Definition
On an attitude indicator, the thickness of the miniature aircraft symbol (the small wings or bar representing the airplane) used as a unit of measure to estimate small pitch changes relative to the artificial horizon. A pitch change of 'one bar width' means the symbol has moved up or down by an amount equal to its own thickness against the horizon line.
Plain English
It's the thickness of the little airplane symbol on the attitude indicator, used as a ruler to judge how much you have pitched up or down. If the symbol moves up by its own thickness above the horizon line, that's one bar width of pitch change.
Context Anchor
Seen when learning to read the attitude indicator and make small pitch changes during instrument flying.
Derivation
Bar' refers to the horizontal bar shape of the miniature aircraft symbol on the attitude indicator. 'Width' is its visual thickness. The phrase simply names the symbol's thickness as a built-in measuring unit on the instrument face.
Why Pilots Care
Proper use of bar width as a pitch reference helps maintain precise altitude control and prevents unintended climbs or descents during instrument flight.
Analogy
It is like using the thickness of a pencil line as a quick measuring guide. The line is not a ruler, but it gives you a repeatable visual reference.
Intuition Check
Do not read bar width as a precise standard measurement. In this context, it is a visual reference on the attitude indicator, not a fixed number of degrees that applies to every instrument.
Example Sentence 1
To level off smoothly, the pilot lowered the nose about one bar width on the attitude indicator.
Example Sentence 2
In the climb, the nose was held two bar widths above the horizon line to maintain a steady five-degree pitch attitude.