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High, Hot and Heavy
Cocktail of Density Altitude

Density Altitude Effects Explained

Spring is here and with it higher ambient temperatures will become more common. Although density altitude is not a common subject for ‘hangar flying’ discussions, pilots need to understand this topic. Density altitude has a significant (and inescapable) influence on aircraft and engine performance, so a pilot needs to thoroughly understand its effects. Hot, high, and humid weather conditions can cause a routine takeoff or landing to become an accident in less time than it takes to tell about it.

Remember the higher the temperature and the more humidity, the less dense the Air becomes.
This reduces:
Lift       (because the thin air exerts less force on the airfoils)
Thrust (because a propeller is less efficient in thin air)
Power  (because the engine takes in less air)
And therefore increases the length of runway required for normal take off. (refer Kock Chart)

Additional Resources :

Density Altitude – “You Are Higher Than You Think”, as published in Airfields Directory for Southern Africa

An explanation of how to calculate Density Altitude
Density Altitude Calculation Explained & Examples 

Koch Chart
To determine the effect of altitude and temperature, connect the temperature and airport altitude by a straight line. Read the increase in takeoff distance and the decrease in rate of climb from standard sea level values.
Access an interactive Koch Chart here for a reference

DID YOU KNOW : We have a tool in Easy Cockpit to assist you with Density Altitude calculations. When using the E6B Calculator in Easy Cockpit (under Settings & Tools), Density Altitude is calculated based on your Temperature and Pressure Altitude input. 
Remember : Your Pressure Altitude can be obtained by setting your Kollsman window of the aircraft altimeter to reading 1013 hPa and then taking the Altimeter Altitude display as the Pressure Altitude.

Wishing you a wonderful weekend ahead !

Andrea, Glynn, Marie, Sean & Stephen
Tel:  +27 (0)11 465 2669

Fax: 086 540 0934

Mobile: +27 (0)72 340 9943





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