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{{Short description|Aircraft anti-stall device}}
{{Unreferenced stub|auto=yes|date=December 2009}}
A '''stick pusher''' is a device installed in some [[fixed-wing aircraft]] to prevent the aircraft from entering an aerodynamic [[stall (flight)|stall]]. Some large fixed-wing aircraft display poor post-stall handling characteristics or are vulnerable to [[Stall (flight)#Deep stall|deep stall]]. To prevent such an aircraft approaching the stall the aircraft designer may install a hydraulic or electro-mechanical device that pushes forward on the [[elevator (aircraft)|elevator]] control system whenever the aircraft’s [[angle of attack]] reaches the pre-determined value, and then ceases to push when the angle of attack falls sufficiently. A system for this purpose is known as a '''stick pusher'''.
A '''stick pusher''' is a device installed in some [[fixed-wing aircraft]] to prevent the aircraft from entering an aerodynamic [[stall (flight)|stall]]. Some large fixed-wing aircraft display poor post-stall handling characteristics or are vulnerable to [[Stall (flight)#Deep stall|deep stall]]. To prevent such an aircraft approaching the stall the aircraft designer may install a hydraulic or electro-mechanical device that pushes forward on the [[elevator (aircraft)|elevator]] control system whenever the aircraft's [[angle of attack]] reaches the predetermined value, and then ceases to push when the angle of attack falls sufficiently.<ref name = "skybrary">{{cite web |url = https://www.skybrary.aero/index.php/Stick_Pusher |title = Stick Pusher |publisher = skybrary.aero |access-date = 21 July 2020}}</ref> A system for this purpose is known as a stick pusher.


The safety requirements applicable to fixed-wing aircraft in the [[transport category]], and also to many military aircraft, are very demanding in the area of pre-stall handling qualities and stall recovery. Some of these aircraft are unable to comply with these safety requirements relying solely on the natural aerodynamic qualities of the aircraft. In order to comply with the requirements aircraft designers may install a system that will constantly monitor the critical parameters and will automatically activate to reduce the angle of attack when necessary to avoid a stall. The critical parameters include the angle of attack, [[airspeed]], wing flap setting and [[Load factor (aeronautics)|load factor]]. Action by the pilot is not required to recognise the problem or react to it.
The safety requirements applicable to fixed-wing aircraft in the [[transport category]], and also to many military aircraft, are relatively demanding in the area of pre-stall handling qualities and stall recovery. Some of these aircraft are unable to comply with these safety requirements relying solely on the natural aerodynamic qualities of the aircraft. In order to comply with regulatory requirements, aircraft designers may opt to install a system that will constantly monitor the critical parameters and will automatically activate to reduce the angle of attack when necessary to avoid a stall. The critical parameters include the angle of attack, [[airspeed]], wing flap setting and [[Load factor (aeronautics)|load factor]]. Action by the pilot is not required to recognise the problem or react to it.


==History==
Aircraft designers who install stick pushers recognise that there is the risk that a stick pusher may activate erroneously when not required to do so. The designer must make provision for the flight crew to deal with unwanted activation of a stick pusher. In some aircraft equipped with stick pushers, the stick pusher can be overpowered by the pilot. In other aircraft, the stick pusher system can be manually disabled by the pilot.
In October 1963, a [[BAC One-Eleven]] airliner was lost after having [[1963 BAC One-Eleven test crash|crashed during a stall test]]. The pilots pushed the [[T-tail]]ed plane past the limits of stall recovery and entered a deep stall state, in which the disturbed air from the stalled wing had rendered the [[elevator (aircraft)|elevator]] ineffective, directly leading to a loss of control and crash.<ref>''Report on the Accident to B.A.C. One-Eleven G-ASHG at Cratt Hill, near Chicklade, Wiltshire on 22nd October 1963'', Ministry of Aviation C.A.P. 219, 1965.</ref> As a consequence of the crash, a combined [[stick shaker]]/pusher system was installed in all production One-Eleven airliners. A wider consequence of the incident was a new design requirement related to the pilot's ability to identify and overcome stall conditions; the design of a [[Transport category]] aircraft that fails to comply with the specifics of this requirement may be acceptable if the aircraft is equipped with a stick pusher.<ref>{{cite news |url= https://leehamnews.com/2019/01/18/bjorns-corner-pitch-stability-part-5-2/ |title= Bjorn's Corner: Pitch stability, Part 6 |date= 18 January 2019 |work= Leeham News }}</ref><ref name = "skybrary"/>


