FAA-H-8083-25C, ch. 4 and 11

What affects aircraft performance?

Thin air weakens a drone or airplane. Here is how pressure, temperature, altitude and humidity combine into density altitude, the exam traps and practice questions, with the FAA source under each answer.

Part 107, explained · Last reviewed October 25, 2026 against the eCFR and faa.gov. UAV Campus is not affiliated with the FAA.

What is density altitude, and what factors affect aircraft performance?

Density altitude is pressure altitude corrected for nonstandard temperature. A high density altitude means thin air and lower performance. It results from high elevations, low atmospheric pressure, high temperatures, high humidity, or a combination. Thin air reduces engine power, propeller thrust and wing lift.

Sources: FAA-H-8083-25C ch. 4, Density Altitude · FAA-G-8082-22 ch. 3b, Density Altitude

What the FAA handbook says

FAA-H-8083-25C ch. 4, Density Altitude

Density altitude is pressure altitude corrected for nonstandard temperature.

FAA-H-8083-25C ch. 4, Density Altitude

The conditions that result in a high density altitude are high elevations, low atmospheric pressures, high temperatures, high humidity, or some combination of these factors.

FAA-H-8083-25C ch. 4, Effect of Humidity (Moisture) on Density

Water vapor is lighter than air; consequently, moist air is lighter than dry air. Therefore, as the water content of the air increases, the air becomes less dense, increasing density altitude and decreasing performance.

Sources: FAA-H-8083-25C ch. 4, Density Altitude · FAA-H-8083-25C ch. 4, Density Altitude · FAA-H-8083-25C ch. 4, Effect of Humidity (Moisture) on Density

Exam traps

  • Increasing the temperature decreases air density, and decreasing the temperature increases it.
  • As air density decreases (higher density altitude), aircraft performance decreases.
  • Higher humidity makes the air less dense, increasing density altitude and decreasing performance.
  • A propeller is less efficient in thin air, so high density altitude reduces thrust.

Try it: practice questions

Similar to the FAA test, not the actual test questions.

Practice question 1

Which factor would tend to increase the density altitude at a given airport?

  1. A A decrease in relative humidity.
  2. B An increase in barometric pressure.
  3. C An increase in ambient temperature.
Show the answer
Answer: C. An increase in ambient temperature.

Density altitude increases with an increase in temperature, a decrease in pressure, and/or an increase in humidity.

FAA source: FAA-H-8083-25C ch. 11, Density Altitude

Practice question 2

What effect, if any, does high humidity have on aircraft performance?

  1. A It increases performance.
  2. B It has no effect on performance.
  3. C It decreases performance.
Show the answer
Answer: C. It decreases performance.

Humidity will have the same effect as low pressure or high temperature, aka it will increase the density altitude and affect performance negatively.

FAA source: FAA-H-8083-25C ch. 11, Effect of Humidity (Moisture) on Density

Practice question 3

How would high density altitude affect the performance of a small unmanned aircraft?

  1. A Decreased performance.
  2. B Increased performance.
  3. C No change in performance.
Show the answer
Answer: A. Decreased performance.

Density Altitude is the altitude corrected for non-standard pressure and non-standard temperatures. A high density altitude means your UAS will “feel” like it’s operating at a higher altitude, hence the performance will be diminished.

FAA source: FAA-H-8083-25C ch. 11, Density Altitude

Does cold weather help drone performance?

Generally yes for air density: decreasing the temperature increases the density, and as the density of the air increases, aircraft performance increases.

Source: FAA-H-8083-25C ch. 4, Effect of Temperature on Density

Does altitude change air density?

Yes. Both temperature and pressure decrease with altitude, but the fairly rapid drop in pressure usually dominates, so pilots can expect the density to decrease with altitude.

Source: FAA-G-8082-22 ch. 3b, Effects of Temperature on Density

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