Autopilot PreFlight Test and SPD Warning

[lynnb]

We have about a hundred hours on our RV-10 with Dynon HDXs with the Autopilot panel installed. On preflight we'll turn on the Autpilot and test it by setting it in heading mode and seeing if it moves the stick left and right, and make sure we can over power and cancel, same with a climb. Today when testing, we would turn on the auto pilot, try and set it and then get a message the autopilot was disconnecting. Sometimes it would disconnect and sometimes I'd notice the SPD indicator replacing the AP at the top of the screen. This is the first time we've encountered this in the 100 flight hours and it happened on both ends of our flight when testing during our pre-flight runup. Now during the flight, it worked fine and at some point during the first runup when we were having the issue, it started testing fine. So is this an issue with the auto pilot, or is there just a setting that needs to be adjusted? The only thing that has changed since the last flight is the standard dynon US Aviation Database update was installed.

Not sure if it will help, but here's a link to the video of when we were trying to test it before our return leg:

New video · Sunday, Jul 18, 2021 ð¬

Tap to view!

photos.app.goo.gl

As always, thanks in advance,
Lynn

 

[lynnb]

Follow up for those watching, First steps from support:

Lynn,
I suspect it was seeing some airspeed when sitting on the ground. Let's make sure it is calibrated correctly. Go to the setup menu's, go to HARDWARE CALIBRATION > ADAHRS CALIBRATION > ZERO PRESSURE IAS / AOA CALIBRATION and perform the procedure, preferably in a hangar.
That should make sure the airspeed is truly zero on the ground. If we see any airspeed, it won't engage until airspeed is above the minimum airspeed.
Don Jones

 

[Rhino]

Did you recently upgrade to 16.0? It has speed limits for the autopilot, and it may be possible for it to cause problems if you don't have it configured correctly. Go to Setup Menu>Autopilot Setup>Pitch Axis and check the minimum and maximum airspeeds.

 

[Dynon]

The speed limits aren't new behavior - that envelope protection has always been there. One artifact of that limiting is that the AP won't turn on if there's any IAS present that's below the minimum airspeed. So if you're on the ground with zero IAS, it will turn on. If there's any airspeed that's below the minimum, it won't. The two most likely cause for the latter condition is wind that's causing IAS to be non-zero, or the issue lynnb describes above.

 

[lynnb]

Well after running through the zero pressure calibration, everything started working fine, but yesterday the pitch servo wouldn't engage. I went into Autopilot configuration this morning and walked through moving full pitch right left etc... then it asked for the yaw servo configuration, well I don't have a yaw servo so I couldn't figure out how to get past that point and just clicked the ok button twice. Well now I don't show any servos installed when I go into the configuration, but I can see them in the Network Status screen set to ready. At that point I walked away to try and regroup and figure out what my next steps should be.

 

[kellym]

We have about a hundred hours on our RV-10 with Dynon HDXs with the Autopilot panel installed. On preflight we'll turn on the Autpilot and test it by setting it in heading mode and seeing if it moves the stick left and right, and make sure we can over power and cancel, same with a climb. Today when testing, we would turn on the auto pilot, try and set it and then get a message the autopilot was disconnecting. Sometimes it would disconnect and sometimes I'd notice the SPD indicator replacing the AP at the top of the screen. This is the first time we've encountered this in the 100 flight hours and it happened on both ends of our flight when testing during our pre-flight runup. Now during the flight, it worked fine and at some point during the first runup when we were having the issue, it started testing fine. So is this an issue with the auto pilot, or is there just a setting that needs to be adjusted? The only thing that has changed since the last flight is the standard dynon US Aviation Database update was installed.

Not sure if it will help, but here's a link to the video of when we were trying to test it before our return leg:

New video · Sunday, Jul 18, 2021 ð¬

Tap to view!

photos.app.goo.gl

As always, thanks in advance,
Lynn

I guess I don't see the point of doing this test before every flight. The amount of force to override a servo should not change from flight to flight. The direction a servo moves the stick with a heading change should always be consistent and not change between flights. I understand doing it once, but what are you protecting against with repeated tests?
Kelly
RV-10, 320 hours
SV Classic with 3 axis servos.

 

[lynnb]

I guess I don't see the point of doing this test before every flight. The amount of force to override a servo should not change from flight to flight. The direction a servo moves the stick with a heading change should always be consistent and not change between flights. I understand doing it once, but what are you protecting against with repeated tests?
Kelly
RV-10, 320 hours
SV Classic with 3 axis servos.

Kelly,

I originally felt the same way, until yesterday morning when the test told us the pitch wasn't working, but roll was. Considering we were going IFR it's good to know what you can and can't depend on. Made for some good hand flying practice though.

Lynn

 

[kellym]

Kelly,

I originally felt the same way, until yesterday morning when the test told us the pitch wasn't working, but roll was. Considering we were going IFR it's good to know what you can and can't depend on. Made for some good hand flying practice though.

Lynn

The ground test doesn't tell you anything about in flight operation of the servos unless you have a shear pin that has failed. Even then the system will function, if somewhat poorly. IMHO, you are more likely to screw up the network configuration, autopilot configuration, etc and cause a failure, that just assuming that it will work after takeoff. If it is that critical, you can engage it at 1000 ft, and if it doesn't work, return to land. Just my point of view, having never had a good, working autopilot in either of my previous planes, requiring every flight, whether IFR or not to be hand flown.

Your ground test simply is not guaranteeing anything. The system will tell you if it doesn't find a servo on the network during boot up. That is really the only thing you are checking. The polarity and wiring doesn't change. It stores your last calibration as to the travel limits.