Ron Gray Posted October 8, 2021 Share Posted October 8, 2021 (edited) Can't really get my head around what happened, just completing a lovely flight and was making final turn onto finals and model spun in. Now I know that the immediate reaction is 'tip stall' but I know a tip stall when it happens and this wasn't one. Having checked the telemetry it makes for an interesting read and I welcome any thoughts. I should add that I've not shown the readouts for RSSI and battery both of which were fine. This all happened in the space of 3 seconds! Fortunately the LA-7 landed in a field where the soil was quite soft so the damage is not as bad as it could have been so it will be back in the air in a couple of weeks, just very annoying. Edited October 8, 2021 by Martin Harris - Moderator Edited CoC breach - please don't use wildcard characters to disguise coarse language... 3 Quote Link to comment Share on other sites More sharing options...
Andy Gates Posted October 8, 2021 Share Posted October 8, 2021 First off I am sorry to hear of your machines uncontrolled trip to terra firma. Good luck with the repairs. Can I ask what receiver was installed in your plane? There look to be a number of weird things happening there in my view, although it is difficult to read the data properly. From my experience of something similar with my Beaufighter which crashed 3 times before I found the culprit, I would suggest that one of the antennae connections in the receiver has come loose. I had this with a FrSky V8FR2 receiver, which suddenly went into safe mode on 3 separate occasions. The fault did not show during range checks or in ground running. Please notice I suggest a loose connection not a disconnect. If the connection is loose and can move around then vibrations in the plane can cause the movement and spurious interference. Open the receiver up and check the paint for cracks around both antennae connections. My particular receiver is now marked up and only used for ground set up purposes during building. Quote Link to comment Share on other sites More sharing options...
John Stainforth Posted October 8, 2021 Share Posted October 8, 2021 Ron, please can you tell us what the different coloured lines are showing. I think it's: Green - throttle, pink -aileron, yellow - rudder, magenta - elevator. (The resolution on my computer screen is not good enough to read the captions, so I can't be sure.) If I am right, there is a lot of elevator coming in after you start your turn on to finals, but I don't know whether this is up or down elevator. Did the spin start immediately you turned on to finals? Quote Link to comment Share on other sites More sharing options...
Kim Taylor Posted October 8, 2021 Share Posted October 8, 2021 Ron, I believe that you use FrSky (as do I). Have you updated to the latest v2.3.?? firmware? (I haven't yet) If not, could this be the sudden control deflection glitch which said firmware was designed to fix? It doesn't look typical of the reported problem there though, which was (I think) a random full scale deflection for 0.8 of a second. I hope you get to the bottom of it and repairs to the LA-7 are not too difficult. Kim Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 9, 2021 Author Share Posted October 9, 2021 Sorry guys, the screen shot didn't come through as well as I'd hoped, but here's another which should make it clearer! More information, Tx - FrSky Horus 10 Express running OTX 2.3.13, Rx - FrSky X4R with ailerons and landing gear operating through SBus. The elevator plot shows up elevator when the line is below 0 so in the screen shot there is slight up elevator coupled with left aileron as I enter the turn, easing off the aileron and applying little bit more up, then things go crazy with the throttle going to full couple with full left aileron and up elevator. Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted October 9, 2021 Share Posted October 9, 2021 Ron I believe these are raw stick outputs recorded in the Tx and are therefore no reflection at all on the RF link or anything in the model. I'd be looking at gimbals and gimbal wires etc. Maybe Tx calibration. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 9, 2021 Author Share Posted October 9, 2021 You know what Chris, I was just discussing the same with my flying buddy who was with me at the time, is it stick inputs or Rx outputs? We came to the conclusion that it was the former as he said those were my responses to what the ‘plane was doing, in other words I applied throttle, opposite (to the spin) aileron and up elevator. His view was that had it been 10ft higher it would have recovered! Hey ho, still none the wiser as to what caused it in the first place but as 3 other ‘planes have met their end in exactly the same place / same circumstances before now (not mine and not FrSky) and as the location is close to a small factory (producing wood chip / shavings)………………………………………… On the bright side, I was thinking of changing the colour scheme to winter camo anyway! Quote Link to comment Share on other sites More sharing options...
SIMON CRAGG Posted October 9, 2021 Share Posted October 9, 2021 Looks like an RX issue to me. Might be worth doing another range check. Sure you have checked all soldered connections, Lipo condition, fail safe etc. etc. I have had similar happen with a large Corsair, and and in the end I could only put it down to the dreaded tip stall!. Quote Link to comment Share on other sites More sharing options...
Tim Flyer Posted October 9, 2021 Share Posted October 9, 2021 Sorry to hear that Ron . It’s really frustrating when you can’t see exactly what went wrong. Good though you can get it back in the air ok . I find repairs are quite fun once I actually get “stuck in “ it’s the initial frustration/disgust that’s the worst bit , . Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 9, 2021 Author Share Posted October 9, 2021 Thanks guys for your replies and encouragement etc! The damage The fuselage should be an easy fix and a plus is that I wanted to retrofit a steerable tailwheel, so now I can! The wing has a few dings but the crease slightly concerns me but when I try and bend the wing there is still a lot of strength there so maybe a re-skin to that area. The cowl is basically mullered, I thought I had another one but can't find it so I will try and repair this one. Engine, apart from mud on the front there are no signs of any anywhere near the carb so I don't think any was ingested but I will strip it just in case. 2 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted October 9, 2021 Share Posted October 9, 2021 Sorry to see that Ron, but, as you say looks repairable. I'll be very interested to see how you repair that creased foam wing, as I have a very similar repair to make, not from crash damage but from a model that I bought which was posted to me in a bin bag, rather than in a box. Seriously. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 9, 2021 Author Share Posted October 9, 2021 That is what I am just about to investigate @leccyflyer, scalpel at the ready, hope it won't be a bloody experience (sorry Mods, am I allowed to say bloody???) Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 9, 2021 Author Share Posted October 9, 2021 @leccyflyer the repairs: Damaged veneer cut out, tried not to cut straight lines! New veneer in place, ideally the grain would follow that of the existing but my veneer isn't wide enough and I didn't want a join. 5 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 9, 2021 Share Posted October 9, 2021 7 hours ago, Ron Gray said: That is what I am just about to investigate @leccyflyer, scalpel at the ready, hope it won't be a bloody experience (sorry Mods, am I allowed to say bloody???) In that context no problem Ron, sorry about your model by the way. 1 Quote Link to comment Share on other sites More sharing options...
