Definition
A pitch-up adjustment of approximately one and a half pitch bar widths on the attitude indicator, applied immediately after takeoff to compensate for a known small-angle error in older attitude indicators caused by acceleration and pitch-up forces during the takeoff roll and initial climb.
Plain English
Right after takeoff, the attitude indicator can briefly show the airplane as more nose-up than it really is. To correct for this, the pilot raises the displayed nose by about one and a half of the small horizontal bars on the instrument so the picture matches the actual climb attitude.
Context Anchor
Seen in instrument flying when using the attitude indicator to make precise pitch corrections without outside visual references.
Derivation
Named after the spacing of the pitch reference bars on the attitude indicator face. Each short horizontal line represents a fixed amount of pitch, so 'one and a half bars' simply describes how far up to set the miniature airplane against those reference lines.
Why Pilots Care
Allows precise altitude recovery without overcorrecting during IFR flight.
Analogy
It is like nudging a picture on a wall by a measured amount instead of shoving it and then having to fix the overcorrection.
Intuition Check
Do not read “one-and-one-half bar” as exactly 1.5 degrees. Here it means about one and one-half visual bar widths on the attitude indicator.
Example Sentence 1
On the takeoff roll, the instructor reminded the student to apply the one-and-one-half bar correction once airborne to maintain the proper climb attitude.
Example Sentence 2
The pilot chose a one-and-one-half bar correction rather than a full two-bar adjustment for smoother altitude control.