1. Understanding Spatial Disorientation
Humans have sensory systems well suited for moving on the surface of the earth but poorly suited for flying. In flight, humans have many difficulties in orientation, particularly if the input to the primary sense, vision, is degraded or removed.
A visual illusion exists when looking at a misleading visual scene, this distortion of sensed information can have strong effects on situation assessment and decision making.
Spatial disorientation occurs when there are difficulties in orientation, or there is a mismatch between the real world and what is sensed.
Visual illusions and spatial disorientation have contributed to many aircraft accidents; their effects are most pronounced at night and in instrument meteorological conditions (IMC).
Spatial disorientation can take many different forms. The only solution to all forms of spatial disorientation is for the pilot to trust his instruments and not his own sensation or perception of orientation. This is the essential skill in all instrument flying and represents the only advice which may be given to pilots on this topic.
This presentation provides an overview of the visual illusions and spatial disorientation. It is intended to enhance the reader's awareness but it shall not supersede the applicable regulations or airline's operational documentation; should any deviation appear between this presentation and the airline’s AFM / (M)MEL / FCOM / QRH / FCTM, the latter shall prevail at all times.

2. Spatial Disorientation
Visual illusions and spatial disorientation have contributed to many aircraft accidents; their effects are most pronounced at night and in instrument meteorological conditions (IMC)
A visual illusion exists when looking at a misleading visual scene. This distortion of sensed information can have strong effects on situation assessment and decision making
Spatial disorientation occurs when there are difficulties in orientation, or there is a mismatch between the real world and what is sensed
Humans have sensory systems well suited for moving on the surface of the earth but poorly suited for flying. In flight, humans have many difficulties in orientation, particularly if the input to the primary sense, vision, is degraded or removed.
A visual illusion exists when looking at a misleading visual scene, this distortion of sensed information can have strong effects on situation assessment and decision making.
Spatial disorientation occurs when there are difficulties in orientation, or there is a mismatch between the real world and what is sensed.
Visual illusions and spatial disorientation have contributed to many aircraft accidents; their effects are most pronounced at night and in instrument meteorological conditions (IMC).
Spatial disorientation can take many different forms. The only solution to all forms of spatial disorientation is for the pilot to trust his instruments and not his own sensation or perception of orientation. This is the essential skill in all instrument flying and represents the only advice which may be given to pilots on this topic.
Spatial orientation defines our natural ability to maintain our body orientation and/or posture in relation to the surrounding environment (physical space) at rest and during motion. Genetically speaking, humans are designed to maintain spatial orientation on the ground. The flight environment is hostile, unnatural and unfamiliar to the human body. The ‘machine driven propulsion’ accelerations other than the gravitational acceleration suddenly confuse the sensory system, and the veridical (subjective vertical) is not any longer pointing to the earth; it creates sensory conflicts and illusions that make spatial orientation difficult, and, in some cases, even impossible to achieve. Statistics show that between 5 to 10% of all general aviation accidents can be attributed to spatial disorientation, and 90% of these accidents are fatal.
21% of approach and landing accidents involved disorientation/visual illusion.
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This presentation can be printed in the notes format to provide a personal reference document.

3. Spatial Disorientation
The body has five senses: vision, hearing, touch, smell and taste.
The sensory inputs that provide orientation and balance are the eyes, inner ear (vestibular), and tactile (motion or position) systems; they work simultaneously.
Tactile
Gravity
Distance, Height
Horizontal, Vertical
Movement
The body has five senses: vision, hearing, touch, smell, and taste.
The sensory inputs that provide orientation, gaze stabilization and balance are visual (sight), vestibular (balance and rotation), and proprioceptive (feedback from skin and muscle sensors for detection of body and limb positions), they all act simultaneously.
Orientation is achieved through the perception of these combined sensory inputs.
Failures in orientation:
a. Vertigo: A sensation of spinning or dizziness. Typically caused by a malfunctioning of the vestibular system, either caused by unnatural movements such as continuous spinning followed by a sudden stopping or in clinical circumstances by a disease of the inner ear. The term vertigo is often misused by aircrew members as a generic term to represent all forms of spatial disorientation that they may experience.
b. Sensory illusion: A false perception of reality caused by the conflict of orientation information from one or more mechanisms of the equilibrium. Sensory illusions are a major cause of spatial disorientation.
c. Spatial disorientation: Spatial disorientation is a subset of loss of situational awareness. It is the inability to determine position, attitude or motion relative to the surface of the earth or other significant objects (i.e., airfields, runways or buildings).
d. Orientation or balance: Orientation or balance involves the accurate perception of position, attitude, and motion relative to the earth.
Ref: US Army School of Aviation Medicine
Rate
Rotation
Acceleration