Following the crash of [[American Airlines Flight 191]] on 25 May 1979, the [[Federal Aviation Administration]] (FAA) issued an [[airworthiness directive]], which mandated the installation and operation of stick shakers on both sets of flight controls on most models of the [[McDonnell Douglas DC-10]], a [[trijet]] airliner.<ref>{{Cite web |url=http://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/83D4FF29A77B501C862569F200686555 |title=MCDONNELL DOUGLAS DC-10, -10F, -30, -30F, -40 Series |website=rgl.faa.gov |access-date=24 May 2019}}</ref> In addition to regulatory pressure, various aircraft manufacturers have endeavoured to devise their own improved stall protection systems, many of which have included the stick shaker.<ref>{{cite web |url = https://patents.google.com/patent/US5803408 |title = US5803408A: Autopilot/flight director stall protection system |access-date = 22 July 2020}}</ref> The American aerospace company [[Boeing]] had designed and integrated stall warning systems into numerous aircraft that it has produced.<ref name = "seattle max"/><ref name = "flying pusher"/>
Stick pushers should not be confused with [[stick shaker]]s. A stick shaker is a stall warning device whereas a stick pusher is a stall avoidance device.

According to aerospace periodical [[Flying (magazine)|Flying]], the traditional stick pusher arrangement was established by [[Boeing]].<ref name = "flying pusher"/> The [[Seattle Times]] has observed that Boeing had historically avoided the integration of stick pushers upon many of its aircraft as matter of flying philosophy to avoid overly-automating actions.<ref name = "seattle max">{{cite web |url = https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ |title = The inside story of MCAS: How Boeing's 737 MAX system gained power and lost safeguards |publisher = [[The Seattle Times]] |author1=[[Dominic Gates]] |author2=Mike Baker |date = 22 June 2019}}</ref> Amongst other aircraft Boeing were involved in the development of, the 300 Series of the [[De Havilland Canada Dash 8]] [[regional airliner]] was equipped with this system.<ref>{{cite journal |url = https://jglobal.jst.go.jp/en/detail?JGLOBAL_ID=200902011372947644 |title = Development of the stall warning/stick pusher system for the Boeing/ De Havilland Dash 8 Series 300 |journal = Canadian Aeronautics and Space Journal |last = Paige |first = A. B. |volume = 36 |issue = 3 |pages = 112–121 |issn = 0008-2821 |date = September 1990}}</ref>

There are several variations and functionality differences amongst the stick pushers installed in different aircraft.<ref name = "flying pusher"/> [[Textron Aviation]] developed their own arrangement for its [[Cessna Citation Longitude|Citation Longitude]] [[business jet]], opting to automate the aircraft's augmented pusher system via its integration with the computerised autopilot, thus eliminating the need to involve any electro-mechanical mechanisms. Accordingly, Textron's pusher function has the autopilot servo push the nose down to reduce the angle of attack.<ref name = "flying pusher"/> A relatively similar stall warning arrangement has been adopted on the [[Pilatus PC-24]] light business jet.<ref>{{cite web |url = https://www.flightglobal.com/in-depth/we-fly-the-pilatus-pc-24/132416.article |title = We fly the Pilatus PC-24 |publisher = [[Flight International]] |first = Mike |last = Gerzanics |date = 10 May 2019}}</ref> [[Bombardier Aviation]] also incorporated a stick pusher onto their [[Bombardier Challenger 600 series|Challenger 600 family]] of business jets.<ref>{{cite web |url = https://www.flightglobal.com/in-depth/how-business-aviation-safety-is-stuck-in-a-rut/134681.article |title = How business aviation safety is stuck in a rut |publisher = [[Flight International]] |first = David |last = Learmount |date = 18 October 2019}}</ref>

