A Few Simple Ways To Keep Aircraft Tires Up and Costs Down By

Douglas R. Bodne I EAA 6095)

14833 College Alien Park, Mich. 48101

Tires are an often neglected item on our check off list and many times receive only a cursory kick as we make our walk around inspection. Tires are not only expensive but they can save your life so treat them with respect and a little tender loving care. Here are a few rules for careful inspection that apply on the roadway as well as the runway. They include control of speed, braking, cornering and inspection for proper inflation, cuts, bruises and signs of tread wear. Contrary to what most pilots think, the toughest demand on aircraft tires is not the abrupt scurp-scurp heard at the instant of touch down but the rapid buildup of heat during lengthy ground operations. Aircraft tires are designed to flex more than auto tires. Flexing causes internal stress and friction as tires roll on the runways and taxiways. The resulting high internal temperatures damage the tire body. Riding the brakes is especially harmful as it not only wears the linings rapidly but generates a great amount of heat which is transmitted through the wheel to the tire. The best safeguards against heat buildup in aircraft tires are short ground rolls, slow taxi speeds, minimum braking, and proper tire inflation. Correct inflation assures the correct amount of flexing and keeps heat buildup to a minimum. Consult your aircraft owners manual or tire dealer for your correct inflation pressure. Remember to adjust tire pressure for climate change and to compensate for differences in load. Check tire pressures regularly only when the tires are cool, preferably before each flight but never sooner than 2 or 3 hours after a flight. Use a good gauge, preferably the more precise dial type and when you're through checking tires don't throw your gauge in the bottom of your tool box. It's a precision instrument. Now that we understand the importance of proper tire pressure let's look at some causes of tire failure. In your travels around the country have you ever seen a Beech 18 or the famous Old Gooney Bird sitting on the ramp with oil dripping from the engine nacelle, you guessed it, right on the tires? Or have you ever drained your dirty engine oil right onto the ground at your tie-down slot and then taxied through it or parked on the oil soaked dirt? Most EAA'ers don't fly DC-3's or Beech 18's but we are often guilty of the latter. Keep tires clean and free of oil, brake fluid, grease, tar and degreasing agents, these all have a deteriorating effect on rubber. If your tires become contaminated with any of the above substances wipe them off with a gasoline dampened cloth and follow with soap and water. Ever notice flat spots on your treads? These can be caused by many reasons other than the normal scuffs caused by landing on hard surface runways. One way is turning with one wheel locked. An aircraft should never be turned by locking one wheel and forcing the plane around under power. This practice generates considerable shear forces which severely strain the casing plies, sidewalls and the bead of the tire while wearing a flat spot on the tread. A small stone or sharp rock which could be rolled over without harm will be literally screwed into the tread causing tire failure.

For you experimenters with sophisticated retractable gear machines who are developing mysterious flat spots on the side walls and/or tread, brake the wheels before sucking up the gear. To sum up, when inspecting your tires look for the following: — Cuts or cracks on the tread or sidewall. If any cuts or cracks expose a casing ply or if they extend across more than 5Qf7< of any rib, replace it. — Bruises or bulges in any part of a tire or an area of loose tread indicate damage and the tire should be replaced. — Inspect bead area next to wheel flange for any indication of excessive heat. Replace if there is evidence of severe blistering. — Inspect wheels for cracks and/or any damage. — Tires with flap spots need not be replaced unless casing plies are exposed or severe unbalance develops. — Weather checking is small random pattern cracks on tread and sidewall. These tires need not be replaced unless cracks expose casing plies. — Remember, tires are cheap compared to the cost of the whole machine. — Keep them properly inflated and in good repair and all your landings will be happy ones.

TECH TIPS By

Jim Peale (EAA 15132)

511 Ashby Way Warner Robins, Ga. 31093 Getting your aircraft ready for the spring and going to the Big Fly-In usually starts with a good wash job. Well, remember, use a mild soap and a soft rag because our aircraft are usually painted with a soft paint. If it's real greasy and oily (like behind one of those round engines) add a cup of kerosene to about a gallon of water/soap mixture; sure helps cut through the grease and oil. Lots of people like to polish their metal props. It sure looks good, but it's a lot of work and you have to polish it every week from now on. Also, there are those who like a polished metal aircraft instead of painting them. This, too, looks good but it takes many, many hours of work. The pros do it this way: They start by using one of the heavy-duty car polishes and jeweler's rouge to do the hard work till the shine is how they want it; however, this leaves swirls and curls. To get these out, they use a very soft cloth and flour — that's right, flour that you make bread, biscuits, rolls, cakes, etc. from. The flour has just enough abrasive value to remove those swirls from the polished metal, but not enough to ruin the shine. Using the mechanical polisher and the flour will sure save you a lot of elbow grease. SPORT AVIATION 11