The airplane wheels are another part of the undercarriage, or landing gear. While most aircraft have a minimum of three wheels, larger aircraft require many more to support the immense weight . Typically aircraft wheels are filled with nitrogen instead of air. This is because the pressure of nitrogen gas changes very little with changes in altitude or temperature, which is something aircraft constantly experience.
The wheelbase of an aircraft is defined as the distance between the center of the aircraft’s main landing gear and the center of its nose gear, or tail-wheel, in the case of a tail-wheel aircraft. An aircraft’s wheel track is defined as the distance between the outer wheels of an aircraft’s main landing gear. The wheelbase and wheel track of an aircraft determine its minimum turning radius, which in turn plays a large role in the design of taxiway turnoffs, intersections, and other areas on an airfield which require an aircraft to turn.
Aircraft currently operating in the world’s civil use airports have been designed with various configurations of their landing gear. Most aircraft are designed with one of three basic landing gear configurations; the single-wheel configuration, defined as a main gear of having a total of two wheels, one on each strut, the dual-wheel configuration, defined as a main gear of having a total of four wheels, two on each strut, and the dual-tandem configuration, defined as two sets of wheels on each strut.
Helicopters using facilities on land are usually supported on tubular skids or wheels equipped with rubber tires. Helicopters equipped with conventional landing gear wheels are normally supported by two main airplane wheels and one tail or nose wheel. For larger helicopters each main landing gear consists of two wheels. Each main gear typically supports 40 to 45 percent of the weight of the helicopter and the tail or nose wheel supports the remainder of the weight, approximately 10 to 20 percent. If the helicopter is supported by tubular skids, 50 percent of the weight is supported by each skid.
References :
Planning and Design of Airports/ Fifth Edition