Wheels and tires on an airplane are essential for safe operation and landing. Here’s everything you want to know about airplane wheels and tires.
Airplane wheels and tires are vital parts of the plane’s landing gear that are necessary for taking off, landing, and taxiing. Airplane wheels are typically made of aluminum alloy and need to be able to handle the full weight of the aircraft, sometimes requiring more than 20 of them to do so.
If you are flying in a seaplane meant to land on water, wheels and tires are absolutely necessary for safe operation. That said, relatively little is actually known about airplane wheels and tires, from single-engine aircraft through passenger jets. In this article, we aim to change that. We’ll discuss airplane wheels and tires including what the difference is and just about everything there is to know about both.
At SkyTough we want to provide our readers with only the best, most helpful content that they’ll find on the web. To do this, we combine our own knowledge and experience with research as well as input from others in the aviation industry. This way, you can leave our site with the confidence that you’ve received accurate information. So by the time you’re done reading this, you’ll know everything you need to know about airplane wheels.
Airplane Wheels vs Tires: What’s The Difference?
There is a common misconception out there about wheels and tires in general (not just for airplanes) that they’re the same things. But they are most certainly not! Just like any vehicle — car, bike, airplane, etc. — the wheels and tires are two completely different parts. But they work in conjunction with one another to act as the main point of contact between the vehicle and the road.
For all of these vehicle types, the easiest way to describe tires is the black rubber part that actually comes in contact with the road. We all know what tires are, so I won’t waste your time describing those. But wheels, on the other hand, wheels are often misunderstood. Most people seem to think that wheels refer to the exact same thing. Wheels are just the black rubber part, right?
That’s actually not right! Wheels are actually the metal part that the tires are wrapped around. Trust me, I thought the exact same way when I was younger, and actually learned the difference in my early years when I became a car enthusiast. I actually worked at a tire shop for many years when I was younger, and the difference became clear. But for people that don’t regularly separate wheels and tires and work on them, I know that they can be misunderstood.
On airplanes, it’s the exact same way as it is on cars. Okay, maybe not the exact same way, but the premise is identical. Airplane wheels and tires are both parts of the airplane. More specifically, they are two of the biggest parts of what makes up the plane’s landing gear, in addition to the struts and brakes.
Airplane wheels are the large metal objects in the center of the tires, and tires are, of course, the black rubber circles wrapped around the wheels that the planes actually drive around on. While the general premise and idea of airplane wheels and tires are similar to a car, they’re also very different. It’s almost like they’re car wheels and tires on steroids.
So let’s dive in, here’s everything you’ve ever wanted to know about airplane wheels and tires.
As one of the major components of an airplane’s landing gear, the wheels are essential for safely landing and operating an airplane. Without the wheels, there would be no place for the tires to be mounted and there would be absolutely no way to use the brakes or taxi the airplane around the runway and the rest of the airport.
In no time at all, you’ll be an expert on everything related to airplane wheels.
What Are Airplane Wheels Made Of?
If they’re so vital for landing, taking off, and taxiing around the airplane, it would make sense for airplane wheels to just be made out of the strongest material that’s reasonably feasible, right? Think of things like trailers and many semi trucks for a second. Oftentimes those wheels are made out of steel, so that might be your first guess.
After all, the wheels have to be able to support the entire weight of the airplane. And for those that are curious, some types of planes, like the Airbus A380, weigh a ridiculous 1,265,000 pounds. You read that correctly, that’s over 1 million pounds or over 632 tons. Yeah, planes are incredibly heavy. And all of that weight ends up on the landing gear when planes are taking off, landings, and taxiing about.
So, a metal like steel would make sense. But actually, that’s not the case. Almost uniformly across the board, airplane wheels are actually made out of an aluminum alloy. In some cases, a magnesium alloy is used, but for most wheels, the choice is aluminum. To go a step deeper, airplane wheels are typically constructed in two separate pieces, through either a forging or casting process.
After that, the two halves are bolted together and contain a groove at the point that they meet where an o-ring is used for an airtight seal. Additionally, the area where the tire meets the wheel once mounted — known as the bead seat — is often prerolled and strengthened to ensure the wheel can withstand the forces experienced during normal operation.
After all, just imagine how much force there is on the landing gear when a million pound airplane touches down. No matter how gentle the pilot is able to land the aircraft, there’s going to be a lot of force that the wheels have to be able to withstand. If they can’t, there will potentially be devastating consequences.
How Long Do Airplane Wheels Last?
Even though that last section ended with a bit of doom and gloom about airplane wheels, there isn’t a whole lot to worry about. To make this easier to think of, just imagine your car for a second here. Sure, you’ve probably replaced your tires once or twice (or at least know that you’ll have to at some point). But I’d be willing to bet you've never needed to replace your wheels. Right?
