Under ordinary conditions a pilot is able by his senses of sight, hearing, and feeling to know just about how his plane is performing without focusing his attention on the instrument panel. In fact, for an experienced pilot, most of the instruments serve chiefly to check his estimate of the ship’s performance. The more experienced the pilot, the more independent he can be of his instruments, generally speaking, but no amount of experience will enable a pilot to determine how far he is above the surface of the earth. It may be considered one of the hazards of aviation that the one instrument, the altimeter, for which no amount of experience can substitute, should be subject to so many corrections. An understanding of the altimeter and a few thumb rules pertaining to its corrections should enable a pilot to have sufficient altitude at all times to clear in safety the high ridges and tall trees which frequently give trouble on cross-country flights during thick weather.
Thumb Rules For Altimeter Corrections
By Lieutenant Frederick J. Nelson, U. S. Navy