Hi there,
Could someone help me solve this question/calculation?
I am not sure I am doing it right, most probably I am not
QNH 981 station at MSL
temperature = minus 14 ISA,
what is your true altitude at FL090?
standard pressure = 1013
1013 - 981 = 32
32 times 30(some use 27) = 960
Pressure is lower so ground is closer.
FL090 = 90.000 ft
90.000 ft - 960 ft = 89.040 ft
So pressure altitude is 89.040 ft, correct??
Then for true altitude
we have minus 14 ISA, so:
120ft x -14 = -1.680 ft
89.040 ft - 1.680 ft = 87.360 ft