Definition
The relationship between the horizontal distance an airplane travels and the altitude it loses while gliding without engine power, expressed as a ratio such as 9:1, meaning the airplane moves nine units forward for every one unit it descends. Glide ratio depends on the airplane's aerodynamic design, weight, configuration (flaps, gear), and airspeed, and is maximized at the airplane's best glide speed.
Plain English
How far forward an airplane can travel for each foot of altitude it loses when the engine is not producing power. A higher first number means the airplane travels farther for the same height lost.
Context Anchor
Seen when planning or practicing a 180° power-off approach, where the pilot must judge whether the airplane can reach the runway after power is reduced.
Derivation
Glide' comes from Old English 'glidan,' meaning to move smoothly. 'Ratio' comes from Latin 'ratio,' meaning a calculated relationship between two quantities. Together they describe the calculated relationship between forward travel and altitude loss during an unpowered descent.
Why Pilots Care
Knowing the glide ratio lets a pilot decide if the airplane can reach a runway or field from its current altitude and position after an engine failure.
Analogy
Think of it like a slide at a playground. A long, shallow slide carries you far for each foot of height; a steep slide drops you quickly for the same height. A higher glide ratio is the long, shallow slide.
Grounding Statement
In no wind, a 10:1 glide ratio means 1,000 feet of height could carry the airplane about 10,000 feet forward if flown correctly.
Intuition Check
Glide ratio is not the same as descent speed. It is the forward distance gained compared with the height lost.
Example Sentence 1
During the 180° power-off approach, the pilot used the airplane's known glide ratio to judge whether the runway was within reach.
Example Sentence 2
The pilot used the airplane's published glide ratio to pick the correct turn point for the 180-degree power-off approach to the runway.