The key to FPV drone flight is precision and control. One of the main factors that can affect your flight experience is latency, specifically how quickly the drone responds to pilot controls. Whether you’re racing, freestyle, or capturing cinematic footage, reducing latency can make a big difference in your drone’s performance and your connection to it. In this guide, we’ll explain in detail what FPV drone latency is, why it’s important, and how to reduce it to improve your flight experience.
What is Latency?
Latency in FPV drone flight refers to the delay between when you move the control stick on the transmitter and when you see the drone react in your FPV goggles. These delays are caused by various components in the control loop, including the transmitter, receiver, flight controller, motors, and FPV system.
Typically, the latency of an FPV drone can range from 10ms to over 100ms, and the longer the latency, the more difficult it becomes to control the drone. Lower latency is important for faster response times and better control.
Why Latency Matters
When flying an FPV drone, every millisecond counts. Here’s why minimizing latency is important:
- Accuracy and Responsiveness: Lower latency means the drone responds faster to inputs, allowing for more precise control. This is very important in FPV racing and freestyle flying, where split-second decisions can make a big difference.
- Smooth flight experience: Long latency can make the drone feel slow or unresponsive, which can negatively affect the smoothness of its flight. This may affect video quality and overall flight experience.
- pilot reaction time: The faster a drone responds to inputs, the better it can avoid obstacles or respond to sudden changes in its surroundings. For example, if a drone is moving at 100 MPH (~45 m/s), even a 10 ms delay means the drone has moved 0.45 meters before responding to input. This can be the difference between avoiding an obstacle and crashing into it.
Reduce FPV Drone Latency
To understand how latency works, imagine sending a package through the mail. First, it is left at the post office, sorted at the distribution center, and then delivered to your doorstep on a delivery truck. Each step in this process adds a little bit of time, just as each component in the FPV control loop affects the overall latency.
- visual input: You can see the drone’s movements through goggles.
- cognitive processing: Your brain processes visual information.
- physical reaction: Move the control stick according to what you see.
- Transmitter Transmit Command: The transmitter processes the input and sends it to the drone.
- Flight Controller Processing: The drone’s wireless receiver passes the signal to the flight controller, which processes it and adjusts the motor speed.
- motor response: The motor reacts and changes the drone’s movement.
- visual feedback: The camera captures the drone’s new position and sends an updated video feed to the goggles.
The total control latency is the sum of the latency of each of these events. Factors that affect latency include:
- human reaction time
- Gimbal input encoding rate (e.g. 500Hz polling on EdgeTX)
- Wireless link speed (e.g. 150Hz for Crossfire vs. 1000Hz for ExpressLRS)
- Receiver protocol rate (e.g. CRSF vs. SBUS)
- PID loop frequency (e.g. 4K vs. 8K)
- ESC protocol speed (e.g. DShot300 vs. DShot600)
- motor acceleration time
- FPV system latency
- Screen refresh rate of FPV goggles
Reduce control latency
To minimize control latency for your FPV drone, focus on optimizing each component of the control loop.
- RC link: Invest in a low-latency wireless control system, such as ExpressLRS, that offers the lowest latency available. All radios I recommend support ExpressLRS: https://oscarliang.com/radio-transmitter/
- flight controller: Most Betaflight flight controllers today use 4KHz and 8KHz PID loop frequencies, but you can still fine-tune your settings. Depending on your build, adjust the PID appropriately and use less filtering and RC smoothing to reduce latency.
- motor: Select a motor with sufficient torque to rotate the desired propeller. For example, for a typical 5-inch drone, it can take up to 50ms or more for the motors to go from 0% to 100% throttle, which is a significant amount of latency. If the motor is too weak, it will take much longer to accelerate to the desired speed, resulting in longer latency. FPV motor recommendations: https://oscarliang.com/motors/#Recommendations
- FPV system: FPV system latency, often referred to as “glass-to-glass” latency (camera lens to goggle screen), is very important. Analog and HDZero systems have lower latency than HD systems like DJI and Walksnail, but that’s the price you pay to enjoy superior image quality and a more powerful connection. However, DJI and Walksnail allow you to use higher frame rates to reduce latency. For digital systems, latency can fluctuate depending on signal quality, so maintaining a strong signal is essential. For example, using maximum output power and appropriate antenna settings.
- Improved reaction time: Beyond equipment, improving your reaction time through practice, especially on an FPV simulator, will help reduce the impact of latency. Building muscle memory is key to becoming a more skilled pilot.
conclusion
FPV drone latency plays an important role in your flight experience, especially when precise control is required. Understanding the factors that affect latency and making targeted upgrades to your equipment, whether upgrading to a high-refresh-rate RC system or choosing a low-latency FPV system, can significantly reduce latency. The result is smoother flight, better handling, and a more enjoyable FPV experience. For pilots looking to take their flying skills to the next level, reducing latency is an important step in mastering FPV drones.
