transmitter. This was the 105th flight I have had with this exact configuration and the first time I have seen this many frames lost. Mabye it was interference of some sort.

I did just order a couple of extra satellites. For the short term, I am going to add them to my bigger helicopters (580/700) and unplug the 4651Ts. On the smaller helicopters (a pair of 380s), I am going to just to the software update and see how that goes. I figure I will find a use for the extra satellites in the future anyway. After some time I may revert back to the 4651T satellites.

Thanks again for your input! I would love to hear your theories on the receivers after your testing.
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Old 06-07-2021, 02:13 PM   #4
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Re: Kraken 580 - Flight 105 - 4651T issue

Yes, having a hold on the SPM4651T should be OK if you have other remotes as backups. The specific bug the SPM4651T's have effectively nulls the additional remotes though with an Ikon/Brain FBL. It is not the fault of the Ikon/Brain of course, it is just following the data received by the receivers.
My bigger issue is that the SPM4651T should never have a hold to begin with. There are other FBL systems out there with pretty much the same hardware, they use no additional remotes at all. A poor installation can always be an issue, in your case it sounds like everything was installed correctly though.
So why do the holds occur to begin with, that is what I am looking into. I had a heli drop out of the sky only 50 ft away from me, the receiver went into a hold. It was an SPM4650 which runs the same firmware as the 4651 but it has less range and telemetry transmit power. This is on a 250 gram heli so it is fine, I run no extra remotes.
It is possible it was Wifi interference which is extreme these days if near houses. Both Telus and Shaw(in the west anyway) love to install all Wifi based TV boxes that use 2/3rds of the 2.4 GHz spectrum in one shot. You get a few of those in each house and the amount of interference on 2.4 GHz is extreme. It is bad enough a product I designed at my office had to be switched to 900 MHz, yet 10 years was perfectly fine on 2.4 GHz. Many flying fields don't have houses around so interference isn't often an issue.
A generous user on Helifreak just sent me 3 SPM4651T's to experiment with, so we'll see if I can find any other anomalies.
Anyway, at this point I do feel comfortable flying my Goblin fleet with the SPM4651T(with the new firmware) as the primary receiver and a single remote as backup on each.
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Old 06-07-2021, 06:23 PM   #5
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Re: Kraken 580 - Flight 105 - 4651T issue

I went through this exact same thing 2 years ago with SPM4649T's, 2 satellites and ikon's. What I learned after painful experience is that you have to keep the antennas coming from the telemetry satellite split. I used tubing for holding antennas from rotorquest, ran one up each side of my heli's, have not had one re-occurrence.

I would get signal lost messages in the event log in my ikon when this happened, before that I saw a weird string of gov eng/gov diseng messages, if you see these messages, split your antennas. I was very dissappointed that this would happen even when running 2 additional satellites...
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Old 06-07-2021, 07:12 PM   #6
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Re: Kraken 580 - Flight 105 - 4651T issue

Just to be clear this is a firmware issue with the SPM4651T and SPM4650 SRXL2 receivers. This specific issue doesn't occur with the SPM4649T(SRXL).
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Old 06-08-2021, 08:31 AM   #7
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Re: Kraken 580 - Flight 105 - 4651T issue

Thanks again for all of the inputs. Keep us updated on your findings Steve.

I literally crashed in a farmer's field. I don't think it was wifi or tv boxes. We do hundreds of flights in the same area. Occasionally there is a glitch but it certainly isn't a common thing.

I did have another look at my grounding wire. I am now questioning if it was really working. I may not have taken enough paint off the tail plate to make good contact. When I tested it was from the wire to the motor and not from the tail shaft to the motor. Retesting from the motor to the tail shaft showed nonconductivity.
I have sanded some more of the paint off the plate and now have conductivity. Another member of the club lost a 580 Kraken and concluded it was because of tail belt static. I will definitely keep an eye on the frame losses investigate further if I see them high again. As mentioned previously, I don't see double-digit frame losses on my other helicopters, or on prior flights with the 580, so something was going wrong.
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Old 06-09-2021, 03:54 PM   #8
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Re: Kraken 580 - Flight 105 - 4651T issue

David,

I was one of the guys that helped get the message through to one of the product developers of the 6250 gyro about the issue related to the 4651T giving a false signal to the gyro. Steve did a lot of behind the scenes testing electronically, which I don't even have anything better than a multi-tester which I can do tests with, but with following his lead, did the test with the 6250 gyro in my CH-139 project. It did exactly what was described and that is where I was finally able to get an acknowledgement from the developer that something was really wrong. What the 4651T did was not questioned but you know, I don't think that the initial cause was the bug in the firmware but a problem with the satellite placement which exacerbated the problem.

Recently, I found that I was getting very poor fade counts in the same installation that I did the tests with. I tried to place the DSMX satellite horizontally at the front of the chassis and thought that I had fixed it but no, the counts were still over 1300 to 1400 fades per 7 minute flight. The results from the 4651T were remarkable at two or less per flight. I then stood the satellite on end and had it parallel with the center of the chassis. The counts were still high but not as high.

I don't even know why I did this but I turned the upright standing satellite around 180 degrees and then did a standard range test. Oh, I was using a brand new iX20 for these last two tests as the first set was done with my iX12. Normally when you do a range test, there will be some fades lost even with well placed satellites so you can imagine my surprise at finding no fades at all for the reversed placement. So, with the same satellite but switched in orientation, I would get up to a thousand fades by the end of a 7 minute flight. With the new position, not only did I get no fades when ground tested for distance but got no fades in the air and none on the 4661T as well.

