FAA Powerplant Written Practice Test

Which two atmospheric factors are crucial when checking and performing trim adjustments of a turbine engine?

1. Humidity and altitude

2. Wind speed and temperature

3. Ambient temperature and barometric pressure

4. Cloud cover and visibility

The correct answer is: Ambient temperature and barometric pressure

The correct answer is based on the understanding that both ambient temperature and barometric pressure significantly influence the performance characteristics of a turbine engine. Ambient temperature affects air density; in warmer temperatures, the air is less dense, which can reduce engine efficiency and thrust. Conversely, lower temperatures increase air density, enhancing the engine's performance. Barometric pressure, which is closely related to altitude, also plays a pivotal role in engine operation. As altitude increases, barometric pressure decreases, leading to less dense air, which can affect the engine's ability to produce thrust and may require adjustments to the fuel-air mixture for optimal performance. The interplay of these two factors—ambient temperature and barometric pressure—directly impacts the operational parameters that must be considered when performing trim adjustments to ensure the engine runs smoothly under varying atmospheric conditions.