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{{short description|System that allows a pilot to control thrust without manually setting fuel flow}}
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[[File:Thrust levers of an Airbus A320.jpg|thumb|Thrust levers of an [[Airbus A320 family|A320]] set to the autothrottle position during cruise flight]]
{{for|a similar system in cars|cruise control}}
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An '''autothrottle''' (automatic [[throttle]]) allows a [[aviator|pilot]] to control the power setting of an [[aircraft]]'s engines by specifying a desired flight characteristic, rather than manually controlling the 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 phases of flight. A/T and AFDS (Auto Flight Director Systems) work together to fulfill the whole flight plan and greatly reduce the pilots' work load<ref name=":0">{{Cite web|url=http://www.flyingmag.com/avionics-gear/autothrottle-advances|title=Autothrottle advance|last=Pope|first=Stephen|date=April 29, 2015|website=|archive-url=|archive-date=|dead-url=|access-date=}}</ref>.
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[[File:Thrust levers of an Airbus A320.jpg|thumb|Thrust levers of an [[Airbus A320 family|A320]] set to the autothrust position during cruise flight]]

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An '''autothrottle''' (automatic [[throttle]], also known as '''autothrust''', A/T or A/THR) is a system that allows a [[aviator|pilot]] to control the power setting of an [[aircraft]]'s engines by specifying a desired flight characteristic, rather than manually controlling the fuel flow. The autothrottle can greatly reduce the pilots' workload and help 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 phases of flight. A/T and AFDS (Auto Flight Director Systems) can work together to fulfill the whole flight plan.<ref name=":0">{{cite web |last1=Pope |first1=Stephen |title=Autothrottle Advances |url=http://www.flyingmag.com/avionics-gear-autothrottle-advances |website=Flying |access-date=29 December 2022 |date=29 April 2015}}</ref>


==Working modes==
==Working modes==
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There are two parameters that an A/T can maintain, or try to attain: speed and thrust.


⚫
In '''speed mode''' the throttle is positioned to attain a set target speed, subject to safe operating margins. For example, if the pilot selects a target speed which is slower than [[Stall (flight)|stall speed]], the autothrottle system maintains a speed above the stall speed.
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There are two parameters that an A/T (autothrottle) can maintain, or try to attain: speed and thrust.


⚫
In the '''thrust mode''' the engine is maintained at a fixed power setting according to the different flight phases. For example, during [[takeoff]], the A/T maintains constant takeoff power until takeoff mode is finished. During [[climb (aeronautics)|climb]], the A/T maintains constant climb power; in [[descent (aircraft)|descent]], the A/T reduces the setting to the idle position, and so on. When the A/T is working in thrust mode, speed is controlled by [[flight dynamics|pitch]] (or the control column), and not by the A/T. A [[radar altimeter]] feeds data to the autothrottle in this mode.<ref name=":0" /><ref name=":1">{{Cite web|url=http://www.flaps2approach.com/journal/2014/9/2/b737-autothrottle-at-normal-and-non-normal-operations.html|title=B737 Autothrottle (A/T) - Normal and Non-Normal Operations|date=September 2, 2014}}</ref>
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In '''speed mode''' the throttle is positioned to attain a set target speed. This mode controls aircraft speed within safe operating margins. For example, if the pilot selects a target speed which is slower than [[Stall (flight)|stall speed]], or a speed faster than [[V speeds|maximum speed]], the autothrottle system will maintain a speed closest to the target speed that is within the range of safe speeds.

⚫
In the '''thrust mode''' the engine is maintained at a fixed power setting according to the different flight phases. For example, during [[takeoff]], A/T maintains constant takeoff power until takeoff mode is finished. During [[climb (aeronautics)|climb]], A/T maintains constant climb power; in [[descent (aircraft)|descent]], A/T retards the throttle to IDLE position, and so on. When A/T is working in thrust mode, speed is controlled by [[flight dynamics|pitch]] (or the control column), and '''NOT''' protected by A/T. A [[radar altimeter]] feeds data to the autothrottle mostly in this mode. (In [[Boeing]] it feeds data to the autothrottle every time. See below.)<ref name=":0" /><ref name=":1">{{Cite web|url=http://www.flaps2approach.com/journal/2014/9/2/b737-autothrottle-at-normal-and-non-normal-operations.html|title=B737 Autothrottle (A/T) - Normal and Non-Normal Operations|last=|first=|date=September 2, 2014|website=|archive-url=|archive-date=|dead-url=|access-date=}}</ref>

