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Tarannis X9D Radio failure


EssexBOF
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1540027644_CrashFlight13thOctober21.thumb.jpg.1f551bc46bbbf96a622f3b3e2b2accb2.jpgFirst time in some 50+ years of flying multi channel radio, that I have sufferred total radio failure.

Had been flying for some 14 minutes, when the model started down into a dive,with crow deployed. Radio started calling "RS Critical" "RS Critical" . No control, no failsafe appeared to cut in either. Model bunted inverted (never seen an F5j model bunt, well never tried it myself!!), pulled out, then stall turned and landed in a tree. This probably saved it being a total write off.

Having sought the services of a friend at Stow Maries Aerodrome, who has a drone business, as I could not locate the model from a search ( Thanks Dennis), who found it in the tree on the other side of the boundary of the field where I thugh it had come down, the local farmer, came to the rescue with a Cherry Picker plusa cage and lifted me up to wrestle the model from the tree.

Up until the warning the model had been flying with no problems and at height, where the range might be a problem ( see Altis reading, that terminates when the problem surfaced)

Having stripped the gear out of the model, cannot find what the radio fault may have been, as the battery was charged up as it had been over 2 days stuck in the tree, and everything works OK. Both Tx & flight battery, were fully charged before flight. Aerials in the FrSky D8 Rx seem fine, no breakage and connections to board are fine. So I am at a loss as to what it might be. Will take the complete model out and do a range test/check at the field.

I have had the usual"RS Signal Low" warnings as most people seem to get, but never the critical warnings before, so any ideas would be helpful. The way out would be to use a spare Tx plus another Rx, to eliminate hose items from the equation. Over 6 years use never had a problem like this with the Taranis, before.

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Edited by EssexBOF
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If the Altis stopped logging (independent from rx) surely it must have been an electrical problem but then how did the servos change position? Good luck with diagnosing that one!

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+1.

Assuming the rx is powered by a BEC via the Altis, it may cast some suspicion on the BEC/ESC. Especially since the failure occurred when pulling the brakes (which will increase the current draw).

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1 hour ago, Nicholls said:

If the Altis stopped logging (independent from rx) surely it must have been an electrical problem but then how did the servos change position? Good luck with diagnosing that one!

Agree - and the fact the battery still had reasonable charge suggests you lost connection between battery/BEC and Rx, even loss into the Altis - I would expect the Altis to go on recording all the while it had power on it.  I believe in the past you have had issues with the Altis wiring/connectors going open circuit.  So I would start with a careful inspection of the Altis, and also that the BEC is still working under load.  I don’t see this as a radio issue/lost link.

Simon

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1 hour ago, simon_t said:

Agree - and the fact the battery still had reasonable charge suggests you lost connection between battery/BEC and Rx, even loss into the Altis - I would expect the Altis to go on recording all the while it had power on it.  I believe in the past you have had issues with the Altis wiring/connectors going open circuit.  So I would start with a careful inspection of the Altis, and also that the BEC is still working under load.  I don’t see this as a radio issue/lost link.

Simon

My piece ws not clear,Simon, should be battery was totally flat and needed charging, onto a NlMh setting then Li Po setting, to bring it back up to 12.6 V. As to past issues with the Altis problem, I now follow  what I read some time ago, and only have the signal wire running to the Altis, no +/- wires. Works fine, with a Castle Creation UBEC running off the Li Po, via a separate lead. Having gone over the things again and thinking it had something to do with the Rx, checked the aerials to Rx and found the insulation broken, as in picture, so feel this may be the cause. As they have been in the model for 5/6 years now.

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Are you using a back up power system? Or just a bec from the main battery.

 I once had a similar experience when I flew a model for too long. The 6 servos, were being driven by a 2s 300mah battery via  castle creations 5v voltage regulator. Battery voltage dropped , CC VR tried to give 5v, couldn't, so cut power to all servos!

 

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1 hour ago, EssexBOF said:

My piece ws not clear,Simon, should be battery was totally flat and needed charging, onto a NlMh setting then Li Po setting, to bring it back up to 12.6 V. As to past issues with the Altis problem, I now follow  what I read some time ago, and only have the signal wire running to the Altis, no +/- wires. Works fine, with a Castle Creation UBEC running off the Li Po, via a separate lead. Having gone over the things again and thinking it had something to do with the Rx, checked the aerials to Rx and found the insulation broken, as in picture, so feel this may be the cause. As they have been in the model for 5/6 years now.

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If it had just been (one) Rx aerial then the Altis would keep logging - also the aerial doesn’t look damaged - only the coax insulation, but the screen braid looks intact.  Has to be power loss somewhere in the chain.  The flight battery would be drained whether the rx was getting power or not, as the BEC(s) would still be drawing some current.  As you lost power to Rx and Altis, it sounds like something at the LiPo end

Simon

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Very sorry to read all this Brian.

Where did the Altis get it’s power from, is it from the esc or is it is the same power source that supplied the rx?

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Pretty sure that te Castle Creations Ubec failed, as checked the Altis log voltage reading and it drops off a cliff at the end of the graph.

