Tony Smith 7

Correct, the servo's in the wing exactly as BEB describes. The model is a TW-742 Skyhawk, see thread Here, and on other web sites "RC GROUPS"  and Dmitry Nizhegorodov on his own web site.    Aileron linkage is one of the issues discussed.

That Graupner Terry looks like its rudder/elevator, rather than 3 axis if I read it right?   I was set on ailerons.  I found a few planes like that which looked OK at first glance, but then I thought they couldn't really work that well with rudder and almost no dihedral.  Could just be my prejudice of course.

Yes, quite nimble although I have the control throws set quite short at the moment.   There's a long thread on another site about the plane, including all sorts of modifications such as beefy brushless motor, fancy batteries and aileron upgrades. TW-742 Sky Hawk [Official Thread]  

Dealer's photo of the complete plane ....  Elevator/rudder servo fitment ...    Receiver and ESC (arming switch on port side of fuselage)  1100mAh NiMH power pack under the canopy.  Brush motor not visible, two blade folding 6x3 propeller  ...  Aileron servo and linkages on the underneath of the wing .... No-frills 4 channel 35MHz transmitter ... I'm sure everyone could have a field day finding fault with the model, but the fact is that when assembled with a bit of common sense it flies OK.   CofG even comes out more or less right without fiddling around. The worst thing really is the instructions, some of which are hilarious, for example the low voltage warning light is described as "The low pressure reports to the police the light".   In the assembly instructions plugging in the aileron servo is "Insert electron adjust into the LCD oscillate" I accidently got the throttle channel reversed, and sorting that out I found the reversing switches weren't correctly described in the instructions or on the transmitter ... Function   TX Label                             Instructions Throttle     CH1 Rolling Yawing         Television Aileron      CH2 Pitching                      Rudder Elevator    CH3 Motor Power               Elevat Rudder     CH4 Yawing Rolling          Aileron       Edited By Tony Smith 7 on 20/04/2010 19:50:05

I was wondering about that.   I started off using no more tension on the mountings than needed to keep the wing secure for normal operation.   I find that landing on rough grass you're pretty well guaranteed that one wing will catch before the plane comes to a halt.   I can try more rubber bands and see how that goes.

Thanks for the comments.   It sounds as if you think the existing layout ought to be OK if I keep things neat.   From memory I think the control rods run pretty much parallel - ie the horns are about the same distance apart as the ends of the control arm.    I'm not using the outermost hole, so I will trim the control arm down.  I put off doing that in case I wanted to increase the control throws. 

Hi, My plane has the aileron servo mounted upside-down on the underneath of the wing, with two wire push rods running back to control horns for the ailerons.   All this, the top part of the servo, linkages and control horns, are therefore  inside the fuselage with not much clearance to the sides.  The problem is that if the wing shifts on landing, and even a tuft of grass could do that on landing, then the linkage can foul the inside of the fuselage.  This has happened to me a couple of times.  Any suggestions for a better configuration?  The whole point of rubber bands is to allow the wing to shift rather than break, but if in doing so it wrecks the controls or servo then that's not ideal. Thanks in advance, Tony S

Thanks for references.  I can't help laughing a little at all the references to TV remote controls.  Someone's had a bad experience with one, haven't they?   Or maybe we're the only people whose remotes behave themselves.  Ours hasn't had the battery touched at least since we moved house, which was two and a half years ago.

I certainly recognise the issue with disposable dry cells, the quandary between changing out possibly still-good cells, vs risking a disaster by keeping them.  My first model used dry cells (in exactly the sort of holder that everyone hates) and I was always conscious of the issue.   Of course that problem goes away with loose rechargeable AAs and is nothing to do with welded packs or contact reliability. By the way, does the BMFA advice (or rule) specify "welded"?  If so, that would rule out making your own packs which would be a shame.

