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Warning X8R RX - do not use with CDI on IC powered 'planes

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Ron Gray30/04/2019 17:16:52
2520 forum posts
1009 photos

As per the title. I have just lost a brand new, Laser GA30 powered Sbach and couldn't understand what had gone wrong, on the third pass I got a 'telemetry lost' warning followed by a complete loss of control (no RSSI warning). The 'plane ended up as matchwood with only the tail feathers surviving the impact. This model was fitted with an Optipower Ultraguard to ensure that I had battery backup, having lost the previous Sbach last year to what I put down to battery failure. Thinking that there must be a fault in my Horus TX I spoke to Rich at T9 and he advised that the X8R RXs were know to have a problem with some CDI units and that is why FrSky brought out the RX range of Professional RXs as their attempt at a firmware fix didn't work. To say I was gob smacked would be an understatement. Rich did point out that he has a warning on his website against using these RXs with CDI units since late last year but I had already bought my X8Rs prior to that so knew nothing about this fault. Interestingly enough I have checked 6 other FrSky equipment suppliers in the UK and none of them have a similar warning!

The circumstances of this latest loss were identical to last years loss so I went back through my telemetry log files for that plus 2 other losses that I had in similar situations but ones that I put down to pilot error or unexplained. All log files show that telemetry was lost a few seconds before impact (I can remember the attitude of the 'planes so can relate that to the log files). On the basis of my memory plus the log files I have come to the conclusion that in all cases the X8R were the root cause, after all I have flown many other glow and electric 'planes with no losses and a lot of these have had X8Rs in them too.

The financial cost of these losses, to me, must be approaching the 2K mark but now that I know of the issue I will go about replacing the X8Rs with the RX versions in all of my CDI equipped 'planes. So be warned and don't leave yourselves open to this risk.

I would also suggest that this gets added as a sticky to this thread as a note to all FrSky users.

Alan Hilton30/04/2019 17:51:29
142 forum posts

Hi Ron

Sorry for your loss but many thanks for the post .I am fitting out a newly acquired model with a cdi and was going to install ax8r RX


Geoff S30/04/2019 17:52:39
4033 forum posts
68 photos

Does that still apply if the supply to the electronic ignition is from a separate supply physically separated from the receiver supply as far as possible and the signal connections (ie on/off switch) is via an opto isolator?

I only have one model with electronic ignition but that is on 35Mhz with a Multiplex DSP receiver but I took care to isolate the ignition as far as possible and have had no problems. However if I had decided to fit a 2.4gHz receiver it would have been a Frsky one and more than likely an X8R so this concerns me.


Mike T30/04/2019 18:04:04
607 forum posts
41 photos

I'm a long term fan of FrSky, being an 'early adopter' from the time when Rob Carpenter (aka 'Giant Cod' ) first brought them in to the UK.

IMO, bringing out a new range to cover defects in an existing product (which they then continue to sell) is an appalling way to treat your customer base, when the very least they should do is offer cost-free no-quibble swap outs for the defective products via a model media wide recall campaign.


Edited By Mike T on 30/04/2019 18:04:45

Denis Watkins30/04/2019 18:11:15
4692 forum posts
135 photos

Reports like this started about a year ago Ron,

And was confirmed by experimentation

This is heartbreaking Ron.

We wrongly assume that everybody knows

Ron Gray30/04/2019 18:43:54
2520 forum posts
1009 photos

The problem is Denis that you have to dig deep to find those reports, I couldn't find them on this forum which is my first port of call. Having spoken to Rich I understand that the LMA have some reports but other than that I do not think that it's widely know. I certainly didn't see them and I've been a user of FrSky equipment for the last 4 years and was also one of the beta testers for the Horus. Unfortunately I bought a lot of my X8Rs in 2017 and early 2018 before these reports started to surface so missed the warning that Rich has on his website. But even now if you look on the FrSky website there is no mention of this problem, and as I said in my post above, I could not find any other UK FrSky distributor with a mention of it either. This is why I think it should be put as a sticky on this forum so that others don't suffer losses.

@Geoff - my system had opto isolation in place, so as far as I'm concerned where CDI is used, an X8R will go nowhere near it.

@Mike - totally agree with you but as far as I can make out, FrSky do not accept that it's a problem, their RX8R PRO has, in its details, the line 'A feature that deserves mention is the decreased effect of interference caused by the ignition process'

to be honest I have seriously considered going to Jeti but the cost of replacing all of my RXs with Jeti ones just scares the hell out of me so I'll probably stay with FrSky and just replace the 4 or 5 X8R RXs I have in gas 'planes with the RX8R PRO ones.

Alan Hilton30/04/2019 19:00:28
142 forum posts

The T9 hobby sport site doesn’t make it clear that the standard 8x receiver shouldn’t be used with a cdi unit


Bruce Collinson30/04/2019 19:25:07
582 forum posts


this is dreadful.

Dont take this the wrong way but you’d need an awful lot of Yeti rxs to cover the £2,000 you’re approaching and I am including the tx in that.


Paul Marsh30/04/2019 19:25:19
4132 forum posts
1247 photos

What a shamecrying , sorry for your loss of your plane and mentioned how I like Sbach's and want one like yours.

Also, I just bought a Taranis and some X8R rx's some might've have gone into petrol powered models.Thanks for letting us know and now I've deffo not going to use them for that!

