Aircraft landing gears are complex devices designed to support the aircraft’s weight on the ground and withstand immense loads during landing. Aircraft tires take the primary beating, especially during landing. In general, the size of the aircraft tires seems much smaller in relation to the aircraft’s size.
However, the tire size is determined based on various factors, including the empty weight of the aircraft, landing weight, and required ground clearance. Larger aircraft generally require either larger tires or more of them. Aircraft tires are inflated with inert gas, such as nitrogen, and pressurized to around 200 psi (approximately six times the pressure of a car tire).
Most modern commercial airliners have two tires on the nose landing gear and several on the main landing gear, depending on the aircraft size. It is common for most aircraft to have different-sized (smaller) nose tires than the main tires. This is because nose tires’ load requirement differs from main tires.
Moreover, slightly smaller nose tires provide an improved tipping moment on the ground. While the nose wheels on aircraft can turn, the main wheels are mounted on fixed axles. That means the main wheels must absorb axial and radial forces when turning.
Commercial twinjet tires
All variants of the Boeing 737 aircraft have different-sized nose wheel tires and main wheel tires. While all variants have two nose wheel tires and four main tires, the nose tires are much smaller. For example, a 737 Classic is fitted with H40x14.5-9 main gear tires and 27x7.75-15 tires. The Boeing 757 and 767 also have different-sized main and nose gear tires. Both aircraft have eight main gear tires compared to four on the 737.
The nose wheel tires on the Boeing 787 and the 777 are slightly smaller and narrower than the main wheel tires. Once again, this is because the nose gears have less weight requirement. Most Airbus twinjets also feature smaller and narrower nose wheel tires than the main wheel tires.
Regional jets such as the Bombardier CRJ series and Embraer E Jets feature smaller nose gear tires and larger main gear tires.
Boeing 747 tires
The most recognizable aircraft, the Boeing 747, has the same-sized nose and main tires. The aircraft is fitted with two H49x19.0-22 on the nose wheels and 16 (of the same size) on the main wheels. Unusual for modern airliners, the Boeing 747 was planned as a military transport aircraft.
Having interchangeable tires that are all the same size was a design requirement. Each of the 747 tires can be retreaded up to seven times to reduce the operating cost of the jet.
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Airbus A380 tires
The Airbus A380 has the largest tire size of any commercial airliner. The A380 tires are 56 inches in diameter and 21 inches in width. A total of 22 giant tires withstand more than 500 tons of aircraft on the ground.
These tires can typically last up to 180 landings. Two nose wheel tires are slightly smaller than the 20 main gear tires on the A380.
What are your thoughts on the different-sized tires on commercial aircraft? How about the Boeing 747? Tell us in the comments section.