How does atmospheric pressure affect instrument readings during an IFR flight?

Atmospheric pressure plays a crucial role in determining the accuracy of instrument readings, particularly the altimeter, during an IFR flight. The altimeter is designed to measure the height of an aircraft above a reference pressure level, typically standard atmospheric pressure at sea level, which is 29.92 inches of mercury (Hg). However, actual atmospheric pressure can fluctuate due to weather systems, resulting in variations from this standard.

When the atmospheric pressure changes, the altimeter may not reflect the true altitude of the aircraft above ground level. If the pressure is lower than the standard setting, the altimeter will read higher than the actual altitude, and if it is higher, the opposite occurs. This discrepancy can lead to either flying too low or too high, posing significant safety risks.

Therefore, pilots must regularly check weather reports for current altimeter settings and adjust accordingly. This ensures that the altimeter reflects the correct altitude, helping maintain safe separation from terrain and other air traffic. Understanding the impact of atmospheric pressure on altimeter settings is essential for accurate navigation and situational awareness during IFR operations.