4. Spatial Disorientation
Pilots can suffer from illusions of orientation in many ways, e.g. the misinterpretation of visual information; vision is the most important contributor to the perception of orientation.
Other contributors are the vestibular system (inner ear) and the somatosensory system (pressure and position nerve receptors distributed throughout the body). These can produce spatial disorientation.
Errors of perception (disorientation) are ‘normal’ sensations. The human equilibrium system is designed to function on the earth, to chase animals…, not to fly aircraft. Humans are not designed to fly.
There area number of ways in which the pilot can suffer from illusions of orientation. Some of these are caused by the misinterpretation of visual information (vision is the most important contributor to the perception of orientation). Other contributors to the perception of orientation are the vestibular system and the somatosensory system (pressure and position nerve receptors distributed throughout the body).
Spatial disorientation can take many different forms. They are caused by a conflict between what the pilot’s senses tell him and what the aircraft’s attitude instruments indicate. With increasing experience, pilots learn to disregard these incoming sensations and to fly the aircraft by reference to the instruments.
Good spatial orientation on the ground relies on the effective perception, integration, and interpretation of visual, vestibular (organs of equilibrium located in the inner ear), and proprioceptive (receptors located in the skin, muscles, tendons, and joints) sensory information. Changes in linear acceleration, angular acceleration, and gravity are compared in the brain with visual information.
Spatial orientation is mainly based on the perception of the vertical, measured by a special organ in the inner ear that senses the sum of all linear accelerations imposed on us. Under normal circumstances, not in an accelerating airplane, this acceleration is mainly the gravitational acceleration. This sense therefore allows us to know at any time where the ground is. When other accelerations are imposed such as occurring during take-off, the inner ear has a ‘false’ sensation of the true vertical since it perceives the combined vector sum of true gravity and the plane’s linear acceleration as the subjective vertical.
Therefore, it is perfectly normal that in flight it is sometimes difficult to achieve perfect orientation, particularly because the various types of sensory stimuli vary in magnitude, direction, and frequency. Additionally, 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.
TYPES OF SPATIAL DISORIENTATION
TYPE I (UNRECOGNIZED)
A disoriented aviator does not perceive any indication of spatial disorientation, he does not think anything is wrong. What he sees—or thinks he sees—is corroborated by his other senses. This is the most dangerous type of disorientation. The pilot is unaware of a problem and fails to recognize or correct the disorientation. An example of this type of SD would be the height-/depth-perception illusion when the pilot descends into the ground or some obstacle above the ground because of a lack of situational awareness.
TYPE II (RECOGNIZED)
The pilot perceives a problem (resulting from spatial disorientation), however, may fail to recognize it as spatial disorientation:
The pilot may feel that a control is malfunctioning or that an instrument failure as in a continuous spiral. The pilot fails to correct the aircraft roll attitude, as indicated by the attitude indicator, because his vestibular indications of straight-and-level flight are so strong.
TYPE III (INCAPACITATING)
The pilot experiences such an overwhelming sensation of movement that he or she cannot orient himself or herself by using visual cues or the aircraft instruments. Type III spatial disorientation requires change of control to regain control of the aircraft.
UKFSC “FOCUS” Winter 91/92 ‘Human Factors For Pilots’ pt 4
Graphic credit, Airbus

