What is the purpose of setting the standard pressure of 29.92 inches of mercury during flight levels?

• A. To reference standard pressure regardless of local pressure
• B. To correct for temperature
• C. To measure wind speed
• D. To determine air density

Answer: (A)

Setting the standard pressure of 29.92 inches of mercury creates a fixed reference for altimeters at higher levels. When you’re above the transition altitude, the altimeter is set to this standard so the reading indicates pressure altitude, a height in a standard atmosphere. This gives all aircraft a common, uniform vertical reference, which allows air traffic control to separate flights by flight level regardless of local weather pressure. Temperature can affect true altitude, but this setting’s purpose is to provide a consistent pressure reference, not to correct for temperature, measure wind speed, or determine air density.