The Effects of Humidity on Aircraft Performance

 

One of the environmental factors that affects aircraft performance, and that pilots must take into account while flying, is humidity. Due to water vapor being lighter than air, and therefore moist air is lighter than dry air, the air becomes less dense when it has more water in it (PHAK 11-5). Aircraft performs to the best of its ability in dense air because the engine takes in more air and there is a greater force on the airfoils, therefore, less dense air is not a favorable condition for flying (PHAK 11-2). Since humidity is a cause for less dense air, it can cause longer takeoffs, loss of efficiency, loss of speed, and being able to fly longer distances.

We cannot change the environment, but we can minimize the impact that humidity has on aircraft performance. One way to do this is by including humidity in the density altitude calculations. The Pilot’s Handbook of Aeronautical Knowledge states that when determining aircraft performance and density altitude, humidity is not an essential factor and there is no chart for computing its effects on the density altitude (PHAK 11-5). By adding humidity to your density altitude calculations, you get a more accurate answer which in turn can give the pilot the proper altitude of where he/she needs to fly, thus allowing the aircraft to maintain the peak fuel efficiency and engine performance.

Unless we somehow figure out how to control Mother Nature, or just not fly on a humid day, getting a proper density altitude by factoring in humidity will maximize the performance of aircraft.

 

References

Federal Aviation Administration. (2016, August 24). Pilot’s Handbook of Aeronautical Knowledge (PHAK). Retrieved July 16, 2022, from https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/.