Is Tacking A Viable Solution To An Overpowering Headwind?

[raymacke]

The question has come up in a different thread about using tacking (zig-zagging diagonally to the wind) as a workable solution when faced with an overpowering headwind. This works with sailboats but will it work with a drone or aircraft?

 

[Meta4]

The question has come up in a different thread about using tacking (zig-zagging diagonally to the wind) as a workable solution when faced with an overpowering headwind. This works with sailboats but will it work with a drone or aircraft?

No .. tacking won't help you make headway against a strong headwind.
It will make your drone travel twice as far and expose it to the wind for a lot longer.

Sailboats don't tack to deal with strong winds.
They tack because they cannot sail directly into even the lightest winds.
They also have no battery limitations.

If you put your drone into a situation where it cannot fight against a strong headwind to come home, your only option is to get the drone down low and out of that strong wind.
Too often the battle is already lost by the time flyers realise the problem.
The most effective solution is prevention.

 

[old man mavic]

The question has come up in a different thread about using tacking (zig-zagging diagonally to the wind) as a workable solution when faced with an overpowering headwind. This works with sailboats but will it work with a drone or aircraft?

this is something that has been discussed a lot,and when i first came on the forum, i thought that it should work as you say like tacking a sail boat
but as someone much cleverer than me pointed out it works because the boat has a nice big weight suspended from its keel that give it drag
with the drone there is nothing but the power of the motors and the props to provide forwards movement,and therefore if the wind is too strong for the drone to overcome, then it will continue to blow away,no matter which way it is flying relative to the wind direction and in fact as the surface area of the side of the drone is greater than the front or rear it would compound the problem

 

[dirkclod]

As Meta said get as low as you can but not so low as to lose LOS and your app goes blank as if you do and your battery is low what time it takes to get into RTH and rise to your set height at which time you should regain LOS and get the app back you might be just out of luck.
In a time like that and i know i am not going to make it back i start looking for a spot to just set it down.
Course if you're over water which i normally am you can just kiss it goodbye.

 

[RogerDH]

I think it will make the situation worse. A sailboat generates thrust from the wind, then uses the keel to vector it at an angle into the wind, but a drone can only generate thrust by spinning the props. If you can't generate enough thrust to overcome the wind drag when you're pointed directly into it, then vectoring some of your thrust to one side should mean losing even more ground.

 

[sar104]

The question has come up in a different thread about using tacking (zig-zagging diagonally to the wind) as a workable solution when faced with an overpowering headwind. This works with sailboats but will it work with a drone or aircraft?

Tacking requires something to push against that is independent from the medium that it is fighting (the wind). A sailboat is moving in two different media - a moving wind field that pushes on the sails, and an approximately stationary water that can push on the keel. Tacking works because the sailboat keel resists sideways motion - it's essentially constrained to move forwards relative to the water. As a result, if you want to make progress into the wind you can point the boat at an angle (less than 90°) to the desired direction of travel and the resolved force on the sail will push it forwards along that heading, thus making progress upwind. You can also think of it as using mechanical advantage.

An aircraft, in contrast, moves in just one medium - the wind field - and it has nothing equivalent to a keel to be able to push sideways against and keep it moving in the direction it is facing, and so tacking is a meaningless concept for an aircraft. An aircraft attempting to tack is simply blown sideways in the direction the wind is blowing.

 

[Thomas B]

Gotta add one thing... Check the weather.... thenalways fly out against the wind and fly back with it. That way you know if the wind is too high as soon as possible.

 

[bumper]

There's only a couple of instances where "tacking" (actually referred to as "S - turns") might be used in aviation - and it's all about going slower! When you are too close to an aircraft ahead, say on final, or that aircraft has delayed clearing the runway, S-turns might be used in slowing your effective approach speed. The aircraft can't otherwise be slowed up much while still going straight, as it's already typically slowed to a fairly small margin over stall speed (1.3 times Vs0, or stalling speed in landing config.). Another time it might be used, is if the aircraft on final is too high on approach - instead of going around and trying again.

