Pressure Altitude

PA = Field Elevation + (29.92 − Altimeter) × 1000

= 5,000 + (29.92 − 29.92) × 1000

= 5,000 ft

Corrects for non-standard barometric pressure. When the altimeter setting is below 29.92, pressure altitude is higher than field elevation.

ISA Standard Temperature

ISA Temp = 15°C − 2°C × (PA ÷ 1000)

= 15 − 2 × (5,000 ÷ 1000)

= 5.0°C

The International Standard Atmosphere defines temperature as 15°C at sea level, decreasing 2°C per 1,000 ft.

ISA Deviation

Deviation = OAT − ISA Temp

= 30°C − 5.0°C

= +25.0°C

Temperature is above standard — air is less dense, reducing aircraft performance.

Density Altitude

DA = PA + 120 × ISA Deviation

= 5,000 + 120 × 25.0

= 8,006 ft

At this density altitude, expect approximately 24% less engine power and 80% longer takeoff distance.