the aircraft is considered unsafe for IFR flight. Indicated altitude corrected for instrument
error is called Calibrated Altitude.
In order to calculate True Altitude, which is the height of the aircraft above Mean Sea
Level (MSL), calibrated altitude must be corrected for density. The two major factors
affecting air density are temperature and pressure.
Outside Air Temperature (OAT) or Indicated Air Temperature (IAT) is measured with
aircraft instruments. These temperatures may or may not be corrected for aircraft
instrument error. Aircraft instruments are calibrated for standard lapse rates. An incorrect
instrument indication will result if the temperature deviates from the standard.
For every 11 C that the temperature varies from the standard lapse rate, the altimeter will
be in error 4%. If the air is colder than the standard atmosphere, the aircraft will be lower
than the altimeter indicates; if the air is warmer than standard, the aircraft will be higher
than the altimeter indicates. For purposes of this course always assume a standard lapse
Temperature's effects on pressure and density translate directly to corresponding affects