Definition 1 of 2
Definition
The ratio of the horizontal distance an aircraft travels to the vertical distance it descends while gliding without engine power, measured in still air. A glide ratio of 10:1 means the aircraft moves forward 10 feet for every 1 foot it descends.
Plain English
How far forward an aircraft travels for each foot it drops when it is gliding with no engine power. The bigger the first number, the farther it can glide from a given height.
Context Anchor
Used in engine-out planning, glider flying, and aircraft performance discussions when deciding whether a landing area is within reach.
Derivation
Glide' comes from Old English glidan, meaning to move smoothly. 'Ratio' comes from Latin ratio, meaning a calculation or proportion. Together: the proportion describing how smoothly an aircraft trades altitude for distance.
Why Pilots Care
Knowing an aircraft's glide ratio helps determine whether a suitable landing spot can be reached after engine failure.
Analogy
Think of a child's slide. A long, shallow slide carries you far forward for a small drop in height (high glide ratio). A short, steep slide drops you straight down with little forward travel (low glide ratio).
Grounding Statement
If an aircraft has a 10:1 glide ratio and is 1,000 feet above the ground, it could glide about 10,000 feet forward in still air if flown properly.
Intuition Check
Glide ratio is not the same as how long the airplane stays in the air. It compares forward distance to height lost, not time.
Example Sentence 1
With a glide ratio of 9:1, the pilot calculated she could reach the airport 8 miles away from her current altitude of 5,000 feet above the ground.
Example Sentence 2
The preflight checklist included confirming the published glide ratio for the planned power-off approach.