Futaba T6K Flap-Elevator Mixing? Arrows Bigfoot electric model

[Skippers Walker]

I have the flaps set up to operate on a 3 position switch (C) Channel 5 on my Futaba T6K TX. Please is there anyone that can provide a simple to understand method of mixing the Flap/Elevator to prevent 'ballooning' when the flaps are lowered incrementally? I have a manual but I'm getting a bit confused as to how to set the required values during the two down flap positions.

Thanks SW 

[MattyB]

From the manual it looks like you can only set one compensation position, there is nothing about two stage flaps. It may well just be a limiation of the TX, whcih sis at the bottom of Futaba's range. This kind of inflexibilty is exactly why I dislike the canned mixer, "you have to set it up like I tell you" approach beloved of Futaba, Spektrum et al...

Edited July 5, 2023 by MattyB

[MattyB]

Ah, hang on... Enable the mix, then flip switch C between it's different positions whilst you have this menu up. At each switch position setdifferent weights and offsets for n (don't worry about what they are initially, just make them verydifferent so it is clear what is happening when you flick the switch). Once done, flip the switch back and forth, watch the elevator, and validate it moves to different positions for each change of state. If you can prove it works this way, then you can refine the actual rate and offset values to give you what you want afterwards.

[Gary Binnie]

It's a standard mix for gliders, 'Butterfly' in your manual. That is generally using the throttle stick for flap deployment. 

 

Another way is Program Mix 4 which is a five point curve. The ballooning effect is strongest in the first 1/3 of flap travel (on gliders where the flaps lower to 80° plus) so the curve is set with most of the compensation happening at the start of travel. The settings are usually guessed or sometimes given as a distance movement by the designer (i.e. flaps down 50 mm, elevator up 5 mm) for the initial settings then the values are fine tuned by pulling the flaps and adjusting the values in the air or doing a series of flights and adjust the values between each.

 

Another method would be to use flight modes but it looks like that transmitter doesn't have the facility. You could set one flap position and elevator trim for take off and another for landing (and a 'clean' wing position that I call 'cruise').     

[Gary Binnie]

Just reading the first post again, ballooning implies the model nose is pitching up but the effect of positive flap is to pitch nose down and the elevator compensation is nose up to stop it. Or...if you've set some elevator compensation it was in the wrong sense.

 

If the model is actually rising (fuselage level) then it could be carrying too much speed for the approach.

Edited July 5, 2023 by Gary Binnie

[MattyB]

1 hour ago, Gary Binnie said:

It's a standard mix for gliders, 'Butterfly' in your manual. That is generally using the throttle stick for flap deployment. 

 

This is a power model, so unfortunately he is not going to be able to do that with a TX like this that is prescritptive on how it must be setup. 

[Skippers Walker]

Hmm! I just wanted to set say 5% down elevator for flap  down position 1 and say 8% down elevator for flap down position 2 (full down).  The flying videos suggest an 'up nose' ballooning effect when any flap is applied. Still confused, perhaps best to leave well alone and try and compensate with manual input of down elevator?

SW

[MattyB]

Have you tried my second suggestion? It will only take seconds to do that test. Unless you experiment you will never truly learn how your TX works or be able to use its maximum capability.

 

9 hours ago, MattyB said:

Ah, hang on... Enable the mix, then flip switch C between it's different positions whilst you have this menu up. At each switch position setdifferent weights and offsets for n (don't worry about what they are initially, just make them verydifferent so it is clear what is happening when you flick the switch). Once done, flip the switch back and forth, watch the elevator, and validate it moves to different positions for each change of state. If you can prove it works this way, then you can refine the actual rate and offset values to give you what you want afterwards.

 

[Skippers Walker]

Thanks Matty I'll give your suggestion a try 🤔SW

[MattyB]

21 hours ago, MattyB said:

This is a power model, so unfortunately he is not going to be able to do that with a TX like this that is prescriptive on how it must be setup. 

 

Skippers, I see you may have been confused by this post - apologies. I'll try again...

 

Basically your TX has multiple setup modes - one mode each for multicopters, gliders, airplane (their term) for power models, and helicopters. You select which mode you'll use at the start of your setup, and the choice you make affects the mixing options you have available. 

 

The butterfly mixing (more commonly known as crow braking) that Gary mentioned is only available in glider mode, but as you need throttle on the throttle stick for your model. This is what I mean by "prescriptive" - Futaba have decided what functionality you need for each model type, and you can't do anything to change that. As a result you will have to stick with airplane mode, whereas in some other TXs you have absolute flexibility to setup any model with whatever mixing and control setup you like.

 

[Dave Greer]

My use of the T6K is gliding and e power but, as with most computer radio choices, the more you experiment the more you find and I particularly luv the light and compact T6K for long soaring flights.

 

Page 70 Pmix for four free mixes I assume to be common to both glider and power and has sorted me out on all the soaring mixing tricks I wanted over and above the easy to use stock offerings.

