Definition
An abbreviation used in aviation weather reports, NOTAMs, and operational messages to indicate that a value, condition, or procedure does not match the standard reference. For example, an altimeter setting may be flagged as Not Std when it falls outside normal expected ranges, or a procedure may be marked Not Std when it deviates from the published standard.
Plain English
A short way of saying 'this isn't the usual value or setup.' It tells the reader to pay attention because something here is different from what would normally be expected.
Context Anchor
Seen on FAA instrument procedure charts and related chart listings, especially where takeoff minimums or departure instructions are shown.
Derivation
Std is common aviation shorthand for standard. Not Std literally means not standard, which helps remind the pilot that the usual default is not the one to use.
Why Pilots Care
Non-standard conditions change aircraft performance and true altitude, so pilots must apply corrections to avoid altitude or climb errors.
Intuition Check
Not Std does not mean the information is optional or less official. It means the standard rule has been replaced by a specific published rule for that situation.
Example Sentence 1
The altimeter setting on the report was marked Not Std, so the crew double-checked the local pressure before descent.
Example Sentence 2
Because the temperature was Not Std, the altimeter read higher than our actual height above the ground.