Rudders On An Airplane: What Is It's Purpose?

Airplanes need all their systems to work with one another in order to fly, but some are tougher to understand than others. What does a rudder actually do?

The rudder on an airplane is one of the main components of the steering and stability systems. While many people think it’s only there to help the airplane turn, it does much more than that. The rudder is used to control the yaw of the plane, keep it level during turns, and combat crosswinds.

Like most parts and systems of an airplane, the rudder is vital to the plane flying as expected. Even though it’s a well-known part of the airplane, many people don’t really understand what it actually does. Not fully at least. In this article, you’ll learn everything you want to know about an airplane’s rudder and what it does. So consider this your one stop shop for all things rudders!

Providing our readers with the most insightful and useful aviation info on the web is our top priority at SkyTough. To make sure you get the most accurate information you can, we’ve combined hours of research into airplane rudders with our own extensive knowledge of all things aviation and input from other experts in aviation. So rest assured knowing that when you finish this article, you’ll know everything you need to know about airplane rudders!

‍What Is The Rudder On An Airplane?

Even if you’re brand new in the exciting world of aviation, you’ve likely heard the term rudder before. When we’re kids and getting blasts of information about seemingly every topic imaginable in grade school, we all seem to somehow learn what a rudder is at some point, on either an airplane or a ship. Why do we all know the word? Who knows considering that 99% of the population will never actually use a rudder at any point in their lives.

But I digress. We might all know the word rudder and have a general idea of what it is, but few people truly understand what its real purpose on an airplane is.

Before we get too far into the usefulness of a plane’s rudder, it’s important that you know what it is in case you don’t. The rudder is sort of like a movable, vertical wing located on the tail of the airplane. A plane often has an upper and lower rudder, able to be controlled independently of each other. The rudder is controlled by the pilot and is used to deflect wind to move and control the plane in more ways than you are probably thinking.

Even some of the most experienced pilots out there don’t truly understand the usefulness of a rudder. If we asked you right now what a rudder was used for, if you had any idea you would likely say that it has something to do with steering the plane. And that would be sort of correct, but not really. That may be its purpose on a boat, but it’s not quite the same on an airplane. On an airplane, the purpose of the rudder is to control yaw, which is a bit different than steering.

In any case, it does so much more than that! Steering the plane is what most people in the industry think a rudder does, but this useful part of the plane can be a pilot’s best friend in many less than ideal scenarios if they know how to use it. Rudders are typically underused by pilots because many people don’t really know just how useful they can be.

That’s where we come in. So if you want to be the best pilot you can be, continue reading to learn everything you can about the rudder on an airplane.

How Does The Pilot Control The Plane’s Rudder?

While some aircraft may be a bit different and have differing controls for the rudder, or even not have a rudder at all (we’re looking at you, Ercoupe 415-C), almost all aircraft have the same general controls for the rudder. The pilot has full control over the plane’s rudder using foot pedals on the floor area in front of their seat.

It’s a fairly simple device to control and one that’s also very intuitive. If you press the left pedal (keep in mind there might be two sets of pedals if there’s an upper and lower rudder), the rudder deflects to the left and starts affecting the airflow around it. While the pilot is pressing the left pedal, excess lifting force is pushing against the ride side of the rudder. In turn, the plane’s nose will start heading left, thus controlling the yaw.

But more on the nuances of what the rudder does later!

The Connection Between The Skid Ball And The Rudder

As you read that heading, we know what you’re thinking. What the heck is a skid ball? And that’s a great question! While you’re studying to become a pilot, you will undoubtedly come across the skid ball at one point or another. The best instructors out there will really hammer the point home until you know what it is, what it does, and what it’s used for.

But unfortunately, some don’t really put the focus on it that they should and you leave a lot of information on the table if you don’t really understand it. But don’t worry, you aren’t alone! So here’s a very brief refresher of what the skid ball is and what it has to do with the rudder.

The skid ball is also often referred to as the coordination ball or even just the slip/skid indicator. It’s basically a visual representation of how the pilot is controlling the yaw of the airplane, i.e. how effectively the pilot is using the plane’s rudder. The skid ball basically shows the direction of g-forces on the plane and gravity is the only force acting on the indicator, making it an effective way of showing how well the pilot is doing by using the rudder.

In just about any normal flight situation, if the ball is not centered, it’s a quick and easy way for a pilot to know that they are not properly using the rudder to control the yaw of the plane. The pilot could be either not using the rudder when they should (to compensate for adverse yaw) or they might be using it when they shouldn’t (thus creating adverse yaw). In any case, the skid ball should be centered at all times to ensure there’s no adverse yaw occurring.

