When the rubber hits the road… from the sky

Shakib Rahman
10 March 2015

Above: Tires on a Boeing 737 (Wikimedia Commons/Politikaner)

Did you know? Airplane tires are made by hand. They are individually constructed and inspected to meet strict requirements established by regulators like the US Federal Aviation Agency (FAA).If you’ve ever flown in an airplane, you know that funny feeling during takeoff when you're no longer in contact with solid ground and that bump when you touch down at the end of the journey. But have you ever wondered how airplane tires handle all that stress and pressure without bursting on contact with the hard runway? In fact, airplane tires need to be specially designed to give them the strength necessary to stay intact during takeoff and landing.

One thing’s for sure: airplane tires are very different from the ones on the family minivan. In fact, airplane tires have about as much in common with car tires as they do with sneakers. All three are made of rubber, contain air, and provide support and cushioning for what’s on top of them, but that's about it.

When landing, airplane tires have to support the weight of the plane and its passengers without bursting from the strain. In particular, they have to deal with enormous forces upon landing, especially friction from contact with the runway surface. Friction is the result of two surfaces moving against each other, like when you rub your hands together.

Did you know? Kevlar comes in several different grades, including regular Kevlar, Kevlar 29 and Kevlar 49. Kevlar 29 is the bulletproof variety and Kevlar 49 is used in boat hulls.The friction created when an airplane tire hits the runway generates heat and wears down the outside layer of the tire. For this reason, airplane tires are reinforced with the synthetic polymer Kevlar and other strong, flexible materials. Flexibility is an important feature of airplane tires because it allows them to absorb more of the shock of landing and to wear down more slowly. As well as being strong and flexible, Kevlar is also heat resistant and lightweight.

Airplane tires also have conducting strips built into the tire grooves to dissipate any static charges that may have built up. If static electricity were allowed to build up during takeoff or landing, it could cause a spark and ignite the fuel in the plane. The grooves themselves are offset at 30o and 60o from the centre of the wheel. This way, the forces generated when landing are redirected outwards instead of going straight through the tire, putting less strain on the landing gear.

Another way to help maintain airplane tires is to fill them with nitrogen, a non-flammable gas that doesn’t corrode the metal parts of a plane and doesn’t oxidize (break down) the rubber in the tires. The tires themselves are made from at least three layers of rubber, each of which is laid down in a different direction to make the tire stronger and give it better traction when landing.

Did you know? There are three main types of airplane tire, each with its own specifications: commercial aviation (used by passenger and cargo airlines), military aviation, and general aviation.But airplane tires are more than just rubber (and Kevlar). Each tire had more than 14 other parts that each serve a specific purpose in making takeoffs and landings safer and easier. The typical airplane tire can go through about 100 landings before it needs to be repaired. Usually, the top layer is simply peeled off and replaced with new treads. That way, the other parts, which are very expensive, don’t need to be replaced.

So the next time you're enjoying a flight, think about all the technology and engineering that goes into the specially-designed tires that ensure you can take off and land safely!

Learn more!

Learn more!

What’s so special about aircraft tires? (2013)
Jeff Simon, Aircraft Owners and Pilots Association

Brief introduction to the different types of airplane tires available.

What Are Aircraft Tires (2015)
Mary McMahon, wiseGeek

Short explanation of how airplane tires are built and maintained.

Shakib Rahman

 Shakib Rahman is a coordinator with Let's Talk Science at the UofA.  He an avid soccer player and a sports nut in general.  He also has a a passion for science, science literature and TV. In his spare time, he writes science articles, some of which you can read here at CurioCity.

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