My understanding is that the JBM range card function uses density altitude. My understanding is also that the temperature inputs are for transonic calculations. Density altitude is pressure altitude corrected for temperature, and, to a minute extent, humidity. It is a measure of air density. 4000 DA is 4000 DA whether the temperature is 0F or 120F. What is confusing is in a given DA column in JBM, the comeups actually increase with temperature. Only by .2 mils in the most extreme conditions, but there nonetheless. That would indicate that that at higher temps in any given DA, the air density increase. This is completely counter to the definition of DA. Can someone explain this to me?

Thanks,

John

If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then I will hear from heaven, and I will forgive their sin and will heal their land. 2 Chronicles 7:14