FAA Sport Pilot Airplane (SPA)WeatherEasy
Under conditions of the International Standard Atmosphere, temperature decreases by approximately how much for every 1,000 feet of altitude gain (up to the tropopause)?
- A4°C
- B3°C
- C1°C
- D2°C
Show answer & explanationAnswer & explanation
Correct answer: D. 2°C
The standard lapse rate is 2°C (3.5°F) per 1,000 feet of altitude increase, used as the baseline for density altitude and performance calculations.
Why the other options are wrong
- A. Far exceeds the standard lapse rate and would indicate very unstable air.
- B. Overstates the standard rate; sometimes confused with local superadiabatic conditions.
- C. Too slow a rate to match the standard atmosphere model.
Standard Lapse Rate
The rate at which temperature decreases with altitude in the standard atmosphere, used as a baseline for performance charts.
- 2°C (3.5°F) per 1,000 ft
- Standard sea-level temp = 15°C, pressure = 29.92 in Hg
- Used to compute pressure altitude and density altitude corrections
Memory trick: "Two degrees a grand" — 2°C per 1,000 ft.