General Advice and Review Regarding Tuning and Performance

Hi all,
In order to gain more confidence in my setup and plane, I would like to request general review/advice of a flight log. My concerns are the following:

  1. There seem to be small oscillations in roll and pitch. Whether they are due to wind or tuning, that eludes me.
  2. There seems to be a higher noise level in one of the radios, perhaps ground as per my readings (need confirmation whether remote radio means aircraft or ground? is it named from the pilot’s point of view?).
  3. The radio transmit buffer seems to hover around 100. Does this indicate slow radio comm?
  4. Any other comments regarding FC set-up to make it safe for flight.
  5. Would it make any sense to increase the SCHED_LOOP_RATE to make the plane fly better? (I have seen it increased by advanced users e.g. naterater)


Will appreciate any advice/answers.

I see a few issues. I think the tune could be improved. And there seems to be an issue where it’s consistently rolled a few degrees to one side. There are also repeated failsafes being triggered. My suggestions:

  • make sure your FC is level. Verify the physical trim of the ailerons, this might need some adjustment of the control rods. You want to see the plane fly level and at the same time recognize it’s level.
  • Consider updating to 4.1 and re-doing the auto tune. I’ve had luck with it and I think it may clean up the performance. I didn’t see big oscillations to be worried about but both pitch and roll can be improved. Fix the ailerons and FC level first though.
  • Investigate why you are getting the throttle failsafes. Check your antenna positions (ground and air) and your wiring. I’m not sure how far you were from your radio, is your radio gear adequate for the distance?

Thank you for your reply. Could you kindly identify where you observed the consistent roll?

  1. The FC was calibrated outside of the model. Do you suggest re-adjusting the level after installation in the model? How do I make sure the model is level in this case? The ailerons have been physically adjusted to level position when the model is level in manual mode.

  2. I shall update once a stable version is released. I am already afraid whether the plane might crash lol.

  3. The throttle failsafe is to be expected. It’s an SBUS receiver paired with T14SG. This flight was the longest flight and the furthest. The maximum distance was maybe 4 km from the home position. I am worried about the telemetry radios though. They’re a pair of RFD900x. I am not using their RC passthrough function.

I don’t have the same computer handy with MP on it, otherwise I’d show a screen shot. But the demanded roll never went to 0. It was always around 2 or 3 degrees. Levelling the FC in the plane (or resetting the level with the plane level would probably solve that, and the aileron issue. Use a spirit level (or if the plane is big enough, even an app on your phone) to make sure the wings are level in roll. You will need to set the pitch at the same time, typically 3 or 4 degrees nose up. Once this has been done and you fly it again, check the trim on the ailerons. (SERVOx_TRIM). Depending on the plane, a level roll attitude may require the ailerons to be offset a little bit. Maybe because of a twist in the wings, or an antenna on one side creating drag, or the weight not being perfectly centred. Normally for me, I start with servos centred at 1500us, so if the trim has adjusted them to between 1450 and 1550, I don’t get too excited. But if I see the trim beyond that, or if I feel it’s worth it, I will mechanically adjust the servos so they are mid travel, with the ailerons in the trimmed position (that means the aileron won’t necessarily be centred when the servo is in the middle of it’s travel)

I understand. The Beta versions are very reliable however.

On a standard SBUS receiver… wow. Yeah, that’s good. I didn’t look at the telemetry radios. I’ll have to check that later. RFD900X radios should have no problem at 4km. Even on default settings. I’ve found with them that antenna placement is important, and a clear line of sight will make a difference. I had an issue that I was flying at 3km while standing beside a building. If I got too close to the building I would drop signal even at a few hundred meters, but once I took a few steps away the link was solid and I had no issues. The other issue with RDF900X is making sure you have a proper power source for them. Some FC will not or cannot provide enough power for them if you have them set to 30dbm/1watt power. If you are using that you need to provide a separate 5vdc power supply that can support the radio. I found the radios would “brown out” or loose connection even at close distances when they didn’t get the power they needed.

Yes I have observed that as well. I thought it might be related to cross wind. Maybe Ill recalibrate to see how it fares. Thanks for the advice.

Not good enough apparently. It started having failsafes a couple of kilometres out.

Im powering it from another 5v BEC from the matek PDB. On the ground side, I have made a diy PCB bridge that can accommodate the rfd900x and dronebridge on an esp32 to mount the antenna high and away from obstructions. Its powered by liion cells that can last for 3 days in a single charge.
I am not comfortable with the rc passthrough though. It has the option to just connect the Futaba receiver to it to pass rc through but I am not comfortable with the delay yet.
The trouble I have with the telem radio is that the one of the radios has a higher noise level than the other. Cant seem to figure out which one lol.

Could you give me any pointer regarding this as well?

My experience with 2.4GHz RC links is to be happy with anything over 1km. I know I’ve had over 10km with DJI 2.4GHz links but I’d never try that with a standard “hobby” system. That’s what the RDF900X or Crossfire is for. I’m still impressed you made it to 4km.

Do you mean the RAD.Noise and RAD.RemNoise graphs? The ground radio seems to be seeing a higher noise ratio than the air radio. If you’re powering that of the computer USB, maybe try a different USB cable, or move it further from your computer. Experiment with the placement. The air radio (RAD.RemNoise) seems very consistent so that’s good.

I’ve never adjusted that parameter. I can’t offer any advice.

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Thanks. I’ll try to sort the ground radio out. Not powering from USB. powering it from Li-ion cells.