An autothrottle (automatic throttle) allows a pilot to control the power setting of an aircraft's engines by specifying a desired flight characteristic, rather than directly controlling fuel flow. These systems can conserve fuel and extend engine life by metering the precise amount of fuel required to attain a specific target indicated air speed, or the assigned power for different phrases of flight. A/T and AFDS (Auto Flight Director System) work together to fulfill the whole flight plan and greatly reduce pilots work load. In an engine, the throttle is the mechanism by which the engines power is increased or decreased. ... For other uses, see Aviator (disambiguation). ... Look up aircraft in Wiktionary, the free dictionary. ... Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted. ... Aircraft display an Indicated Airspeed (abbreviated IAS) on an instrument called an airspeed indicator. ...

Simply put, when engaged AutoThrottle replaces manual throttle input with an electronic (or in older systems, mechanical) feedback loop that controls fuel flow to the engines. This reduces pilot workload as well as being more accurate than manually adjusting fuel flow.

Working Modes

There are two parameters that an A/T (autothrottle) can maintain, or try to attain: Speed and Thrust.

In Speed mode, A/T, without going beyond its limitations, moves the throttle to a position to attain target speed, meanwhile to protect the speed within the aircraft safety margin. For example, if the pilot selects a target speed which is slower than stall speed, or a speed faster than maximum speed, A/T will maintain a speed that is within the safety region though to the most extend to close to target speed. In another word, when the A/T is in Speed mode, speed is protected, and maintained to the target speed provided the target speed is a reasonable one. In aerodynamics, a stall is a condition in which an excessive angle of attack causes loss of lift due to disruption of airflow. ... V speeds are speeds that define certain performance and limiting characteristics of an aircraft and the V stands for velocity. ...

In Thrust mode, A/T, disregarding speed, maintains a fixed power setting according to the different flight phrases. For example, during Takeoff, A/T maintains a constant Takeoff power until Takeoff mode is finished. During Climb, A/T maintains a constant climb power; Descent, A/T retards throttle to IDLE position, etc. When A/T is working in Thrust mode, speed is controlled by pitch (or control column), and NOT protected by A/T. A Ryanair Boeing 737 takes off from Bristol International Airport, England Takeoff is the phase of flight where an aircraft transitions from moving along the ground (taxiing) to flying in the air (see flight), usually on a runway. ... An Embraer ERJ 145 of Air France on the climb The climb is the part of a flight of an aircraft, after take off, consisting of getting the aircraft to the desired cruising altitude. ... A descent during air travel is any portion where an aircraft decreases altitude, and is the opposite of an ascent. ... Flight dynamics is the science of air and space vehicle orientation and control in three dimensions. ...

Usage

On Boeing type aircraft, A/T is able to work the whole flight phrases from Takeoff, Climb, Cruise, Descent, Approach, all the way to Land or Go-around provided there is no malfunction. Taxi is not considered as a part of flight, and A/T does not work for Taxi. Under most cases, A/T mode selection is automatic without the need of any manual selection unless interrupted by pilots. The Boeing Company (NYSE: BA, TYO: 7661 ) is an aerospace and defense corporation headquartered in Chicago, Illinois. ... Boeing 747 in cruise at roughly 35000 feet, showing contrails from the four engines. ... MyTravel Airways Airbus A320 landing Landing is the last part of a flight, where a flying animal or aircraft returns to the ground. ... A go around, overshoot or missed approach is an aborted landing of an aircraft which is on final approach. ... Taxiing refers to an airplane moving under its own power on the ground, usually on wheels, but also includes aircraft with skis or floats (for water-based travel). ...

According to Boeing published flight procedure, A/T is engaged in BEFORE T/O procedure and is automatically disconnected 2 seconds after landing. During flight, manual override of A/T is always available. A release of manual override allows A/T to gain the control back, and the throttle will go back to the A/T commanded position except for 2 modes (Boeing type aircraft): IDLE and THR HLD. In these 2 modes, throttle will remain at the manual commanded position.

Origins

A primitive autothrottle was first fitted to later versions of the Messerschmitt 262 jet fighter late in World War II. Nowadays it is often linked to a Flight Management System, and FADEC is an extension of the concept to control many other parameters besides fuel flow. The Messerschmitt Me 262 Schwalbe (Swallow) was the first operational jet powered aircraft. ... Look up jet in Wiktionary, the free dictionary. ... This article or section does not adequately cite its references or sources. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... A Flight Managment System is a little computer onboard almost every aircraft that will guide the aircraft to it designated destination. ... FADEC is the acronym for Full Authority Digital Engine Control. ...