Which four parameters are needed to calculate density altitude?

Density altitude is an important concept in aviation that affects aircraft performance. To calculate density altitude, the parameters involved represent the conditions affecting the density of the air.

The correct choice includes barometric pressure, air temperature, field elevation, and dew point. Barometric pressure is crucial because it indicates how much air is above a given point, affecting how dense the air is. Air temperature impacts the density since warmer air is less dense than cooler air. Field elevation provides a reference for altitude, affecting the density of the air; the higher the elevation, the thinner (less dense) the air becomes. Finally, dew point plays a role in determining humidity, which also influences air density.

By comprehensively looking at these parameters, one can accurately compute the density altitude, which is vital for pilots to understand performance metrics such as takeoff and climb rates. Other choices either focus on parameters not directly needed for calculating density altitude or include measurements that do not contribute to the basic understanding of air density relevant for this calculation.