Density altitude is higher in which scenario?

• A. -18°C at 9,000 ft PA
• B. 15°C at 7,000 ft PA
• C. 4°C at 5,500 ft PA
• D. -9°C at 3,000 ft PA

Answer: (B)

Density altitude is how high the air density corresponds to in a standard atmosphere. It increases with higher pressure altitude and with air that is warmer than the ISA at that altitude, because warmer air is less dense. A handy estimate is: density altitude ≈ pressure altitude + 120 × (OAT − ISA temperature at that altitude).

• At 9,000 ft with -18°C, ISA at 9,000 ft is about -3°C, so the deviation is -15°C. Density altitude ≈ 9,000 + 120 × (-15) ≈ 7,200 ft.

• At 7,000 ft with 15°C, ISA at 7,000 ft is about 1°C, deviation +14°C. Density altitude ≈ 7,000 + 1,680 ≈ 8,680 ft.

• At 5,500 ft with 4°C, ISA is about 4°C, deviation 0. Density altitude ≈ 5,500 ft.

• At 3,000 ft with -9°C, ISA is about 9°C, deviation -18°C. Density altitude ≈ 3,000 - 2,160 ≈ 840 ft.

The highest density altitude occurs in the scenario with 7,000 ft pressure altitude and 15°C, because the air is warm relative to ISA, pushing the density altitude higher despite the moderate altitude.