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== Usage ==


⚫
==Usage==
On [[Boeing]]-type aircraft, A/T can be used in all flight phases from [[takeoff]], [[climb (aeronautics)|climb]], [[cruise (flight)|cruise]], [[descent (aircraft)|descent]], [[final approach (aviation)|approach]], all the way to [[landing|land]] or [[go-around]], barring malfunction. [[Taxiing|Taxi]] is not considered a part of flight, and A/T does not work for taxiing. In most cases, A/T mode selection is automatic without the need of any manual selection unless interrupted by pilots.
On [[Boeing]]-type aircraft, A/T can be used in all flight phases from [[takeoff]], [[climb (aeronautics)|climb]], [[cruise (flight)|cruise]], [[descent (aircraft)|descent]], [[final approach (aviation)|approach]], all the way to [[landing|land]] or [[go-around]], barring malfunction. [[Taxiing|Taxi]] is not considered a part of flight, and A/T does not work for taxiing. In most cases, A/T mode selection is automatic without the need of any manual selection unless interrupted by pilots.


According to Boeing-published flight procedures, A/T is engaged BEFORE the takeoff procedure and is automatically disconnected two seconds after landing. During flight, manual override of A/T is always available. A release of manual override allows A/T to regain control, and the throttle will go back to the A/T commanded position except for two modes (Boeing type aircraft): IDLE and THR HLD. In these two modes, the throttle will remain at the manual commanded position<ref name=":1" />.
According to Boeing-published flight procedures, A/T is engaged BEFORE the takeoff procedure and is automatically disconnected two seconds after landing. During flight, manual override of A/T is always available. A release of manual override allows A/T to regain control, and the throttle will go back to the A/T commanded position except for two modes (Boeing type aircraft): IDLE and THR HLD. In these two modes, the throttle will remain at the manual commanded position.<ref name=":1" />


== History ==
==History==
⚫
A primitive autothrottle was first fitted to later versions of the [[Messerschmitt Me 262]] [[Jet aircraft|jet]] [[fighter aircraft|fighter]] late in [[World War II]]. However, the first commercial airplane with this system (named AutoPower) was the DC-3 (since 1956). The first version was able to keep a constant [[angle of attack]] but speed-only during approach. When the possibility of maintaining speed during an entire flight was introduced, it led to the creation of the modern autothrottle. The [[North American A-5 Vigilante|RA-5C Vigilante]] used an autothrottle actuated by the input from accelerometers installed in the tail which caused the throttle to be sensitive to movement of the stabilator. This allowed the pilot to adjust the throttle setting during landing approach by stick input alone.<ref>https://www.carrierbuilders.net/articles/20050901_RA-5C_Review/RA5C_Vigilante2.htm</ref><ref>North American Rockwell A3J/A-5 Vigilante' by Dennis R. Jenkins, ISBN 0 942548 14 0, First published: Sept 1989, 56 pages.</ref><ref>https://airwingmedia.com/downloads/a5-vigilante/</ref>


⚫
Shortly after AutoPower's success, two companies, Sperry (now part of Honeywell) and Collins started competing in the development of an autothrottle, with more and more liners and business jets being equipped with it.
⚫
A primitive autothrottle was first fitted to later versions of the [[Messerschmitt Me 262]] [[Jet aircraft|jet]] [[fighter aircraft|fighter]] late in [[World War II]].However, the first commercial airplane with this system, which was named AutoPower, was DC-3 (since 1956). The first version was able to keep constant angle of attack but speed only during approach. When the possibility of maintaining of speed during entire flight was introduced, the modern autothrottle was created.


⚫
Today, it is often linked to a [[Flight Management System]]. [[FADEC]] is an extension of the autothrottle concept and controls many other parameters besides fuel flow.<ref name=":0" />
An important element of this system has been a voter. It has compared a demanded speed with 1,3 of a stalling speed and chosed the higher one. This protection is used up today, it prevents from setting the speed dangerously low.

⚫
Shortly after AutoPower's success companies Sperry (now part of Honeywell) and Collins have started competising in autothrottle's development, equipping with it more and more liners and business jets.

