XPS Technical Support Forum

Jim,

I hope you and you family are well.

I had a failsafe event today with an airplane equipped with an RFU and an X10+ V2. 

I was flying through a stall turn about 200 feet away.  The airplane yawed to the left over the top and was flying downward with the top of the airplane facing me.  The throttle was as a low-to-medium setting at the time.  I started to pull out when the plane pitched up and continued until it was facing nose high, like it was trying to fly a loop.  I did not command that additional up elevator, I was just going to level out.  I recovered airspeed and continued flying it.  It was only a momentary event, lasting a second or two.  I felt that something went wrong so I immediately landed safely.

With the airplane safely on the ground I remembered that my failsafe commands are:

   THROTTLE OFF and
   ELEVATOR UP

Since the throttle was relatively low during the maneuver I did not notice that the throttle may have gone all the way off, but I did experience the up elevator.

I reckon that it was not a power problem because the up elevator went into effect.

My theory was that the RFU antennas were blocked by the airplane's battery and wiring at the "perfect" angle.  I verified it by taping the "range test" button down and walking far enough away to cause a failsafe.  Than I moved in a few steps to where the controls were solid.  Then I oriented the airplane around to various orientations relative to the transmitter (which was sitting still on a chair) and found an angle that caused the system to go into failsafe.  The angle was similar the orientation at the time of the stall turn maneuver.

Only thing - now this gets eve weirder:  My failsafe was set up to put the elevator DOWN, not UP!  I must have not set the failsafe again after putting the X10 into the new plane.  But I felt an uncommanded UP elevator control.  I have no good explanation.  Maybe power?  Maybe the flight battery shifted aft while the plane was going up into the stall turn?

I do not like my current RFU antenna installation because while both antenna elements are oriented 90 degrees to each other, they are both situated horizontally (picture attached).  I reckon with both horizontal, they both could be blocked in the same geometric plane.

I will relocate the RFU and its antenna elements so that one element faces downward and the other faces in a horizontal direction.

Do you agree that this was not a power problem because the servo moved the the failsafe position?  (I'm not ruling it out.)  The airplane uses a Castle BEC regulator set to 5.2 volts.  How about the horizontal and vertical antenna orientation?

Thank you,

Paul

If your failsafe was elevator DOWN (not up), then it is possible that you either had a power failure or that you were trying to pull-up and the servo moved to that position and a sporadic lockout occurred. This would hold the servo in that position until failsafe kicks in, which may not have occurred. If you are moving in and out of valid signals the elevator may stay there until you release it and you might not have released it until the up-line.

Moving the RFU's antennas to be a bit more separated would be helpful, especially since you can create a scenario where the battery (and possibly motor) do fully block the signal.

When you landed, was the RFU or the X10+'s LED flashing? That would indicate a loss of power.

(09-09-2022, 11:00 AM)XPS Wrote: [ -> ]If your failsafe was elevator DOWN (not up), then it is possible that you either had a power failure or that you were trying to pull-up and the servo moved to that position and a sporadic lockout occurred.  This would hold the servo in that position until failsafe kicks in, which may not have occurred.  If you are moving in and out of valid signals the elevator may stay there until you release it and you might not have released it until the up-line.

Moving the RFU's antennas to be a bit more separated would be helpful, especially since you can create a scenario where the battery (any possibly motor) do fully block the signal.

When you landed, was the RFU or the X10+'s LED flashing?  That would indicate a loss of power.

Jim,

Regrettably I did not look at the LED on the RFU or X10 after landing.  Everything was working normally (of course).  It would be nice to have black box logs on both the transmitter and the receiver to determine what my control inputs were and what controls were seen by the receiver and or output by the X10 during the perceived event.

I reckon that when the X10 loses a valid signal from the RFU, the two-second failsafe countdown begins.  I also reckon that any new received good signal aborts the 2-second countdown.  So you could have brief periods of controls getting blocked with some getting through.

