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capability of the tire, not the number of plies. Win a bar bet at the next han- gar social with that one.
If your airplane has a max gross weight of less than 12,500 pounds and is not turbine powered, the POH should specify the approved tire size and ply rating. You can also find it in the aircraft’s Type Certificate Data Sheet. As long as the tire is the proper size, ply rating, and is FAA TSO certified, you can use any manufac- turer you’d like.
If you operate a turbine airplane or an airplane with a gross weight over 12,500 pounds, your tire op- tions are more limited. The certifi- cation standards of these airplanes are different than their lighter, gas- burning cousins, so manufacturers don’t specify tire sizes, they specify approved tire part numbers. These manufacturers did tons of testing to get the airplane certified for use on various runway surfaces and condi- tions, and whatever tires they used during those tests are what’s approved for use on the airplane.
If the manufacturer only used Mi- chelins to meet their certification standards, Michelin tires are your choice. If they threw a set of Good- year tires on the airplane and repeated all the tests, you’re welcome to use either tire as long as they’re installed as a matched set.
It’d be great if we could mix and match Michelin and Goodyear tires, but if Textron Aviation (or Pilatus or Embraer) wanted us to use any tire installed in any position, they would have certified every conceivable com- bination of Michelins and Goodyears. That’d be a very expensive endeavor for a very small return.
Now that we know what tires are made of and which ones you can use let’s take care of them. The best way to get the most life out of your tires is to perform a good preflight inspection. If you own your airplane or are part of a flying club, you’ll see the same tires each time you fly, so you’ll know the history and pedigree of the tires. That is, you’ll know when something has changed, like a cut that wasn’t there last time or tread starting to
The best way to get the most life out of your tires is to perform a good preflight inspection.
separate. These are just a few clues that you’ll use to know when it’s time to do something or not.
Speaking of inspection criteria, if you need help determining if a cut is superficial or if that tire is toast, there are ways to find out for sure. Some aircraft manuals have somewhat useful tire criteria. FAA AC20-97B is a good source of information available online for free. I recommend using your Google machine to download the fantastic guides that Goodyear and Michelin have each created and made available as free pdf downloads. Other manufacturers may produce something similar, but these are the two with which I’m familiar. They contain tons of useful information along with pictures of anomalies so you can make an informed decision. These guides can also educate you enough so that when your airplane is down for maintenance, you don’t have to take your IA’s word as to the condition of your tires; you’ll know their status before you even show up at the shop.
If you rent airplanes from a flying school, you won’t have as good a grasp on the history of the tires, so you’ll have to look a little closer during your pref light. It’s almost impossible to tell just by looking at a tire if it’s over or under-inf lated. The rule of thumb is
that if you can visibly tell that the tire is under-inf lated or takes full power to taxi out of the chocks, the tire pres- sure is dangerously low and, in some cases, may be unairworthy. Most tire manufacturers publish a pressure that
January 2023 / TWIN & TURBINE • 15