Aircraft tires are filled with which gas?

• A. Oxygen
• B. Nitrogen
• C. Argon
• D. Helium

Answer: (B)

Filling aircraft tires with nitrogen helps keep the inside of the tire and wheel assembly drier and less reactive. Nitrogen is dry and inert, so it minimizes moisture in the tire and reduces the potential for oxidation and corrosion of components, while also helping keep tire pressure more stable as temperature and ambient conditions change. Oxygen would bring moisture and promote oxidation, which isn’t desirable; argon and helium aren’t practical choices due to cost, availability, and performance characteristics, so nitrogen is the preferred, standard fill gas.