There’s nothing like the joy of going on holiday. Your excitement builds even further as your taxi drops you at the airport loading zone. You finally clear security and arrive at your gate. As you sit back in the waiting area chair, you glance out the window and become mesmerized by the constant movement on the tarmac. One thought leads to another, and now you become curious.
Are aircraft tires solid? No, they are not. Regardless of the size of the airplane, the tires are made of casing layers of thick rubber, nylon, or aramid cords, filled with air or nitrogen depending on the type of plane. As you see, airplane tires are specially designed to withstand the heavy wear that comes with landings and takeoffs at high speeds.
Below we will explore more about the tires various aircraft use. You’ll also learn why most bigger airplanes have their tires filled with nitrogen instead of air! Let’s start!
Table of Contents
Airplane Tires VS Car Tires
You may find it interesting that airline tires are made by the same manufacturers that make automobile tires. With that in mind, it isn’t surprising to find that Goodyear, Michelin, Bridgestone, and McCreary are the top producers of aircraft tires, although McCreary typically sells to the smaller airplane owners.
Similar to your automobile tire, aircraft tires are sold in sizes designated by diameter, section width, and wheel rim size. The difference is that automobile tires are sold based on centimeter measurements; aircraft tires are sold based on non-metric (inch) measurements.
For example, a Boeing 787-8, for example, requires a 40 x 16 R16 tire designation. This would suggest the aircraft’s tire needs to be 40 inches round by 16 inches wide and should be mounted on a 16-inch rim.
However, there are some quite big differences between airplane and car tires.
Let’s have a look at how aircraft tires are made.
How Aircraft Tires Are Made
Tires used for airliners are different from your automobile tires. Looking at tires starting from the outside.
Tread
Street tires typically have some sort of a block or chevron tread pattern that has been used as part of the molding process. Airline tires, on the other hand, usually have parallel grooves unless they are specifically used for unpaved runways.
That intense speed achieved at takeoff and needed for a successful landing is the reason airplane tires have a different tread. That speed impact would most likely tear the block tread off the tire. The other thing to consider is that each set of landing gear on a passenger or freight aircraft usually has a full set of two or four tires to provide additional stability.
Cords
The layers beneath the tread are the cords. These are the nylon or aramid fabric casings encased in rubber that give the tire its strength and air pressure resistance. The number of layers is known as plies.
Aircraft tires are specifically rated based on the strength of the plies they have. The higher the ply rating, the more strength the tire has and the heavier load it can bear. Makes sense, right?
Bead
The bead anchors the outside of the tire to ensure a firm mounting surface to the tire’s rim. These are usually bundled and are made from high-strength carbon steel wires surrounded by layers of rubber and fabric.
These are an important part of the tire design – they disperse the tire’s impact load from the ball of the tire to the rim.
Sidewalls
The sidewall is made of a different, more flexible rubber than the tread. Similar to the tread, the sidewall also has multiple layers. The sidewall’s purpose, however, is to protect the tire from the damaging effects that ozone diffusion can have on aircraft’s tires.
Tubed and Tubeless
The winter sport of tubing is simply the inside tube of a tire that is being used once the external part is no longer viable.
Tubed tires include a thin layer of rubber attached to the sidewall to protect the tube from leakage.
Mechanics know if a tire is of the tubeless variety because it is designated as such on the sidewall. Tubeless tires have a thick liner of rubber attached to the sidewall acts as a tube and restricts gas from leaking into the casing plies.
What Tire Pressure is used for Airplanes?
Just as for your automobile, the aircraft’s tires must be properly inflated. Your automobile tire may require 35 pounds of air pressure, but an airline’s tire needs to have about 200 pounds per square inch of air pressure.
It’s interesting. An overinflated tire will most likely damage the wheel of the plane but is unlikely to blow. An underinflated tire, however, is more likely to suffer a blowout because it heats the bead area up to 50-percent hotter than a properly inflated tire.
This is part of why the pilot and groundcrew conduct constant safety checks to include the tires and their current air pressure.
Nitrogen VS Air: Why Some Airplanes Have Their Tires Filled With Nitrogen
Most heavier airplanes have their tires filled with nitrogen instead of air. This is mainly to do with the following two reasons:
1. Tires with nitrogen maintain pressure longer
Without getting too bogged down in the chemical reactions, nitrogen diffuses through rubber much slower than oxygen. This means that a tire filled with nitrogen will maintain pressure for longer, which means less maintenance and lower costs.
2. Safety
Perhaps the most important aspect is safety. Here are some safety benefits that come with nitrogen-filled tires:
- In case of dragging wheel brakes or other heat-inducing events, an air-filled tire has a much higher chance of developing flammable vapors. In a worst-case scenario, this could mean that the tire explodes. In 1986, a Boeing 727 crashed due to this exact reason, and killed all 166 passengers on board!
- Tires filled with nitrogen will keep the air pressure (nearly) constant regardless of temperature swings. This saves maintenance and mileage.
- Oxygen reacts much more easily with rubber. And since oxidized rubber gets weaker, this could make the tire more prone to breaking.
Do all planes have their tires filled with nitrogen?
No, while the FAA does require that nitrogen is used in most larger passenger aircraft, this is not a requirement for lighter aircraft, which often just use compressed air.
Here you may read more about the regulations enforced by the FAA
How Often do Airplane Tires Need to be Replaced?
When an airplane lands, it is going at an approximate velocity of 150 knots, although some tires are rated for up to 250 knots. Aircraft also are carrying approximately the tonnage of a multi-story apartment building – up to 38-tons (76,000 pounds!)
This is why the tires smoke when the plane first lands – they are basically drug down the runway because they can’t immediately catch up with the plane’s initial touchdown velocity.
Even though the tires take a lot of abuse in the takeoff and landing processes, it’s amazing to think that they are purported to be able to withstand about 500 landings or takeoffs (250 cycles) before they need to be replaced. This just goes back to how strong the rubber is and all of the layers that are used in the tire construction. Without all of this material, they would be bald after each landing.
Along those same lines of thought, if the airliner’s tires were solid instead of inflated, they wouldn’t allow the necessary give and spread that protects the rest of the plane’s landing gear from damage.
Different Tire Types
Large passenger and cargo airplanes aren’t the only ones that need special tires. Smaller, private planes and jets do too.
Tire Classifications
For those who fly a more classic private airplane, Type I tires are still available, but due to the lack of consumer volume, they are no longer being redesigned.
If you have a more modern, private airplane or jet, chances are likely that you are using the Type III tire. They’re designed to give the plane flotation and cushion. These tires are usually reserved for smaller aircraft that have limited landing speeds of under 139 knots.
The passenger airliners and cargo or freight airplanes typically use the Type VII tires. These are the high-performance tires that are designed to withstand higher loads.
If you’re interested in Top Gun or fighter/high-performance jets, they will usually use Type VIII tires designed for high speeds and loads.
Ending Words
Regardless of whether you are preparing to take your first flight or if you’re a seasoned veteran, you can rest assured that the tires used are built to last. They may not be solid, but they are expertly engineered to ensure their ability to make it through hundreds of takeoffs and landings.
While many people take time to ponder about how a plane stays in the air, few think about the magnificent rubber that gets them down safely!
Your tires are built to last. Sit back and fasten your seatbelt tight and low across your lap. Make sure your tray table is in its upright and locked position. Turn off all cellular devices. And have an incredible flight.
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