5. Vision
The visual system consists of central and peripheral vision. Vision is the dominant sense for orientation when good visual cues are present, then attention to the other senses is easily and often suppressed.
Central vision allows us to perceive images clearly, it is the basis of judgments of distance and depth (relative distance).
Peripheral vision provides orientation. It is the primary mode for detecting our own motion or the motion of other objects around us. it provides orientation information if information from the inner ear is unavailable.
Visual orientation requires perception, recognition and identification; people must determine their position (the situation) by understanding where other objects are in relation to themselves.
Vision is the most important bodily sense for orientation. During flight, 80 percent of orientation is dependent on the visual sense. When the visual system is functioning normally, the motion and position systems add to the visual system to give orientation and situational awareness. During flight without the visual system (instrument flight rules [IFR], or at night), the motion and position systems become much more important to provide orientational information. However, the vestibular system may be misinterpreting the ongoing movements, and therefore cannot always be relied on.
Visual orientation requires perception, recognition and identification, a person must determine their position by understanding where other objects are in relation to themselves.
The visual system is comprised of two modes, central vision and peripheral vision. When good focal and ambient visual cues are present, vision is dominant, and attention to the other orientation senses is often minor or easily suppressed..
Central vision allows us to perceive images clearly. It involves relatively fine detail, it is concerned with object recognition and identification, e.g. looking at flight instruments.
Central vision is the basis of judgments of distance and depth (relative distance) are made. The images we perceive throughout our lifetime are stored in memory so that we may compare their size to our own position relative to them. For example, a five ton cargo truck is a known size, therefore, we can judge our distance from it.
Peripheral vision provides orientation within the environment. It is the primary mode for detecting motion.
Peripheral vision is mainly independent of central vision, e.g. central vision can be busy with reading, but peripheral vision enables simultaneous orientation cues for walking or riding a bicycle.
Peripheral vision detects motion, either our own motion or motion of other objects around us, it provides orientation information, regardless of the information that is coming from the inner ear. A typical example of self-motion perceived by peripheral vision is when sitting in a train watching the train on the next track departing. Initially this is perceived as self motion, until the sensors in the inner ear and the proprioception tells the brain that we are still stationary.
It can be very misleading during approach in heavy snow. Using the landing lights will even increase this effect of disturbing peripheral input. It is therefore recommended to use the landing lights only when the runway is clearly in sight.

6. Visual Illusions – False Horizon
The false-horizon illusion occurs when the pilot confuses cloud formations with the horizon or the ground. A sloping cloud layer may be difficult to perceive as anything but horizontal if it extends for any great distance in the pilot’s peripheral vision. A cloudbank below may be perceived to be horizontal although it may not be horizontal to the ground, resulting in the pilot perceiving a banked attitude.
Visual illusions may occur when visual cues are reduced by clouds, night, and/or other obscurities to vision. When there is no horizon, visual cues arising can easily be misinterpreted and lead to disorientation. Types of illusion:-
False horizon: The false horizon illusion occurs when the pilot confuses cloud formations with the horizon or the ground. A sloping cloud layer may be difficult to perceive as anything but horizontal if it extends for any great distance in the pilot’s peripheral vision. A cloudbank below may be perceived to be horizontal although it may not be horizontal to the ground, resulting in the pilot perceiving a banked attitude. This condition is often insidious and goes undetected until the aviator recognizes it and transitions to the instruments and corrects appropriately.
This illusion can also occur if an aviator looks outside after having given prolonged attention to a task inside the cockpit. The confusion may result in the aviator placing the aircraft parallel to the cloudbank.
Flicker vertigo is technically not an illusion, however, as most people are aware from personal experience, viewing a flickering light can be both distracting and annoying.
(a) Flicker vertigo may be created by helicopter rotors blades or airplane propellers interrupting direct sunlight at a rate of 4 to 20 cycles per second.
(b) Other sources include such things as anti-collision strobe lights flashing, especially while in the clouds.
Confusion with ground lights: Occurs when an aviator, mistakes ground lights for stars. This illusion prompts the aviator to place the aircraft in an unusual attitude to keep the misperceived ground lights above them. Isolated ground lights can appear as stars and this could lead to the illusion that the aircraft is in a nose high or one wing low attitude. When no stars are visible due to overcast conditions, unlighted areas of terrain or sea can blend with the dark overcast to create the illusion that the unlighted terrain is part of the sky. This illusion can be avoided by referencing the flight instruments and establishing of a true horizon and attitude.
Ref: US Army School of Aviation Medicine
Make the instruments read right !
Rely on the flight instruments – never on your perception. Ignore your internal instruments.