Tim Flyer Posted October 9, 2021 Share Posted October 9, 2021 The cowl should be quite repairable with no outward signs of damage. . Once cleaned up I would stick gaffer tape on the outside to retain shape and use epoxy and glass from inside then use polyester filler “P47” on outside. Basically re make the “tube construction” then re cut out the openings afterwards. It should be as good as new afterwards. I’m sure you will do a great job . Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted October 9, 2021 Share Posted October 9, 2021 Hi Ron Sorry to hear of the prang. I must say I think you are remarkably quick to go about repairs! Look forward to seeing it flying again up at the strip. Peter Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted October 10, 2021 Share Posted October 10, 2021 Ron, Shame about the La7, but these things happen sometimes although the repairs look well underway so I guess its a well liked model. Out of interest what glue do you use to hold the veneer down with? For the crashes other than dumb thumbs I employ the "what its not" approach and technique I picked up from a professional forensic investigator (following a couple electrical fires at work!). All quite interesting when you are only left with the charred remains of a very complex piece of electrical equipment! Anyway from the last few seconds what did the model do? What's it fail safe mode? Throttle down, but did it actual do that? do control surfaces stay on last command or return neutral, what about gear does that fail safe up or down. When you found the model were the control surfaces in the expected positions? Depending on the above you should de able to rule out RX battery, switch and wiring due to RSSI signal....which just leaves the RX? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 10, 2021 Author Share Posted October 10, 2021 (edited) @Tim Flyer I’ve tacked the cowl together using cyano and I’ve glassed the inside, as you say over all the holes for them to be recut after. I’ll put another layer on today then, once dry, sand and fill the outside, I need to get some P47! @Peter Jenkins it’s strange, I lost my mojo for building a few weeks ago, hence the delay on finishing the JU-88, but this repair has got me fired up and I’m enjoying it, I think mainly because I will be changing the colour scheme too. @Chris WalbyFail safe set for all surface controls to neutral, throttle to low and U/C to hold. None of these happened and telemetry shows no signal loss. All control surfaces intact and at neutral when I recovered the ‘plane and all work as expected, on the bench with no loose hinges or broken horns. For the glue for the veneer I used Gorilla glue white, applied a very thin layer to the veneer and a thicker layer to the foam. Let it dry then ironed the veneer on, seems to have worked ok. I’m afraid that, much as I don’t want / can’t to believe it, other than outside interference (remember that 3 other models have been lost in exactly the same spot / same circumstances/ same effects) tip stall is the only other likely cause. But, I know the LA-7 I’ve flown it so many times before and I really have explored it’s flight envelope so know it’s slow speed capability (which it is very good at). The only thing different with this flight was that I was running a 14x6 prop rather than a 15x6 and the crying shame was that this was, until the crash, the best it had ever flown, it was truly excellent! Anyway, back to the repairs, onwards and upwards! Edited October 10, 2021 by Ron Gray Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted October 10, 2021 Share Posted October 10, 2021 Ron, apart from interference, it could be that part of the field experiences some form of wind shear under certain weather conditions, so while the model may appear to suffer from interference it's actually an airspeed/angle of attack issue. we have position on our field which causes models to "glitch" on landing approach under certain weather conditions. Also low rpm, say 4,000 rpm a 15x6 prop generates 20%+ more thrust than a 14 x 6 prop so the plane will slow more quickly at a given angle of attack. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 10, 2021 Author Share Posted October 10, 2021 It could just be that Frank, the change of prop and lack of thrust. I must have flown it in excess of 30 times with the larger prop and my landing approaches are always very similar for a western approach. I’ve just got to take it on the chin and change the approach when I take it out again, which will hopefully be next week, weather permitting. Quote Link to comment Share on other sites More sharing options...
Tim Flyer Posted October 10, 2021 Share Posted October 10, 2021 Sorry it’s Isopon P38 I meant ?. Good stuff although there are many alternative polyester fillers . Their adhesion is great and easy sanding plus they set very quickly Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 10, 2021 Author Share Posted October 10, 2021 I thought that was what you meant Tim, I'll be nipping into town tomorrow morning to get some. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 10, 2021 Author Share Posted October 10, 2021 The cowl is now ready to receive the filler, not too bad so far 1 Quote Link to comment Share on other sites More sharing options...
Dad_flyer Posted October 10, 2021 Share Posted October 10, 2021 'heavily weathered'? I like that colour scheme. Wow, you are rapid Ron. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted October 11, 2021 Share Posted October 11, 2021 15 hours ago, Tim Flyer said: Sorry it’s Isopon P38 I meant ?. Good stuff although there are many alternative polyester fillers . Their adhesion is great and easy sanding plus they set very quickly P-38 works best on in-line cowls. As Ron said, for radial cowls it's the P-47 that is needed ? 3 Quote Link to comment Share on other sites More sharing options...
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