Idle Up vs Airmode – which one is better? Betaflight, KISS and all the other

Which is better: Idle Up or Airmode? Which one to use since the best pilots are stating that Idle Up is better than Airmode (Mr Steele). Different pilots state that Airmode is better than Idle Up. So, what is the truth? I’m not the best pilot in the world. Hey, I’m not even good enough to be considered very good, but I know my stuff and I can program. More than that, I know how the flight controller is working internally. And that gives me an edge…

Betaflight 4.0 – improved dynamic filtering on 7 inch quad

The next major release of Betaflight will be 4.0 with new and improved Dynamic Filtering. For now, today I only did a quick test of Betaflight 4.0 running on my TBS Source One 7-inch FPV drone. No tuning, no playing with settings. I only flashed, set modes and radio and that’s all. I pretty much like how it feels. This quadcopter was mainly doing cruising, no freestyle, and it felt good to put those props into more demanding use. Yes, Betaflight 4.0 has a good chance to be just awesome…


A note about the sound. It indeed sounds like a V8 engine. Bear in mind, that those are default settings and Gemfan FLASH 7042 props are light and do not like to have too much D gain.

This is why YOU SHOULD use only 8 channels in Betaflight!

When two weeks ago I said that you should only 8 channels when using FrSky SBUS I meant it and you just had to take my word for it. Today a small proof how Betaflight 3.5 feedforward component looks on the Blackbox with 16 channels and 8 channels. Of course, in both cases, RC smoothing type FILTERING was chosen.

Get your Blackbox logs from SD Card with a USB cable – Betaflight MSC

SD cards are cool: cheap, reliable, a lot of space and you can remove them from the drone and read on a PC. But sometimes, it's really hard to take them out. Either SD slot is in a strange place, or FC is oriented in a strange way or an FC designer has put an SD slot in a most stupid place of them all…

You can use Betaflight 3.4 as an SD card reader (MSC standard compatible) and either use it do get your blackbox logs via USB cable or use it, if you really want to, as a pendrive. With drag and drop and all that stuff. All you have to do is to go to CLI and type "msc" and hit enter. That's all! It's not perfect, but works!

What is Betaflight 3.5 Feedforward and how to use it

Betaflight 3.5 is just around a corner and it brings new cool things. There is no more Dterm setpoint weight and Dterm setpoint transition (relaxation ratio). They all were replaced by easier to understand Derivative and Feedforward (Feed Forward when you refer to the control theory tho).

Betaflight Derivative and Feedforward parameters are the new way of controlling "damping force" of the Dterm and responsiveness of a drone. The more Derivative gain you set, the more "damped", "delicate" and "swooshy" drone will be. The more Feedforward gain you apply, the more responsible to the sticks it will be. It's almost the same as with Dterm setpoint weight, but in my opinion, made simpler and can be set separately for each axis.

Betaflight 3.4 – how to get it and what changed

Competition from Butterflight changed the game. I might not be the biggest fan of Butterflight, but one thing is sure: thanks to it, Betaflight took a big lead forward. The best example of it is Betaflight 3.4 that currently is in Release Candidate stage.

The most important changes, that really influences flight (there are more not flight related changes, I will cover them separately) are revisited filtering and PID defaults:

  • Dynamic filtering enabled by default
  • Antigravity enabled by default
  • Gyro stage 1 LPF bumped to 100Hz
  • Gyro stage 2 LPF (not) Kalman FIR2 filter set at 300Hz
  • Dterm filter type set to PT1
  • Gyro notch filters disabled
  • Dterm notch filter disabled
  • Revisited PID gains

Now, it flies wonderfully!

Betalight 3.3 and Kalman filter (BiQuad+FIR2 to be precise) situation

Betaflight 3.3 RC1

Betaflight is at the end of next release cycle. Betaflight 3.3 RC1 has been released only 2 days ago and that brought us a (not) Kalman filter! Long story short:

  • Raceflight was using Kalman (Fast Kalman Filter – FKF)
  • RS2K left RF and brought FKF to Betalight
  • Betaflight did some changes and replaced Fast Kalman with BiQuad + FIR2 (Finite Response Filter) equivalent that gives more less the same results (same response) as Fast Kalman

Unfortunately, someone at Betaflight forgot that users will want to use it and the process of setting up (not) Kalman filter (I will be calling this (not)Kalman because it just sounds better than BiQuad+FIR2 and says all you need to know) is at least stupid. The filter is gyro update frequency dependent and instead of setting up a cutoff frequency, it has to be tuned using gyro_filter_q and gyro_filter_r CLI settings that you have to guess or compute somewhere else. How awesome is that!

Anyhow, to make life a little easier I prepared an online (not) Kalman filter calculator for Betaflight 3.3 RC1 that allows computing filter cutoff frequency based on gyro_filter_q, gyro_filter_r and gyro update frequency.

Also, here is a YouTube video that shows how to use it and configure BF 3.3 RC1 for (not) Kalman:

And another video that shares some more general thoughts on the topic:

Betaflight 3.3 RC2 (upcoming)

Ah yes, there was a small change… Looks like BF guys decided to make life a little easier for us after all, and sped up a small but very important change. Starting from Betaflight 3.3 RC2 (or today's nightly build), (not) Kalman filter cutoff frequency can be specified with a single CLI setting: gyro_stage2_lowpass_hz. More than that, gyro_filter_q and gyro_filter_r are removed and not available at all.

I always knew that developers need some proper motivation, but why could this not be like that from the beginning?