7. Visual Illusions – Black Hole
The ‘black hole’ approach illusion occurs when approaching a runway at night or in poor visibility with no lights before the runway and with city lights or rising terrain beyond the runway.
These conditions may produce the visual illusion of a high-altitude final approach. If you believe this illusion, you may respond by descending below the normal approach slope.
Check altitude against range for all approaches, monitor vertical speed
Black hole approach
A Black-Hole Approach Illusion can happen during a final approach at night (no stars or moonlight) over water or unlighted terrain to a lighted runway beyond which the horizon is not visible. In the example, when peripheral visual cues are not available to help you orient yourself relative to the earth, you may have the illusion of being upright and may perceive the runway to be tilted left and up sloping. However, with the horizon visible, you can easily orient yourself correctly using your central vision.
Height-depth perception illusion: Due to a lack of sufficient visual cues, the aircrew member will experience the illusion that they are higher above the terrain than they actually are.
(a) Flying over an area devoid of visual references, such as desert, snow, or water will deprive the pilot of his perception of height.
(b) Flight in an area where visibility is restricted by fog, smoke, or haze produces the same illusion.
Fascination or fixation: Occurs when aircrew members ignore orientation cues and focus their attention on their object or goal.
Fixation: Target fixation, commonly referred to as target hypnosis, occurs when an aircrew member ignores orientation cues and focuses their attention on their object or goal; this can occur during approach and landing where the focus of attention is on the runway at the expense of other cues.
Fascination: may occur during the accomplishment of simple tasks within the cockpit. Crewmembers may become so engrossed with a problem or task that they fail to properly scan outside the aircraft. Other types of fascination are associated with wheels-up landings and over concentration on one instrument during instrument flight.
Black hole approaches encourage pilots to develop a glideslope based on the orientation of the lights to a standard of lights in their previous history.  This causes a whole variety of approach paths based on many previous experiences.  The main problem is in judging distance to go, but close into the runway lack of visual cues may encourage variable flare techniques with undesirable landing outcomes.
Graphic credit – Airbus

8. Visual Illusions - runway
Perspective Illusions may change (increase or decrease) the slope of your final approach. They are caused by upsloping or downsloping runways, upsloping or downsloping final approach terrain and runways with different widths
upsloping runway may produce the illusion of a steep approach.
downsloping runway may produce the illusion of a shallow approach.
upsloping terrain may produce the illusion of a shallow approach.
downsloping terrain may produce the illusion of a steep approach.
a narrow runway or long runway may produce the illusion of a steep approach.
a wide or short runway may produce the illusion of a shallow approach.
Aerial Perspective Illusions may make you change (increase or decrease) the slope of your final approach. They are caused by runways with different widths, upsloping or downsloping runways, and upsloping or downsloping final approach terrain. Pilots learn to recognize a normal final approach by developing and recalling a mental image of the expected relationship between the length and the width of an average runway.
A final approach over a flat terrain with an upsloping runway may produce the illusion of a high-altitude final approach (steep). If you believe this illusion, you may respond by pitching the aircraft nose down to decrease the altitude, which, if performed too close to the ground, may result in an accident.
A final approach over a flat terrain with a downsloping runway may produce the illusion of a low-altitude final approach (shallow). If you believe this illusion, you may respond by pitching the aircraft nose up to increase the altitude, which may result in a low-altitude stall or a missed approach.
A final approach over an upsloping terrain with a flat runway may produce the illusion of a low-altitude final approach. If you believe this illusion, you may respond by pitching the aircraft nose up to increase the altitude, which may result in a low-altitude stall or a missed approach.
A final approach over a downsloping terrain with a flat runway may produce the illusion of a high-altitude final approach. If you believe this illusion, you may respond by pitching the aircraft nose down to decrease the altitude, which, if performed too close to the ground, may result in an accident.
A final approach to an unusually narrow runway or an unusually long runway may produce the illusion of a high-altitude final approach. If you believe this illusion, you may respond by pitching the aircraft nose down to decrease the altitude, which, if performed too close to the ground may result in an accident.
A final approach to an unusually wide or short runway may produce the illusion of a low-altitude final approach. If you believe this illusion, you may respond by pitching the aircraft nose up to increase the altitude, which may result in a low-altitude stall or a missed approach.
Graphic credit - FAA

9. Force illusions
Pilots are taught to fly the aircraft in trim. Conventional control systems use a combination of force and position to provide feedback to the pilot.
Trimming the pitch control is routine, trim varies with speed.
Lateral trim seldom varies, but an out-of-balance force due to fuel or configuration asymmetry disturbs the normal force/position relationship. In these circumstances, do not judge the position of control neutral position on force alone.
Rudder trim is used with asymmetric thrust, but the force and position of the rudder controls will vary with both change of thrust and airspeed. Beware of potential false control position sensations due to residual untrimmed forces.
Graphic credit Airbus
Scan all instruments and believe their readings.
Do not make control inputs based on your ‘feelings.’

