Plane & Pilot
Wednesday, September 1, 2004

Just Tires?

Very few pilots realize how important they really are

When we were student pilots, we were told to check the tires for condition and inflation before each takeoff. But as we progressed in our flying careers, some of us have taken tires for granted. Sure, we’re careful to check the “important” stuff—engine oil, fuel, headset batteries and radios—but we keep tires on a second-class status, merely glancing at them to make sure that they’re all accounted for and aren’t flat.
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More Than Just Tires
Perhaps even more surprising is that properly inflated tires not only keep you safe, but also make you look good. According to Robson, “Anything that helps your tires will help your ground handling.”

Properly inflated tires, in good condition, put less stress on the rest of the airframe, and maintaining all tires at the right pressure will minimize asymmetric brake and steering action, giving you a better feel for the airplane and better ground-handling skills—all while extending the service life of your gear and airframe, and increasing tire life.

Take Responsibility
Although it’s ultimately up to you when it comes to checking your tires, don’t blame yourself for pressure loss. There are several reasons for this problem to occur. The casing itself, for example, is slightly porous, and there’s an intentional vent in the tire body itself. There also may be a safety plug in the wheel that leaks a bit, and the O-ring in the wheel may leak some. The bead may leak, too. Even the weather makes a difference. A five-degree F drop in temperature, for example, can account for a 1% loss of air pressure.

Just remember that tires lose pressure. That’s their nature. But it’s your obligation to keep them full. So don’t take your tires for granted, and check the pressure before every flight.

Tire & Tube Tips
The inner tubes for a wheelchair or wheelbarrow may fit properly, but they’re not adequate substitutes for real airplane parts. Some cheap butyl tubes can shatter at minus-four degrees F. And non-aviation tube construction isn’t robust—you don’t want to leave your valve stem behind. For a few more dollars, get real tubes for safety’s sake. And make sure it says “aircraft use.”

Reusing tubes isn’t recommended by manufacturers. A tube, inflated inside its tire, will stretch as much as 30%. Putting it back inside a new tire risks a pinch or a fold, which is a recipe for a flat tire and a nightmare to balance.

When you’re mounting a new tire or installing a new tube, it doesn’t hurt to use talcum powder on the outside of the tube. This allows the tire and tube to move relative to each other, minimizing the chance for pinching and folding. Experts also recommend an especially formulated tire-mounting lube or no lubrication at all. Some say a diluted soap solution helps, although they warn that water may contribute to corrosion. Never use a petroleum product since oil eats rubber.

Check that no harmful chemicals are used on your tires. Brake fluid will take the paint off just about anything it touches, especially tires. Silicone is just as harmful—although it won’t hurt the rubber, it can allow the tire to slip on the rim, permitting air to escape and making your brakes useless, all while throwing the assembly out of balance and shearing the stem off your tube.

You may use a tube inside a tubeless tire. You might feel the extra weight, but the assembly may be useful when you’re stuck with having only a tubeless tire available, and your airplane has tube-type rims.

If you detect leakage on any part of your tire, apply dishwashing soap solution to the suspected area. If it produces bubbles, then you have a leak.


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