I guess what I am saying is that it may be critical with some installations that you place your satellites based on actual ground testing regardless of what experience you have had placing satellites in the past. I have a Diabolo 800+ that has the 6250 with the 4651T and a 9645 DSMX satellite and it has maybe 15 fades at the most from the 9645 and fewer from the 4651T. I placed the satellite on my CH-139 based on the positioning of that Diabolo and got horrible fade counts from the 9645 yet the fade count from the 4651T was pretty much identical on both and their positions were identical on the boom, horizontally placed with the antennae drooped down to the rear so they are below the boom and splayed out to each side.

I have not flown the Diabolo this year (going to have to change that soon) but I don't expect any differences when I take it out to fly it. I have updated its 4651T like I did with the one in my CH-139. Both of these are pretty expensive helicopters and if I didn't trust what I saw in testing and from the product developers, one, I wouldn't have flown the CH-139 with the 4651T and two, I would not have changed transmitters in mid stream. A good tip for range testing of your aircraft is to use a wooden table that is at least three feet off the ground (more if it is available) and to walk around at distance if you can. Getting to the field early is a way you can do this testing before it becomes busy or do it on a very windy day so that you can use the entire grounds to do the testing.

It's funny that even with a known good satellite position on the Diabolo, it didn't work on the CH-139 which shows me that it is not always about the placement but always about the individual model and how it can change the signal getting to the satellite. I would load the firmware update and go out and fly. Yesterday, Matt, from Horizon, posted on the SRXL2 remote forum in RVG that the Beta was changed to a final update with no changes from the Beta. It seems that the testing from their group had come back all good like those of us that loaded the Beta and then tried to duplicate our original testing to cause the resetting of the ESC. No more shutdowns. Hope this helps you and others reading this.

Don
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Old 06-09-2021, 07:56 PM   #9
TheSteve
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Re: Kraken 580 - Flight 105 - 4651T issue

The problem with the SPM4650 and SPM4651 was indeed tricky to get Spektrum engineers listening. The Ikon/Brain entering failsafe when the SPM4651 was disconnected and reconnected wasn't technically a bug. Spektrum had purposely decided to have the receiver send the failsafe packet data at power up. They added that in one of the early firmware releases. At the time I don't think they envisioned people using an SRXL2 receiver with regular remotes for redundancy. Of course they now do it themselves with the FC6250HX FBL controller. So that was itself an issue with Spektrum's own product. Then we had the mystery of entering failsafe even with remote receivers. Brian(the engineer who writes the 6250 firmware) was not able to reproduce that problem. I think they really were blaming it on the Ikon/Brain. It was only when I showed him the odd serial data packet he looked into it further. He wasn't able to reproduce that either initially. He tried many transmitters but had no luck. That is when I tried my DX6 G2 and noticed the corrupted packet didn't seem to be there, but it always was with an iX12. He then used an iX12 and was able to see the bad packet. He forwarded all of the info to Matt(firmware maintainer for the 4650/4651). It was confirmed the bad packets could actually occur with any transmitter. I don't know why it was easier to see with the iX12, probably because it has more channels, but that is just a guess. With the bad packets easy to reproduce Matt was able to track down the bug and get it fixed. At the same time they removed the receivers sending the failsafe values at power up. This is useful if the receiver was to brownout for whatever reason(of course if that happens you have bigger issues).

End of the day the most important thing is to do a proper range check - as Keyrigger mentioned small changes can make a big performance difference.

btw the typical Spektrum remote receiver with the two 1 inch wire antenna's really only has one of those antenna's as the "active" element, the other is a counterpoise. So if the active part is near metal/carbon it might perform very poorly even if the counterpoise portion is in clear air. Flipping it 180 degrees to get the other side away from anything can give a massive performance improvement in situations like that.
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Old 06-09-2021, 10:06 PM   #10
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Re: Kraken 580 - Flight 105 - 4651T issue

Hi David, sorry to hear about your Kraken 580. That is the reason I have had my 4651 disconnected on my Oxy 5 these last couple of months I have been flying at the club. I only have the two sats connected. I encountered the motor cut out twice during the maiden and subsequent test flight on my Oxy 5 while flying it at a local park nearby. I think TheSteve may have a point about 2.4Ghz interference... There are houses nearby and wifi signals could have interfered with the 4651T to cause it to glitch and send those bad packets to the IKON. I usually fly my X3s at the local parks with no issues whatsoever... knock on wood. Then again I am using AR7200BX with a sat on my X3s... No telemetry receiver.

In my case, I had the autorotation bailout setup by default on my ESC which I was using to govern the head speed (not the IKON governor). That caused the motor to start again after 2 or so seconds and I was able to save the heli from crashing both times it occurred.

BTW, Artin also encountered a glitch when he had a Kraken 580 while flying it at the club. He attributed it to a static hit... Luckily his 580 landed on top of fully grown corn plants at the edge of the field and there was only minor damage.

As you have probably read by now from the HF thread, Spektrum has released a new firmware (now out of beta) for the 4651T. I am too busy with work stuff and haven't updated mine yet. There also appears to be a new firmware released for the MSH Brain/IKON firmware. I will wait a while to install that one.
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