FAA Sport Pilot Airplane (SPA)WeatherMedium
A pilot at a pressure altitude of 3,000 feet finds the outside air temperature is 30°C. Using the rule that density altitude increases roughly 120 feet for each degree above standard temperature, what is the approximate density altitude?
- A7,000 feet
- B3,000 feet
- C5,500 feet
- D4,500 feet
Show answer & explanationAnswer & explanation
Correct answer: C. 5,500 feet
Standard temperature at 3,000 feet is 15°C minus (3 x 2°C) = 9°C. The temperature is 30°C, which is 21°C above standard. Density altitude = 3,000 + (120 x 21) = 3,000 + 2,520 = 5,520 feet, approximately 5,500 feet.
Why the other options are wrong
- A. Overestimates the correction beyond the calculated value.
- B. This ignores the temperature deviation entirely.
- D. Underestimates the temperature deviation correction.
Density Altitude
Pressure altitude corrected for nonstandard temperature; it represents the altitude the aircraft 'feels' it is performing at.
- Standard temp decreases 2°C per 1,000 ft
- High density altitude reduces engine power, lift, and propeller efficiency
- Hot, high, humid conditions produce the highest density altitudes
Memory trick: 'High, Hot, Humid = Hurts performance'