How Air Pressure and Air Density Affect Aircraft Performance

Our Earth’s atmosphere is composed of many gases, mainly nitrogen and oxygen, that we call air. Air, though invisible, consists of mass which are atoms and molecules up in our atmosphere. The amount of atoms and air molecules in a given space is called air density. Gravity plays an important role in air density because it has the force to compress air atoms and molecules in a given space. This is known as air pressure. Gravitational forces are stronger closer to the earth’s surface, thus increasing air pressure and consequently increasing air density. As the chart below shows, air pressure and air density decrease as we go up in altitude.

 

So how do they affect aircraft performance? Air pressure affects aircraft instruments that are essential for safety of flight like the barometric altimeter and airspeed indicator. Lack of air pressure will produce erroneous indications from these instruments. As an aircraft goes higher in altitude air becomes less dense. At those altitudes there’s just not enough air mass to produce lift and maintain an aircraft afloat. Low air density can also affect engines because there’s not enough air for the engine to use and maintain power. It is also worth mentioning that in a low air density environment there’s a lack of oxygen. Aside from affecting aircraft performance it also affects human performance. Lack of oxygen in an aircraft can cause hypoxia which is the lack of oxygen saturation in the human body. Hypoxia will reduce human performance and if not corrected, will cause death and an aircraft disaster. 

 

Not every aircraft is designed equally. Some aircraft are designed to perform better at higher altitudes and some others are designed to perform better at lower altitudes. Knowing how air pressure and air density affects aircraft performance will ensure a safe flight.

 

 

Federal Aviation Administration (FAA). (2016). Pilot’s Handbook of Aeronautical Knowledge (PHAK). Retrieved

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/13_phak_ch11.pdf

Ahrens, D. & Henson, R. (2020). Meteorology Today, An Introduction to Weather, Climate, and the Environment. Chapter 1, Section 1.3b.