propulsive efficiency

Propulsive efficiency is a measure of how effectively a jet engine converts the energy of its exhaust into thrust for propelling an aircraft. This process is governed by Newton's second law of motion, which relates force to mass and acceleration. In a jet engine, thrust is generated by accelerating a stream of air. The propulsor, whether it's a fan, propeller, or the engine's core exhaust, exerts a force on the air, and the reaction to this force is the propulsive thrust transmitted to the aircraft.1

The efficiency of this conversion is maximized when the exhaust jet velocity is only slightly higher than the aircraft's flight speed. A large difference between these velocities significantly reduces propulsive efficiency. Different engine types, such as turboprops and turbofans, are designed to optimize this balance for various flight speeds and altitudes.12