SR10 Pro changes trim when active

[ccaputo]

I hope I can explain this clearly enough. Archer SR10 Pro receiver/Ethos/X20S combination here.

When adjusting the elevator gyroscopic deflection within the SXR app on the radio, I notice that my elevator trim varies considerably between the 2 states of SXR enabled and SXR disabled. And this is irrespective of whether gyro mode being is in off, stabilize mode or auto-level.

Probing further I discovered that when the "Ele inverted" needed to be set to OFF this also reverses the normal surface deflection from the sticks. I don't recall this behavior in older S8R or S6R receivers. Shouldn't the "Ele inverted" option just change the direction of elevator servo travel as directed by the gyro and not also the sticks?

The result of this behavior is moot when there's no need for subtrim. But when a surface requires sub trim, the gyro reverses the direction of necessary subtrim! Thus, if the gyro is disabled the elevator is wildly out of trim compared to when the gyro is enabled. Not a big deal, but something to be aware of if turning on/off the gyro functions of the SR10 Pro.

This just doesn't seem logical to me. But the behavior was reproducible in the last 3 or 4 firmware revisions from 2.1.10 thru 2.1.14.

 

[HENNY]

I hope I can explain this clearly enough. Archer SR10 Pro receiver/Ethos/X20S combination here.

When adjusting the elevator gyroscopic deflection within the SXR app on the radio, I notice that my elevator trim varies considerably between the 2 states of SXR enabled and SXR disabled. And this is irrespective of whether gyro mode being is in off, stabilize mode or auto-level.

Probing further I discovered that when the "Ele inverted" needed to be set to OFF this also reverses the normal surface deflection from the sticks. I don't recall this behavior in older S8R or S6R receivers. Shouldn't the "Ele inverted" option just change the direction of elevator servo travel as directed by the gyro and not also the sticks?

The result of this behavior is moot when there's no need for subtrim. But when a surface requires sub trim, the gyro reverses the direction of necessary subtrim! Thus, if the gyro is disabled the elevator is wildly out of trim compared to when the gyro is enabled. Not a big deal, but something to be aware of if turning on/off the gyro functions of the SR10 Pro.

This just doesn't seem logical to me. But the behavior was reproducible in the last 3 or 4 firmware revisions from 2.1.10 thru 2.1.14.

This sounds like you have not accurately leveled / calibrated the model, so when you switch to auto it's trying to level the model to the wrong point.

 

[ccaputo]

It does not appear to relate to calibration or self check, I have dug a little deeper and confirmed this behavior on 2 different SR10 Pro's.

1. For example, the position of "Ele inverted" within the SXR config app on the radio can be in only one position (ON or OFF) that correctly deflects the elevator to compensate for nose up/nose down.
2. The position of this slider directly affects the "polarity" of the PWM signal that comes from the transmitter and reaches the servo. I am referring to normal operation. Stick movements (as well as subtrims) affecting service deflection. This has nothing to do with auto level or stabilization as GYRO is OFF.
3. It just so turns out that when the "Ele inverted" switch is in the OFF position it creates these "reversal" issues and when it is in ON position it does not.
4. I am giving elevator as an example, but I confirmed it can happen on all surfaces.

I confirmed that the S6R and S8R never worked this way. Whether the gyro was enabled or disabled, a left aileron control input always caused a left aileron deflection, etc.

Sub trims work much the same way as a stick deflection. Therefore, when "Ele inverted" switch is off my sub trim is changed from -5% to +5%, for example, thus deflecting the surface out of trim. When the "Ele inverted" switch is on, the subtrim does not change.

On browsing forums on internet I have found a few people who echoed these findings so I apparently am not alone.

This is bizarre behavior coming from a gyro that I cannot explain but I am hesitant to say it's a bug in the firmware, because I would expect a larger audience of people talking about it.

I would appreciate anyone's ideas. Thanks!

 

[ccaputo]

One small but important related point:

The reason this probably hasn't come to people's attention is most of us set up our plane, including gyro, with SXR enabled, adjust deflections appropriately and never think about it again. But on the off chance that you're at the field one day and for some reason decide to fly not with just the gyro off (on 3 position switch), but disabled via the SXR config app, some of your surfaces may be significantly out of trim (depending upon how much trim/subtrim is dialed in) and may deflect in the opposite direction from intended! If you fail to inspect the surfaces before takeoff, this would almost certainly lead to a very rapid crash (especially if aileron or elevator are involved).