While not included in earlier models of the aircraft, [[Lockheed Martin]] chose to include a stick pusher in the new generation [[Lockheed Martin C-130J Super Hercules|C-130J Super Hercules]] transport plane, which suffered from unexpected stall characteristics that had delayed the type's entry into service and could not be resolved via multiple aerodynamic alterations.<ref>{{cite web |url = https://www.flightglobal.com/lockheed-martin-completes-final-tests-on-c-130j-stick-pusher/15022.article |title = Lockheed Martin completes final tests on C-130J stick-pusher |publisher = [[Flight International]] |date = 8 October 1997}}</ref> The [[Embraer ERJ family]] has been equipped with a stick pusher, despite the reportedly completion of all stall tests without incident.<ref>{{cite web |url = https://www.flightglobal.com/basic-appeal/6506.article |title = Basic appeal |publisher = [[Flight International]] |first = Peter |last = Henley |date = 3 July 1996}}</ref> In Europe, airliners not known for possessing deep-stall characteristics, such as the [[McDonnell Douglas MD-80]] narrowbody airliner, have been routinely required to be outfitted with stick pushers even where other regulatory bodies have found such devices unnecessary.<ref>{{cite web |url = https://www.flightglobal.com/difficult-birth/21560.article |title = Difficult birth |publisher = Flight International |date = 24 June 1997}}</ref><ref>{{cite web |url = https://www.flightglobal.com/showdown-looms-on-jaa-rules/16731.article |title = Showdown looms on JAA rules |publisher = Flight International |date = 5 April 1995}}</ref>

The principle of the stick pusher is also applicable to rotorcraft. [[Helicopter flight controls#Collective|Collective]] pull down devices have been made available typically as an [[Automotive aftermarket|aftermarket]] addition, which function in much the same way as the stick pusher.<ref>{{cite web |url = https://helitrak.com/collective-pull-down |title = Collective Pull Down |publisher = helitrak.com |access-date = 21 July 2020}}</ref> However, a stick pusher should not be confused with a [[stick shaker]], the latter being a device that warns pilots of an imminent stall through rapid and noisy vibrations of the control yoke (the "stick").<ref name = "flying pusher">{{cite web |url = https://www.flyingmag.com/how-it-works-stick-shaker-pusher/ |title = How it Works: Stick Shaker/Pusher |publisher = Flying |first = Rob |last = Mark |date = 14 August 2017}}</ref>

To unfamiliar flight crew, the activation of the stick pusher can feel particularly abrupt, vigorous and alarming, but this is an intended and normal part of its functionality to ensure it takes effect before a serious stall sets in.<ref name = "flying pusher"/> Furthermore, aircraft designers who install stick pushers recognise that there is the risk that the device may activate erroneously when not required to do so, and thus must make suitable provisions for the flight crew to address the unwanted activation of a stick pusher. In some aircraft equipped with stick pushers, the stick pusher can be overpowered by the pilot; in some implementations, the stick pusher system can also be manually disabled by the pilot.<ref>{{cite web |url = https://www.legislation.gov.au/Details/F2005L03929 |title = AD/DO 328/30 - Stick Pusher Disarm Switch/Light |publisher = legislation.gov.au |date = 2006}}</ref>

During the 2000s, there was a series of accidents that were attributed, at least in part, to their flight crews having made improper responses to the activation of the stick pusher.<ref name = "skybrary"/><ref>{{cite web |url = https://www.flightglobal.com/many-airline-pilots-do-not-understand-aerodynamics-conference-learns/90735.article |title = Many airline pilots do not understand aerodynamics, conference learns |publisher = [[Flight International]] |first = David |last = Learmount |date = 7 December 2009}}</ref> During the early 2010s, in response to this wave of accidents, the [[Federal Aviation Administration]] (FAA) issued guidance urging operators to ensure that flight crews are properly training on the use of stick pushers.<ref>{{cite web |url = https://www.ainonline.com/aviation-news/2013-02-04/training-enhanced-stall-and-stick-pusher-update |title = Training: Enhanced Stall and Stick Pusher Update |first = Robert P. |last = Mark |publisher = AIN Online |date = 4 February 2013}}</ref><ref>{{cite web |url = http://www.aero-news.net/index.cfm?do=main.textpost&id=ebbd5f80-c8e0-4a2d-8630-c0290297ad83 |title = NTSB Makes ATR-42 Stick-Pusher Recommendations To FAA, EASA |publisher = aero-news.net |date = 28 June 2012}}</ref>


==See also==
==See also==
* [[Aircraft flight control system]]
* [[Dual control (aviation)]]
* [[Maneuvering Characteristics Augmentation System]]