It’s actually the same way with airplanes! Airplane wheels are typically not something that wears down over time, just like car wheels. If there is never an accident that causes damage to a wheel, aluminum wheels don’t usually ever have to actually be replaced. Whenever the tires are getting replaced, the maintenance team can take a grinding pad or sander to the bead area to remove any corrosion, but that’s about it.
Without getting too far into the details of metallurgy, aluminum has a bunch of properties that make it ideal for lots of things. Besides being lightweight and relatively affordable, it also doesn’t rust and is fairly resistant to the elements. This helps things like airplane wheels last a long time, and won’t usually need replacing throughout the life of the airplane. And if so, it’s a relatively easy fix to make!
How Many Wheels Do Airplanes Have?
Pretty much all vehicles on the road have four wheels. We all know that. Of course in this case we are barring motorcycles, tractor trailers, and dually trucks. But more than likely 99% of the vehicles you see on the road everyday have just four wheels. That helps distribute the vehicle’s weight evenly, keeps it balanced and upright, and allows for a simple driving experience.
But what about airplanes? How many wheels do they have?
Let’s step away from commercial planes for a second (we’ll come back, don’t worry), and look at personal aircraft, like affordable planes that you might be in the market for. Often, these planes have just three wheels. That’s even less than your car! These smaller planes typically have two wheels at the front (or under the wings) and then one in the back. Or they’ll have one in the front and two further back. In any case, just three wheels.
For these small personal aircraft, three wheels are all that’s needed. This gives the plane plenty of stability, makes taxiing easy, and more than enough capability to take off and land as expected. But for larger airplanes like commercial passenger jets, that configuration just wouldn't be enough. After all, with a plane weight over 1.2 million pounds, if there were just three points of contact with the ground, that would be a big issue come time to land.
In fact, commercial airplanes typically have 10 or more wheels, with 10 being at the very low end of the spectrum. The aforementioned Airbus A380, for example, has a total of 22 wheels, compared to the Airbus A330 which just has 10. Looking at Boeing, the 787 Dreamliner has just 10 wheels, but the massive Boeing 747 has 14 wheels.
So it’s not as simple as just thinking about personal aircraft versus the behemoths that you’ll fly as a commercial pilot. It really comes down to the actual make and model of the airplane and what it was designed to do. It’s always better to have some factor of safety built-in and have more wheels than needed!
What Do Airlines Do With Old Wheels?
As you learned above, there actually isn’t really much of an issue when it comes to dealing with old airplane wheels. Since they very rarely need replacing, airlines are rarely faced with needing to figure out what to do with them. But in the rare case that an airline is faced with an excess of old airplane wheels, the solution is actually a rather simple one.
They get recycled.
It’s really that simple! Just like an automotive shop that’s got a few extra spare wheels stacked up from cars that have had accidents, the easiest way to handle the extra wheels is via recycling. Most commonly, old airplane wheels are just taken to the local recycling plant or scrap yard so that they can be melted down and reused as fresh aluminum. This is both economical and good for the planet, so no other option really compares!
That’s about it when it comes to airplane wheels, so let’s jump into the thing that you might be even more interested in — airplane tires!
I’m going to go out on a limb here and say that when most of you searched for information on airplane wheels, you were actually more interested in airplane tires. If that’s not the case, then I certainly hope the wheel information above was enough to satiate your appetite! But if you really wanted to know more about the tires, then I’ve got you covered.
Like wheels, airplane tires are absolutely critical for safely landing and operating an airplane. If a tire blows out on landing, it will be tough for the pilot to keep control of the airplane and avoid crashing. That said, don’t think that having a blowout is the end; many times pilots are still able to corral the aircraft and get it under control.
But for safe, normal operation of the plane, tires need to remain in good condition and be inspected regularly. But we’ll touch on all that in greater detail shortly. This is everything you’ve ever wanted to know about airplane tires.
How Long Do Airplane Tires Last?
Just like with the tires on your car, airplane tires also need to be replaced. Due to the abuse that these tires take under normal operation, it’s vital that they get replaced to ensure they can stand up to the forces and wear and tear necessary for safe flights. But compared to your car, airplane tires need to be replaced far more often.
Think about the tires on your car for a minute. They probably have a 50,000 to 70,000-mile warranty from the manufacturer. This means that if you maintain them properly, you should get that many miles out of them. For the average driver, this equates to about 4 to 6 years’ worth of driving. Airplane tires, on the other hand, do not last that long!
The most important factor on airplane tires is the number of landings. As you might expect, landing an airplane is the portion of flight that’s the most stressful on the tires (and most pilots!). For most airplanes, personal to commercial, tires need to be changed out every 120 to 400 landings. This will be dictated by how well they’re wearing and if there are any bald or flat spots.
