Understanding Betaflight Airmode for Better Aerobatics

Airmode in Betaflight can seem daunting for those new to the drone hobby. In this guide, I’ll break down Airmode in simple terms and guide you through setting it up in Betaflight.

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Learn how to setup Betaflight the first time: https://oscarliang.com/betaflight-firmware-setup/

What is Airmode?

Typically, when you drop your throttle stick to the lowest, the motors on a quadcopter would either be running at their minimum speed constantly or stop entirely (depends on your setting). However, Airmode changes this behavior. It keeps the PID loops active even when your throttle is at zero, motor speed can change even without throttle inputs from user which allowing you to maintain control of the quad during a free fall. This feature is essential for executing complex aerobatics and maintaining precise control throughout the throttle range.

Airmode enables the quad to maximize throttle to control its angular position independently of the throttle input from the pilot. Before Airmode was introduced, the quad’s propellers could only spin as fast as the throttle setting allowed. This limitation made certain maneuvers impossible without maintaining some throttle input (you couldn’t lower throttle to zero). Now, with Airmode, you can leave your throttle at zero, and yet still perform a flip, and you can re-engage the throttle at any time seamlessly. This capability is standard in Betaflight, whereas systems like KISS still require some throttle input for flips because they do not have a true Airmode.

Downsides of Airmode

While Airmode enhances maneuverability, it also has its drawbacks. The quad will attempt to correct its orientation even when held in your hand, potentially leading to unexpected behavior or injury if not handled carefully. It’s particularly sensitive to ground effects, which can cause bouncy landings or erratic behavior during low-altitude maneuvers. Furthermore, a collision while Airmode is active could cause the motors to throttle up aggressively, increasing both damage and danger, especially if flying near people. For safety, it’s wise to assign Airmode to a switch so you can deactivate it when it’s more hazardous than helpful.

The Trick to Flying as if Gravity Barely Exists

Ever watched top pilots perform moves like inverted stalls, where the copter seems to hang in the air indefinitely? It almost looks as if they’re defying gravity. The secret lies in their throttle management. By setting the throttle just above the minimum (min_throttle), pilots can minimize downward force when inverted, yet keep the PID loops active to maintain stability.

To prevent the quad from becoming a free-falling object if the throttle is accidentally reduced too much, some pilots disable the motor_stop feature. This setting ensures the motors continue spinning even at zero throttle input. Additionally, many pilots use an “idle-up” switch to keep the throttle slightly engaged, ensuring the PIDs remain active below the min_throttle threshold. This setup helps maintain smooth control and prevents the quad from losing orientation during critical maneuvers.

Understanding and configuring these settings in Betaflight will enhance your flying experience, making your drone more responsive and capable of impressive aerobatics.

Why Was Airmode Created?

Originally, Betaflight’s mixer logic wasn’t very active at lower throttle ranges because it wasn’t expected to fly in that range. The feature “pid_at_min_throttle” allowed the copter to continue processing the PID algorithm at minimum throttle, but it only kept the P and D components active, zeroing out the I component. This often led to quads tumbling during drops at zero throttle.

To address this, Airmode was developed to replace “pid_at_min_throttle.” Airmode keeps all components of PID—P, I, and D—active, even when the throttle command is zero. This enhancement allows for smoother recovery and control during zero throttle maneuvers, differentiating it from simply disabling motor_stop, which doesn’t ensure control over the quad at zero throttle.

Setting Up and How to Use Airmode

To begin, ensure your Betaflight firmware is updated to version 2.1.5 or newer. In the Betaflight configurator:

1. Disable motor_stop.
2. In the Modes tab, assign a switch to Airmode or enable the Airmode feature permanently.

Assigning Airmode Switch: One Switch or Two?

Initially, it was recommended to use separate switches for Arming and Airmode due to potential issues with PID “I term wind-up” on the ground, where the quad could unexpectedly spool up. However, improvements by developer Boris B have introduced a safety feature that prevents I term wind-up by activating Airmode only when the throttle is above min_check for at least one second, and roll or pitch is not centered.

Many pilots now successfully use a single switch for both ARM and Airmode without issues, though using two switches may add an extra layer of safety.

PID Values and TPA

With Airmode’s more active mixer, it’s often advisable to slightly lower your PID values. Additionally, TPA (Throttle PID Attenuation) may not be necessary when Airmode is active, according to insights from experienced pilots.

Here is my first flight with Airmode enabled (very old video).

Tuning On Airmode?

Typically, no special changes related to Airmode are needed—just enable it and experience the improved flight dynamics. However, powerful quads might react unpredictably during takeoff with Airmode enabled. To ensure a stable takeoff, set the airmode_start_throttle_percent near your hover throttle value. For a quad that hovers at 20% throttle:

set airmode_start_throttle_percent = 20

For racers who need to maintain an angle on the starting block without taking off, adjusting the start percentage slightly below the hover point, such as 10-15%, can be effective.

In conclusion, understanding and correctly setting up Airmode can significantly enhance your flying experience by providing better control at low throttle settings and enabling more dynamic maneuvers.