What does 'glide ratio' refer to in aviation?

The term 'glide ratio' specifically refers to the relationship between the vertical distance an aircraft descends and the horizontal distance it travels during a glide. This metric is crucial in aviation as it provides pilots with an understanding of how far they can glide horizontally for a given loss of altitude. A higher glide ratio indicates a more efficient glide, allowing the aircraft to travel further horizontally before losing significant altitude.

For example, if an aircraft has a glide ratio of 10:1, it means that for every 1 unit of altitude lost, the aircraft can travel 10 units horizontally. This concept is vital for pilots when considering emergency situations, such as engine failures, where maintaining control and maximizing distance to a safe landing area is of utmost importance.

The other options listed pertain to different aviation concepts; they do not correctly define 'glide ratio.' For instance, engine efficiency and climb/descent rates deal with different aspects of flight performance and operational metrics, while the speed of descent during a glide is a separate factor that influences but does not define glide ratio. Understanding the glide ratio helps pilots make critical decisions in-flight, particularly when managing fuel efficiency and navigating emergencies.