I guess I was discounting experience from 40 years ago.    Although come to think of it most problems I remember from those old "Ever Ready" lights were contacts on the switches and the brass contact that bore on the back of the bulb.  More of a design problem than inherent in the use of separate cells.   Actually taking that further ... those light did use a welded pack didn't they?  I can easily see how IC models need special attention, maybe any powered model is a pretty harsh environment.    My lifebuoy light is tested every time we prepare to go to sea.  It switches on automatically when turned upright its quite easy to test while fitting it into its holder.   On commercial ships where they'd be mounted all the time, I don't know how often they're tested but they will probably have a service life like flares and liferafts.  

Cheers.  I understand the theoretical issues, but just wondered if there was a history of actual incidents arising from them. Of course I would abide by the rules of any club or association that I was a member of, even if I didn't necessarily agree.    I suppose to me the examples cited above don't really ring true.  OK cheap kit needs the batteries fiddling with now and again.   Ironically the TX that came with my RTF model is one of those - but the BMFA says that loose cells are OK in that case!    As side from that I can put hand on heart to say that I have never needed to fiddle with the batteries on my hh VHF, GPS, cycle lights, digital camera.   OK most of those aren't safety critical, but cycle lights for example would be useless if they were liable to stop working.  To go back to my man overboard light - that hangs from the pushpit of the boat any time we're at sea, and in the event of an emergency it would be thrown overboard along with  lifebuoy drogue and danbuoy.   No time to take it apart and fiddle with batteries in those circumstances!   For those unfamiliar with this sort of thing, here's an example and note that they even boast about using standard cells .. Lifebuoy LightEdited By Tony Smith 7 on 16/04/2010 11:34:15

Hi, I just noticed this issue cropping up here, people saying unambiguously that you most never use non-welded airborne battery packs, and some clubs banning transmitters which take loose batteries.       What's the history behind this? I don't see the same in other industries, where plenty of safety-critical equipment uses separate cells.   Hang gliding flight instruments for example, or hand-held marine VHF radios.   Even more striking our "man overboard" floating light which uses 4 standard D cells.  That's a SOLAS and MCA approved piece of emergency equipment.     Is there some special risk with RC equipment, or some history of high-profile issues?    

Well its all assembled, trimmed and flight tested now.   No significant problems, but I guess it needs a bit more tweaking than suggested by the adverts. The control fouling was resolved with a little strategic bending of the aileron push-rods. Edited By Tony Smith 7 on 16/04/2010 08:56:36

Chewing it over, I think I'm never going to make up my mind by reading manuals and speculating about possible future models.    For the two that I have at the moment, could anyone point out any particular limits with the DX6i ? (1) A twist-wing + elevator slope glider (effectively aileron/rudder)  Just two servos.  (2) A four channel electric glider,  I intend to convert this to separate servos for the ailerons, and program differential throws.  Thanks

Cheers.  I think the problem the need to choose a "System" as well a the transmitter.   For example if I went DX6i then in a few years needed to upgrade to a better Spektrum TX then maybe that's not the end of the world.   If that upgrade meant replacing receivers, servos, chargers and other accessories as well then that's more of a pain. 

Thanks for all the comments.   The 1000' separation tallies with what I've heard in separate discussions with our ATC.   For example at the microlight strip the ILS would put inbound flights at 2000' overhead, and flights to and from the microlight strip are always cleared "not above 1000''" to maintain that separation. I would very much rather not talk to ATC myself, because I think I would be in a difficult position if they said "No".   In the hang gliding club we quite often found them trying to prohibit stuff that was perfectly reasonable, legal and safe, and trying to enforce reporting on us even when we were outside their airspace in any case! I would prefer to confirm 100% to myself that I am legal and not creating any hazard.

