maybe it's a little impolite to ask but I got stuck with knowing bunch of formulas and not understanding how to use it:
Can you help me on understanding how the correct answer 7300ft came out of the following question:
Given the following information, what is the true altitude? (rounded to the nearest 50 ft) QNH: 983 hPa; Altitude: FL 85; Outside Air Temperature: ISA - 10° (1,00 P.)
My attempt based on the fomula from here:
- $A_T$ is our estimated true altitude, in feet
- $\Delta_{ISA}$ is the difference above ISA, in °C
- $A_I$ is our indicated altitude, in feet
- $A_{Ik}$ is our indicated altitude, in thousands of feet
$A_T = (4\times A_{Ik} \times \Delta_{ISA}) + A_I$
- $A_{Ik} = 8.5$
- $\Delta_{ISA} = -10° - ( 15° - (8.5 \times 2) ) = -10° - ( 15° - 17°) = -10° - (-2°) = ISA-8$
- $A_i = 8,500$
Therefore,
$A_t = ( 4 \times 8.5 \times (-8) ) + 8,500 = ( 34 \times (-8) ) + 8,500 = -272 + 8500 = 8288$
So my incorrect answer is 8288'. The correct is 7300' :(
I also realize I did not use QNH in my calculations.