Humidity and Density Altitude

[mhcasey]

From a random FAA handout: "Humidity is not generally considered a major factor in density altitude computations because the effect of humidity is related to engine power rather than aerodynamic efficiency."

My meteorology prof used to say something to the effect of, "H20 is a lot smaller than 02 and N2, so moist air is typically less dense."

So does humidity have a significant effect on density altitude, or not?

[Flyin_bryan]

Originally Posted by mhcasey

From a random FAA handout: "Humidity is not generally considered a major factor in density altitude computations because the effect of humidity is related to engine power rather than aerodynamic efficiency."

My meteorology prof used to say something to the effect of, "H20 is a lot smaller than 02 and N2, so moist air is typically less dense."

So does humidity have a significant effect on density altitude, or not?

No

[tgrayson]

Originally Posted by mhcasey

So does humidity have a significant effect on density altitude, or not?

It's clear that it does. You'll find a number of density altitude calculators around on the web. Here's one:

http://wahiduddin.net/calc/calc_da_rh.htm

Plug in values for sea level on a 100 degree F day, with humidities of 0 and 100%, and you'll see a difference of over 800 feet.

[Mad Doggy Dog]

Something to consider.

Density altitude typically becomes a concern when operating at high elevation airports.

If you are flying in the USA, all the high elevation airports are out west, where the air tends to be very dry.

[B767Driver]

Originally Posted by tgrayson

It's clear that it does. You'll find a number of density altitude calculators around on the web. Here's one:

http://wahiduddin.net/calc/calc_da_rh.htm

Plug in values for sea level on a 100 degree F day, with humidities of 0 and 100%, and you'll see a difference of over 800 feet.

I don't know why the FAA doesn't require humidity corrections...because it can be a 10% or more penalty.

I find it interesting when I'm playing golf...someone always remarks how heavy the hot/humid air is. Actually...it's very light air!