Additionally, it’s important that the age of the tires is well monitored. Car tires should be replaced every seven years, regardless of the mileage. That’s because they wear down over time, the sun dries them out, and more. Airplane tires, however, should be replaced every 12 months at a minimum. They wear down and suffer many of the same issues as car tires, but they are subjected to significantly higher forces during normal operation.
Do Airplane Tires Use Nitrogen Or Regular Air?
The discussion of what airplane tires are filled with is the exact same one that’s had with cars. I’ll stop making car comparisons after this, I promise! But if you’ve had your tires replaced in the last decade or so, you might’ve heard mention of them being filled up with nitrogen instead of normal air. Well, it’s the same way for airplane tires these days.
More often than not, airplane tires are filled with nitrogen instead of normal air. But why?
Before we get into it, let me preface this by saying that “normal air” is roughly 78% nitrogen in any case. So there isn’t really that big of a difference between a molecule of normal air and a molecule of nitrogen. But with airplanes, time is money and money is time, so every little bit helps. These are the main reasons why nitrogen is typically used in airplane tires.
Since a pure nitrogen molecule is slightly larger than regular air, tires filled with nitrogen are usually able to maintain pressure for longer than an identical tire filled with normal air. While this won’t be any sort of world-breaking difference, it alone makes it worth filling airplane tires with nitrogen in the first place.
Less Chance of a Blowout
Again, the difference here is almost negligible, but not quite! But a tire filled with air is much more capable of producing flammable vapors thanks to the 21% oxygen concentration that we humans require to breathe. And in the event of a dragging wheel or overheated brakes, this could increase the likelihood of a tire blowing out. And if one blowout is saved over the course of a million flights, this could save not only significant amounts of money, but also human lives.
Rubber Can Be Oxidized
The last one is pretty simple — rubber has the tendency to react with oxygen in the air and begin to oxidize. When rubber oxidizes, it begins to weaken. Over time, this could again end up leading to a very slight chance of having an issue such as a blowout. And which element is necessary for oxidation to occur? Oxygen, of course!
And the easiest way to eliminate this issue (at least from the inside out), is to use pure nitrogen instead of air. This again goes back to the aforementioned 21% concentration of oxygen that’s in normal air. If nitrogen is used, this amount of oxygen is removed from the equation and far less oxidation can occur. Of course there will still be oxygen reacting with the tire from the normal atmosphere from outside, but at least it won’t be reactive from inside the tire.
Airplane Tire Safety Devices
To help prevent issues like blowouts and over/under pressurization from occurring, airplane tires and wheels have safety devices built-in, especially in modern day aircraft. Over the years there have been even more safety features used, but these are the two most common ones.
Tire Pressure Monitoring System
Okay I know above I said no more car references, but this is one we’re all likely aware of — TPMS. A tire pressure monitoring system, or TPMS, is a fairly simple system that reads the pressure in the tires of a vehicle — such as a car or airplane — and presents this information to the person in control (i.e. the driver or pilot).
In most cases, it’s a simple system that will display a light if one of the tires is registering a pressure that’s below a certain setpoint. But in some modern cars and airplanes, the system reads the pressures in real-time and displays the values to the driver or pilot. This way, a pilot can tell if a tire is low as soon as the instrument panel is ready to go and the maintenance crew can be notified of the issue.
Over Pressure Relief Valves
As the name suggests, these are devices designed to prevent an airplane tire from being overpressurized. These are typically there to help keep maintenance crews safe due to the massive amounts of pressure that airplane tires are required to have, often up to 200 psi or more for many airplanes.
These valves are simple. Once a certain pressure is reached, the valve is forced open and air is evacuated from the tire until there’s not enough excess pressure to force the valve open again. This device is usually built directly into the wheel and can help prevent death or dismemberment from an exploding tire due to overpressurization.
Do Bush Planes Use Special Tires?
If you know anything about bush planes, or you’re thinking about becoming a bush pilot, then you probably know that these specialized planes have quite a few things that make them different from other aircraft. And one of the biggest things that can quickly distinguish a bush plane from other types of planes is the tires.
Although bush planes can have all sorts of different types of landing gear, most have what are known as tundra tires. Compared to the size of the plane, tundra tires will appear to be way oversized and unnecessary. But they’re designed that way. These tires usually have low pressure to absorb rougher impact while also being oversized to more easily traverse some of the more difficult terrain than bush planes are expected to be able to navigate.
Other than the size of the tire and what it’s designed to do, there isn’t a whole lot different about tundra tires and regular airplane tires. They still need the same type of air, just at a lower pressure. And they still need to be replaced. In fact, bush plane tires might even need to be replaced more often since they’re likely to absorb more abuse.
In any case, there you have it! At this point you should know more than you ever thought you wanted to know about airplane wheels and tires!
About THE AUTHOR
After spending years watching every video I could find about flying, I finally scratched the itch and got my pilots license. Now I fly every chance I get, and share the information I learn, here.Read More About Joe Haygood