CDFA Calculation in Charts
Hello,
I'm trying to find the accurate formula which is used on a 2D and sometimes 3D approach which calculates the ALT you have to be at a specific distance for a CDFA. Using trigonometry yields a result which is off by 4' to 10' sometimes even more. Is the curvature of the Earth used for this calculations?
Ex.
LAX RWY 24R
My calculation to find 2,200' at 6.3nm from rwy threshold:
TDZE= 122'
Distance= 6.3nm
Alt= x
x= tan(3) * (6.3 * 6076.12)
x= 2006.1465' + 122'
ALT at 6.3nm = 2128.1465'... I'm off by roughly 70'+.
Any insight will be appreciated, thank you in advance.
Regards,
mabg