DO THEY USE NITROGEN GASS TO INFLATE THE TYRES ?
yes large and small. I fly a 7 passenger turboprop and we have to use nitrogen. I have seen -47 F at altitude. The Little bit of moisture in the shop air would surely freeze up there.
Nitrogen is used for a few reasons, first it is a inert gas. This means that it is a stable gas and non oxidizing. These things that are important for safety. As a non oxidizing gas, it is a fire retardant, and prevents corrizion of the rims. Second it that is has no water vapor. Water vapor can freeze at high altitudes making ice in the tire, or even worse, when landing, and the heat buildup, can cause steam which will result in a tire blow out. (Water when turned into steam, will expand over 1000x its orginal volume). Third, is the ease of storage and cost. Nitrogen gas is relativly cheap compared to other inert gases, and can be stored in a metal tank for long periods of time with out any negative effects. This is the main reason N is used, even though there are many other types of inert gases. Another reason, is that N maintains a more constant pressure 3 to 4 x longer becasue of the lack of oxygen and water vapor found in shop air. .
On large aircraft you must use nitrogen. The tire pressures are so high (over 200psi on some) and the temperatures so great from landing and braking that there is a risk of explosion if regular air is used. Also the nitrogen is essentially inert with regards to causing corrosion in the rim in the case of tubeless tires. On smaller aircraft, it is quite common to use ordinary shop air.
