Calculations

How to calculate temperature?

ISA at sea level: 15° C

Temperature lapse rate 2° C or 3.5° F per 1000 feet.

Examples:

Determine pressure altitude by using this formula:

\text{PressureAltitude} = (\text{StandardPressure} - \text{CurrentPressure}) \times 1000 + \text{FieldElevation}

e.g. field elevation is 5,000 ft, pressure setting 29.45, density pressure is 5470 ft.

\text{PressureAltitude} = (29.92 - 29.45) \times 1000 + 5000 = 5470

\text{DensityAltitude} = \text{PressureAltitude} + [120 \times ( \text{OAT} - \text{IST})]

What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 feet MSL is 70 °F and the dewpoint is 48 °F?

As a rule of thumb, divide the difference between the temperature and dew point by 4.4 to determine the height of the cloud base.

E.g. 70° F - 48° F = 22. 22 / 4.4 = 5 (in thousands of feet). Add the field elevation of 1,000' to the 5,000' to find 6,000'.

Check POH.

Add 2 percent to the CAS for each 1,000 feet of altitude. At 10,000 feet, you are flying approximately 20% faster than your indicated airspeed.

\text{TAS} = \text{CAS} \times (1 + \text{Altitude} / 1000 \times 2\%)

100LL: ~6 lb per gallon.

lb per hour = power / 20;

e.g.

V_A = V_{A_{max}} \times \sqrt{\text{CurWeight / MaxWeight}}

So if your current weight is 80% of MTOW, $V_A$ is ~90% of the $V_{A_{max}}$ .

Divide the true airspeed by 10 and add 7. e.g.