What Is P-Factor And What Does It Have To Do With The Rudder?

This is about as technical as we’re going to try to get in this article so that we don’t end up putting anyone to sleep. But in any discussion about skid balls and rudders, P-factor is essential to bring up as well. Without understanding what P-factor is and how it affects the rudder (and yaw) on an airplane, it’s tough to really know what to do to compensate for its effects.

P-factor in an airplane is caused by the plane’s propeller, so it’s typically only an issue on single-engine aircraft that use propellers. And for the majority of our readers, that’s exactly the type of plane that you’ll be flying. So bear with us for a minute as we give you a 10,000-foot overview of what we’re talking about here so that you can be the best pilot you can be. The good thing is that modern planes negate much of the effect of P-factor, but it cannot totally be eliminated.

In as simple of terms as we can put it, P-factor is the result of the different areas of the propeller having different angles of attack while the plane is climbing. Due to the fact that blades on one side of the propeller will be going up as it turns and the blades on the other side will be going down, there will be a P-factor as a result. It basically means that since the blades on the right side of the propeller are going up during rotation, the center of lift drifts towards the right.

In turn, the nose of the plane wants to naturally drift left and begin turning unexpectedly. This effect is more prominent the bigger the propeller and more powerful the engine is, so the smallest aircraft don’t have to deal with it nearly as much. But regardless, the issue is that the plane begins to yaw. If the rudder is not used to compensate for the yaw, the plane will turn left.

This isn’t always going to be devastating or anything like that, but as a pilot, you want to avoid adverse yaw as much as possible. To see if the P-factor is affecting your flight as you climb, take a look at the skid ball and see if it’s off-center or not. If so, use the rudder to compensate (by stepping on the right pedal) and you’ll straighten yourself right out.

As we said, we won’t get too far into the technical details of the skid ball and P-factor, but we just wanted to make sure you understood a few things about the system as a whole so that you better understand the final section here — what a rudder really does.

What Does An Airplane’s Rudder Actually Do?

As we’ve mentioned on a few occasions earlier in the article, the main purpose of the rudder is to control the plane’s yaw. As alluded to as well, most people think that means the rudder steers the plane. But those two things are not quite the same. Outside of just the basic use of controlling yaw in the general sense, the rudder does even more.

Let’s take a look at the three major things that a rudder can do if a pilot is able to master how to truly use it.

Controlling The Yaw Of The Airplane

We aren’t going to harp on this one, since you should know by this point in the article that the rudder is used to control the yaw. But what we haven’t really talked about yet is what yaw really is. Yaw refers to the twisting or rotating about a vertical axis. So in terms of an airplane, yaw is typically seen and felt by the nose of the plane drifting one way or another.

The key here is that this is not the same thing as the plane turning one way or another. It’s a subtle distinction to make, but an important one. That’s because to turn a plane, it has to go into a bank, with one wing dropping relative to the other. Yaw on the other hand just means that the plane is not flying while pointed straight forward, although it could be moving forward.

And since yaw is not really the turning motion of the airplane, then the rudder is not technically used to steer the plane! So we’ve finally come full circle back to the beginning of the article when we mentioned how people think that a rudder is used to steer. Not quite, it’s used to control the yaw!

Keeping The Airplane Straight During Turns

We briefly touched on this just above, but turning an airplane is not like turning a car. You don’t just turn the nose of the plane one way or the other and the aircraft turns. To turn in the air, you need to start banking the plane by adjusting the ailerons on the wings. This creates an imbalance in lift on the wings, which naturally puts the plane into a bank and allows it to turn.

During a bank, the outboard wing will have more lift and therefore more drag. This will cause the wing to try to slow down faster than the inboard wing, which then in turn yanks the nose of the plane to the outside of the turn. This is exactly what adverse yaw is and the perfect time for the pilot to use the rudder to compensate and keep the nose straight.

Combatting Crosswinds

The last big benefit of knowing how to correctly use the rudder is to combat the adverse effects of crosswinds, particularly during approach and landing. As the vast majority of pilots will tell you, the hardest part of flying a plane is landing. And the difficulty of landing an airplane is heavily exacerbated if there are strong crosswinds, or wings blowing against the broad side of the plane as it comes in for a landing.

These winds tend to create adverse yaw as they hit the plane and try to turn along its vertical axis. Effective use of the rudder will compensate for the turning of the plane due to crosswinds. This will make the landing much easier and far safer, since as a pilot you want the entire approach and landing process to be as smooth as possible.

So learn how to use your rudder effectively and your entire flying experience can be better for it!