 

[raymacke]

For the record, I agree it isn't a viable solution but that opinion was questioned in another thread. Just making I wasn't full of (Mod Removed)

 

[brett8883]

The question has come up in a different thread about using tacking (zig-zagging diagonally to the wind) as a workable solution when faced with an overpowering headwind. This works with sailboats but will it work with a drone or aircraft?

I fly high up in the mountains regularly with high winds that come out of nowhere so I have lots of experience flying in high winds and I use this method all the time. The benefit of “tacking”(zigzagging) is making forward progress when otherwise don’t have the power to overcome a head wind. It is a longer route but because you aren’t going head into the wind you don’t need as much air speed to to get from A to B. I use it all the time and it is effective. If you try to fly straight into a strong headwind it’s almost like the DJI flight controller limits the maximum power/tilt available to the pilot. I’ve been in many a situation where flying directly into headwind causes the drone to effectively stop dead in the air but I can “break free” by zig zagging back.

Another effective technique is to gain vertical height and then fly forward while descending because the power used to maintain altitude can be used instead for forward progress.

 

[sar104]

I fly high up in the mountains regularly with high winds that come out of nowhere so I have lots of experience flying in high winds and I use this method all the time. The benefit of “tacking”(zigzagging) is making forward progress when otherwise don’t have the power to overcome a head wind. It is a longer route but because you aren’t going head into the wind you don’t need as much air speed to to get from A to B. I use it all the time and it is effective. If you try to fly straight into a strong headwind it’s almost like the DJI flight controller limits the maximum power/tilt available to the pilot. I’ve been in many a situation where flying directly into headwind causes the drone to effectively stop dead in the air but I can “break free” by zig zagging back.

Another effective technique is to gain vertical height and then fly forward while descending because the power used to maintain altitude can be used instead for forward progress.

Sorry - you are completely imagining any benefits. The physics here is unambiguous - see the earlier explanations.

 

[Meta4]

No need to comment on zigzagging, that's been addressed already.

Another effective technique is to gain vertical height and then fly forward while descending because the power used to maintain altitude can be used instead for forward progress.

If that was true, you would be able to fly forward while descending faster than you can fly straight and level.
It's pretty easy to test to see how that works out.
And gaining altitude to do that is not going to work out well.

 

[brett8883]

Sorry - you are completely imagining any benefits. The physics here is unambiguous - see the earlier explanations.

I think this is a programming matter and not a physics one. I’ve flown in no wind conditions where my motor speed can get up close to 900 RPMs on the Mavic Pro full elevator forward in sport mode but in high wind conditions when I full elevator into the wind it A) won’t tilt the aircraft as far and B) the motor speed won’t go up as high.

You can however override this by using atti mode or increasing the RC_scale parameter. However, I’d rather not push my bird to the outer limits as far as current draw and motor speed so zigzagging works better.

This is just speculation but I think this has to do with the higher wind increasing some kind of calculated error factor which reserves more tilt for the flight controller as the the wind increases. It’s the same reason you can’t fly 60 mph ground speed into a 15 mph tail wind unless you are in atti mode.

 

[sar104]

No need to comment on zigzagging, that's been addressed already.

If that was true, you would be able to fly forward while descending faster than you can fly straight and level.
It's pretty easy to test to see how that works out.
And gaining altitude to do that is not going to work out well.

If the aircraft is pitch-limited rather than speed limited, which it may be into a headwind, and if the maximum tilt is set higher than that required for altitude hold, then flying forwards and descending does permit higher forwards airspeed.

 

[sar104]

I think this is a programming matter and not a physics one. I’ve flown in no wind conditions where my motor speed can get up close to 900 RPMs on the Mavic Pro full elevator forward in sport mode but in high wind conditions when I full elevator into the wind it A) won’t tilt the aircraft as far and B) the motor speed won’t go up as high.

You can however override this by using atti mode or increasing the RC_scale parameter. However, I’d rather not push my bird to the outer limits as far as current draw and motor speed so zigzagging works better.

This is just speculation but I think this has to do with the higher wind increasing some kind of calculated error factor which reserves more tilt for the flight controller as the the wind increases. It’s the same reason you can’t fly 60 mph ground speed into a 15 mph tail wind unless you are in atti mode.

