Odd radio incident, Or not.

[John Wagg]

Coming a bit late to this but have you tried a different RX ?

I was going to suggest the same a Dickw and see if the servos returned to their "normal" mid position when trying one of the other Rx outputs.

I can't see it being a problem with the servos as both have moved the same amount. That is unless there was a mechanical issue due the crash impact. i.e. - Both servo arms jumped the splines ?

If none of the above then I would suspect some change in the TX.

 

 

 

 

[Paul De Tourtoulon]

Am i the only one who regularly does range checks, with and without the engine running, 41.000 and 2.4.

[John Wagg]

37 minutes ago, Paul De Tourtoulon said:

Am i the only one who regularly does range checks, with and without the engine running, 41.000 and 2.4.

If it was a range issue then wouldn't the servos return to normal when back in range ?

Edited September 16 by John Wagg

[Andy Stephenson]

Could it be that the ailerons were plugged crossed and the effect was only noticed on finals?

[Martin Harris - Moderator]

That’s a good thought.  Having both ailerons droop would give a wash in effect and increase the possibility of a wing drop as you slowed up.  I don’t suppose you recall needing to re-trim the elevator during the early stages of the flight?

[J D 8 - Moderator]

Hi All, Issue is still where I left it last night. Busy on this proper summers day here  cutting grass and shed repairs/painting chicken shed for Batam birds, black one called Cilla. Back later.

[PatMc]

32 minutes ago, Andy Stephenson said:

Could it be that the ailerons were plugged crossed and the effect was only noticed on finals?

That sounds like the most likely scenario, in fact possibly the only logical explanation.

[MattyB]

4 hours ago, Dickw said:

How a bout swapping the connectors around at the receiver (e.g swap one aileron and rudder, and one aileron and elevator) to see if the offset follows the servos or stays with the Rx port. That should confirm if a radio or a servo problem.

 

Dick

Good idea. Before doing that though now I would definitely  try a totally new model memory and setup the ailerons from scratch and see if they still behave the same. 

[MattyB]

35 minutes ago, MattyB said:

Good idea. Before doing that though now I would definitely  try a totally new model memory and just setup the ailerons from scratch and see if they still behave the same. 

That way when you do start swapping plugs around as suggested by Dick the Tx mixer setup has already been crossed off as a potential root cause.

Edited September 16 by MattyB

[John Wagg]

Take a good servo and check it on another model set up with the transmitter.

Then plug the servo into one of the sockets of the two affected ones. Does it droop as per those.

If not then cancels out servo problem. If it droops then Rx or TX.

[J D 8 - Moderator]

Been a long day, just got in having been rounding up those darn birds in pic above. Nice tidy shed for them but had to get them down from small tree where they decided to roost.

Anyway, John W, have not yet tried different RX yet.

Andy S, and PatMc No way are aileron connections crossed, model is kept assembled and fits in car as is.

 

 Matin H, No retrim on elevator but did on aileron a bit a two/three times, this could be a sign of problem developing?

 MattyB, My next move I recon along with John W suggestion

  Rather worn out to fiddle with tonight, back soon.

[Phil Green]

Feed the servos 1500uS from a tester and see if they centre. 

Removes any radio doubts. Basic faulting techniques, divide & conquer 🙂

Edited September 16 by Phil Green

[John Wagg]

17 hours ago, John Wagg said:

Take a good servo and check it on another model set up with the transmitter.

Then plug the servo into one of the sockets of the two affected ones. Does it droop as per those.

If not then cancels out servo problem. If it droops then Rx or TX.

Can also suggest, if you have a spare Rx to substitute that for the one in the Citabria and see how that performs.

[RottenRow]

My thought is that your original suggestion that you had got caught out either by a gust or by flying too slowly downwind caused the model to stall and drop into a spiral dive.

 

The dropped ailerons then occurred when the model hit the ground (tussock). The sudden deceleration could have caused the ailerons to force the servos / pushrods. Then one of the following would have happened:

 

The pushrods kinked which effectively shortened them.

 

The horns have got bent backwards.

 

The servos jumped a tooth on their output gears.

 

The servo arms moved on the output splines. This can happen if the wrong arms are fitted (mixing different makes for example).

 

I would doubt that the transmitter aileron stick pot would be the cause (shifted centre) because that would make one aileron move upwards. The same goes for the Tx aileron trim.

 

You have already discounted a mix in the Tx (flapperon mix). Not sure how a faulty receiver could cause an offset in just the two aileron outputs, but easily proven by substitution.

 

I’ll be interested to learn the final outcome.

 

Brian.

