Which reading should be used as the altimeter setting when two different readings are observed?

When determining the altimeter setting for flight operations, it is important to know that the safest and most precise approach is to use the lower reading. This aligns with aviation safety practices aimed at ensuring aircraft maintain adequate clearance above terrain and obstacles.

The reason for using the lower altimeter reading is to prevent the risk of flying at an unsafe altitude. If the higher reading were used, it might lead to the aircraft operating closer to obstacles than intended, particularly in areas with varied terrain.

Using the average of both readings, while providing some compromise, does not guarantee safety, as it could still result in an inaccurate altitude reference. Thus, when faced with two altimeter readings, opting for the lower reading serves to enhance safety by ensuring that the altimeter is set in a manner that helps promote adequate vertical separation from the ground.

In summary, using the lower reading is a critical consideration for maintaining safety during flight operations.