Sometimes we can be guilty of giving little consideration to innocuous things that don’t seem to matter. However, when such things are not properly taken care of, major problems can arise. Take your automobile for instance: are you a bit lax when it comes to checking if your car’s tires are properly inflated? A lot of people are. Let’s face it: it’s a nuisance to check their pressure and top them up if needed. We put little value in it: “They’ll be fine,” we say to ourselves. Or, “I’ll do it later.”
Given that your tires are your first line of defence against the force of the earth, you may want to re-consider their value. And this, assuredly, applies to the tires on your aircraft too. Have you walked a flight line and taken note of the condition of some of the tires on the airplanes that you’re passing by? Those aren’t treads on some of those tires: they’re cracks in the rubber. And, boy: are a lot of them under-inflated.
Aircraft tires have to withstand a lot of load, especially during a landing. And with so much load to support, they’re designed to have much more flex than the tires on your automobile. Too much flex, however, is not a good thing. Under-inflated tires will flex more than your tires’ manufacturer will want them too. That additional flexing builds up internal heat that may cause material damage to the inner lining and sidewalls of the tire. Rare though such occurrences are, there are documented cases wherein an overheated tire has led to the breakout of fire in the wheel-wells of an aircraft. Since airplanes generally store their fuel in their wings – where retracted wheels and tires also happen to be tucked away – catastrophe is very likely an ensuing result.
When the tire’s rubber deforms more than it should due to under-inflation, its lifespan is going to be shorter than it should. The rubber breaks down and wears away much more than it otherwise is designed to do. You’ll be incurring the cost of replacing them. And if you don’t replace them, you’ll be incurring the penalties that worn tires bring about. For instance, take off distances tend to increase given that the greater rolling resistance of your worn tires will commandeer your aircraft’s acceleration. Think about this latter fact if you need to clear obstacles at the end of the runway.
Low tire pressure can also facilitate the slipping on the rim of a tube-type tire, thus shearing off the tire’s valve. If that valve gets annihilated, you’re not going to get very far on the ground. Under-inflated tires can be a bugger on wet surfaces too: they can enable hydroplaning leading to loss of control.
Remember that your tires seep air: ambient temperature directly affects their pressure. Tires lose, about, one psi of pressure for every two to three degrees Celsius drop in pressure. Therefore, a lower outside air temperature will result in lower tire pressures too. In a place like Canada, with its widely varying changes in temperatures at certain times of the season, a significant loss of tire pressure can happen overnight where there’s a big drop in overnight temperature.
When replacing a worn tire, should you change the tube too? The answer is yes, no matter how good the tube’s condition appears to be. Old tubes tend to grow during their life. Stick an old tube into a new tire, and you risk binding up the tube inside that tire. This could lead to tire (or tube) failure. So, swallow the cost of a new tube when you’ve also swallowed the cost of a new tire. If your tires have cracks or cuts in the sidewalls that extend deep into the rubber and into the bead areas, throw them away. Do the same of you find bulges in the tread, sidewall or bead areas. If the tires are so badly worn that their deeper chords are exposed – saying nothing of any tread remaining on their surface – best to give them the heave-ho too. It’s not worth the risk riding on them again.
Even though the circumstances that brought the Concorde down were the result of negligence and bad luck, it was the shredding of a tire that created the flaming tragedy. Probably because airplanes are for flying in the air and not driving along the ground, pilots somewhat easily ignore the value of their airplane’s tires. Check them thoroughly. And kick them before every flight, just to make sure they’re not going to pop.