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A Dutch roll can be an uncomfortable experience for the passengers and the crew. Here’s everything you need to know about what it is and what causes it.
Whether you’ve been flying a plane or been riding in one that’s experienced a Dutch roll, you probably didn’t enjoy it very much. It can be unsettling at the least, and perhaps even a bit scary if you’re not sure what it is. But that’s just it, many people don’t really know what it is in the first place. So what is Dutch roll?
Dutch roll is a series of decreasing oscillations on both the rolling and yawing axes. As the plane tries to stabilize itself on both axes, the plane oscillates back and forth on each one, creating a very unsettling experience. After enough oscillations, it should stabilize and go back to normal.
The stability of an airplane is something that many people don’t really understand. Planes are actually much more stable than you might think, and they naturally want to get back to straight ahead, wings-level flight as soon as possible after a disturbance. In this article, we’ll explain the different types of stability first and then tell you everything you want to know about Dutch roll.
The reason that SkyTough has become one of the top aviation sites on the web is because we focus on providing nothing but the best, most helpful content. On a topic like this one that’s mostly flight theory, extensive research was done and the information was thoroughly vetted to ensure accuracy.
Airplane Aerodynamics and Stability
Before we can start talking about Dutch roll and what it means, we have to first take a look at the aerodynamics and stability of an airplane. Without having at least some foundational understanding of these two concepts, Dutch roll wouldn’t really make much sense in the first place!
While I could go on for days about aerodynamics and stability in their own full-length articles, I’ll touch on the high points here so that we can actually get to talking about Dutch roll. There are two main areas of interest here — axes of rotation and stability.
What are an Airplane’s Axes of Rotation?
Axes of rotation are just the straight line through a rigid body upon which all other points of that body circle around. The Earth, for example, rotates around its axis. In a similar way, airplanes also rotate on their axes of rotation, but there is more than just one.
Up first is the pitch axis. This axis runs perpendicular to the fuselage and parallel to the wings of the airplane and is the axis that the plane pitches upwards and downwards on. So when you nose up or nose down in an airplane, it is rotating on its pitch axis. It’s important to note that pitch and the pitch axis is not relevant to Dutch roll, so there isn’t going to be much of a focus on it in this article.
Since we’re talking about Dutch roll here, you can probably guess that the roll axis is pretty important. This axis runs straight through the length of the fuselage from front to back. Upon this axis, the plane can roll towards the right or the left in a banking manner. When the plane banks and one wing gets lower than the other, it is rolling on this axis.
Lastly, we have the yaw axis. This axis runs straight up and down through the fuselage in a perpendicular manner. Yaw is fairly easy to understand because it’s just the left and right movement of the airplane. This is different from roll, in which the airplane is banking on its roll axis. When it yaws, level flight is maintained but the nose of the aircraft is just pointed left or right off center.
Airplane Stability: How Does it Work?
Now that you’ve finished the crash course in rotation axes above, we can take a look at stability. Stability in aviation simply means the airplane’s natural disposition to return to straight ahead, wings-level flight following a disturbance of any kind. In other words, due to the way they’re designed and the forces of flight, an airplane will naturally want to return to equilibrium without any additional input from the pilot.
This occurs along all three rotation axes described above. So if the plane pitches upwards, it will naturally want to go back down to level. If it rolls it the right, its stability will naturally cause it to roll back towards the left to compensate. And if it yaws one way or the other, the plane will then yaw in the other direction to return to equilibrium.
Different types of planes have different levels of stability based on what they’re designed to do. This is because with higher stability, the plane is more difficult to turn and adjust your flight path. But with low stability it can be hard to control the plane without advanced computer systems. For example, commercial airliners have significantly higher stability than a fighter jet, because they’re designed to be used for vastly different things.
In the end, it’s this very stability that ends up causing Dutch roll in the first place.
What is Dutch Roll?
Dutch roll begins when some sort of disturbance causes the airplane (almost always a commercial airplane) to roll one way or the other. Let’s say it rolls to the right for posterity’s sake. Due to the natural lateral stability of the plane, it will want to roll itself back to the left to compensate.
Due to the high stability of these planes, it overshoots itself and then rolls too far left. The plane then compensates by oscillating back and forth until it eventually settles in wings-level flight. But this is only one half of the equation that makes up a Dutch roll. There is also yaw oscillation to consider.
This happens because when the plane starts to roll, the wing that’s lower generates more lift than the higher wing since more of the airfoil is perpendicular to the relative wind. As it creates more lift, it simultaneously creates more drag since the two forces are directly related to one another.
So when the plane starts to roll to the right, the right wing creates more lift and drag. The lift is what causes it to roll back left towards stability. But the excess drag causes the plane to also start yawing to the right. As it begins to yaw, the tail (and rudder) start to compensate and force it to yaw back to the left to compensate.
Recall that at the same time, the lateral stability referenced above causes the plane to overshoot its equilibrium and roll left, which will then create more drag on that wing and cause the plane to yaw left. This is compounded by the effect of the rudder, and the plane then overshoots its directional equilibrium and yaws too far left.
As the rolling and yawing rotations counteract each other while the plane tries to return to straight ahead, wings-level flight, it oscillates on both axes. This causes a wobbling effect as it rolls and yaws back and forth.
This is Dutch Roll.
It’s important to note that the oscillations on both axes should decrease each time it goes back and forth, so it’s not a never-ending cycle. But once it starts, it will create a very uneasy feeling in the airplane as if you’re being forced in multiple directions at once.
How Can You Prevent Dutch Roll While Flying?
The way that Dutch roll is prevented is by adjusting the rudder as soon as the plane begins to roll in order to prevent the additional yawing back and forth. If the rudder is adjusted perfectly in conjunction with the rolling motion, the plane will never overcompensate on both axes to the degree required to cause Dutch roll.
Unfortunately, doing it by hand is almost impossible. This is where modern-day computer systems come into play. On most airliners, rudder control is automatic. As soon as there is a minute change in the roll or yaw of the airplane, the rudder is adjusted to compensate and create a smooth flight.
These systems detect the smallest of changes that we as humans just simply never could by looking at dials and instrumentation. So in most airplanes, Dutch roll is just prevented by technology. If you ever do experience Dutch roll, don’t panic. The wobbling effect should decrease with each oscillation and the plane will eventually get back to its stable position on all axes.