If the pressure altitude is 5,000 ft and the outside air temperature is 6°C hotter than ISA, density altitude is approximately what?

• A. 4,000 ft
• B. 5,720 ft
• C. 6,000 ft
• D. 7,000 ft

Answer: (B)

Warmer-than-ISA air is less dense, so the density altitude rises above the pressure altitude. Density altitude is the altitude in ISA at which the air density would match the current conditions, and it increases as temperature rises.

At 5,000 ft pressure altitude, the ISA temperature is about 5°C. The outside air temperature is 6°C warmer, so the actual temperature is about 11°C. A common quick-mental-math rule is that for each degree Celsius the air is warmer than ISA, density altitude increases by roughly 120 feet. Here, 6°C above ISA gives an increase of about 6 × 120 = 720 ft. Add that to the pressure altitude: 5,000 ft + 720 ft ≈ 5,720 ft.

So the density altitude is approximately 5,720 feet.