Definition
A contraction used in NOTAMs and aviation weather products meaning 'accumulate' or 'accumulation' — the gathering or build-up of something over time, most commonly snow, ice, or precipitation on a runway, taxiway, or aircraft surface.
Plain English
A short way of writing 'accumulate' or 'build-up.' It tells you that something — usually snow or ice — is piling up or has piled up over time.
Context Anchor
Seen in official flight notices, airport condition reports, and weather-related descriptions where space is limited.
Derivation
From the Latin accumulare, meaning 'to heap up' (cumulus = a heap or pile). The same root gives us cumulus clouds, which look like heaped piles of cotton. In a NOTAM, ACCUM signals that something is heaping up over time.
Why Pilots Care
Accumulation of ice reduces lift and increases drag, which can make the aircraft difficult or impossible to control.
Intuition Check
Do not read ACCUM as the name of a device, fix, or airport location. Here it is simply a shortened way to say “accumulate” or “build up.”
Example Sentence 1
The NOTAM read 'RWY 27 SNOW ACCUM 2 IN,' meaning two inches of snow had accumulated on runway 27.
Example Sentence 2
Moisture can accumulate in the fuel tanks if the aircraft is left outside in humid conditions.