Bypass ratio the velocity of a very large volume and consequently mass of air produces a very large change in momentum and thrust: thrust is the engine's mass flow (the amount of air flowing through the engine) multiplied by the difference between the inlet and exhaust velocities in—a linear relationship—but the kinetic energy of the exhaust is the mass flow multiplied by one-half the square of the difference in velocities. A low disc loading (thrust per disc area) increases the aircraft's energy efficiency, and this reduces the fuel use. The Rolls–Royce Conway turbofan engine, developed in the early 1950s, was an early
Velocity air meter of the air - and the ECU cannot distinguish, for a given door angle, whether the air is less dense but traveling faster or whether the air is denser but traveling more slowly. Therefore air velocity must be corrected for air density (temperature and barometric pressure) in order to reflect air mass (actual number of air molecules entering the engine per unit of time). Velocity air meters from Bosch have been commonly used on systems such as older Bosch L-Jetronic and as a part of many factory systems, though they now have mostly been superseded by mass airflow sensors which