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Controlling an airplane’s yaw is essential to stable, predictable flight. In this expert guide, learn about yaw dampers, damping, and how it all works.
If you’re ever in an airplane that has started yawing back and forth, trust me, you’d notice it. Usually when this happens, the problem builds on itself and the plane begins to Dutch Roll, which can be all sorts of uncomfortable. That’s where yaw dampers and damping come into play. But who are they and how do they work?
Yaw dampers are parts of airplanes used to counteract rotation on the vertical yaw axis. For all intents and purposes, rudders are yaw dampers. The yaw damping system works by constantly measuring the plane’s yaw and making minute adjustments to the dampers to prevent Dutch Roll.
In this article, you’ll learn everything you want to know about yaw dampers and the entire yaw damping system. We’ll go over what yaw is in the first place, what yaw dampers are, how they work, and more. You’ll even learn about all the different things that yaw dampers do to make flying a plane simpler and safer for everyone involved.
Our biggest goal here at SkyTough is to provide you with the information you really want to know. So we research and vet everything that we write about before putting any content out there so that you can be confident in what you’re reading. This way, you’ll know exactly what yaw dampers are and how yaw damping works.
What is Yaw in Aviation?
Airplanes have three main axes of rotation while flying — pitch, roll, and yaw.
The pitch axis runs perpendicular to the body of the airplane, similar to its wings and is the axis that the nose of the airplane goes up and down on. The roll axis runs along the plane’s fuselage, directly through its center. When the plane turns and one side of the plane dips lower than the other side, it’s rolling along this axis.
That leaves the yaw axis.
This is the vertical axis that runs up and down through the center of the airplane. When the nose of the airplane goes left or right upon this axis — what’s known as directional rotation — it is yawing in that direction. All three of these rotations need to be monitored, understood, and controlled by the pilot in order to have predictable flight that’s safe for all people on the plane.
While the pilot is always the last line of defense for just about anything that happens in the air, including yawing, they’re not on their own up there. To help prevent an airplane from yawing enough for the pilot to notice in the first place, most planes have yaw damping systems installed.
How is an Airplane's Yaw Controlled?
As the name suggests, yaw damping systems are systems that, well, control the yaw… via damping. By using a series of sensors, indicators, and yaw dampers, this system is able to keep the airplane flying straight-ahead without much input from the pilot, often working in conjunction with the plane’s autopilot system. We’ll dig deeper into this shortly.
If a plane doesn’t have an integrated yaw damping system, then the pilot is solely responsible for controlling the plane’s yaw. This is typically done by manipulating the rudder. For more information on what a plane’s rudder is and how it works, check out our complete guide to rudder systems.
What are Yaw Dampers?
Yaw dampers are basically flaps and/or control surfaces on an airplane that are used to control the rotation of the airplane on the vertical yaw axis. By deflecting the wind hitting the tail of the aircraft, the yaw dampers are able to prevent the plane from yawing much at all. As a damper, they’re designed to lessen the effect of yawing, and if operating correctly, they do a heck of a job!
Are Yaw Dampers and Rudders the Same Thing?
In the general sense of the words, yaw dampers and rudders aren’t necessarily the same thing. By that I mean all devices that could potentially be used for yaw damping aren’t necessarily rudders. But rudders are, in fact, yaw dampers. For most cases and on most airplanes, the rudder and the yaw dampers are the same thing.
How Do Yaw Dampers Work?
I’ll start off by saying that the pilot can control the rudder (think yaw damper) manually by using the rudder control pedals in the cockpit. And sure, that’s one way that the yaw dampers work, via pilot input, but that’s not really what we’re talking about when we think about how the overall yaw damping system works.
The yaw damping system on an airplane is designed to be a standalone system that’s not reliant on anything else. I mentioned above that it often works alongside the autopilot system, and that the pilot can use the rudder to control yaw, but the overarching system is not actually reliant on input from either of these. Instead, the yaw damping system relies only on itself and its own measurement devices, indicators, filters, actuators, and more.
