With which gas should a landing gear shock strut be inflated?

Landing gear shock struts are specifically designed to be inflated with nitrogen or dry air due to their chemical and physical properties that make them ideal for this application. Nitrogen is an inert gas that does not support combustion and has a low moisture content, which is critical for maintaining the integrity of the hydraulic fluid within the shock strut. Using nitrogen helps prevent issues such as corrosion and fluid contamination that could occur if moisture were present.

Additionally, nitrogen's consistent pressure characteristics under varying temperature changes make it a stable choice for maintaining proper shock strut operation during landing and taxiing. This stability is crucial for the effective absorption of shock loads transmitted to the aircraft's structure.

In contrast, the other gases listed may pose problems. Oxygen, for example, is highly reactive and can support combustion, creating safety hazards in aviation environments. Helium is less commonly used in hydraulic systems, and while it has some inert qualities, it does not provide the necessary pressure characteristics for effective shock absorption. Carbon dioxide, though it can be used in specific applications, is not suitable for inflating shock struts because it can change states, which could lead to unpredictable pressure changes. Thus, nitrogen or dry air is the appropriate choice for inflating landing gear shock struts, ensuring safety