Types of Undercarriage
The undercarriage has an attachment point to the aircraft and can have more than one strut (i. e., support point). Chart 7.1 classifies various types in an elementary way, as if each support point has one strut with one wheel, with designations similar to a common bicycle. For example, the Airbus 380 aircraft has five support points (i. e., one nose wheel, two fuselage-mounted wheels, and two wing-mounted wheels) (see Figure 7.11) and many wheels and struts.
A nose wheel-type tricycle undercarriage is, by far, the dominant type, which is the type addressed in this book. The tail wheel type (i. e., fixed undercarriage) causes less drag, which can increase aircraft speed by 2 to 3%. However, on the ground, the raised nose impairs forward visibility and is more prone to “ground looping”
Figure 7.2. Undercarriage strut and bogey types
(described in Section 7.7). Currently, tail wheels are adapted for some lighter aircraft.
The simplest form of undercarriage was the earliest rigid axle type not in use any longer. Some form of shock absorber is favored nowadays. Struts with shock absorbers also are designed in many variations, as shown in Figure 7.2. When one strut has more than one wheel, it is seen as a bogey, as shown in the figure. There is a range of bogey designs not included in the figure.