===Aircraft stall accidents===
* [[British European Airways Flight 548]]
* [[British European Airways Flight 548]]
* [[Colgan Air Flight 3407]] ([[codeshare agreement|codeshared]] as Continental Connection Flight 3407)
* [[Continental Connection Flight 3407]]

==References==
{{reflist}}

==External links==
* [http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%20120-109.pdf FAA Advisory Circular 120-109, Stall and Stick Pusher Training]
* [https://www.icao.int/Meetings/LOCI/Documents/10011_draft_en.pdf Manual on Aeroplane Upset Prevention and Recovery Training via icao.int]


{{Aircraft components}}
{{Aircraft components}}
{{Aviation lists}}


{{DEFAULTSORT:Stick Pusher}}
{{DEFAULTSORT:Stick Pusher}}
[[Category:Aircraft components]]
[[Category:Aircraft components]]


{{Aviation-stub}}

Latest revision as of 17:27, 8 June 2024

A stick pusher is a device installed in some fixed-wing aircraft to prevent the aircraft from entering an aerodynamic stall. Some large fixed-wing aircraft display poor post-stall handling characteristics or are vulnerable to deep stall. To prevent such an aircraft approaching the stall the aircraft designer may install a hydraulic or electro-mechanical device that pushes forward on the elevator control system whenever the aircraft's angle of attack reaches the predetermined value, and then ceases to push when the angle of attack falls sufficiently.[1] A system for this purpose is known as a stick pusher.

The safety requirements applicable to fixed-wing aircraft in the transport category, and also to many military aircraft, are relatively demanding in the area of pre-stall handling qualities and stall recovery. Some of these aircraft are unable to comply with these safety requirements relying solely on the natural aerodynamic qualities of the aircraft. In order to comply with regulatory requirements, aircraft designers may opt to install a system that will constantly monitor the critical parameters and will automatically activate to reduce the angle of attack when necessary to avoid a stall. The critical parameters include the angle of attack, airspeed, wing flap setting and load factor. Action by the pilot is not required to recognise the problem or react to it.

History

[edit]

In October 1963, a BAC One-Eleven airliner was lost after having crashed during a stall test. The pilots pushed the T-tailed plane past the limits of stall recovery and entered a deep stall state, in which the disturbed air from the stalled wing had rendered the elevator ineffective, directly leading to a loss of control and crash.[2] As a consequence of the crash, a combined stick shaker/pusher system was installed in all production One-Eleven airliners. A wider consequence of the incident was a new design requirement related to the pilot's ability to identify and overcome stall conditions; the design of a Transport category aircraft that fails to comply with the specifics of this requirement may be acceptable if the aircraft is equipped with a stick pusher.[3][1]

Following the crash of American Airlines Flight 191 on 25 May 1979, the Federal Aviation Administration (FAA) issued an airworthiness directive, which mandated the installation and operation of stick shakers on both sets of flight controls on most models of the McDonnell Douglas DC-10, a trijet airliner.[4] In addition to regulatory pressure, various aircraft manufacturers have endeavoured to devise their own improved stall protection systems, many of which have included the stick shaker.[5] The American aerospace company Boeing had designed and integrated stall warning systems into numerous aircraft that it has produced.[6][7]

According to aerospace periodical Flying, the traditional stick pusher arrangement was established by Boeing.[7] The Seattle Times has observed that Boeing had historically avoided the integration of stick pushers upon many of its aircraft as matter of flying philosophy to avoid overly-automating actions.[6] Amongst other aircraft Boeing were involved in the development of, the 300 Series of the De Havilland Canada Dash 8 regional airliner was equipped with this system.[8]

There are several variations and functionality differences amongst the stick pushers installed in different aircraft.[7] Textron Aviation developed their own arrangement for its Citation Longitude business jet, opting to automate the aircraft's augmented pusher system via its integration with the computerised autopilot, thus eliminating the need to involve any electro-mechanical mechanisms. Accordingly, Textron's pusher function has the autopilot servo push the nose down to reduce the angle of attack.[7] A relatively similar stall warning arrangement has been adopted on the Pilatus PC-24 light business jet.[9] Bombardier Aviation also incorporated a stick pusher onto their Challenger 600 family of business jets.[10]