⚫
. Today 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.<ref name=":0" />


==See also==
==See also==
*[[Thrust lever]]
*[[Thrust lever]]
*[[Asiana Airlines Flight 214]] - crashed when the pilot changed the auto pilot setting that disengaged the auto-throttle
*[[Atlas Air Flight 3591]] – 2019 crash of a [[Boeing 767]] freighter in which the pilot unknowingly switched the A/T to [[go-around]] mode in [[instrument meteorological conditions]] and suffered a head-up [[somatogravic illusion]]
*[[TAROM Flight 371]] - crashed after an auto-throttle failure and incapacitation of the captain
*[[Sriwijaya Air Flight 182]] - crashed after an auto-throttle failure


==References==
==References==
{{reflist}}
<references />


==External links==
* {{US patent reference
* {{US patent reference
| number = US3362661
| number = US3362661
Line 40: Line 43:
| title = Autothrottle
| title = Autothrottle
}}
}}



{{Aircraft gas turbine engine components}}
{{Aircraft gas turbine engine components}}
{{Aircraft components}}
{{Aircraft components}}
{{Flight instruments}}


[[Category:Aircraft controls]]
[[Category:Aircraft controls]]

Latest revision as of 22:37, 8 November 2024

For a similar system in cars, see cruise control.
Thrust levers of an A320 set to the autothrust position during cruise flight

An autothrottle (automatic throttle, also known as autothrust, A/T or A/THR) is a system that allows a pilot to control the power setting of an aircraft's engines by specifying a desired flight characteristic, rather than manually controlling the fuel flow. The autothrottle can greatly reduce the pilots' workload and help 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 phases of flight. A/T and AFDS (Auto Flight Director Systems) can work together to fulfill the whole flight plan.[1]

Working modes

[edit]

There are two parameters that an A/T can maintain, or try to attain: speed and thrust.

In speed mode the throttle is positioned to attain a set target speed, subject to safe operating margins. For example, if the pilot selects a target speed which is slower than stall speed, the autothrottle system maintains a speed above the stall speed.

In the thrust mode the engine is maintained at a fixed power setting according to the different flight phases. For example, during takeoff, the A/T maintains constant takeoff power until takeoff mode is finished. During climb, the A/T maintains constant climb power; in descent, the A/T reduces the setting to the idle position, and so on. When the A/T is working in thrust mode, speed is controlled by pitch (or the control column), and not by the A/T. A radar altimeter feeds data to the autothrottle in this mode.[1][2]

Usage

[edit]

On Boeing-type aircraft, A/T can be used in all flight phases from takeoff, climb, cruise, descent, approach, all the way to land or go-around, barring malfunction. Taxi is not considered a part of flight, and A/T does not work for taxiing. In most cases, A/T mode selection is automatic without the need of any manual selection unless interrupted by pilots.

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

History

[edit]

A primitive autothrottle was first fitted to later versions of the Messerschmitt Me 262 jet fighter late in World War II. However, the first commercial airplane with this system (named AutoPower) was the DC-3 (since 1956). The first version was able to keep a constant angle of attack but speed-only during approach. When the possibility of maintaining speed during an entire flight was introduced, it led to the creation of the modern autothrottle. The RA-5C Vigilante used an autothrottle actuated by the input from accelerometers installed in the tail which caused the throttle to be sensitive to movement of the stabilator. This allowed the pilot to adjust the throttle setting during landing approach by stick input alone.[3][4][5]

Shortly after AutoPower's success, two companies, Sperry (now part of Honeywell) and Collins started competing in the development of an autothrottle, with more and more liners and business jets being equipped with it.

Today, it is often linked to a Flight Management System. FADEC is an extension of the autothrottle concept and controls many other parameters besides fuel flow.[1]

See also

[edit]

References

[edit]
  1. ^ a b c Pope, Stephen (29 April 2015). "Autothrottle Advances". Flying. Retrieved 29 December 2022.
  2. ^ a b "B737 Autothrottle (A/T) - Normal and Non-Normal Operations". September 2, 2014.
  3. ^ https://www.carrierbuilders.net/articles/20050901_RA-5C_Review/RA5C_Vigilante2.htm
  4. ^ North American Rockwell A3J/A-5 Vigilante' by Dennis R. Jenkins, ISBN 0 942548 14 0, First published: Sept 1989, 56 pages.
  5. ^ https://airwingmedia.com/downloads/a5-vigilante/
[edit]
  • US patent US3362661, Booth George C, Post Morris H, Prilliman Floyd W, Redmond Jr William G, "Autothrottle", issued 1968-1-9 
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