alex nicol Posted June 18, 2018 Share Posted June 18, 2018 Gents, this ones a bit of a mystery to me. last week I resurrected an old black horse home run, sports aerobatic model, powered by Irvine 53, new gear installed. Funabashi 12z and 2048 pcm receiver, 5 revo's and 2 electric retract units on 35mhz. fully range checked . off down the runway, slightly premature take off (or so I thought) model got to about 10ft rolled and went in. Initially I put it down to pilot error and tip stall due to lack of airspeed. This week duly repaired, held it on the ground for as long as possible, smoothe take off with very shallow climb......solid as a rock same as above model rolled on its back and stuffed in. Examination of the wreckage showed full left aileron. Thing is all the gear checks out, not even the slightest hint of a glitch, also it was a new 6v flight pack. no matter what I do switching on/off etc I can't get anything to twitch or full left aileron to happen........thoughts and ideas please Quote Link to comment Share on other sites More sharing options...
alex nicol Posted June 18, 2018 Author Share Posted June 18, 2018 sorry that should read Futaba 12z ......auto correct lol Quote Link to comment Share on other sites More sharing options...
will -0 Posted June 18, 2018 Share Posted June 18, 2018 Reversed ailerons? Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted June 18, 2018 Share Posted June 18, 2018 Ok, lets get rid of the obvious things first! I'm sure you have this under control as they say, but just for the record you are 110% certain that the ailerons are working the right way round? I know,...but its worth asking. You wouldn't be the first, or the last, experienced modeller to send a model up ailerons reversed! BEB Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted June 18, 2018 Share Posted June 18, 2018 Ha! Snap! BEB Quote Link to comment Share on other sites More sharing options...
alex nicol Posted June 18, 2018 Author Share Posted June 18, 2018 Ailerons were correct......model had just taken off dead straight - no aileron signal given at this point reached about 10ft flicked and in it went......no time to do anything Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted June 18, 2018 Share Posted June 18, 2018 Wings straight, unwarped and secure? BEB Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 18, 2018 Share Posted June 18, 2018 Aileron from the back Alex, lifts the aileron that the stick points too You say everything is OK, until you put in an input Double check, like the lads suggest Edited By Denis Watkins on 18/06/2018 15:01:41 Quote Link to comment Share on other sites More sharing options...
alex nicol Posted June 18, 2018 Author Share Posted June 18, 2018 yes, two piece wing with joining tube and locating bolts, impossible not to put in straight. Id flown it before albeit several years ago. When it took off it flew poker straight, the only signal given was a small amount of up elevator to maintain a shallow climb ( circa 20 degrees) Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted June 18, 2018 Share Posted June 18, 2018 I see 6 volt pack and retracts had you just put the retracts into up mode ? Quote Link to comment Share on other sites More sharing options...
alex nicol Posted June 18, 2018 Author Share Posted June 18, 2018 hadn't touched the retract switch at this point, although retracts were checked as part of the static preflight check. With regard to the previous post point, ailerons were and still are correct.......just been to the hut and checked......standing from behind left stick, left aileron up, right down, right stick opposite happens, also part of static preflight checks Aileron extension leads are colour coded with tape, red for right wing yellow for left Quote Link to comment Share on other sites More sharing options...
Devcon1 Posted June 18, 2018 Share Posted June 18, 2018 Maybe do a further range check by replicating the position of the model(remains)/tx during the fateful flight. Was the Tx aerial extended for the flights. Can you remember how the Centre of Gravity checked out. Quote Link to comment Share on other sites More sharing options...
Paul C. Posted June 18, 2018 Share Posted June 18, 2018 Hi Alex when you reached the crashed model you inferred that it had full left aileron this should have centered from your transmitter unless you had lost power. Suspect a switch issue especially after a long lay upPaul. Quote Link to comment Share on other sites More sharing options...
simon barr Posted June 18, 2018 Share Posted June 18, 2018 Many years ago, I had a similar thing, although still on the ground.... A range check showed that although all was good up to about fifteen feet, after that all contact was lost. A change of Rx crystal solved the problem. I put it down to a faulty crystal. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted June 18, 2018 Share Posted June 18, 2018 Another possibility, pointing the transmitter aerial at the model, and lost signal. But that full over servo after crash needs explaining. Quote Link to comment Share on other sites More sharing options...
