You must have wondered at some point which element is used to fill the tire from a plane, right? Many people think at first that air is the main medium used, mainly because they think of the same philosophy as cars, but to the surprise of many, in the tire of a Boeing 737, for example, nitrogen is the main and primordial element for its proper use.
Nitrogen in Airplane tire instead of regular air
The main reason for the use of nitrogen in the inflation of commercial aircraft tires is the fact that it is an inert gas that maintains its physical form regardless of temperature or pressure.
According to Boeing, it is recommended that calibrations be checked daily when the aircraft is undergoing maintenance, which most often occurs at night, when a large part of the aircraft fleet is not in operation. Interestingly, after an intense routine of operations, the tires end up having a pressure loss of 5% every 24 hours.
“To prevent the tires from expanding or contracting during operation, especially when the plane is taking off or landing, there is overheating of the same, if it were normal air, this air would expand making the tire get bigger and could cause an explosion of the same . It is also worth ing that at cruising level, when the plane is at 40 feet, the air around the plane is around -30º Celsius, so the common air in the aircraft's tires would compress, leaving the tire so flat. that he could get off the wheels”, explains the aircraft mechanic, Alex Sandro.
Alex Sandro also explains that the calibration between the landing gear tires cannot have a pressure difference greater than 20%, which can directly affect the weight of the aircraft, making it necessary to change the wheels so that the aircraft can operate not be compromised.
Know the anatomy of an aircraft tire
Designed to withstand high weights and pressures, tires designated for aeronautical operations have some special parameters to alert the level of wear thanks to special materials, which have the role of guaranteeing safety, including wear indicators that can be easily seen during preventive inspections by mechanics and ground crews.
To talk about materials, it is necessary to understand the construction of a tire and other protective layers.
Protector Ply (Protective Cover): Composed of a nylon fabric impregnated with rubber, this layer is the first to appear after the grooves disappear due to wear;
Undertread (Layer Reinforcement*): This layer only exists in retreaded tires (repair procedure that reuses the carcass of a damaged tire), with a reinforcement consisting exclusively of a layer of rubber;
Belt Plies (Belt Straps): These are safety tarps made up of rubber-impregnated nylon strips, and serve as a parameter for changing or condemning the tire carcass. The amount of this layer varies according to the tire model, but generally when wear reaches the level of the ply, the useful life of the tire carcass ends;
Casing Plies: Known as tire carcass plies, they go down to the bottom edge and “hug” the rim made of steel, thus preventing the of this layer with the wheel fairing.
Procedures for assessing the service life of an aircraft tire
There are some routine inspection techniques for deciding whether to replace a tire. Usually the lines on the outside of the tire indicate the wear that a tire has suffered during operations, in addition, the difference in calibration mentioned above can be decisive if there is a 20% difference in calibration between the tires that make up the left landing gear and right of an aircraft.
Brakes
With its greater composition in steel, the most recent brakes have pads of composite material that, during use, reach high temperatures. Hence the importance of using nitrogen in tires. Because at the moment they are triggered, the intense temperature rise plus oxygen could generate combustion, and consequently, an explosion due to the release of gases at the moment an aircraft touches the ground and activates the brakes if it used air to inflate the tires.
The brakes are always assembled in two sections: the rotor and the stator. The rotor rotates with the aircraft wheel, the stator is the part responsible for suffering the wear caused by braking.
Brake wear is measured daily so mechanics know when this component should be replaced. During the inspection procedure, an indicator pin shows the level of wear the brakes have.
Curiosities about the brake of the Airbus A320
In the first design of the A320, the aircraft's wheels were completely enclosed, making it impossible to cool from outside air. To work around this situation, the
Airbus installed the “brake fan” in the wheel fairing, which is nothing more than a fan installed inside the wheel to cool the brake set after landing in moments of greater demand, it is worth ing that this system was not exclusive to Airbus, as the Concorde also used a similar brake system.
However, over time, Airbus began to use wheels with “spoke” to facilitate cooling and not depend on an additional system, leaving it up to the air operator to install or not the Break Fan.