Now you are conflating two completely different things. The aircraft will pitch exactly the same in all conditions unless it is constrained by being unable to hold altitude at those pitch levels. It has nothing to do with the wind.

 

[Marv McCarthy]

I'm a new pilot and also a sailor, so I've been wondering about this myself. Thank you for the explanations, very helpful. The CE (Center of Effort) and the CLR (Center of Lateral Resistance) are the two forces at work on a sailboat. Proper sail trim ensures the best CE for a given course, and the CLR is the opposing force that the keel exerts on the water to maintain stability.

I do have a question though... if you are flying back directly into a strong headwind at full throttle, wouldn't you reach a point of diminishing return as the attitude of the aircraft presents a larger cross section to the wind? In other words, the wind force generated on the body of the aircraft increases as the attitude increases. Or is this negligible since the mass of the drones are relatively small. Hope the question makes sense...

And I agree prevention is the best option!

 

[sar104]

I'm a new pilot and also a sailor, so I've been wondering about this myself. Thank you for the explanations, very helpful. The CE (Center of Effort) and the CLR (Center of Lateral Resistance) are the two forces at work on a sailboat. Proper sail trim ensures the best CE for a given course, and the CLR is the opposing force that the keel exerts on the water to maintain stability.

I do have a question though... if you are flying back directly into a strong headwind at full throttle, wouldn't you reach a point of diminishing return as the attitude of the aircraft presents a larger cross section to the wind? In other words, the wind force generated on the body of the aircraft increases as the attitude increases. Or is this negligible since the mass of the drones are relatively small. Hope the question makes sense...

And I agree prevention is the best option!

That's correct, but lateral thrust is proportional to the sine of the tilt angle, while drag increases with the square of the airspeed and the vertical cross section, which increases by less than the sine of the tilt angle. So the diminishing return is dominated by airspeed, as is the case whatever the wind speed is.

 

[Marv McCarthy]

Great, thank you, got it. I'm rusty on my math, so that saves me sorting through all the formulas myself!

 

[Trackerputnam]

I think the answer about tacking back and forth being a possible option to high head wind is certainly a viable solution to the problem of being held back by the force of the wind! At ground level the wind can be nothing and at 50’ it can be raging! Why? If wind is obstructed by something there are areas or pockets where the wind will be less! That can be something miles away creating those pockets! Sailplanes look for these pockets all the time! So by tacking back and forth you are looking for a pocket of less resistance allowing you to gain forward momentum! Case in point! I flew up a mountain ridge until I reached 1642’ AGL! I turned around to come back down the mountain and the drone would not move! Wind held it in place. I was new to drones at the time. I started going back and forth, up and down. Nothing! I thought she was a goner! But then I notice a few feet forward progress in one area to the side! So I headed back that way and when it got there and started gaining I dove it down and raced it down the mountain. Later in watching the video I realized what I had done was put the drone in the shadow of two trees on the ridge thus blocking it from the wind giving it a chance to survive! So tacking is more a search for a pocket of survivable wind!

 

[sar104]

I think the answer about tacking back and forth being a possible option to high head wind is certainly a viable solution to the problem of being held back by the force of the wind! At ground level the wind can be nothing and at 50’ it can be raging! Why? If wind is obstructed by something there are areas or pockets where the wind will be less! That can be something miles away creating those pockets! Sailplanes look for these pockets all the time! So by tacking back and forth you are looking for a pocket of less resistance allowing you to gain forward momentum! Case in point! I flew up a mountain ridge until I reached 1642’ AGL! I turned around to come back down the mountain and the drone would not move! Wind held it in place. I was new to drones at the time. I started going back and forth, up and down. Nothing! I thought she was a goner! But then I notice a few feet forward progress in one area to the side! So I headed back that way and when it got there and started gaining I dove it down and raced it down the mountain. Later in watching the video I realized what I had done was put the drone in the shadow of two trees on the ridge thus blocking it from the wind giving it a chance to survive! So tacking is more a search for a pocket of survivable wind!

That's not tacking but yes - that could be a workable strategy in a non-uniform wind field.