Why is it essential to reset your altimeter before descent during a flight?

Resetting the altimeter before descent is crucial for ensuring accurate altitude readings. An altimeter measures sea-level pressure to determine altitude, and as the aircraft descends, its pressure needs to be recalibrated to reflect changes in atmospheric pressure. If the altimeter is not reset, it can lead to inaccurate altitude readings, which may cause the aircraft to be at a different altitude than what the pilot believes. This is vital for safe operations, as accurate altitude information is key for avoiding terrain and ensuring proper separation from other aircraft during descent.

Accurate altitude readings are particularly important as an aircraft transitions from cruise to descent phases, where adherence to altitude restrictions is critical for safe aviation operations. By resetting the altimeter, pilots can make informed decisions based on the correct altitude, ensuring safety throughout the flight, especially when in proximity to airports or congested airspace.