How Does Humidity Impact Aircraft Performance?

The primary factors most affected by performance are the takeoff and landing distance, rate of climb, ceiling, payload, range, speed, maneuverability, stability, and fuel economy. (PHAK 11, n.d.)

Although humidity alone does not majorly contribute to aircraft performance, according to PHAK chapter 11, it is a factor that contributes to density altitude.  Pilots should expect a slight decrease in performance and reduced climb rate when flying in high humidity conditions (FAA, n.d.). Humidity refers to the "amount of water vapor contained in the atmosphere and is expressed as a percentage of the maximum amount of water vapor the air can hold" (PHAK 11, n.d.). However, the air is never 100% dry.  But as the water content of the air rises to higher percentages, the air becomes less dense as a result.  This increases density altitude and decreases the expected performance of an aircraft (PHAK 11, n.d.). The main factors most affected by performance in the situation of high humidity are the engine and the wings.  In the event of high humidity, there are less oxygen molecules reaching the engine which can reduce the output of power, and there are also fewer oxygen molecules traveling across the wings which reduce lift (Lavenson, 2019).  

Since we cannot control the temperature, the only way to minimize these effects is for a pilot to use caution on extremely hot/humid days and schedule flights early morning or late evening when the humidity is lower. Flying at reduced gross weight, not filling fuel tanks to the top, and giving longer time/distance for takeoff and landing are also things recommended to pilots for safer operations in high-density altitude conditions (FAA, n.d.). 




Cite for Images: Udris, A. (2014). 3 Factors That Affect Density Altitude. BoldMethod. Retrieved from https://www.boldmethod.com/learn-to-fly/performance/density-altitude/



Other References: 

Pilot’s Handbook of Aeronautical Knowledge (PHAK). (2016). Federal Aviation Administration. Retrieved https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/ 

Lavenson, M. (2019). Proficiency: It's Not (Just) The Heat: The Effects of Humidity on Aircraft Performance. AOPA. Retrieved from https://www.aopa.org/news-and-media/all-news/2019/july/pilot/proficiency-it-is-not-the-heat

Comments

  1. Manuel GamarraJuly 10, 2020 at 1:38 PM

    Hi Aaerial,

    This is a great topic in which humidity plays a big role in aircraft performance specially during the months of June during the Monsoon. During this hot summer days the air is warmer at the earth surface which causes less dense air relative to the surrounding atmosphere consequently, as you mentioned humidity affects the way an airplane flies because of the change in pressure that accompanies changes in humidity.

    This weather changes need to taken with respect and consideration during your flight planing, specially if humidity is combine with hot weather, high altitude airports which imposes an even critical barrier to performance to piston airplanes including large transport aircraft.

    Thank you for taking the time to write about this topic and environmental threat that imposes to all kinds of pilots.

    I hope you have time to review my blog and comment as well. Link below

    https://gamarram.blogspot.com/2020/07/the-operating-environment-and-aircraft.html


    Thanks

    Manuel

    ReplyDelete

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