Lets Talk Tires, Nuts, Bolts & Electrons – FAA Safety Briefing Magazine
By Rebekah Waters, FAA Safety Briefing Magazine
It’s that time of year again. Time to get aircraft out of storage and ready for flight, or inspected for any wear and tear that winter weather may have caused. All aspects of aircraft inspection and maintenance are important, but there is one component that is often overlooked with varying consequences as a result: aircraft tires. Aircraft tires operate at the most extreme conditions for load and speed. They are extremely well-engineered and tested, and when operated and maintained properly, are relatively dependable. Proper tire maintenance ensures not only the longest tire life but more importantly contributes to overall aircraft safety.
Inflation
Let’s start with inflation. Making sure that tires are always properly inflated is the most important service you can perform on them. Both underinflation and overinflation can be harmful to tires and dangerous for the aircraft and those in it. Underinflated tires can lead to reduced braking performance and valve stem damage or cause the tire to creep or slip on the wheel or the sidewalls to be crushed. Underinflation can cause excessive shoulder wear, ply separation, and casing degradation that could lead to a blowout. Overinflation can make tires susceptible to damage and reduce traction and ride quality. Tires could explode or burst and lead to serious or even fatal injuries in cases of extreme overinflation.
How often you check tire pressure depends on how often the aircraft flies. For aircraft that fly one or more flights a day, check pressure daily. If an aircraft flies less than once a day, check tire pressure before every flight. When tires are newly installed on an aircraft it is important to check pressure every day for several days until the tires start to maintain proper pressure. This is because the initial inflation can stretch the materials that make up the internal structure of the tires. Depending on the type of tires, this growth can be as much as 6% to 10%. The corresponding drop in pressure is equal to the tire growth.
Inspection
Whether tires were used or stored this past winter, they all need a good inspection. It is important to use a systematic approach to make sure all areas of the tire are properly inspected. Tires should always be inspected before each flight. Look for cracks, wear, bulges, foreign objects, and if any cords are showing. If cords are exposed or damaged, remove the tire from service. Check the tread area for cuts and other damage, as well as the depth of the tread. Look for uneven wearing and inspect both sidewalls for evidence of weather or ozone damage, radial cracks, cuts, or gouges.
Tires may need to be inspected after a flight due to a hard landing or heavy braking action. When this is the case, remember that tire pressure should be measured at ambient temperature, as a hot tire will expand. This can cause temporary higher-pressure readings and can also make it dangerous to bleed air.
Storage
How you store tires can also impact safety. Always store tires vertically on the tread if possible. Stacking them on their sides can cause deformations and make the mount process difficult. If vertical storage is not possible, stacking is permissible only if care is used to prevent distortion of the tires on the bottom of the stack, and they should not be stacked for more than six months. How high you can safely stack them depends on their size. Always store tires in a dry, dark environment that is free from sunlight and ozone-producing appliances or lights like welding equipment or fluorescent lights. When moving tires in or out of storage, always roll them, or use mechanical lifting tools rather than carrying them to protect yourself from injury.
Aircraft tires, unlike car tires, take a lot of stress over short amounts of time. While they are only used a small percentage of the time during a typical flight, tire-related incidents have the potential to be deadly since high stress can lead to failures at critical moments like touchdown or roll out. Help reduce the risk of tire-related incidents by making sure tires are properly stored, inspected, and inflated.
