Flying in High Winds – What Could Possibly Go Wrong?

Propeller Spin-off

Wind Gusts Caused This Problem

In this blog, we explain why we limit our flights to wind speeds of 10 mph or less. Seem drastic? Please read on; this is good information.

Drone electronics are quite sophisticated, as they use inertial navigation to stabilize the drone’s camera so it’s almost free from the effects of wind patterns. However, there’s a design limit at which the stabilization reaches the “stops” and no longer holds the camera level.

When the drone is buffeted by gusty winds, the magnitude and direction of the wind can shift quite suddenly. This gives the drone’s stabilization system a workout and sometimes the requirements go beyond the linear operating range. The result is a momentary tilting of the image sent to your remote control.

OK, Crooked Photos And Videos; Is That It?

Not really – something much worse can happen when the drone is buffeted by strong gusts: Such as the sudden loss of your drone! The drone’s stabilization system works very hard to keep the camera steady, but when the wind vector tries to tilt the drone, the motors will adjust speed AND DIRECTION, as necessary, to maintain level. If the wind vector is strong enough, one or more motors can momentarily be driven in reverse.

If your propellers screw on, such as the Phantom 3 series, they rotate in a direction that is usually self-tightening. However, if the motor momentarily reverses in a gusty situation then the propeller can actually unscrew and spin-off. The best way to safeguard against a spin-off is to screw the propellers on very tightly. If you’re flying a DJI drone, this means using the supplied wrench.

If your drone uses the new quick release propellers, they can still spin-off, but you’re at a lower risk. Take the Phantom 4, Inspire 2, and Mavic series for example. Their propellers mount with a push and 1/8 of a turn. You (we all) feel safe because there’s a relatively strong spring to hold the propeller in place. However, these drones’ control systems can still drive the motors in reverse. When thrust is reversed and the propeller pushes hard enough against the spring then it will fly-off.

Having some speed on the drone reduces the forces that can drive the motors in reverse. But the pilot should be very careful about low speeds and hovering because these are the conditions that make it more likely that a gust will try to pitch the drone over.

Of course, the best way to safeguard against a spin-off is to avoid flying in high winds. The graphic above was taken from telemetry received from an actual spin-off event.

Why Can’t The Drone Fly With One Propeller Missing?

If a propeller spins off your aerial drone this is what you can expect:

A drone with six or more propellers can survive a one-propeller spin-off. But drones with four propellers are doomed. These drones have two props that rotate clockwise and two that rotate counterclockwise. They were designed this way to cancel the drone’s tendency to rotate. But if you remove one propeller, the drone will go into a spin.

Without a propeller there’s no lift so that corner drops down. So in addition to spin, the drone goes into an uncontrolled roll/pitch. The drone is hopelessly out of control and falls to the earth.

Recommendations

Inspect the propellers before every flight. If you must fly in winds greater than 10 mph, understand that gusts can easily double the wind speed. Take precautions that the propellers are screwed on tightly with a wrench. If you see the image tilting on your remote control, land your drone immediately. Better to fly another day than to take chances on a windy day.