What is density altitude?
Density altitude is the height above sea level whereby a given density is obtained in relation to the standard atmosphere. In other words, density altitude can also be known as the pressure altitude adjusted to non standard temperature (Federal Aviation Authority, n.d.).
Why density altitude?
To gain a better understanding as to how density altitude affects aircraft performance, we must first understand that temperature decreases at a rate of 3.5 degrees Fahrenheit, or 2 degrees Celsius for every 1000ft (Federal Aviation Authority, n.d.) in our atmosphere. As temperature decreases, density increases due to the air molecules being closer together. Because some airports are located high above mean sea level, the condition at which the airport is situated can affect density altitude. Tentatively, as altitude increases, density increases as well which means better aircraft performance. However, that is not the case after it has been adjusted to local conditions.
How does density altitude affect aircraft performance?
Density is a contributing factor that affects lift on the aircraft wings, and an increase in temperature and altitude generally means lower density which in turns reduces lift (Coffel, E. D., & Horton, R., 2017). In other words, a hot and humid environment will lead to increase in altitude density. When there is high altitude density, there will be a loss in engine power, which generates less thrust, which also ultimately reduces lift as mentioned before (Federal Aviation Authority, n.d.). All these will in turn lead to an increase in take-off roll for an aircraft as shown in the illustration below. Airports usually adopt a longer runway to combat such scenarios whereby longer take off roll is required due to higher density altitude to ensure a safer take-off (A., 2022).
References
A. (2022, July 8). Why do some airports have unusually long runways? Science ABC. Retrieved July 12, 2022, from https://www.scienceabc.com/eyeopeners/airports-unusually-long-runways.html
Bold Method. (2021, December 6). 3 Rules-Of-Thumb for flying in hot weather [Illustration]. Boldmethod. https://www.boldmethod.com/learn-to-fly/performance/hot-weather-flying-and-three-rules-of-thumb-that-are-easy-to-use/
Coffel, E. D., & Horton, R. (2017, August 3). How hot weather – and climate change – affect airline flights. The Conversation. https://theconversation.com/how-hot-weather-and-climate-change-affect-airline-flights-80795
Federal Aviation Authority. (n.d.). Chapter 4 - Principles of flight. FAA. Retrieved from https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/phak/06_phak_ch4.pdf
Hello Thaddeus,
ReplyDeleteAfter reading your blog, I have a better understanding of how density altitude changes with temperature and its overall effect on aircraft performance.
I do have a few suggestions to help clear up some of the information. In the section "Why density altitude", you forgot to add how much altitude change causes the 3.5* change in temperature.
I would recommend taking your blog and copying it into a word document, highlighting it, right-clicking the text, and selecting the "read aloud" function. This will help you hear any mistakes in the text that are difficult to catch by just reading.
Overall it is a good synopsis of how density altitude effect aircraft performance.