While many of us can sit and talk for days about the aircraft we are about to board on our next trip, do many of us ever think about the airplane’s tires? Airlines frequently lease their tires directly from the manufacturer for several reasons, one of the most important being that they can quickly obtain replacements. To understand why airlines prefer leasing aircraft tires, it’s important to know the kind of wear and tear these components go through.
Understanding why airlines lease airplane tires instead of owning these outright
Aircraft tires spend a short amount of time on the ground compared to total flight cycles and hours in the air, but they have a relatively short lifespan due to the immense pressure they experience during take-off and landing. While the tires are only used briefly daily, they are still integral to the aircraft and its mechanics.
Planes use their tires to move around the airport apron, push back from the airport gate, taxi to and from the runway, and, most importantly, take off or land. The immense pressure on aircraft tires can fluctuate depending on weather or physical loads. An example is the Boeing 737 MAX 9, which has a maximum landing weight of just under 164,000 pounds (74,389 kilograms).
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A spotlight on Air Canada’s aircraft tires
Air Canada
, one of the largest airlines in North America noted in an analysis of their aircraft tires that each of the 12 tires on the main landing gear of the airline’s Boeing 777 comes in at 248 pounds (120 kilograms). The main wheel tires have an average lifespan of 300 to 450 landings, while nose wheels are much shorter and can withstand around 200 to 350. This is due to the nose wheel wearing heavily when it pivots left or right when turning the aircraft. Tires can last up to 600 landings, depending on overall wear and tear.
Photo: American Airlines
According to Air Canada, all airplane tires are leased from suppliers, including Goodyear, Michelin, and Bridgestone; these are all identified and monitored by serial numbers. Each model has a different baseline requirement for airplane tire maintenance, which will be closely analyzed by the length of service, retreadings, landings, and tire wear and tear. Each supplier will use these readings to decide which tires must be retreaded or replaced.
Special grooves to help roll and expel water quickly
Aircraft tires have special treaded long grooves, allowing the plane to accelerate and roll faster than a standard vehicle. The grooves also serve as a channel, which helps expel water backward. Due to the extreme weight of an aircraft on landing, it is common to see the tires leaving black marks on the runway at each landing, which can build up and is commonly removed by airport maintenance teams.
Aircraft tires are not filled the same as common vehicle tires. Instead, they are inflated with nitrogen gas. The reasoning behind this is due to air containing moisture, which would freeze at -70 degrees Fahrenheit (-57 degrees Celsius), and given an aircraft’s cruising altitude temperature, this is impractical. Nitrogen doesn’t form a liquid until it reaches -279 degrees Fahrenheit (-173 degrees Celsius).
Another reason behind the ultimate force the tires can experience on landing is heat, and using nitrogen gas limits the chance of combustion. Rust is another factor in using nitrogen; the gas is non-reactive, prolonging the overall wheel life.
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A look at the tires offered by Michelin
French tire manufacturer Michelin is based in Clermond-Ferrand, France, and is the second largest tire manufacturer globally, only second to Bridgestone. Michelin, while it is known more commonly for road maps, restaurant stars, or the company mascot, Bibendium, its tire market sees its products used on space shuttles, cars, motorcycles, other heavy equipment, and ultimately, aircraft.
The group has a presence in over 18 countries. To understand the four different tires that Michelin offers, read below:
Air |
|
---|---|
Air X |
|
Air X Sky Light |
|
Pilot |
|
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Understanding how tires are changed on an aircraft
The maintenance required for aircraft to change tires involves many moving pieces. Different companies, regulatory bodies, and maintenance staff are involved.
Looking back at aircraft crashes or incidents, a common denominator is that these happen at either takeoff or landing. This emphasizes that the tires are an essential piece of aircraft engineering and the principal machinery to help the aircraft arrive or depart safely.
While the tires are only on the ground for a fraction of the time of the aircraft overall lifespan, continued wear and tear means that they frequently need to be replaced or retreaded.
Lufthansa Technik, and changing tires at Germany’s busiest airport
Spotlighting Frankfurt Airport, the German flag carrier Lufthansa
utilizes Lufthansa Technik to administer tire changes. On average, 20,000 tires are changed in the workshop yearly, and workloads can fluctuate depending on the season. Due to summer temperatures, this can see heavier tread wear. Once the airline has identified that the tire requires replacement, the new tire will be brought to the aircraft hangar, and the safety lid on the airplane will be removed. New tire pressures are checked, and then it’s time to replace it.
The aircraft must be lifted to ensure necessary clearance, which is done using heavy-duty hydraulic jacks, depending on the aircraft’s overall weight and size. The jack will be placed safely under the landing gear to prevent any potential movement during the replacement process. Mechanics will safely remove the old tire, and a lifting cart is used to wheel it off its mount. The new tire is fitted, safety checks are completed, and the plane will be lowered off the jacks and can be redeployed back into regular service.
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Landing or taxiing? Understanding what is tougher on airplane tires
Given that aircraft come in all different shapes and sizes, it’s essential to understand that, for example, a fully loaded Boeing 747
could exert up to 25 metric tons of weight on its landing gear. In simpler terms, the tire load for an aircraft can be up to one hundred times the load compared to a standard car.
Not just taking into consideration the weight of the landing gear
but also the fact these aircraft can reach speeds of up to 235 miles (380 kilometers) when taking off or landing.
Photo: Jaromir Chalabala/Shutterstock
For the hotly anticipated Airbus A321XLR, according to Airline Economics, Airbus approved tire manufacturer Goodyear for tires on its aircraft, which is set to revolutionize long-haul travel. When it entered service last year, the Goodyear radial tires were the first to be fitted on the aircraft.
Airlines don’t outright own the tires fitted to their aircraft, and the leasing process means that it is in the manufacturer’s best commercial interest to ensure their tires last and continue to be fit for purpose. Frequently, the tires will be retreaded and can be used up to seven times before retirement.
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In general, this is done every 150 to 400 flight cycles