Cannot calculate Accurate Method
Hi everyone,
I have a simple question, cannot calculate following formula for use following example value as Ln value was minus. (excel shows "#NUM!" error)
How can I get a correct answer ?
Ex.
Airport Temp; -40C
Airport Elevation; 10ft
Aircraft Altitude; 3000ft
=(-"ISADEV"/-0,0019812)*LN((1+-0,0019812*"MDH")/(288,15+-0,0019812*"APAlt"))
where "ISADEV" is the temperature deviation from ISA (usually a negative number in cold weather)
"MDH" is the minimum descent height in ft
"APAlt" is the airport altitude in ft
-0,0019812 is the lapse rate in K/ft and 288,15 is ISA/sea level in K.