hi,

you can get a decent approximation of your density altitude at your field by doing the following. it may seem a bit complicated at first, but its rather simple:

the conditions for this example are the following: 85ºF, true field elev. is 800 ft.

1. find the TRUE elevation above sea level at your field (800 ft in this case). if you cannot do this, use the closest airport field elevation near you.

2. get the current barometric pressure.

3. calculate the difference between the current barometric pressure (lets say it was 29.70) and the standard barometric pressure (which is always 29.92) (i.e., 29.92 - 29.70 = .22)

4. now add a zero and drop the decimal from the answer in step #3... .22 = 220.

5. now add or subtract this number to the airport elevation to find the current PRESSURE altitude. you add the number if the reported barometric pressure is below standard, and subtract it if it is above standard. in this case it's below, so you add 800 + 220 = 1020. 1000 ft pressure altitude is close enough.

6. now look at the temperature at the bottom of the chart available at http://bellinghamaero.com/densaltchrt.pdf which is 85ºF. be careful not to confuse it with the celcius scale. draw a line straight up until you reach the diaganol pressure altitude line of 1000 ft in this case. once there, go straight across to the left unril you hit the edge. you will see in this example i gave the density alt was between 2700 and 2800 ft.

7. you can see another example of this at
http://virtualskies.arc.nasa.gov/wea...tudeChart.html