I agree with your assessment that the signal was blocked and the system momentarily locked out while I was giving an up elevator command - that's an explanation that makes sense for what I experienced.  I should be glad that it did not go into failsafe - if it did, and gave my incorrectly configured down elevator command, the airplane surely would have crashed.

I just factory reset the RFU and X10, and re-programmed them.  I found that the RFU's default telemetry type is 1 = on, and not 3 = off as indicated in the documentation.  It comes up as 1 after a factory reset (firmware v1.4).  I do not want the telemetry signal on.  Can you please verify that 3 is the correct setting if I do not want to use telemetry?

If 1 = on, then that means I had the telemetry signal on during my mysterious event - could that have made any difference?

Thanks,

Paul

Looking at the source code (because it's been almost 9 years ago that this product was created), it seems that the telemetry setting is NOT changed on a reset. The units are shipped with the telemetry set to 3 (off). Having telemetry enabled might have helped if you had a laptop recording the data, but it would not have changed anything otherwise.

(09-09-2022, 06:51 PM)XPS Wrote: [ -> ]Looking at the source code (because it's been almost 9 years ago that this product was created), it seems that the telemetry setting is NOT changed on a reset.  The units are shipped with the telemetry set to 3 (off).  Having telemetry enabled might have helped if you had a laptop recording the data, but it would not have changed anything otherwise.

Ok, makes sense.  I did use the telemetry almost nine years ago when I was just learning about such things (I pelted you with questions about it).  Apparently I never changed it back to off on this RFU, which I am using for good old RC flying.

I have the RFU and X10 installed in a scratch-built Jensen Ugly Stik airplane.  The shape of its fuselage and locations of its motor, battery and servos makes it challenging to find a spot for the RFU and its antenna elements that are not behind the plane's equipment at some orientation.

Then I remembered that the X10 supports a second receiver.  Can I use a Nano for the second receiver?  Would the RFU and Nano act to give diversity, that is, if one receiver can't see the transmitter's signal and the other can, the X10 would take the good signal and a lockout could be prevented?

New Information

While testing on the bench I noticed uncharacteristic flickering on the X10 LED. I took it outside to get away from my home wifi router and the flickering persisted. Then I performed a range test with the transmitter button pressed for low power mode. I could get no more than 30 feet before failsafe kicked in.

I usually got about 125 feet doing the same test, so something is wrong with either the RFU or the X10. I'll check the programming again, but was curious if you do repairs if I send in the RFU and X10?

Thanks,

Paul

It could be the transmitter or antenna. The X10+ won't cause the flickering, that comes from a signal issue with the RFU. We can repair or replace the RFU, but this is far more likely to be a transmitter related issue.

(09-10-2022, 01:25 PM)XPS Wrote: [ -> ]It could be the transmitter or antenna.  The X10+ won't cause the flickering, that comes from a signal issue with the RFU.  We can repair or replace the RFU, but this is far more likely to be a transmitter related issue.

Replaced the RFU with a Nano Rx and got a successful 150 feet low power range test with the same transmitter.

Is the RFU damaged at all? Antenna ends or u.Fl connectors unsnapped inside of the case? We have never had a RFU just fail without being damaged. Did you try re-connecting it to see if it works again? I have seen this once with a Nano at an airfield that had a Nexrad tower in easily visible distance - and then they had to close the airfield because of it!

If it fails again, return it for a replacement.

(09-12-2022, 09:16 PM)XPS Wrote: [ -> ]Is the RFU damaged at all?  Antenna ends or u.Fl connectors unsnapped inside of the case?  We have never had a RFU just fail without being damaged. Did you try re-connecting it to see if it works again?  I have seen this once with a Nano at an airfield that had a Nexrad tower in easily visible distance - and then they had to close the airfield because of it!

If it fails again, return it for a replacement.

The RFU has no apparent damage, the connectors are in place and it wasn't in a crash.  I sent it to you by way of US Mail and kindly ask you to evaluate it.

Thank you,

Paul