Definition
Sideways forces applied to the landing gear at touchdown when the airplane's longitudinal axis is not aligned with its direction of travel along the runway. These loads stress the gear structure laterally rather than vertically and can cause damage to the wheels, struts, and gear attachment points if severe.
Plain English
Sideways stress on the wheels and gear legs that happens when the airplane touches down while moving partly sideways instead of straight down the runway.
Context Anchor
Encountered during crosswind landing discussions, especially when learning how to align the airplane with the runway before touchdown.
Derivation
“Load” originally meant a burden or weight carried. In aviation, a load is any force a part must carry, so a side load is a force the landing gear must carry from the side, not cargo loaded on the airplane.
Why Pilots Care
High side loads can bend or break gear components, damage tires, and cause directional control problems, especially on narrow runways or in gusty conditions.
Analogy
It is like pushing a rolling shopping cart sideways instead of straight ahead; the wheels can still roll, but they are being forced in a direction they are not designed to take easily.
Intuition Check
Side load does not mean weight placed on one side of the airplane. Here it means sideways force on the landing gear, usually caused by touching down while still drifting or not lined up with the runway path.
Example Sentence 1
Touching down in a crab without straightening the airplane first puts heavy side loads on the landing gear.
Example Sentence 2
Touching down with the nose still crabbed into the wind creates unnecessary side loads that shorten tire life and stress the gear.