Q. You intend to overfly a mountain ridge at an altitude of 15000ft AMSL.The average air temperature (=ISA Deviation) is 15 degree lower than ISA. The Sealevel Pressure (=QNH)1003Hpa. Which altimeter indication is needed?
15 x 15 x 4 = 900
1013 - 1003 = 10 x 27 = 270
900 + 270 = 1170
15000 + 1170 = 16170
Read Angleofattacks post.. and use the formulae
TA = IA + (4 x IA/1000 x ISA Dev) + (27 x (QNH – Subscale))