While not included in earlier models of the aircraft, Lockheed Martin chose to include a stick pusher in the new generation C-130J Super Hercules transport plane, which suffered from unexpected stall characteristics that had delayed the type's entry into service and could not be resolved via multiple aerodynamic alterations.[11] The Embraer ERJ family has been equipped with a stick pusher, despite the reportedly completion of all stall tests without incident.[12] In Europe, airliners not known for possessing deep-stall characteristics, such as the McDonnell Douglas MD-80 narrowbody airliner, have been routinely required to be outfitted with stick pushers even where other regulatory bodies have found such devices unnecessary.[13][14]

The principle of the stick pusher is also applicable to rotorcraft. Collective pull down devices have been made available typically as an aftermarket addition, which function in much the same way as the stick pusher.[15] However, a stick pusher should not be confused with a stick shaker, the latter being a device that warns pilots of an imminent stall through rapid and noisy vibrations of the control yoke (the "stick").[7]

To unfamiliar flight crew, the activation of the stick pusher can feel particularly abrupt, vigorous and alarming, but this is an intended and normal part of its functionality to ensure it takes effect before a serious stall sets in.[7] Furthermore, aircraft designers who install stick pushers recognise that there is the risk that the device may activate erroneously when not required to do so, and thus must make suitable provisions for the flight crew to address the unwanted activation of a stick pusher. In some aircraft equipped with stick pushers, the stick pusher can be overpowered by the pilot; in some implementations, the stick pusher system can also be manually disabled by the pilot.[16]

During the 2000s, there was a series of accidents that were attributed, at least in part, to their flight crews having made improper responses to the activation of the stick pusher.[1][17] During the early 2010s, in response to this wave of accidents, the Federal Aviation Administration (FAA) issued guidance urging operators to ensure that flight crews are properly training on the use of stick pushers.[18][19]

See also

[edit]

Aircraft stall accidents

[edit]

References

[edit]
  1. ^ a b c "Stick Pusher". skybrary.aero. Retrieved 21 July 2020.
  2. ^ Report on the Accident to B.A.C. One-Eleven G-ASHG at Cratt Hill, near Chicklade, Wiltshire on 22nd October 1963, Ministry of Aviation C.A.P. 219, 1965.
  3. ^ "Bjorn's Corner: Pitch stability, Part 6". Leeham News. 18 January 2019.
  4. ^ "MCDONNELL DOUGLAS DC-10, -10F, -30, -30F, -40 Series". rgl.faa.gov. Retrieved 24 May 2019.
  5. ^ "US5803408A: Autopilot/flight director stall protection system". Retrieved 22 July 2020.
  6. ^ a b Dominic Gates; Mike Baker (22 June 2019). "The inside story of MCAS: How Boeing's 737 MAX system gained power and lost safeguards". The Seattle Times.
  7. ^ a b c d e f Mark, Rob (14 August 2017). "How it Works: Stick Shaker/Pusher". Flying.
  8. ^ Paige, A. B. (September 1990). "Development of the stall warning/stick pusher system for the Boeing/ De Havilland Dash 8 Series 300". Canadian Aeronautics and Space Journal. 36 (3): 112–121. ISSN 0008-2821.
  9. ^ Gerzanics, Mike (10 May 2019). "We fly the Pilatus PC-24". Flight International.
  10. ^ Learmount, David (18 October 2019). "How business aviation safety is stuck in a rut". Flight International.
  11. ^ "Lockheed Martin completes final tests on C-130J stick-pusher". Flight International. 8 October 1997.
  12. ^ Henley, Peter (3 July 1996). "Basic appeal". Flight International.
  13. ^ "Difficult birth". Flight International. 24 June 1997.
  14. ^ "Showdown looms on JAA rules". Flight International. 5 April 1995.
  15. ^ "Collective Pull Down". helitrak.com. Retrieved 21 July 2020.
  16. ^ "AD/DO 328/30 - Stick Pusher Disarm Switch/Light". legislation.gov.au. 2006.
  17. ^ Learmount, David (7 December 2009). "Many airline pilots do not understand aerodynamics, conference learns". Flight International.
  18. ^ Mark, Robert P. (4 February 2013). "Training: Enhanced Stall and Stick Pusher Update". AIN Online.
  19. ^ "NTSB Makes ATR-42 Stick-Pusher Recommendations To FAA, EASA". aero-news.net. 28 June 2012.
[edit]
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