Chasing my tail with programmable mixes on a FutabaT7CP

[Phil Cooke]

Not sure if there IS actually a solution to this (other than use another Rx) but thought I'd raise the question with the wise on here...

I've recently acquired a nice little Me-163 for slope use, its fitted with a std servo in each wing and a small Jeti 5 ch Rx. In setting up my T7CP Tx I've encountered a few hurdles, all now cleared bar one, something I've not seen before.

The first problem was that with only 5 ports on the Jeti Rx I couldn't use Ch 1 and 6 as would be conventional for the Elevon mix on a Futbaba Tx, so with servos plugged into Ch 1 and Ch 2 and with the mix activated I was effectively getting Elevator response when I moved the aileron stick, and Aileron movement when I twiddled the elevator stick. I've combatted this by creating 2 programmable mixes, I've effectively 'slaved' Ch 1 to Ch 2 on one mix, at 100% + and - and then slaved Ch 2 to Ch 1 on the other to the same degree. This sounds mad as a pint of chips, but it appears to work fine, and with a little bit of fine adjustment on centres, rates and expo I quite quickly got to a flyable programme.

Now the problem. With everything set up and centred nicely I don't even know why I tried this on the bench, but for some reason I tried the effect of the trims on the Tx - and of course ELEVATOR trim now gives aileron movement, and AILERON trim now adjusts the elevator.

Without the use of a more capable Tx or fitting a std 6 ch Futaba Rx and getting rid of the slave programmes is there any way of fixing this cross trim effect on the tranny???

Told you it was a silly one.

Look forward to hearing your thoughts - thanks in advance

[Frank Skilbeck]

If you can't reassign channels, what about programming it as a V tail, i.e. elevator and rudder, and then putting in a rudder aileron mix and making the aileron trim active on rudder, would that work.

Also have you done an elevon mix, for that I would have thought you would have plugged into the aileron and elevator ports, what you've done sounds like flapperons (But i maybe wrong as I don't have a T7CP but on my old FF6 for elevon mix they went into 1 and 2)

[Phil Cooke]

The Servos have gone into 1 and 2 and the Elevon mix is activated. Tried the V-tail mix as part of tonights experimentation but got to exactly the same result, went back to Elevon mix to try again but same result. Its all working fine apart from the digital trims.

[Frank Skilbeck]

Phil, it couldn't be something as simple as swapping the servos around, i.e. the one that is in 1 move to 2 and vice versa and then using servo reverse on the relevant channel. Even Futaba wouldn't have made setting up an elevon mix that complicated.

Edited By Frank Skilbeck on 27/07/2015 23:00:33

[cymaz]

Have you tried Page 42 + 43 of the manual? Here is a short extract

5-channel receiver? Set up AIL-2 (see p. 43) in FLAPERON. FLAPERON:

Uses CH6 for the second servo (see AIL-2 to use CH5 orCH7.)
Allows flap action as well as aileron action from the ailerons.
Provides FLAP-TRIM function to adjust the neutral point of the flaperons for level flight. Also allows aileron differential in its own programming.

full link here

Edited By cymaz on 27/07/2015 23:02:41

Edited By cymaz on 27/07/2015 23:03:23

[Phil Cooke]

Ill give it another go with the servos swapped over - you might be onto something. My first post is incorrect, Elevon SHOULD be Ch 1 and 2, not 1 and 6 as I typed, so there should be no need for the slave programming Ive done... there might be another mix employed somewhere on the programme when I read it across - Ill wipe it all clean and start afresh.

[Frank Skilbeck]

Just read the manual online, elevons are on page 45 and it is channels 1 and 2, sounds like all you need to do is reverse one servo and then if this give ailerons in the right direction but reversed elevator swap the servos over. And get rid of all the other mixes

[Phil Cooke]

Frank, you were spot on.

It was as simple as reversing 1 of the 2 servos - this was left reversed from the copied programme at the start of the set up. Amazing. Having one servo reversed with the elevon mix activated made ailerons operate as elevators and elevators worked as ailerons, then, having not identified the simple route cause and corrected just that, I went into all those silly mixes thinking it was a limitation of the Rx - but it wasn't.

Anyway, with the mixes all out, the 2 servos in Ch1 and 2 as per the manual, and with the servos all operating conventionally, the elevon mix works perfectly, as do the trims.

Lesson learnt - when copying over old programs to new models reliant on mixes like Elevon or Flapperon ensure you are working from a clean slate to avoid silly confusion...

[Frank Skilbeck]

now all you need is the right wind and then we can have a flight report