Stick pusher

Last updated

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 pre-determined 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.

Contents

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

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

Aircraft stall accidents

Related Research Articles

<span class="mw-page-title-main">Stall (fluid dynamics)</span> Abrupt reduction in lift due to flow separation

In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded. The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid, foil, and Reynolds number.

<span class="mw-page-title-main">American Airlines Flight 191</span> May 1979 plane crash in Chicago, US

American Airlines Flight 191 was a regularly scheduled domestic passenger flight in the United States from O'Hare International Airport in Chicago, Illinois to Los Angeles International Airport in California. On the afternoon of May 25, 1979, the McDonnell Douglas DC-10-10 operating this flight was taking off from runway 32R at O'Hare when its left engine detached from the wing, causing a loss of control, and the aircraft crashed less than one mile (1.6 km) from the end of the runway. All 258 passengers and 13 crew on board were killed, along with two people on the ground. With 273 fatalities, it is the deadliest aviation accident to have occurred in the United States.

Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Articles related to aviation include:

<span class="mw-page-title-main">Stick shaker</span> Mechanical device in an aircraft cockpit to warn the pilot of an imminent stall

A stick shaker is a mechanical device designed to rapidly and noisily vibrate the control yoke of an aircraft, warning the flight crew that an imminent aerodynamic stall has been detected. It is typically present on the majority of large civil jet aircraft, as well as most large military planes.

<span class="mw-page-title-main">Aircraft flight control system</span> How aircraft are controlled

A conventional fixed-wing aircraft flight control system (AFCS) consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.

<span class="mw-page-title-main">Grumman Gulfstream II</span> Type of aircraft

The Gulfstream II (G-II) is an American twin engine business jet designed and built by Grumman and then in succession, Grumman American and finally Gulfstream American. Its Grumman model number is G-1159 and its US military designation is C-11A. It has been succeeded by the Gulfstream III. The first Gulfstream II flew on October 2, 1966.

Aircraft upset is a dangerous condition in aircraft operations in which the flight attitude or airspeed of an aircraft is outside the normal bounds of operation for which it is designed. This may result in the loss of control (LOC) of the aircraft, and sometimes the total loss of the aircraft itself. Loss of control may be due to excessive altitude for the airplane's weight, turbulent weather, pilot disorientation, or a system failure.

<span class="mw-page-title-main">Thai Airways Flight 365</span> 1987 aviation accident

Thai Airways Flight 365 was a Thai Airways Company Boeing 737-2P5 with the registration number HS-TBC. On 31 August 1987, the plane crashed during a scheduled flight from Hat Yai International Airport to Phuket International Airport, killing all 83 people on board: 74 passengers and 9 crew. It was the deadliest aviation accident in Thailand at the time, before being surpassed four years later by the crash of Lauda Air Flight 004. Concerned by another aircraft in their vicinity, the crew reduced their approach speed while attempting to land, and failed to recover from an aerodynamic stall. In addition to pilot error, the air traffic controller was blamed for failing to keep Flight 365 and the other aircraft adequately separated.

<span class="mw-page-title-main">Birgenair Flight 301</span> Aviation accident in 1996

Birgenair Flight 301 was a flight chartered by Turkish-managed Birgenair partner Alas Nacionales from Puerto Plata in the Dominican Republic to Frankfurt, Germany, via Gander, Canada, and Berlin, Germany. On February 6, 1996, the 757-200 operating the route crashed shortly after take-off from Puerto Plata's Gregorio Luperón International Airport. All 189 people on board died. The cause was pilot error after receiving incorrect airspeed information from one of the pitot tubes, which investigators believe was blocked by a wasp nest built inside it. The aircraft had been sitting unused for 20 days, and without pitot tube covers in place for the preceding 2 days before the crash.

<span class="mw-page-title-main">ADC Airlines Flight 053</span> 2006 aviation accident

ADC Airlines Flight 053 (ADK053) was a scheduled passenger flight operated by ADC Airlines from Nigeria's capital of Abuja to Sokoto. On 29 October 2006, the Boeing 737-2B7 crashed onto a corn field shortly after take-off from Nnamdi Azikiwe International Airport in Abuja, killing 96 out of 105 people on board.

<span class="mw-page-title-main">Alliance Air Flight 7412</span> 2000 aviation accident in Patna, Bihar, India

Alliance Air Flight 7412 was a scheduled Indian domestic passenger flight from Calcutta to Delhi, operated by Indian regional airliner Alliance Air. On 17 July 2000, while on approach to its first stopover in Patna, the Boeing 737-2A8 operating the route nose-dived and crashed into a residential area in Patna, killing 60 people including 5 on the ground.

