Air crash investigators needed.

I ditched my 48” Extra yesterday, and I’m trying to piece together what I did wrong and also what’s salvageable from the wreckage. The motor and speed controller are fine, as are the wings and the fuselage from the wing tube back, it’s just a little bit of damage to the front end. :pinch:

I tested the tail plane servos whilst they were still within the airframe and noticed that when I moved the elevator the rudder twitched. I’ve now taken all the servos out and I’m trying to get to the bottom of the problem.

Details:
Elevator Servo: Hitec HS-5085MG
Rudder and Aileron servos: Hitec HS-5065MG
Receiver: Spektrum AR6210 (DSMX)

Issue:
When moving the Elevator servo the Rudder servo occasionally twitches.

Replacing the Rudder servo with an Aileron servo (i.e. identical servo) = No twitches, this would suggest a dodgy servo.

Putting the Rudder servo back in and exchanging the Elevator servo (HS-5085MG) with an Aileron servo (HS-5065MG), = No twitch, so maybe it’s not the servo.

Finally go back to the original twitchy configuration but try a different receiver, an AR7610, and the rudder servo doesn’t twitch!

If it was the servo, the same issue should be replicated using a different receiver but it’s not…

…exchanging the rudder servo with an identical servo in the original receiver does rectify the problem suggesting it is the servo…

…I’m confused, so far it seems to require a unique combination of one particular HS-5065MG servo together with an HS-5085MG servo in a AR6210, change anyone of these components and the twitch isn’t there.

Anyway here's a video to show what's happening:



Any ideas? Further tests?

Hi Chris
When you swapped the aileron rudder servos did you move all the other controls to test for jitter?

Also what battery did you use and what voltage was it giving?

Try the tests with all servos connected.

Hi Ron,

I did connect all servos to check for jitter but kept it simple with just the two in the video. The receiver is running off of the ESC BEC and giving out 6v (Measured).

Repeat the test with the radio about 2 (or more) metres from the rx. You might be experiencing swamping at this range.

BTW, if you have collected all the little pieces of ply you should be able to jigsaw the front end back together again. It'll take a while, but is a lot quicker than making new parts and scarf joints.

Hi Mike,

:blush: I think you might have pin pointed the issue, I think I must have been swamping the RX :blush:

The odd thing is that it would twitch without fail, now I can only get it to twitch occasionally, if at all! Even with the TX next to the RX.

As to the bit's, I've got most, if not all of it. I plan to park it for a while and revisit it on a wet Sunday.

ok so with the rx thats giving you a twitch. if you swap the elevator and rudder servos in the rx do you get a twitch?

on a side note, I have seen way too many problems with spektrum over the years. Some people never have an issue ever other get lots, I speak to one of the flybarless manufacturers on a regular basis, he's very critical of the components they use, apparently they are mostly domestic components which aren't designed for the temperature ranges etc that we see regularly.

Hi Adrian, the last test I did before the twitch disappeared was to swap the elevator and rudder servos in the RX, I could not get either to twitch, so I put them back in their appropriate ports and could only get a twitch on the rarest of occasions, usually not at all. Slightly irritating as I couldn't then know for sure it was as Mike suggested that I was swamping the RX.

You're not the first person to have mentioned a possible Spektrum problem, are you talking about the old DSM2 protocol or the newer DSMX. The RX also seem to like to see a healthy voltage.

I think there is also some confusion about the satellite receivers, some people think that because it has two antennas coming out of them that they should be at 90º to each other, but apparently they are part of the same antenna and so should be in line with each other, which would seem to concur with the way Spektrum molded the plastic case. It is the RX antenna and satellite antenna that need to be at 90º to each other.

It wasn't the RX or TX that caused my crash, that was all down to me :blush: , I just want to be confident in is that the Servos and RX are okay before I use them again.

Welcome to the club,

Chris

another thought,

set up a pmix of throttle to elevator. waggle throttle, elevator servo moves, does rudder twitch.

or do you have another tx you could try?

Thanks Adrian,

I only have the one TX. I've written a note with your suggested test and put it with the RX, I've packed it all away, along with the remnants of the plane so it's all out of sight for the moment. When I eventually come to do something with it all, I'll be sure to test it all thoroughly and if I have any doubts, I just won't use it.