Paulo Peres Posted June 18, 2018 Share Posted June 18, 2018 Servo with bad electrical connections? A friend of mine lost a DH Vampire EDF on the third flight of the morning as it would suddenly enter a brisk nose down attitude and then recover either by itself or with full up elevator. He would put her flying straight and level, (properly trimmed of course), and no elevator input would be given and it would dive. Decided to land because of the erratic behaviour but on finals happened again and you know what happens when you run out of altitude... The servo was later checked and performed nicely on the tester... but it kept showing an erratic behaviour. He didn't tear it apart, but it was thrown in the garbage as our best assumption was that some inner connections were failing. All of his next models are safer now! Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted June 18, 2018 Share Posted June 18, 2018 A club member had a similar scenario recently . Plane took off rolled without any input and went in . Three crashes and repairs later he spotted the culprit was a broken servo lead causing servo to go full over to the stop . Once the plane crashed and installation was shook up it all worked perfectly . Worth checking servos individually for faults . Hope you find the culprit as its very frustrating PS Did you range check with engine running at full power as vibrations can shake any bad connections and show up problems . Quote Link to comment Share on other sites More sharing options...
Nigel R Posted June 18, 2018 Share Posted June 18, 2018 "Examination of the wreckage showed full left aileron." Does the model have two aileron servos? Were both in the 'full left' position? Are they on a Y-lead, or separate channels? Was one plugged in to the wrong RX channel? Assuming correct connections, is there any mixing set up in the TX which could have resulted in the aileron problem? TBH my first thought was 'dodgy servo'. Quote Link to comment Share on other sites More sharing options...
alex nicol Posted June 18, 2018 Author Share Posted June 18, 2018 Ok I'll try and answer the above Range, immediately after the transmitter was left at the strip with a colleague, everything forward of the wing te was mangled and the battery disconnected from switch due to impact this and the fact after following a rock steady straight line the model snap rolled left and piled in. each aileron has separate servo's the left was up and the right was down. The way the model reacted it was as if I'd put full left aileron on & full up elevator. I reconnected the radio gear at crash site and everything centred. I had a walk around the crash site but no glitches at all. A colleague checked everything from the Tx at the pilot stance all was good - I should mention the crash happened at about 150 yards range. Aerial was fully extended, no other models in the air or switched on Model was at 90 degrees to the aerial CG was same place its always been Receiver doesn't have a crystal, you set the frequency from the Tx - all set ok New battery & switch fitted - the only thing I can find is the battery connection isn't as positive as I'd like but no amount of wiggling causes any glitching or servo buzzing Quote Link to comment Share on other sites More sharing options...
Paul C. Posted June 18, 2018 Share Posted June 18, 2018 Not familiar with this transmitter does it have a fail safe setting if so how was it set. Running out of ideas now.Paul. Quote Link to comment Share on other sites More sharing options...
alex nicol Posted June 18, 2018 Author Share Posted June 18, 2018 Apologies if I don't answer in time, suggestions are coming in thick and fast. To Nigel R, no Y lead, one servo on each aileron colour coded leads from receiver red for right & yellow for left. aileron operation checked after the wing was attached and again at take off. Sifting through the wreckage left wing servo was fully up & Right fully down. I assumed this is the way it went in as the battery lead disconnected on impact - hard to tell what the other servo's were doing as the fuselage above the wing was mangled Quote Link to comment Share on other sites More sharing options...
alex nicol Posted June 18, 2018 Author Share Posted June 18, 2018 To Paul C, Yes it does have a fail safe but it isn't set Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 18, 2018 Share Posted June 18, 2018 I'd put my money on a servo or wiring problem. Some years ago, I was flying one of my models and during a roll, I had a massive glitch and the model stopped responding meaningfully - much stick waggling and I found myself the right way up but with a model rolling and diving for no reason... Until I realised that things were stable with some up elevator and left aileron deployed. I made an immediate landing and walked up to the model - at which point all became clear. The right aileron was sticking up. Taking the wing off revealed that its connecting lead was half out at the receiver - contrary to my normal installation procedure, I'd made a very neatly laced form of the wiring and the combined weight of the cables had acted on the slightly tightest connector (the right aileron) easing it out under various g loads. The point here is that had I not managed to recover control (it was a close run thing) in time to avoid spreading ply and balsa over the field, after picking up the wreckage I would have been convinced that I'd had a radio problem. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 18, 2018 Share Posted June 18, 2018 Posted by alex nicol on 18/06/2018 16:05:49: To Paul C, Yes it does have a fail safe but it isn't set Naughty! Quote Link to comment Share on other sites More sharing options...
Devcon1 Posted June 18, 2018 Share Posted June 18, 2018 Did it feel like you had any form of control like trying to correct the roll for example. When you say it snap rolled did it look like the elevator gave an uncommanded input as well. Could somebody else have been using a 35Mhz set. I'd check the true performance of the battery pack under a load test. Might be worth checking for any unnoticed damage to the integrity of the Rx aerial lead. Curious to check what happens at the Rx and servos if you simulate a failsafe by turning off the Tx, I know you said a failsafe wasn't set but wonder what the setup defaults to. Edited By Devcon1 on 18/06/2018 17:05:05 Quote Link to comment Share on other sites More sharing options...
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