Tire Tech

Few pilots pay much attention to their tires. They kick them a couple of times before lighting the fire, or put air in them when they look really low, but thats about it. Thats a little cavalier to us, considering those three (or more, if youre lucky) small, round, rubber donuts not only support the airplanes weight, but also supply the friction necessary to follow the yellow brick road and stop when you get to its end. As part of a project for sister publication Aviation Consumer, we recently had the opportunity to speak with industry executives about tires and tire failures, as well as a myriad of other related topics, while researching why aircraft tires fail. We found that, short of suffering a puncture, paying close attention to the airframe manufacturers recommended inflation pressure is your best bet to prevent tire failures. We also found that, to understand why proper inflation is key, we need to understand how these tires are made. The basic light-plane tire isnt that much different from the ones your grandparents used on their Model T. The current standards for aircraft tires are embodied in the FAAs Technical Standard Order (TSO) C62e, last revised in 2006 (that TSO only addresses tires; inner tube standards are set by the Society of Automotive Engineers). Instead of the radial-ply tires common on modern automobiles, your light airplanes tires likely are a bias-ply design, where the internal fabric cords are sandwiched between two layers of rubber and laid diagonally-at 30- and 60-degree angles to the tires centerline-and extend from bead to bead. Additional plies are laid opposite to each other. This contrasts with a radial-ply tire, a technology widely used by larger, faster aircraft. Its based on plies laid from bead to bead but at right angles to the tread.

Key Takeaways:

• Pilots often neglect aircraft tires, but maintaining correct inflation pressure is the most critical factor in preventing premature failures.
• Underinflation is dangerous because it leads to "overdeflection" of the tire, generating excessive heat that causes premature wear and potential failure.
• The proper cold inflation pressure for an aircraft tire is specified by the airframe manufacturer in the POH/AFM, not on the tire's sidewall.
• Aircraft tires are typically bias-ply with nylon cords, which can cause them to temporarily "take a set" when parked, and modern inner tubes are made of butyl rubber for improved air retention.

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