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Looking at that Brian I think it is more likely your flight battery dying, as it took over 30s to drop from the BEC 5V to 3.8V - BEC would tend to die suddenly.  It also explains why the Rx was able to put it in failsafe (or partial FS), as the supply failed.  Depending on the servo types, the servos (or some) may have stopped working before the Rx went completely.  

You just have to stop having these long flights!

Simon

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  • 4 weeks later...
On 18/11/2021 at 16:59, taggarc said:

re repair - would love to understand the steps / materials used.  Very impressive  

As you are not the first reply to ask of a how to go about this type of repair,I will give a brief summary. Have done a couple now as these models are not of the disposable type ( well for some they may be).

On this one, fortunately, the spars were intact which is a big bonus, but the decor is not the easiest to match/replace

The wing shown did have a problem as to the ease of the repair, as part of he damage extended into the dihedral break. Although the damage does not look as extending far from what can be seen, this type of carbon over a Rohacell skin, tends to shatter, further than you think. This needs cutting out, to end at firm skin to bond to. 

I used pink foam as an infill finished as best you can to be slightly lower than the surface being matched. You need to make sure that the paints used cannot seep through to the pink foam as hey can disolve it!! Balsa can be used but foam is easier to work and very light in weight, when you are filling halfway along a wing panel. A layer of surface carbon cloth was then, epoxied over the foam. When cured car filler was applied spairingly over the area, so as to match the existing profile. The filler type I was put onto was as below, but different make (Troton) It sands well, but has a polyester base from smell. Goes off VERY QUICK!!!!, I found any excess can be trimmed when semi cured with balsa knife. A piece of 1/8" balsa sheet, that covers the length of the repair by a good 1/2" either side, round off the edge, then wrap Sellotape around the edge, then use this to flow it over the filled in area. Any small holes depressions can be filled when set.

Nearly all the colours used on these moulded models, are car auto colours (RAL)  and if you go to an auto paint supplier, they can mix you up virtually any combination you want. Halfords is a good source, but you need to know exactly what colour you want, as there can be many shades of the same colour. I  buy it as an aerosol, as it saves cleaning up spray gear, after.

Undercoats are needed and the Spray Build up types help to cover areas that may have sunk. Light colours need a white undercoat.

The flouresent colours, like the Orange used here, are not gloss, so a clear laquer is sprayed over it to get a gloss finish.

Masking tape is no good for sharp lines,Tamiya do a tape that gives a pin sharp edge. Car auto shops do one they tell me that is the same, but have not tried it. as yet. There is usually a ridge where the paint meets any masking areas. Best way to get rid of it is to use sharp square edge steel rule, works well.Run this along lightly, to level off. 

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Your repair is super neat.   Something that my upcoming two similar wing repairs may not be even close to.  

Does the CF cloth covering not overlap the existing wing skin?     I can't see how to blend the repair in so well if there is an overlap (on the outer surface).

 

 

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Where do you source the foam from please and is it glued in place with foam safe CA.  Is the replacement simply made up of foam, carbon cloth and filler ?   Not sure I fully understand this bit  - "A piece of 1/8" balsa sheet, that covers the length of the repair by a good 1/2" either side, round off the edge, then wrap Sellotape around the edge, then use this to flow it over the filled in area"

 

Thanks

taggarc

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55 minutes ago, taggarc said:

Where do you source the foam from please and is it glued in place with foam safe CA.  Is the replacement simply made up of foam, carbon cloth and filler ?

Building sites are a source as it is used for insulation, difficult to by in small  quantities you may need, so scrounging is the best way!!!Yes, foam safe CA is fine but you need get the position right, white glue is fine and gives you more time to make sure it is where you want it to be. Carbon cloth is then epoxied in place to match the area being repaired. It needs to be slightly under the finished surface. Do top and bottom separately, not in one piece  around the insert.

BTW use the old trick of laying paper over the cut out area to be replaced, then rub a pencil over the edges to get the outline of the foam insert. Cut paper use a s template.

 Not sure I fully understand this bit  - "A piece of 1/8" balsa sheet, that covers the length of the repair by a good 1/2" either side, round off the edge, then wrap Sellotape around the edge, then use this to flow it over the filled in area"

Place the balsa sheet Sellotape edge down at the back of area t fill , then slide towards the LE ,so as to fill area in, the edges sit over the ends so as you do not dig into the area being filled. This is used like a trowel to smooth the area over its length, to follow the existing wing section profile. You may end up with some areas being shallow,but resist the temptation to try and resolve it then. When cured then fill in any shallow areas. At this stage you can use Polyfilla to fill these areas.

 

 

 

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9 hours ago, DaveH said:

Your repair is super neat.   Something that my upcoming two similar wing repairs may not be even close to.  

Does the CF cloth covering not overlap the existing wing skin?     I can't see how to blend the repair in so well if there is an overlap (on the outer surface).

 

 

No overlap, as you cannot finish it flush with finished surface, Slightly below, then fill,to bring level.

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