What will the pressure altimeter do when there is a temperature deviation from ISA of -36°C?

When there is a temperature deviation from the International Standard Atmosphere (ISA) conditions, it affects the accuracy of pressure altimeters used in aviation. In the case of a temperature deviation of -36°C, the altimeter will over-read the altitude.

Air pressure decreases with altitude, but temperature also plays a crucial role in how pressure is perceived by the altimeter. The ISA standard assumes a specific lapse rate of temperature with altitude, and this lapse rate affects pressure readings. A lower temperature than standard implies that the air is denser than what the altimeter is calibrated for at that altitude. As a result, the altimeter is interpreting the denser air pressure as being at a lower altitude than it actually is, causing the reading to be higher than the true altitude, effectively making it over-read.

This demonstrates the sensitivity of the altimeter to temperature changes. In situations where the temperature is significantly lower than ISA conditions, navigational inaccuracies can occur, which is a critical consideration for pilots in maintaining correct altitude levels and ensuring flight safety.