THEMA:

Hi All,

I have had my DS16 for a few years now, but over the last 8 months it has developed a strange fault which has taken me a while to trace to the transmitter.

Occasionally - maybe once every 30 flights or so - I will take off and discover that I need to put in maybe three or four clicks of rudder trim. It will then be OK for the rest of the flying session. At the start of the next flying session the next day, I will usually have to take those three clicks out.

The trim change never happens during a flight - only when the transmitter has been swithed off after flight then back on for the next flight.

It seems to be more likely to happen when I have started flying in a cool morning and then the day has warmed up.

It affects both of my pattern models and I have swapped servos and even brand of servos to check it wasn't a servo issue. More recently, I have noticed that the throttle (I fly electric so no servo) is also affected with similar symptoms; but never the ailerons or elevator.

I fly F3A at a pretty high level, and have now had a couple of competition flights affected so it is becoming a real pain. At this point in the season I am loathed to return it for repair as I would have to buy a second Tx as I can't afford to miss important competitions.

Has anyone had a similar problem?

Cheers, A.

Hi,

strange....and not good for F3A pattern flying.

Question:

You set rudder trim so that the rudder surface is straight to the fuselage.

If then switching ON the TX/RX, is the rudder surface than not beeing anymore straight ? Can you see that immideatly after turning on the radio ?

Never herad about such a TX issue; but you never know in modelling...

We also fyl F3A FAI pattern and we know that especially the modern models are very very sensetiv to rudder or wrong rudder trim. We are flying BJ biplanes BISIDE and new IMMORTAL. We are using SAVOX 1256 servo on rudder.

Regards
PW

ups ... upload from Ihone does not work correctly

Hi PW,

Thank you for your response.

Yes, these deep fuselage pattern models are very sensitive to rudder trim! I have now used four different rudder servos in my two Leptons - Alturn 645MG, Futaba BLS551, Savox SC-1251MG and now Savox SB-2263. I also use closed-loop for rudder, partly to prevent any slop and issues with pushrods expanding in the sun. When I first noticed this problem I built a centering test jig with a 1m long servo arm and tested all of these servos at 15degC and 30degC. The Alturn had a small offset equal to approx 1/2 trim click, the others were all perfectly repeatable. But I have had the in flight trim problem with them all.

I haven't noticed the rudder being physically offset at power-on, but then 3 trim clicks is a very small amount. When it happens I notice straight after take off as I always continue straight to gauge any cross wind. But you have given me an idea - I will draw a straight line along the top of the fin and rudder which should make it easier to see any offset and therefore confirm it is present straight after power on.

The final thing that convinced me it had to be the Tx was when I noticed it happening on the throttle channel too - I had changed the throttle curve to give a very clearly defined point at which the ESC goes from brake-on to low-idle. With this clear point as reference, I noticed the same problem was occasionally ocuuring on the throttle channel.

I guess I will just have to find a slot in the calendar to return it for service / repair. Hopefully the turn around time is not too long?

Immortal looks like a nice design - from the "judges chair", I always thought the BiSide looked a little challenging to keep locked in, so I look forward to seeing an Immortal fly. Love the Agenda though, always presents very nicely.

Best regards, Adrian.

Hi Adrian,

I would control in servo monitor:

1.

if modell is flying straight, look at servo monitor "centering in percent" for rudder servo.

2.

now if you recognizied that you must trim rudder, please do not trim ! But land immideatly and check in rudder servo monitor, if the rate from rudder servo has changed.

BJ models are really great and yes.... rudder is very critical at this new F3a planes; but you need outstanding knife edge behavior for F-programm...

Regards
PW

That is another great idea. I will do so and next time it happens I will report back.

Thanks!