<span class="mw-page-title-main">Flight envelope protection</span>

Flight envelope protection is a human machine interface extension of an aircraft's control system that prevents the pilot of an aircraft from making control commands that would force the aircraft to exceed its structural and aerodynamic operating limits. It is used in some form in all modern commercial fly-by-wire aircraft. The professed advantage of flight envelope protection systems is that they restrict a pilot's excessive control inputs, whether in surprise reaction to emergencies or otherwise, from translating into excessive flight control surface movements. Notionally, this allows pilots to react quickly to an emergency while blunting the effect of an excessive control input resulting from "startle," by electronically limiting excessive control surface movements that could over-stress the airframe and endanger the safety of the aircraft.

<span class="mw-page-title-main">Colgan Air Flight 3407</span> 2009 aviation accident in the U.S.

Colgan Air Flight 3407 was a scheduled passenger flight from Newark, New Jersey, to Buffalo, New York, which crashed on February 12, 2009. The aircraft, a Bombardier Q400, entered an aerodynamic stall from which it did not recover, and crashed into a house at 6038 Long Street in Clarence Center, New York, at 10:17 pm EST, killing all 49 passengers and crew on board, as well as one person inside the house.

<span class="mw-page-title-main">USAir Flight 427</span> Aviation accident in 1994

USAir Flight 427 was a scheduled flight from Chicago's O'Hare International Airport to Palm Beach International Airport, Florida, with a stopover at Pittsburgh International Airport. On Thursday, September 8, 1994, the Boeing 737 flying this route crashed in Hopewell Township, Pennsylvania while approaching Runway 28R at Pittsburgh, which was at the time USAir's largest hub.

<span class="mw-page-title-main">United Express Flight 6291</span> 1994 plane crash in Ohio, United States

United Express Flight 6291 was a regularly scheduled United Express flight from Washington Dulles International Airport near Washington, D.C. to Port Columbus International Airport in Columbus, Ohio. It was a service operated by Atlantic Coast Airlines on behalf of United Express.

<span class="mw-page-title-main">Northwest Orient Airlines Flight 6231</span> 1974 aviation accident

Northwest Orient Airlines Flight 6231 was the fatal crash of a Boeing 727 on December 1, 1974 in Harriman State Park near Stony Point, New York, just north of the New York City area. The Northwest Airlines 727 had been chartered to pick up the Baltimore Colts professional football team in Buffalo in western New York.

<span class="mw-page-title-main">Bhoja Air Flight 213</span> 2012 passenger plane crash near Rawalpindi, Pakistan

Bhoja Air Flight 213 was a domestic scheduled passenger flight operated by Pakistani airline Bhoja Air from Karachi to Islamabad. On 20 April 2012, the Boeing 737-236A aircraft serving the route crashed in bad weather during its final approach to land. All 121 passengers and 6 crew members aboard were killed. With 127 deaths, it remains as the second deadliest air disaster in Pakistan.

<span class="mw-page-title-main">Maneuvering Characteristics Augmentation System</span> Boeing flight control system responsible for 346 deaths

The Maneuvering Characteristics Augmentation System (MCAS) is a flight stabilizing feature developed by Boeing that became notorious for its role in two fatal accidents of the 737 MAX, which killed all 346 passengers and crew among both flights. Systems similar to the Boeing 737 MCAS were previously included on the Boeing 707 and Boeing KC-46, a 767 variant.

<span class="mw-page-title-main">Airborne Express Flight 827</span> 1996 airplane crash

Airborne Express Flight 827 was a functional evaluation flight (FEF) of an Airborne Express Douglas DC-8-63F that had undergone a major modification. On December 22, 1996, during the test flight, the aircraft stalled and crashed, killing all six people on board. Accident investigators determined the cause of the accident was improper crew control inputs.

<span class="mw-page-title-main">Boeing 737 MAX certification</span> Certification of aircraft

The Boeing 737 MAX was initially certified in 2017 by the U.S. Federal Aviation Administration (FAA) and the European Union Aviation Safety Agency (EASA). Global regulators grounded the plane in 2019 following fatal crashes of Lion Air Flight 610 and Ethiopian Airlines Flight 302. Both crashes were linked to the Maneuvering Characteristics Augmentation System (MCAS), a new automatic flight control feature. Investigations in both crashes determined that Boeing and the FAA favored cost-saving solutions, but ultimately produced a flawed design of the MCAS instead. The FAA's Organization Designation Authorization program, allowing manufacturers to act on its behalf, was also questioned for weakening its oversight of Boeing.

References

  1. 1 2 3 "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. 1 2 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. 1 2 3 4 5 6 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.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.