In general, the yaw damping system works by constantly measuring the yaw of the airplane relative to its straight-ahead motion. In other words, it measures how much the plane is twisted on its vertical yaw axis relative to zero degrees. Then, through a series of signals, filters, and mechanical equipment, the yaw dampers are automatically adjusted to counteract this deviation.
As mentioned above, this is done by deflecting the wind using control surfaces (like the rudder) which makes the plane yaw back in the other direction, canceling the motion out entirely. These movements are so small, nobody onboard, not even the pilot will notice anything is happening. Once the pilot’s indicator shows enough yaw that they would be able to notice, the yaw damping system has already made corrections.
What Makes Up the Yaw Damping System?
Now that you have a general idea of how the yaw damping system works, let’s take a look at its major components.
Yaw Rate Gyro
This gyroscope, as the name suggests, detects the angular rate disturbance on the yaw axis. In other words, this device measures how much the plane is yawing relative to the vertical yaw axis. This measurement is transmitted through a system of modulators, demodulators, filters, and more as the system determines the best way to control the yawing motion.
Signals and Filters
The measurement from the yaw rate gyro then goes into what’s known as a phase advance, which compares the yaw rate to the damping motion. This signal then goes through a demodulator before entering the Dutch Roll filter which cancels all the noise and gets the signal down to a useful form that the yaw dampers can understand.
Valves and Actuators
The signals and filters from above are used to engage various solenoids, valves, and actuators as necessary. These devices work in conjunction with one another to go from a signal to physically moving the parts of the system that can counteract the yaw.
As arguably the single most important aspect of the yaw damping system, we have the rudder. When the system is engaged and begins making adjustments to counteract the yaw of the airplane, it automatically adjusts the rudder(s) as described above.
In the cockpit, there is an indicator known as a trim indicator. This device shows the real-time position of the yaw dampers relative to their straight-ahead position. In other words, this indicator tells the pilot how far the damper(s) are moving and in what direction.
Switches and Warning Lights
Also in the cockpit at the controls of the pilot you’ll find the yaw damper system’s ON/OFF switch. As you can guess, this simple toggle switch is used to power the system. In most cases, the yaw damping system is turned on before takeoff and shutoff upon landing. In fact, some yaw damping systems will prevent the airplane from even taking off if the system isn’t turned on or has malfunctioned.
Speaking of malfunctioning, there is usually a warning light that will illuminate if something in the yaw damping system has failed. Lastly, there’s a test switch that pilots can engage to test the system’s functionality before takeoff.
What Are Yaw Dampers Used For?
As you can see, the yaw damping system is fairly complex. It’s also vital for safe operation of the airplane, which is why some planes simply won’t fly unless the system is working properly. So let’s take a look at why yaw dampers are used and what they can do for you, as either a pilot or a passenger.
Dutch Roll Prevention
The biggest benefit of having yaw dampers is that they prevent Dutch Roll. We have another article on the site that can teach you everything you want to know about Dutch Roll, so I won’t get into the details here. But basically Dutch Roll is when the plane starts to rotate on both its yaw and roll axes, creating an oscillating, wobbling effect.
This can be an unsettling experience for anyone on the plane, as it will feel like you’re being pushed and pulled in multiple directions. Since the yaw damping system detects small changes in yaw and automatically makes adjustments to counteract it, Dutch Roll almost never occurs in planes with these systems.
Counteracting Engine Failure
While it’s true that an airplane can fly even if one of its engines fails, it’s certainly not ideal. Especially because of the yawing that the airplane will naturally want to do. When an engine fails, that side of the plane will immediately begin to produce more drag and force the plane to yaw in that direction.
The yaw damping system can move the rudder (damper) in the opposite direction and counteract the majority of this yawing. Without the yaw damping system, it would be difficult (though not impossible) for the pilot to manually control the rudder as needed to overcome the increased drag.
Assisting with Coordinated Turns
Lastly, the yaw damping system helps the pilot make coordinated turns, which will feel like nothing is happening to everyone that’s onboard. When an airplane turns, it naturally wants to both roll and yaw, which can be a strange feeling for those not expecting it.
With yaw dampers constantly adjusting for change’s in the plane’s directional rotation, coordinated turns feel almost as if the plane is just flying straight the entire time. The yaw damping system really does do some amazing things!