Definition
Sideways forces applied to an airplane's landing gear at touchdown or during the rollout, caused by the wheels contacting the runway while the airplane is moving in a direction not aligned with its longitudinal axis. Side loads typically result from landing in a crab without correcting for crosswind drift, or from touching down with the nose pointed away from the direction of travel.
Plain English
Sideways stress on the landing gear that happens when the wheels touch the ground while the airplane is moving slightly sideways instead of straight down the runway.
Context Anchor
Encountered during landing and touchdown discussions, especially when the airplane is not lined up with the runway or is drifting sideways as it touches down.
Why Pilots Care
Excessive side loads can stress or damage landing gear struts, wheels, and tires.
Grounding Statement
Picture the wheels meeting the runway while the airplane is still sliding a little sideways; that sideways push is the side load.
Intuition Check
Side loads are not cargo loaded on one side of the airplane. Here, “load” means force, and “side” means the force is pushing sideways on the landing gear.
Example Sentence 1
The instructor reminded the student to straighten the nose with rudder just before touchdown to avoid side loads on the main gear.
Example Sentence 2
A crabbed touchdown in a strong crosswind can create damaging side loads on the landing gear.