Editing Spatial disorientation (section)

== Flight safety, history, and statistics ==
[[File:Barany Chair equilibrium test.jpg|thumb|right|Equilibrium test being administered to prospective pilot, via [[Bárány chair]]]]{{Further|Sensory illusions in aviation}}
Spatial orientation in flight is difficult to achieve because numerous sensory stimuli (visual, vestibular, and proprioceptive) vary in magnitude, direction, and frequency. Any differences or discrepancies between visual, vestibular, and proprioceptive sensory inputs result in a sensory mismatch that can produce illusions and lead to spatial disorientation. The visual sense is considered to be the largest contributor to orientation.<ref name=ATSB-SD2007/>{{rp|4}}

While testing an early [[turn and slip indicator]] devised by his friend [[Elmer Sperry]] in 1918, [[United States Army Air Corps]] pilot [[William Ocker]] entered a [[graveyard spiral]] while flying through clouds without visual references; the turn indicator showed he was in a turn, but his senses told him he was in level flight. Emerging from the clouds, Ocker was able to recover from the dive.<ref>{{cite journal |url=https://www.inventionandtech.com/content/father-blind-flying-0 |title=The Father Of Blind Flying |date=Fall 2008 |author=Wolverton, Mark |volume=23 |issue=3 |journal=Invention and Technology |access-date=11 February 2021 |publisher=American Heritage Institute}}</ref> In 1926, Ocker was subjected to a [[Bárány chair]] equilibrium test by Dr. [[David A. Myers]] at [[Crissy Field]]; the resulting duplication of the somatogyral illusion he had experienced and a subsequent re-test, which he passed using the turn indicator,<ref name=AFEHRI-Ocker>{{cite web |url=https://www.airuniversity.af.edu/Portals/10/AFEHRI/documents/EnlistedHistory/ocker.pdf |title=Sergeant William Charles Ocker: The Army's third enlisted pilot |author=Chivalette, William I. |publisher=Air Force Enlisted Heritage Research Institute |date=1998 |access-date=11 February 2021}}</ref> led him to develop and champion instrumented flight.<ref name=AS-2008/> Sperry would go on to invent the [[gyrocompass]] and [[attitude indicator]], both of which were being tested by 1930.<ref name=ACSC-88>{{cite report |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a194001.pdf |archive-url=https://web.archive.org/web/20191101162824/https://apps.dtic.mil/dtic/tr/fulltext/u2/a194001.pdf |url-status=live |archive-date=November 1, 2019 |title=The evolution of instrument flying in the U.S. Army |author=McIntosh, David M. |date=1988 |publisher=Air Command and Staff College |access-date=11 February 2021}}</ref>{{rp|8}} With Lt. Carl Crane, Ocker published the instructional text ''Blind Flying in Theory and Practice'' in 1932.<ref name=AS-2008>{{cite magazine |url=https://www.airspacemag.com/military-aviation/the-disorient-express-474780/?all |title=The Disorient Express |author=LeCompte, Tom |date=September 2008 |magazine=Air & Space |publisher=Smithsonian Institution |access-date=11 February 2021}}</ref> Influential advocates of instrumented flight training included [[Albert Hegenberger]] and [[Jimmy Doolittle]].<ref name=ACSC-88/>{{rp|8}}

In 1965, the [[Federal Aviation Agency]] of the United States issued Advisory Circular AC 60-4, warning pilots about the hazards of spatial disorientation, which may result from operation under [[visual flight rules]] in conditions of marginal visibility.<ref name=AC60-4>{{cite web |url=https://dotlibrary.specialcollection.net/Document?db=DOT-ADVISORY&query=(select+198) |title=AC 60-4: Pilot's Spatial Disorientation |author=Moore, George S. |date=February 9, 1965 |publisher=Federal Aviation Agency |access-date=11 February 2021}}</ref> A new version of the advisory was issued in 1983 as AC 60-4A, defining spatial disorientation as "the inability to tell which way is 'up.{{' "}}<ref name=AC60-4A>{{cite web |url=https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC60-4A.pdf |title=AC 60-4A: Pilot's Spatial Disorientation |author=Hunt, Kenneth S. |date=February 9, 1983 |publisher=Federal Aviation Administration |access-date=11 February 2021}}</ref>

Statistics show that between 5% and 10% of all general aviation accidents can be attributed to spatial disorientation, 90% of which are fatal.<ref name=FAA-spatial>{{cite web |url=https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/spatiald.pdf |title=Medical Facts for Pilots: Spatial Disorientation, safety brochure AM-400-03/1 |author=Antuñano, Melchor J. |access-date=9 February 2021 |publisher=Federal Aviation Administration}}</ref> Spatial-D and [[G-LOC|G-force induced loss of consciousness (g-LOC)]] are two of the most common causes of death from human factors in military aviation.<ref name=Jedick>{{cite web |url=http://goflightmedicine.com/spatial-disorientation/ |title=Spatial Disorientation |author=Jedick, Rocky 'Apollo' |publisher=Go Flight Medicine |date=1 April 2013 |access-date=30 July 2016}}</ref> A study on the prevalence of spatial disorientation incidents concluded that "if a pilot flies long enough ... there is no chance that he/she will escape experiencing at least one episode of [spatial disorientation]. Looked at another way, pilots can be considered to be in one of two groups; those who have been disorientated, and those who will be."<ref name=ATSB-SD2007>{{cite report |url=https://www.atsb.gov.au/media/29971/b20070063.pdf |title=An overview of spatial disorientation as a factor in aviation accidents and incidents |author=Newman, David G. |date=3 December 2007 |publisher=Australian Transport Safety Bureau |isbn=978-1-921165-52-8 |access-date=11 February 2021 |archive-date=19 September 2020 |archive-url=https://web.archive.org/web/20200919000527/https://www.atsb.gov.au/media/29971/b20070063.pdf |url-status=dead }}</ref>{{rp|2}}