 

Would not trade the T6K for nix, especially the pensioner size text. 🤠

 

Cheers

Dave

 

 

[Skippers Walker]

I now begin to understand Matty. I've just tried your suggestion, setting 15% as a nominal down elevator mix to Flap down position 1. Without touching the 'OFFSET' setting I appear to be getting a slightly increased down elevator mix when selecting full down on the Flaps. I haven't quite figured out what effect changing the 'OFFSET will have. At present the values in offset visually change from -100% (-100%) when the flaps are fully raised, -100% (0%) at flap down 1 and 100% (+100%) when flaps 2 are fully down. I apologise for appearing rather dumb about all this but the T6K is my first modern TX since graduating from a Fleet 35MHz system from the 1970's! I'm approaching 80 now and a bit slow in absorbing the modern tech but very willing to keep trying.

Thanks for your patient explanation about the issue. Thanks also to the other folk for their well intentioned offerings about my question😁

SW

[MattyB]

Sounds like you are making progress, good job 👍.

 

OK, next step... When you move the flaps to position 2, what happens to the elevator then? Does it move further, stay where it was in position 1, or revert back to the same position? This will tell you more about what is going on, and help us determine what to do next.

 

Alternatively you can follow @Dave Greer's recommendation above, as the P.Mix functionality will definitely give you what you want with a little more experimentation; P.Mix 4 is probably the best bet in this instance as you can tune the response with a curve. I'm afraid it is more complex than the flap to elevator mix though ...

 

 

 

 

Edited July 6, 2023 by MattyB

[Skippers Walker]

Thanks again Matty.

Re the current mix response that I've achieved; with a 'Rate' set at 15% I appear to get a small elevator down movement in flaps down Pos 1 (about 1/2 flap) and at full flap Position 2, the elevator down movement has incrementally increased ...possibly to 15%?. I'll have to experiment more. 

The folk that I fly with are predominately Spektrum users and therefore the programming on their TX's is quite different to Futaba's approach. I do find the manual for my R/C kit written in a tad Chinese/English at times. The old and limited Fleet system mixes were all achieved with manual slider switches in the rear of the TX  

Such is progress.

SW

[MattyB]

On 05/07/2023 at 10:38, Gary Binnie said:

Just reading the first post again, ballooning implies the model nose is pitching up but the effect of positive flap is to pitch nose down and the elevator compensation is nose up to stop it. Or...if you've set some elevator compensation it was in the wrong sense.

 

If the model is actually rising (fuselage level) then it could be carrying too much speed for the approach.

Sorry, but I have to disagree with this - almost every model I’ve flown with flaps balloons on deployment, unless you have waited until it was on the ragged edge of the stall before putting them down. This post (and those linked from it) should help; the  guidance is from Mark Drela, probably the most famous model aircraft aerodynamicist at least when it comes to gliders. There are also some comments from Joe Wurts, a world class thermal and slope pilot, and also the goy who first demonstrated dynamic soaring was practical with a model glider.

Edited July 6, 2023 by MattyB

[MattyB]

5 hours ago, Skippers Walker said:

Thanks again Matty.

Re the current mix response that I've achieved; with a 'Rate' set at 15% I appear to get a small elevator down movement in flaps down Pos 1 (about 1/2 flap) and at full flap Position 2, the elevator down movement has incrementally increased ...possibly to 15%?. I'll have to experiment more. 

Sounds good. Final question…. If you have the mix menu open as you click the switch, what happens to the value against RATE as you do so? My bet is that it doesn’t change, but tell us what you see. If it doesn’t change that implies that at position 2 you are getting 15% comp, and at pos 1 half of that (7.5%) if the compensation mix is essentially a straight line. 
 

This may be easier to confirm if you set the compensation value to 100% temporarily, that way working out how much movement is occurring at pos 1 will be easier. Remember to look at the change in angle of the servo a rather than the movement at the elevator though, as the latter will be affected by linkage geometry. 

[Skippers Walker]

You are right Matty, at last the penny has dropped in my rather tired brain. I used your suggestion of setting a high value in flap switch position 2 (fully down).  When moving the switch to flap down position 1 (half flap), the corresponding elevator movement does appear to be 1/2 the value at position 2. A straight line! 

 

I'll certainly look at using P.MIX 4 programme (preferred by Dave Greer), at some stage and experiment with the results from various inputs. For simplicity's sake for now, I'll fine tune the achievable settings using the FLP-ELE MIX and carefully fly the model at height and try to find a happy medium for the two Flap down positions.

Thanks again for your guidance, very helpful

Happy flights

SW

[MattyB]

Good stuff. The main thing to take from this is that, when learning a new TX, anything other than the simplest tasks is going to require you to do some practical experimentation. Given the quite advanced functionality available on even the most basic TXs these days you can't expect to read the manual and acheve it first time purely from reading the manual, so get a brew on, settle in your most comfortable chair with the model in front of you, and play with it for a bit until you understand what is going on. Youtube also helps here, though there tends to be fewer videos on Futaba TXs than Spektrum and the open source ones.