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A fixed-wing aircraft propulsion system generates forward thrust when air is pushed in the direction opposite to flight. This can be done by different means such as the spinning blades of a propeller, the propelling jet of a jet engine, or by ejecting hot gases from a rocket engine. [4]
Aircraft with thrust-to-weight ratio greater than 1:1 can pitch straight up and maintain airspeed until performance decreases at higher altitude. [3] A plane can take off even if the thrust is less than its weight as, unlike a rocket, the lifting force is produced by lift from the wings, not directly by thrust from the engine.
The familiar study of jet aircraft treats jet thrust with a "black box" description which only looks at what goes into the jet engine, air and fuel, and what comes out, exhaust gas and an unbalanced force. This force, called thrust, is the sum of the momentum difference between entry and exit and any unbalanced pressure force between entry and ...
This is the case on many large aircraft such as the 747, C-17, KC-10, etc. If you are on an aircraft and you hear the engines increasing in power after landing, it is usually because the thrust reversers are deployed. The engines are not actually spinning in reverse, as the term may lead you to believe.
Pratt & Whitney faced difficulties with the JT9D design during the Boeing 747 test program. Engine failures during the flight test program resulted in thirty aircraft being parked outside the factory with concrete blocks hanging from the pylons, awaiting redesigned engines. Boeing and Pratt & Whitney worked together in 1969 to solve the problem.
The thrust force from a stationary engine becomes thrust power when an aircraft is moving under its influence. Zhemchuzhin et al. [27] show an energy balance for a turbojet engine in flight in the form of a Sankey diagram. Component losses leave the engine as waste heat and add to the heat rejected area on a T~s diagram reducing the work area ...
All of the above considerations are basic to the engine running on its own and, at the same time, doing nothing useful, i.e. it is not moving an aircraft or supplying energy for the aircraft's electrical, hydraulic and air systems. In the aircraft the engine gives away some of its thrust-producing potential, or fuel, to power these systems.
Specific thrust is the thrust per unit air mass flowrate of a jet engine (e.g. turbojet, turbofan, etc.) and can be calculated by the ratio of net thrust/total intake airflow. [ 1 ] Low specific thrust engines tend to be more efficient of propellant (at subsonic speeds), but also have a lower effective exhaust velocity and lower maximum airspeed.