Control reversal: Difference between revisions

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{{Short description|Aeronautical phenomenon}}

'''Control reversal''' is an adverse effect on the controllability of [[aircraft]]. The [[Aircraft flight control system|flight controls]] reverse themselves in a way that is not intuitive, so pilots may not be aware of the situation and therefore provide the wrong inputs; in order to roll to the left, for instance, they have to push the control stick to the right, the opposite of the normal direction.

==Causes==

There are several causes for this problem:, pilot error, effects of [[high-speed flight]], incorrectly connected controls, and various [[Coupling (physics)|coupling forces]] on the aircraft.

===Equipment malfunction===

Equipment failure may cause flight controls to behave unexpectedly, for example the possible rudder reversal experienced onboardon board [[United Airlines Flight 585]].<ref name="AAR01-01 Final Report">{{cite book |url=https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0101.pdf |title=Aircraft Accident Report: Uncontrolled Descent and Collision With Terrain, United Airlines Flight 585, Boeing 737-200, N999UA, 4 Miles South of Colorado Springs Municipal Airport, Colorado Springs, Colorado, March 3, 1991 |publisher=[[National Transportation Safety Board]] |id=NTSB/AAR-01/01 |date=March 27, 2001 |access-date=January 17, 2016 |archive-date=October 2, 2015 |archive-url=https://web.archive.org/web/20151002041524/http://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0101.pdf }}</ref>{{rp|114}}

===Pilot error===

[[Pilot error]] is the most common cause of control reversal. In [[unusual attitude]]s it is not uncommon for the pilot to become [[Spatial disorientation#Senses during flight|disoriented]] and start feeding inmake incorrect control movements in order to regain level flight. This is particularly common when using [[Helmet-mounted display|helmet-mounted display systems]], which introduce graphics that remain steady in the pilot's view, notably when using a particular form of [[attitude indicator|attitude display]] known as an ''inside-out''.<ref name="jenkins-hmd">{{cite journalthesis |last1=Jenkins |first1=Joseph C. |title=The Effect of Configural Displays on Pilot Situation Awareness in Helmet-Mounted Displays |date=2007 |url=https://corescholar.libraries.wright.edu/cgi/viewcontent.cgi?article=1297&context=etd_all |publisher=Wright State University |bibcode=2007PhDT........44J |access-date= December 19, 2021 |format=pdf |degree=PhD |others=Jennie Gallimore (Advisor)}}</ref> which introduce graphics that remain steady in the pilot's view, notably when using a particular form of [[attitude indicator|attitude display]] known as an ''inside-out''.<ref name="aviatn-psych-outside-in">{{cite journal |last1=Previc |first1=Fred H. |last2=Ercoline |first2=William R. |title=The 'Outside-In' Attitude Display Concept Revisited |journal=The International Journal of Aviation Psychology |date=October 1999 |volume=9 |issue=4 |pages=377–401 |doi=10.1207/s15327108ijap0904_5 |url=https://www.researchgate.net/publication/232896204 |access-date=December 19, 2021}}</ref>

===Incorrectly connected controls===

Incorrectly connected controls are another common cause of this problem. It is a recurring problem after maintenance on aircraft, notably homebuilthome built designs that are being flown for the first time after some minor work. However itIt is not entirely uncommon on commercial aircraft, and has been the cause of several accidents including the crash of the [[Short Crusader]] before the 1927 [[Schneider Trophy]] and the 1947 death of [[Avro]] designer [[Roy Chadwick]].<ref name="avsafety-G-AGSU-crash">{{cite web |last1=Ranter |first1=Harro |title=ASN Aircraft accident Avro 689 Tudor 2 G-AGSU Woodford Airport (WFD) |url=https://aviation-safety.net/database/record.php?id=19470823-0 |website=aviation-safety.net |publisher=Aviation Safety Network |access-date=19 December 2021 |quote=''PROBABLE CAUSE: Incorrect assembly of the aileron control circuit.''}}</ref>

===Wing twist===

{{main|Aeroelasticity}}

Another manifestation of the problem occurs when the amount of airflow over the [[wing]] becomes so great that the force generated by the [[aileron]]s is enough to twist the wing itself, due to insufficient [[Torsion (mechanics)|torsional]] stiffness of the wing structure. For instance when the aileron is deflected upwards in order to make that wing move down, the wing twists in the opposite direction. The net result is that the airflow is directed down instead of up and the wing moves upward, opposite of what was expected. This form of control reversal is often lumped in with a number of "high speed" effects as [[compressibility]].

==Examples==