Last week, a friend of mine asked me a seemingly straightforward question: when you’re launching a VTOL aircraft, does it really matter if you point its nose into the wind at the start?
I gave her a decent answer, but now that I’ve had some time to think about the question, I would expand it a bit:
Does pointing the aircraft into the wind at launch matter? No, not really.
Is it still a good idea? Yes, very much so.
The aircraft knows where it isn’t
I say it “doesn’t matter” because most autopilots flying most aircraft will pretty much take care of this for you. Many autopilots that are properly set up for VTOL platforms will have some sort of “weathervane” setting or mode in their logic. When this is active, the autopilot will not try to keep the aircraft pointed at one specific heading. Instead, it effectively releases the aircraft’s yaw control and prioritizes maintaining a level attitude in pitch and roll, as well as staying on-station over the launch waypoint.
Releasing yaw control at this point is safe to do because the aircraft will have been designed to naturally weathervane. That is, it is directionally stable: after any disturbance, such as a gust of wind blowing the aircraft’s nose off from its direction of travel, it will naturally rotate back to its initial equilibrium point.
When that weathervane autopilot setting is active, the aircraft is free to respond to the wind based on its aerodynamics. And because the aircraft is designed with positive directional stability, it will arrive at an equilibrium where there is no crosswind blowing it off its direction of travel—in other words, without any other input it will end up pointing into the wind.
I maintain it’s still a good idea to start out pointing into the wind, though. Watching an aircraft lift off is already a bit anxiety-inducing to watch, and the operators are on alert for any sign of trouble. Seeing it start spinning around could make a tense situation worse. You also may not know exactly what direction the aircraft will spin, nor how fast. The aircraft should find itself pointing into the wind eventually. But in flight operations, we always seek to reduce risk as much as we can—and that includes reducing unnecessary movement during launch and recovery.
Edge cases to consider
There are a handful of exceptions to the behavior I just described. Physics is still physics, but some operational environments will see more unique launch behavior.
One that’s more a consideration than an exception is when launching near structures or people. Good launch and landing plans are usually aligned with the ambient winds. It’s also safest to avoid making a launch plan that goes directly over people in case of mishaps.
But you may need to set up your ground control station, support equipment, vehicles, etc in a particular spot relative to your launching zone. When the ambient winds change, it’s easy to adjust your launch plan to accommodate, but it doesn’t make sense to move all of your equipment just to get out of that plan’s way.
In this case, if you build a flight plan that is offset from the prevailing wind so you don’t intentionally transition over people, you’ll see some more unique launch behavior. The aircraft will still weathervane into the wind, so it may briefly point at the operators. But because its next waypoint is to the side, not in front of it, as soon as the aircraft begins to transition it will start turning itself to seek out that waypoint, avoiding the squishy people it might have flown over.
Shipboard operations create an even more unique scenario. In this case, the “ambient wind” is often caused by the ship’s own sailing speed. But you can’t fly directly into the wind: the ship’s superstructure is in your way, and the captain will not take kindly to a UAV crashing into their vessel.
Just like I described previously, the UAV operator would lay out the launch plan at an angle relative to the ship. Again the aircraft weathervanes into the wind, but once it starts transition it’ll seek that first waypoint and quickly end up with its nose facing away from the ship. It helps even more if the ship is underway, since it’ll also be moving away from the launch “point” as the aircraft transitions.
There is one last, very niche exception I want to touch on: if your aircraft is designed to be directionally unstable.
First of all, please don’t do this—almost no UAVs need the same absurd maneuverability as a fighter aircraft, so they don’t need to be similarly unstable.
But besides that, having an aircraft that’s unstable in yaw means you need to be extremely careful. An unstable aircraft means that, with any disturbance from equilibrium, the aircraft will keep moving further from its initial state. If it’s flying along and a wind gust pushes the nose to the left, it’ll actually keep rotating further left, away from the direction of travel, and make the situation worse.
Fighter aircraft are designed with enough control authority to overcome this intrinsic behavior. But if your UAV is in weathervane mode, where it’s effectively abandoning yaw control, and it’s directionally unstable, it will just stray further from pointing into the wind. It also won’t have any logic to use its control surfaces to turn it into the wind. I honestly couldn’t tell you if the aircraft would just rotate all the way around to point the opposite direction, or if it would keep spinning as it rose up from the ground like a maple tree seed in reverse.
That mental image is terrifying.
Your best mitigation is to design your aircraft to not be directionally unstable—purposefully size your vertical surfaces to give you even a tiny amount of positive stability. If for some reason that’s not possible, the second best option is likely to somehow disable the weathervane setting in the autopilot, and command the aircraft to maintain a prescribed heading during liftoff and transition. I’d highly suggest reaching out to the autopilot’s manufacturer to see if they can help with any customizable launch sequence logic, so your airplane doesn’t give everyone a heart attack at liftoff.
Hopefully that was a straightforward answer with some valuable nuance. Pointing your aircraft’s nose directly into the wind at launch is not so critical that you need to physically rotate it for every tiny wind shift. But aiming it roughly in the right direction and letting the autopilot and aerodynamics handle the rest is most often the safest plan.