An aircraft has IAS 150 kt at 8,000 ft. Using the rule of thumb that TAS increases by about 2% per 1,000 ft, what is the approximate TAS?

At 8,000 ft, the approximate increase is $8\times2\%=16\%$. Therefore, $TAS\approx150\times1.16=174$ kt. This is a rule-of-thumb estimate; actual TAS depends on calibrated airspeed, pressure altitude, and temperature, so performance calculations should use the appropriate method or instruments.\n\n**Key takeaway:** The altitude rule gives a rough TAS estimate, not an exact correction.\n\n**Glossary:** **IAS**: indicated airspeed; **TAS**: true airspeed.