As a commercial drone pilot based in Hawaii, I am regularly asked to fly drones in relatively strong wind. Here on Maui we typically have winds in the 20 knot range with likes in the 30s and sometimes the 40s. It’s safe enough to fly without missing a drone, losing control, or hurting someone. Obviously, a “do not fly” call is not ideal and usually means immediate financial loss in the fast-paced world of commercial drone services. Many times this high wind flight occurs over water (shark infested salt water to be exact!) which increases the risk and complexity of the operation. Also, as you may know, losing a drone in the big blue sea negates your ability to get a replacement through insurance like DJI Care Refresh, unless you can get the drone back to ship back to DJI. The good news is that it normally encounters no obstacles on the water and image transmission is rarely interrupted due to object interference. The challenge is that if you have a problem, you first have to traverse a considerable distance over no man’s land before you have a chance to get your drone back.
To prepare for a scheduled session with a drone, let’s say kitesurfing for example, I do several things. I first check if the location I’m flying to is a “green zone”. This means you are not in an FAA no-fly zone, not within 5 miles of an airport, and have a legal launch and landing area within visual distance of the drone’s area of operations. Next, I deal with the insurance, permits, and necessary FAA clearances to get the job done. Once the location is approved, I check the local weather, conduct a site survey prior to filming, and develop a plan for filming, as well as an emergency plan, based on the prevailing wind direction and coastal topography. . Finally, I reserve my assistant for the shoot, as a visual observer is required by law and is highly recommended when pushing the limits of a drone’s flight capabilities.
What I look for when I check the weather is if it’s going to be sunny (drone shots need sun) and how strong the wind will be. Also the wind flavor factor is an issue. Too much variability in the wind really degrades the flight experience and can cause the drone to pitch and roll much more than constant wind. Depending on the wind speed, I determine if my drone can handle the upper limits of the wind forecast. The direction is also key. Offshore winds present a much higher risk than land winds when flying over water for obvious reasons. And finally, I consider the conditions to determine not only if I can fly, but also how close, what is the subject doing, what other obstacles are there, what is the range of my drone, and what is a safe altitude. With kitesurfing, you have a fast-moving kite at the end of the 30-meter lines, so any shots closer than 100 feet must account for this action and the associated risk.
On the day of the shoot, you want to assess the actual weather and wind conditions (don’t get caught in the rain) and make the final decision to fly or not fly. I like to do this before customers or other aspects of the production show up so I can make the decision without biased influences. If it’s a “go” situation, I fly my drone in normal GPS mode to about 10 feet and see if it can stay put. If it’s very windy in your launch area, don’t launch from the ground or your drone may tip over before taking off. If you can hover in place without losing ground, try flying up to your maximum firing altitude and test the wind speed there. If the wind starts to catch up with your drone and it drifts away, bring it down to a lower altitude and try to recover. If it’s too windy to get your drone back in GPS mode, you can try switching to “sports mode” (DJI Mavic Pro and Phantom 4 series) and fly it back to you. Be sure to familiarize yourself with switching and flying in sport mode before the flight. While your drone is flying away, this is not a good time to go through the settings menu for the first time. If sport mode is not an option and there are obstacles around, you can use them as a windbreak. If you are flying the drone back at you at full speed and the wind is still overpowering the drone, you can dive behind buildings, trees, barriers, and even mountains to enter a more stable environment. Although obstacles can increase wind variability, I have found that a combination of lowering altitude and getting behind things that slow down the wind can get you out of most situations and at least allow you to get the drone down to the ground and not to the ground. Water. If the wind is blowing offshore and out to sea, you have few options for recovery and the wind can be as strong 10 feet off the water as it is 100 feet. Strong and (typically) gusty winds offshore present the greatest risk of losing your drone over water and need to be approached with an extra level of consideration.
In conclusion, just remember to be safe, not sorry. Don’t push your drone into an unrecoverable situation, and have several backup plans in mind for potential emergencies. Know your gear well before you fly in wind or over water, including time and distance limits, as well as the effects of wind on relative speed vs. surface speed. For example, if your drone is flying at a top speed of 25 mph and gusting to 15 to 20 mph, it can fly downwind at a surface speed of 45 mph, but may only be able to go upwind at 5 mph. . If your drone flew a mile downwind, make sure you have enough battery to go back at 5 Mph, which by my calculations would take about 12 minutes. Also, “sports mode” increases speed but reduces battery life. And lastly, try to avoid letting your drone fly empty. Flight performance can be less than expected when the battery is running low and definitely increases the stress level when you are below single digits and have not yet returned to shore.