What’s Propwash in FPV Drone Flying and Learn how to Remove It

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Propwash is a standard challenge in FPV drone flying, particularly throughout altitude drops and sharp 180-degree turns. It manifests as oscillations or vibrations because of the turbulent airflow created by a drone’s propellers, considerably impacting flight stability and video high quality. This tutorial will discover what propwash is, what causes it, and how one can reduce it by way of tuning and configuration changes.

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What’s Propwash?

Propwash happens when the turbulent air created by a drone’s propellers interferes with the drone’s flight. This turbulence may cause instability, leading to wobbling or oscillations, particularly throughout maneuvers like sharp turns, speedy descents, or aggressive braking. The impact is usually seen within the drone’s video footage as jello-like vibrations, which might be significantly irritating for pilots aiming for clean and cinematic pictures.

What Causes Propwash?

Propwash is primarily brought on by the interplay of the drone’s propellers with turbulent air. When a drone is in movement, particularly throughout fast maneuvers, the air disturbed by the propellers doesn’t have sufficient time to settle earlier than the propellers move by way of it once more. This creates a suggestions loop of turbulence that destabilizes the drone.

A number of components could make propwash worse:

Propeller Design: The form, measurement, and pitch of the propellers have an effect on how air is moved.
Flight Maneuvers: Aggressive maneuvers enhance the probability of encountering propwash.
Tuning and PID Settings: Poorly tuned filter and PID settings can exacerbate the results of propwash.
Weight and Body Design: The drone’s weight distribution and body design can affect the way it handles turbulent air.

Tricks to Scale back Propwash

Decreasing or minimizing propwash requires a mixture of correct tuning, flight strategies, and {hardware} changes. Listed below are some efficient ideas.

Guarantee Mechanical Integrity

First, be certain that your quad is mechanically sound:

Make sure the flight controller is soft-mounted, and mounted securely.
Examine for free screws on the body, motors, and different elements.
Confirm that no carbon fiber plates within the body are cracked, and the body is as stiff as it may be.
Guarantee motors are in good situation, bearings are clean, and bells will not be free.

Use Low Pitch Propellers

Utilizing high-quality, low-pitch propellers could make a major distinction in dealing with propwash. Whereas higher-pitch props are nice for reaching greater prime speeds, lower-pitch props can change RPM sooner, making your drone extra responsive and faster to regulate to air turbulence.

Listed below are my propeller suggestions: https://oscarliang.com/propellers/#Suggestions

Allow RPM Filter

It’s advisable to allow RPM filtering, following this tutorial: https://oscarliang.com/rpm-filter/.

When you’ve got BLHeli_S ESCs, you must flash Bluejay firmware onto them. When you’ve got BLHeli_32 or AM32 ESCs, you’re already set for RPM filtering, comply with these guides to configure your ESC for optimum efficiency:

Regulate Filter Settings

As soon as your quad is mechanically sound and working the most recent firmware with RPM filtering enabled, you would possibly need to attempt these filter changes:

Disable Gyro Lowpass 1 Filter: This will often be safely turned off with RPM filtering enabled on most quads. It reduces filter delay and improves propwash dealing with. You must do a brief check flight to test if motors get scorching earlier than commiting.
Scale back Filtering Additional: In Betaflight, go to the PID tuning tab and filter settings. Transfer the Gyro Lowpass filter sliders to the proper (to 1.2 or 1.3) to cut back filtering whereas making certain the quad nonetheless flies effectively with out scorching motors.
Tremendous-Tune: For those who discover issues at greater values (e.g., 1.5), again the sliders down a bit to search out the minimal quantity of filtering you will get away with.

Decreasing filtering may also help push PID good points greater with out inducing oscillations, nevertheless, this requires a clear and well-maintained quad, and with the ability to analyse it by way of Blackbox logs can be strongly advisable.

Correct PID Tuning

Default PIDs in Betaflight are typically excellent, however there may be all the time room to fine-tune propwash dealing with:

Improve D-Time period: The D-term in your PID settings helps counteract speedy modifications in movement. Greater D acquire may also help scale back oscillations brought on by propwash. Nevertheless, rising the D-term an excessive amount of can result in motor overheating and oscillations, so make changes progressively by way of correct tuning strategies.
Regulate P-Time period and I-Time period: An excellent PID acquire requires good ratios between P and D, and between P and I. Due to this fact, when making modifications to D acquire, you also needs to alter P and I good points to keep up these ratios.

Additional Readings:

Implement Dynamic Idle

Dynamic idle ensures your motors preserve a minimal RPM even in reverse stream conditions, minimizing propwash.

When prop wash happens, the flight controller makes an attempt to stabilize the quadcopter by quickly rushing up or slowing down the motors. With out Dynamic Idle, the minimal RPM your motors can attain is 5.5% by default. In distinction, when Dynamic Idle is enabled, Betaflight can command the motors to drop to 0% RPM, so the vary of throttle the motors can attain when preventing prop wash is far wider. This enhanced braking functionality noticeably improves prop wash dealing with.

I’ve an entire weblog put up explaining what Dynamic Idle is and the way to configure it: https://oscarliang.com/how-to-enable-and-configure-betaflight-dynamic-idle/

Change the Means You Fly

Aggressive flying typically results in extra pronounced propwash. By practising smoother, extra managed maneuvers, you possibly can scale back the turbulence created by your drone’s propellers. For instance, when descending, attempt to pitch ahead barely to attenuate air turbulence instantly hitting the propellers, successfully decreasing propwash.

Conclusion

Propwash is a problem that each FPV pilot faces, however with the proper mixture of tuning, {hardware} changes, and flight strategies, you possibly can considerably scale back its impression. By understanding the causes of propwash and making use of the following tips, you’ll be capable of get pleasure from a extra steady flight and seize smoother video footage. Pleased flying!

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