Definition
The sideways portion of the total lift force produced by the wings when the airplane is banked. When an airplane rolls into a bank, the lift vector tilts with it, splitting into two parts: a vertical component that opposes weight, and a horizontal component that acts toward the inside of the turn. This horizontal component is the force that pulls the airplane into a curved path and is what actually causes the airplane to turn.
Plain English
When the wings tilt in a bank, part of the lift no longer points straight up. Some of it points sideways, and that sideways pull is what makes the airplane turn.
Context Anchor
Seen in discussions of slips, banks, and turns, especially when explaining why a banked airplane tends to turn unless rudder is used to control its direction.
Derivation
‘Horizontal’ comes from ‘horizon’, meaning level with the ground. ‘Component’ comes from Latin componere, ‘to put together’, and in physics means one of the parts a force can be split into. So ‘horizontal component of lift’ means the part of lift that points sideways rather than upward.
Why Pilots Care
This sideways force lets a pilot lose altitude quickly or align with a runway during a slip without raising airspeed.
Grounding Statement
Tilt a flashlight beam on a wall: the spot moves sideways. Tilt the lift vector by banking, and part of it now pulls sideways too — that sideways pull is the turning force.
Intuition Check
Do not read “horizontal” as meaning the airplane is flying level. Here it means the sideways part of lift that acts across the ground when the wings are banked.
Example Sentence 1
As the pilot rolled into a 30-degree bank, the horizontal component of lift began pulling the airplane around the turn.
Example Sentence 2
The pilot holds opposite rudder in the slip, allowing the horizontal component of lift to keep the track aligned with the runway.