Editing Spatial disorientation (section)

=== Misleading sensations ===
Without a visual reference or cues, such as a visible horizon, humans will rely on non-visual senses to establish their sense of motion and equilibrium. During the abnormal acceleratory environment of flight, the [[Vestibular system|vestibular]] and [[proprioceptive system]]s can be misled, resulting in spatial disorientation. When an aircraft is maneuvering, inertial forces can be created by changes in vehicle speed (linear acceleration) and/or changes in direction (rotational acceleration and [[centrifugal force]]), resulting in perceptual misjudgment of the vertical, as the combined forces of gravity and inertia do not align with what the vestibular system assumes is the vertical direction of gravity (towards the center of the Earth).

Under ideal conditions, visual cues will provide sufficient information to override illusory vestibular inputs, but at night or in poor weather, visual inputs can be overwhelmed by these illusory nonvisual sensations, resulting in spatial disorientation. Low visibility flight conditions include night,<ref name=AC60-4/> over water or other monotonous/featureless terrain that blends into the sky,<ref name=AC60-4/> [[Whiteout (weather)|white-out weather]],<ref name=AC60-4/> or inadvertent entry into [[instrument meteorological conditions]] after flying into fog or clouds.

[[File:Load factor and the g-force in turn.svg|thumb|left|Lift (L) and weight/gravity (w) forces acting on an aircraft making a banked or coordinated turn]]
For example, in an aircraft that is making a [[Banked turn#Banked turn in aeronautics|coordinated (banked) turn]], no matter how steep, occupants will have little or no sensation of being tilted in the air unless the horizon is visible, as the combined forces of lift and gravity are felt as pressing the occupant into the seat without a lateral force sliding them to either side.<ref>{{cite news |url=https://japantoday.com/category/national/ana-pilots-unaware-for-20-seconds-that-plane-was-almost-turning-upside-down |title=ANA pilots unaware for 17 seconds that plane was almost turning upside down |date=August 31, 2012 |work=Japan Today |access-date=11 February 2021 |quote=The aircraft tipped more than 130 degrees to the left at one point, but the darkness outside meant many of those on board did not realize the craft had almost flipped over.}}</ref> Similarly, it is possible to gradually climb or descend without a noticeable change in pressure against the seat. In some aircraft, it is possible to execute a loop without pulling negative g-forces so that, without visual reference, the pilot could be upside down without being aware of it.{{Citation needed|date=March 2011}} A gradual change in any direction of movement may not be strong enough to activate the vestibular system, so the pilot may not realize that the aircraft is accelerating, decelerating, or banking.

[[File:BASIC_Flight_instruments_Improved.svg|thumb|right|Standard set of [[flight instruments]], including [[attitude indicator]] (top center) and [[turn and slip indicator]] (bottom left)]]
Gyroscopic [[flight instruments]] such as the [[attitude indicator]] (artificial horizon) and the [[turn and slip indicator]] are designed to provide information to counteract misleading sensations from the non-visual senses.