Density Altitude

[aresye 0]

Now that we're getting into the heat of summer, along with some pretty high humidity, it's time to review your basic understanding of density altitude.

As most of you know, and some of you don't, density altitude, to sum it up, is a reference altitude to how current weather conditions other than wind speed and direction affect your canopy performance.

So for example, if your landing at a DZ such as Palatka, FL today, with a high around 94F, the density altitude is approx. 2500ft. In other words, that means when you're landing your canopy at the DZ pressure altitude, which is only a couple hundred feet above sea level at most, your canopy is going to behave as if it were landing at 2500ft MSL. This means you are not going to be getting as much lift during your flare, your forward speed is going to be faster, and for swoopers, your recovery arc will likely be slightly longer.

Pretty much any pilot at a higher elevated airport, or on a hot day, will calculate the Density Altitude prior to takeoff. As canopy pilots, we fly airfoils, so the affects of density altitude are going to impact us as well.

So for all of you in the heat of summer, please take the 5min in the morning to calculate the density altitude for your DZ, find out how your canopy reacts at that altitude normally, and fly it conservatively as you are close to the ground.

I feel a lot of swoop accidents, bad flares, and fast landings can definitely be attributed to density altitude. In aviation of any kind, the more you know about how mother nature affects your flight performance just makes you that much safer a pilot.

Here are some links to calculate the density altitude in your area:

http://www.nws.noaa.gov/ - You can get all the information to calculate density altitude from here, including the dew point, altimeter setting (barometric pressure), humidity, etc.

http://wahiduddin.net/calc/calc_da.htm - Density Altitude Calculator. Just input all your information from NOAA into the calculator to find your density altitude for the day.

Skydiving: You either learn from other's mistakes, or they'll learn from yours.

[MaVriK 0]

good post!!!
being a new skydiver i never really thought about that with a parachute, but i always calculate it before taking off in the c-172, i guess quite a few things transferr from one to another.. (I know learning groudn track and crabbing in the plane definately helped me with some good wind-shift under canopy coming into the pattern)

~MaVriK~
"The Greatest Accomplishment in life is actually Living it"

[azdiver 0]

well today if you are jumping at eloy it would be like landing at 5930 ft msl, no wonder why my canopy never flared for shit in the summer. i knew that temp had an effect on flying performance but didnt realize it was that much considering eloys at 1500 msl. thanks for info for the calcs.

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