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altimeter setting correction factor — Aviation Definition | Keynomen Aviation

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altimeter setting correction factor

Plain English Meaning

When air pressure is lower than standard, your altimeter reads higher than you really are. This correction factor is the number of feet you add to your minimum altitude to make sure you're really as high as the rules require.

Full Definition

A height adjustment, in feet, added to a published minimum flight altitude when the local altimeter setting is below 29.92 inches of mercury. It compensates for the fact that lower-than-standard pressure causes the altimeter to indicate higher than the aircraft is actually flying, and is used to determine the lowest usable flight level so the aircraft remains at or above the required true altitude.

Context Anchor

Seen when planning or flying IFR near the transition to flight levels, especially in the of the lowest usable flight level.

altimeter setting correction factor

Instrument Procedures Handbook

Derivation

Altimeter comes from Latin altus (high) plus meter (measure) — a height-measuring instrument. The setting is the pressure value entered into it. The correction factor is simply the amount of feet you correct by. Together: the feet of altitude you must add because of how the altimeter is set.

Why Pilots Care

Ensures vertical separation from terrain and obstacles remains adequate when flying on a pressure altimeter under non-standard atmospheric conditions.

Grounding Statement

Low pressure makes a standard-setting altimeter overstate the airplane’s real height above sea level, so extra altitude must be allowed.

Intuition Check

Do not think of this as a number you dial into the altimeter or as a repair for instrument error. It is an altitude allowance used to choose a safe lowest usable flight level when pressure is low.

Example Sentence 1

With an altimeter setting of 28.92, the pilot applied a 1,000-foot altimeter setting correction factor to determine the lowest usable flight level.

Example Sentence 2

The lowest usable flight level table lists the altimeter setting correction factor for each tenth of an inch below standard pressure.