Introduction

Density is defined as the mass per unit volume and is generally expressed in terms of grams per cubic metre. Density has a significant impact on aircraft performance, therefore understanding what factors influence atmospheric density is of vital importance for a pilot.

The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density. Increasing the temperature of a substance (with a few exceptions) decreases its density.