To work out the true TAS, i need to put in the 'pressure atitude' on the airspeed window...
Now, im pretty sure it will not work if I just bang in my cruising altitude and temperature (at that altitude)..because it says 'pressure altitude' and the sea lever QNH is most likely not 1013 millibars on that day ... now can some one knowledgabe and who actually works out the true TAS for flight planning confirm that i am doing the correct calculation to find pressure altitude...
Say my planned cruise altitude was 3000ft... if the QNH was 1030mb... i would do 1030-1013=17mb
17 X 30 (as 1mb=30ft) =510 feet
3000ft - 510ft = 2490ft, or 2500 rounded up (pressure altitude to be used to calculate true TAS)
...if QNH was less than the standard sea level pressure of 1013mb...
eg. say 1009mb....1013-1009=4mb
4 X 30 = 120ft
here we ADD the answer to our altitude to get the 'pressure alitude' .... 3000ft + 120ft = 3120ft
Have I got everything right?
Thanks