Ron Gray30/04/2019 20:01:46
2520 forum posts
1009 photos

@ Alan - I think it does:

t9 frsky warning.jpg

@ Paul - I will be getting another one, although it's gong to cost me a lot more that the HK one did! (watch this space)

@ Bruce - I know, it's a lot of money, the RXs are at least 2x the cost of the FrSky ones and even their new TX (the 12) is a couple of hundred more than the Horus. I suppose I could replace the 5 gasser RXs with Jeti, that would cost me approx £400 plus the £500 for the TX, but then I would probably not be happy with that one so would go for the 16 which is £1K. Then reality sets in and says replace the FrSky RXs with the Pros, £170, that then leaves the saving of approx £1200 which buys me some replacement airframes! Ain't figures wonderful?!!!!

Paul Marsh30/04/2019 20:07:33
4132 forum posts
1247 photos

Did the engine survive? Hope it did.

I'm thinking of getting this one. bought the same size Extra a couple of years ago and that goes well.

Edited By Paul Marsh on 30/04/2019 20:09:34

Allan Bennett30/04/2019 20:21:48
1791 forum posts
55 photos

Although it doesn't affect me because all my models are electric, I'm curious whether the type of antenna makes a difference to their susceptibility to CDI interference: Most of my XxR receivers (and SxR) use simple wire antennae, but the current X8R ad on the T9 site is specific to the PCB antenna.

Ron Gray30/04/2019 21:13:36
2520 forum posts
1009 photos

@ Paul - the engine looks to be ok although the top of the carb has disappeared! None of the fins were damaged neither was the plug cap! Anyway it's going back to Jon just to make sure it's all ok as it was a straight nose into ground. Fortunately the spinner acted as a crash absorber and was squashed nearly flat! Regarding the replacement 'plane , this one -  Sbach 342

@ Allan - the first Sbach I lost had the older chunky antenna, the second one (yesterday) had the new pcb antenna, the first Hurricane had the wire antenna, the second one the pcb. So I don't think it makes a difference. I should add that the antenna were positioned at 90 degrees to each other and away from any other wiring and as far away from the front end (CDI unit) as I could get them.

Just to show you some gory details of the first crash (I didn't take anyway of yesterday's as I was too gutted so took all the re-usable bits out of it and burnt the rest at the field). But the first photo shows why you should always take a seat near the back of an airliner!


And the remains of the engine


Edited By Ron Gray on 30/04/2019 21:23:37

Bruce Collinson30/04/2019 21:49:47
582 forum posts


I switched to Yeti when it occurred to me that in 3 years I had progressed from having £200-odd in the air to the thick end of a grand, Laser engine, £300 airframe, several Savox servos etc. We seem to have a “Black Hole” within range of our strip which has a particular appetite for a specific mass market Chinese radio, the one 95% of my club mates were using when I joined and which I naturally bought.

At the new club (strip lost, shirty farmer ... tautology) there were frame and fade issues, charted by a very old hand who understands these things. There are several jet jockeys, whose asset base when airborne dwarfs mine.

They all use Yeti. So does my tutor. So do I, now. It does seem very resilient against sensitive aerial location and orientation, unlike the aforementioned Chinese radio. My entirely novice, amateur theory is that this make is especially sensitive to signal loss where aerial installation is concerned. My Yak started life with a DLE 20 and four antennae, well spaced about the fus as far from the petrolly, sparky bits as possible, yet it had glitches from the off even quite close in, say 100-150 yds and my elders and betters moved the satellite aerial into the wing. It improved things although the DLE was practically impossible to get down to 82 dB and has been replaced.

it is a big investment. Deals are available. As I said to a colleague, it doesn’t make a better pilot but it engenders confidence and serious ownership pleasures. To be fair, we don’t seem to get issues with Futaba or Frisky although they are both in a small minority.

Yer pays yer money ....


MattyB30/04/2019 23:50:03
2418 forum posts
47 photos

Extensive conversation about this on RCGroups... worth trawling through if you plan to use FrSky in petrol aircraft with CDI.

Ps - It’s Jeti and FrSky, not Yeti and Frisky!

john stones 1 Moderator30/04/2019 23:59:16
11919 forum posts
1531 photos

I feel your pain Ron. sad

Ron Gray01/05/2019 09:23:29
2520 forum posts
1009 photos

@MattyB - yep it’s on that forum but not on this one hence my post. Plus you have to search for it which you don’t normally have to do before you fly, one would expect the manufacturer to own up to the issue and make that public. One would also expect all retailers to put warnings against purchasing the defective products as T9 have done!

Former Member01/05/2019 10:56:22
756 forum posts

[This posting has been removed]

Paul Marsh01/05/2019 20:42:16
4132 forum posts
1247 photos

So far, I have 4 X8R rx's but not used the radio yet in any model. Chris Barlow, here uses the protocol and these rx's but luckily, he has only used them on glow models, but does have a couple petrols. I told him yesterday about this thread and see what he makes of it.

The other option in use a 2nd module and have two protocols using the Sbus, and if one has a lock out, the other will resume and vice versa. Jeti has dual protocol which is the reason why it is the radio of choice for higher value models and pilots who want 110% reliability.

Ron Gray01/05/2019 20:58:46
2520 forum posts
1009 photos

I have many X8Rs in use in other models and have not had a single issue with them in 4 years of use. I have only had the problem in the last year on 4 gas powered ones (leccy and glow no problem) and in fact have 3 gassers with them in that I have been flying for 2 - 3 years without issue! But, the RX locking out problems that I've experienced means that all 3 (surviving) ones will have their RXs replaced with the PRO versions before I fly them again, they are all 2m 30cc or greater powered ones and I don't want to lose those too. The alternative is to use the FrSky 868Mhz RXs / TX module which is just like the Jeti.

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