That Cockpit SX looks a super set.    Shame all these systems are proprietary

Cheers. I wonder if legally "real aircraft" do in fact have precedence.   Obviously it would be silly to get in the position where it becomes an issue.  Just for fun, suppose I was flying the model at 200' over my field, and it hit by a microlight.   Clearly the microlight is breaking the 500' rule, but also not conforming to "see and avoid" VFR conventions either.   There is actually a microlight/GA field nearby, but we're nowhere near their circuit and they have no real business overhead since typically they're cleared directly into the field from outside airspace.   Equally their outbound clearance would be along one of the preferred VFR routes, none of which pass over us.  The serious traffic is all under ATC direction into the airport, and generally at or over 2000'.   An occasional helicopter is lower but not below 1000'.    For complete clarity I intend not to fly higher than the nearby hill that's between us and the airport,  and if I keep below 150' then that's lower than the wind turbine that's going up to our North.   By doing this I can put hand on heart and say I am completely sure that my model is well below any possible flight paths.  (edit the wind turbine will be 80m and on higher ground than us - goodness knows where I got 150 feet from) Edited By Tony Smith 7 on 14/04/2010 17:31:10

Thanks everyone.  I have to say I am starting to have doubts after reading all this and looking at the manual.   Digital trim? - so you can't feel the position (can you see it on the display?) and how do you quickly reset trim to the required starting position.  No ratchet on the throttle, that doesn't sound too clever either, unless they have a pretty good friction mechanism to keep it still.   

Thanks for the comments.  I've not flown a model with that sort of sophistication, but I can easily see how a higher performance glider needs something to help it land.   My last hang glider used flaps at 70 degs for landing and that was a dream.  I wonder whether brakes could just be on/off, that's how full size gliders tend to operate.    Or maybe use the throttle as a continuous control from fast glider at one end, through take-off/soaring at the mid point then landing configuration with the stick fully down.  I guess that's all hypothetical till I get a model that needs this!  Funny that these 5, 6, 7, 8 channel TXs don't have more than four proportional channels.

Thanks for all the comments.  The point regarding a full four-servo wing is probably something I'd not find out until I tried to set it up.    Maybe that requirement's a long way off for me in any case.    I suppose you'd use the free mixes on the DX7 for that setup?   Or use Gear to control the brakes.

Hi, I notice a few DX6i transmitters offered second-hand, typically the seller has upgraded to DX7.   That makes me wonder what the differences are, other than the extra channel.   I would appreciate it if anyone who's used both could let me know what, for them, was the reason for upgrading.   There's a pretty massive price difference, but if I'm going to find the DX6i too limiting I should maybe stick with what I've got.    I'm really not planning anything except gliders or electric gliders, definitely not helicopters or multi engine so can't really see the need for loads of channels. I was thinking DX6 rather than DX5 to get the electronic travel adjustment, exponential rates, and independent dual rates.  One day I'll need v-tail mix, and maybe some other odd-ball combinations.  Once you start using these things then model memory sounds a good idea, but I wouldn't need more than a few. Ta in advance, Tony S

Cheers.  Trouble is that with ATC a "courtesy call" tends to get treated as asking permission, and also invites all sorts of other requirements. I remember when we used to fly from a 1750' hill with the CTA above us at 3000'.   At that time we were allowed into the airspace without clearance, but we used to call ATC as a courtesy.    Although we were flying there by right, they often used to try to impose limits, for example telling us not to go above 1500'  (clearly nonsense when the hill's 1750'), or insisting that we phone them again once we had stopped flying.

Hi, I am trying to find out the official position for flying an RC model in Class D airspace, where that airspace goes right down to the surface.    So far I have checked CAP 658 and based on that it appears that only models over 7kg need a clearance (ANO Article 98).     I can't see any reference to the legal position for models below 7kg.    Of course I can see that in some circumstances you'd fall foul of the generic “A person shall not recklessly or negligently cause or permit an aircraft to endanger any person or property.”   Can anyone clarify?   As well as the strict legal position, I would also be interested in any conventions normally followed. Thanks,  Tony S

Posted by paul@scc on 11/04/2010 18:41:24: My Mate gave his FMS it's maiden today.   Looking good.    Very very nice picture.  What lens did you use?  Is this cropped from the centre, or as you framed it?   Cheers.