Density Altitude ... simplified?

[Windchill]

Density Altitude ... it's been asked before but let me see if I've found a simple way to think about it.

A few days ago I went flying, field elevation is approx. 500ft MSL. ASOS said density altitude was 2,400ft. Does this basically mean I just lost 1,900 feet? If my aircraft's service ceiling is typically 13,000 ft ... does this mean I'm likely to experience the loss in performance around 11,100 feet? I realize the actual numbers may change with altitude, but I'm trying to get the gist of it ...


when the density altitude is higher than your actual elevation, basically you just lost altitude for performance, etc. Is this a fair analysis for what is hopefully a simplified version to understanding density altitude..

 

[kellwolf]

Sounds good to me. If you're on the ground in GKY at 600 MSL (give or take a few ft) and the density altitude is 3,500 ft, the aircraft will perform as if it were at 3,500 MSL on the takeoff roll.

 

[planejay]

[ QUOTE ]
Sounds good to me. If you're on the ground in GKY at 600 MSL (give or take a few ft) and the density altitude is 3,500 ft, the aircraft will perform as if it were at 3,500 MSL on the takeoff roll.

[/ QUOTE ]

also means the mixture should be leaned on the ground

 

[MidlifeFlyer]

Pretty much it. Some other ways to think about it (different strokes) are

1. "performance altitude." When the AWOS says "Density Altitude 2400" it means that your airplane will perform as though you are at 2400 msl. (This is probably the most common way)

2. It's high "density altitude" not "high density" altitude. In other words, it's not that the air is denser, but that you are at a higher effective altitude.

 

[bike21]

Good on you for considering and working on density altitude even when near sea level.

Out here in Colorado @ BJC, density altitude has been upwards of 8,500' recently.

I myself never fully understood density altitude until moving out here. What a difference it can really make! One memory aid I was taught awhile back, the 3 H's....

Hot
High (elevation, not cannabis)

Humid

All can really impact your performance...a couple of summers ago I saw a guy takeoff and immediately declare an emergency on a really hot day. He couldn't climb at all, so he quickly came back around and landed. My 172 was flying decently, but my guess is that he was over loaded - seems he had full pax and luggage. Oops.

 

[seagull]

Of interest also is that the newer Cessna's have you start leaning at 3000'. That's pressure altitude ISA, IOW, it is density altitude. Take a 1000' airport elevation and add about an 85 degree day and you're there, time to start leaning before takeoff!