[Cuban8]

Not familiar with modern Futaba gear, so just wondering if their trannies have a 'Servo Monitor' display as with my Spektrum DX7/DX8 gear. Very handy as a graphic display of all the channel outputs as you waggle the sticks and operate switches etc.

Any offset to the dual aileron servos commanded by the TX would be very clearly shown and an indication as to whether that movement was intentionally programmed or not.

Just a thought.

 

Edited September 17 by Cuban8

[Paul De Tourtoulon]

38 minutes ago, Cuban8 said:

Futaba gear, so just wondering if their trannies have a 'Servo Monitor' display

Yes they do.

[kc]

I tend to agree with Brian's explanation but I would add two other items that could affect it would be the spar that holds the hinges or the servo mounts may have moved.   If servo mounts are both fitted to the same spar they could both move.  Holding the ailerons whilst operating aileron stick might tell if some internal servo  mount movement occurs.

[Cuban8]

1 hour ago, Paul De Tourtoulon said:

Yes they do.

Well, if that's the case, if the servo monitor shows the ailerons deflected from centre with sticks centred, that suggests that the tranny is moving the output as  commanded by a setting or mix or whatever - if showing a centred monitor position (with servos previously in the correct centre position but now deflected down) then I'd have thought that would most likely indicate an issue external to the TX. If no clear fault can be found and the other models programmed in the tranny are OK, then I'd delete the 'faulty' programme and start over again with a clean sheet and keep a close watch. Odd that it just happened to be the twin ailerons that were affected rather than some other random weird combination of unrelated controls.

This sort of thing can drive you nuts - look at the way your smart phone has a mind of its own sometimes -  but it is unsettling compared to a phone app playing up and a model possibly doing something nasty.

[J D 8 - Moderator]

Awww rats,🙄 I took the model apart this evening  for a thorough check of everything and I am embarrassed to admit I did not do a good enough job the first time or second time.

Those who suggested spline slip on servo arms are correct, with the push rods off I was able with a fair bit of force able to make both arms slip.

  I think what led me up the garden path was that both had slipped exactly the same amount along with the fact the model had very little damage [ cracked cowl]  from the impact.

Still I am pleased to find it is not a mystery radio issue and was just a boo boo by me as I had first  thought of caught going too slow in a gusting crosswind. 

  Going to pull out those wing servos now and see what they are as I did not build this model it was a swap for an Easy Pigeon I restored.

 Cuban8, Did find the servo monitor page and all normal. 

 Thanks to all who responded, hope I did not waste to much of your time. John.

[RottenRow]

I'm glad that you found the problem.

 

A friend recently had a similar problem with a secondhand model, on his you could wiggle some of the control surfaces by hand without the servos actually moving, just the arms, so it looked like the servos were moving. His model had twin elevator servos, one with and one without the problem. It took a while to find out why it would never stay in trim.

 

Hopefully the servos themselves get a clean bill of health and you can find the correct arms for them.

 

Brian.

[john stones 1 - Moderator]

Pleased for you, unresolved issues create doubt in your gear.

[Geoff S]

It would be easier if all similar sized servos had a standard number of splines so that there were fewer 'issues' when an incorrect servo arm was fitted and was apparently OK.  I try to keep and label spare servo arms with their source but, I admit, not always.

[Chris Walby]

Surprising the amount of force exerted with an unplanned arrival. I had a 80 inch Seagull model go in from about 40ft. lawn dart as the entire front end was destroyed, but the surprising thing for me was the aileron and flap servos including there pockets ripped clean out of the wings. either breaking the control horns or pulling the control surface out of the wing! 

[Frank Day]

Shame about the damage but tufty grass did well. Its a weird one.

 

Never buy a Futaba Tx, planes just fall from the sky!!!

[Rich Griff]

So was the servo arm slippage on the servo output shaft caused by the crash, or by aileron deflection from an external source during flight ?

 

Was the servo arm the correct arm for that servo ?

 

Same effective spline diameter and number of splines, or worn components ?

 

Glad you have found the culprit.

 

So so glad it's not a *futaba fault*. Hopefully futaba controlled planes falling out if the sky will be due to " operator error ", which could be a very very long list......

 

A servo arm slipping with a relatively large *torque* force applied, one might expect a *aileron to control horn interface* failure or servo mounting ( less likely I would have thought ) failure.....

 

May I ask, what is the aileron structure ( solid balsa, no ply reinfirment, built up aileron structure ? ) and any sign of failure due to aileron movement whilst no control horn movement ?

 

Aileron hinges come into play....

 

Anyways, cause found, only limited damage to aircraft, and a reminder for us all to "check, check, check", and probably check again.

 

Absolutely brilliant weather again.

 

Cheers John.

Edited September 18 by Rich Griff