[bongodriver]

Originally Posted by IvanK

Courtesy of Klems data tool and his work it has been established that the basic CLOD atmospheric temperature lapse rate is 1.97 deg C per 1000feet (corrected to 2 decimal places). This has now been measured up to 26,000feet. So its only 0.01 deg C per 1000 feet out ... not much and well and truly in the ball park to the ISA value of 1.98 deg C per 1000feet.

You beat me to it but a squad member from the dogz and I have been doing a little experimenting and found something interesting, much like you we have found the lapse rate to be in the 2 degrees per thousand feet but in addition we stumbled upon an element in the FMB that changes the the atmospheric temperature not sure of its function but it is the mission parameters box, there is an option for 'Breeze/Thermal Activity =0/10' with a sliding scale, default seems to be 0 and this gives an ambient temparature of ISA +10, but if the slider is set to 10 the temp almost lines up with ISA, so far no indication that the temps can be brought to an ISA - figure.

I have attached a screenshot of the FMB tool and a graph showing the results of our quick test today.

p.s. I mean to add the test mission was done on a clear day at 12:00 midday, no other tests done to check for diurnal variations.

p.p.s. also added a usefull graph for density altitude calculations.