Hi Rudderrudderrat
Just verify this calculation. Does it make sense ?
An aircraft at FL230, temperature -41º C, QNH 983 HPA, is at a true altitude of:
OK, so the a/c is flying on 1013 and the QNH at the airfield is 983Hpa. : 1013 -983 = 30Hpa x 30feet/1 Hpa = 900 feet dif in elevation en 1013.25.
ISA @ FL 230 : ISA-10 deg Cel.
: @ MSL ISA is 288 deg Kelvin.
: kelvin is 273 +15 = 288 deg K
: 10 / 288 * 23900 feet = 830 feet.
= 23000 - 830 = 22170 feet (True .Alt)
Last edited by Diesel and Dust; 27th Aug 2012 at 08:49.