Cold weather has arrived — rather brutally this year for many of us. Whether that cold weather translates to life in the mid-50’s (as it often does in the southern climes), or in the sub-zero’s (for northerners), cold weather means we need to keep an eye on our aircraft’s tires, to make sure they stay properly inflated.
AIRCRAFT TIRES ARE DESIGNED TO LEAK
Sure, some tires leak more than others, but pretty much all aircraft tires will leak. The problem is rubber — it is porous, so some of the air is bound to seep out. On tube tires, there are tiny little vents on the side, so this air doesn’t get caught between the tube and the tire — look for them — they look like tiny circles with irregular edges, and a tiny tip in the middle of the circle.
ANYWAY, when the temperature drops, the gas laws dictate that the pressure in our aircraft tires is going to go down. The formula is simple: PV=nRT, which is called the Ideal Gas Law. What it means to you: Since the volume and type of gas in your tire is static, when the temperature drops, your tire pressure is also going to go down.
WHY YOU SHOULD CARE
Sure, the same amount of gas is still in your tire … apart from the leaks, that is. The problem is this: an underinflated tire will generate more heat on takeoff and landing (it also doesn’t roll as well). More heat will make the tire softer, and more likely to have a problem.
Worse yet, if the air pressure started out low (remember, all tires are DESIGNED to leak) and then gets lower, you can actually cause a pinch of the tube, which can cause the tire to go flat. If you’re looking for excitement on takeoff or landing, trying to take off or land with low tires is one good way to find it in a hurry!
CHECK YOUR TIRE PRESSURE
It only takes a minute, and will save you hours of ground loop induced headaches, not to mention the repair bills. (Ponder for a second how much a tube and tire costs to replace and compare that with the cost of a new flying surface). DID YOU SAY YOUR PLANE HAS WHEEL PANTS? That’s no excuse for not checking your tire pressure!
(Many pilots have had their wheel pants modified with small doors to allow them to easily check their air pressure. This costs around $150 with a good mechanic, which is a fraction of the cost of fixing a tire that blows out, let alone the damage it causes as, or after, it goes!)
THE BOTTOM LINE: If you neglect your tires, they’ll be sure to get your attention — likely with a performance you will not soon forget. And since Murphy is a full time passenger on every airplane, the pilot should always try to anticipate and actively thwart those bad events that just might happen at the worst possible time. When the temperatures rapidly change, make sure you check your tire pressure. The insurance claim and aircraft downtime you prevent will be more than worth the extra five minutes of effort!