Definition
The rate at which gravity accelerates a falling object near the Earth's surface, approximately 32.2 feet per second squared (9.81 meters per second squared). In aviation, this value is used as the reference unit for measuring the load forces felt by a pilot and aircraft during maneuvers, expressed in multiples called Gs. One G equals the normal force of gravity felt while sitting still on the ground; two Gs means twice that force, and so on.
Plain English
Gravity pulls everything down at a steady, measurable rate. Pilots use that rate as a yardstick to describe how heavy they and the aircraft feel during turns, pull-ups, or other maneuvers. One G is the normal weight you feel standing still. Pulling two Gs means you feel twice as heavy.
Context Anchor
Seen in discussions of steep turns, pull-ups, unusual attitudes, aerobatic flight, and the causes of stagnant hypoxia.
Derivation
The letter G is simply shorthand for gravity. Using G as a unit lets pilots and engineers describe forces on the body and airframe in terms everyone already feels every day -- the pull of standing on the ground.
Why Pilots Care
Multiples of this acceleration during maneuvers can pool blood away from the brain, producing stagnant hypoxia and possible loss of consciousness.
Analogy
It is like feeling heavier when an elevator starts upward quickly. In an airplane maneuver, that heavy feeling can be much stronger and can affect blood flow in your body.
Grounding Statement
Sitting in a chair right now, you are feeling 1 G. A steep 60-degree banked level turn pushes that to 2 Gs -- you and everything in the cockpit feel twice as heavy.
Intuition Check
Gs do not mean the airplane is simply closer to gravity or farther from it. They mean how much gravity-like acceleration the airplane and your body are experiencing.
Example Sentence 1
During the steep turn, the pilot felt the seat press up firmly as the load increased to about 2 Gs.
Example Sentence 2
Pulling out of a dive at 4 Gs increased the effective acceleration of gravity enough to reduce blood flow to the brain.