10. Turning Illusion and False Climb Illusion
There are two main causes of spatial disorientation:
The turning illusion (somatogyral illusion)
A false sensation of rotation or absence of rotation
Any discrepancy between actual and perceived rate of rotation
It originates in the inability of the semicircular canals to register accurately prolonged rotation (> 30 seconds), e.g. banking during holding pattern
The false climb illusion (somatogravic illusion )
A false sensation of body tilt that results from a longitudinal acceleration.
A discrepancy between actual and perceived pitch angle
It occurs during longitudinal acceleration

11. Turning Illusions - Somatogyral
Leans
The most common form of spatial disorientation is the leans. This illusion occurs when the pilot fails to sense angular motion. With a slow rate of roll, the pilot may not perceive that the aircraft is banked. He may feel that his aircraft is still flying straight and level although the attitude indicator shows that the aircraft is in a bank.
SOMATOGYRAL ILLUSIONS
Somatogyral illusions are caused when angular accelerations and decelerations stimulate the semicircular canals. Those that may be encountered in flight are the leans, and Coriolis illusions.
Leans
The most common form of spatial disorientation is the leans. This illusion occurs when the pilot fails to perceive angular motion. During continuous straight-and-level flight, the pilot will correctly perceive that he is straight and Level. However, a pilot rolling into or out of a bank may experience perceptions that disagree with the reading on the attitude indicator.
With a slow rate of roll, the pilot may fail to perceive that the aircraft is no longer vertical. He may feel that his aircraft is still flying straight and level although the attitude indicator shows that the aircraft is in a bank.
Once the pilot detects the slow roll, he makes a quick recovery. He rolls out of the bank and resumes straight-and-level flight. The pilot may now perceive that the aircraft is banking in the opposite direction. However, the attitude indicator shows the aircraft flying straight and level. The pilot may then feel the need to turn the aircraft so that it aligns with the falsely perceived vertical position. Instead, the pilot should maintain straight-and-level flight as shown by the attitude indicator. To counter the falsely perceived vertical position, the pilot will lean his body in the original direction of the roll until the false sensation leaves.
Make the instruments read right !
Rely on the flight instruments – never on your perception. Ignore your internal instruments.

12. Turning Illusions - Somatogyral
Coriolis Illusion
This illusion occurs in a prolonged turn. If the pilot initiates a head movement in a different geometrical plane, the semicircular canals sense a turn in all three canals creating a new perception of motion in three different planes of rotation at once: yaw, pitch, and roll. The pilot experiences an overwhelming head-over-heels tumbling sensation.
Coriolis Illusion
Regardless of the type of aircraft flown, the Coriolis illusion is the most dangerous of all vestibular illusions. It causes overwhelming disorientation.
This illusion occurs in a prolonged turn and the pilot makes a head motion in a different geometrical plane. This involves the simultaneous stimulation of two semicircular canals and is associated with a sudden tilting (forward or backwards) of the pilot’s head while the aircraft is turning. This can occur when you tilt you head down (to look at an approach chart or to write a note on your knee pad), or tilt it up (to look at an overhead instrument or switch) or look sideways. This produces an almost unbearable sensation that the aircraft is rolling, pitching, and yawing all at the same time. The pilot experiences an overwhelming head-over-heels tumbling sensation. This illusion can make the pilot quickly become disoriented and lose control of the aircraft.
Make the instruments read right !
Rely on the flight instruments – never on your perception. Ignore your internal instruments.

13. Turning illusion
It originates in the inability of the semicircular canals (inner ear) to register accurately prolonged rotation (> 30 seconds), e.g. banking during holding pattern).
After approx 30 seconds, the brain has no sense of turning any more.
If the aircraft is now
straightened, the brain senses a turn in the
opposite direction. If the pilot perceives a turn
in the opposite direction, he may erroneously correct for this illusory turn by re-entering the original turn and overbanking to compensate. Additionally, the pilot’s instrument scan may be disturbed, and that disables clear reading of the solely reliable instruments.
Suppose the aircraft makes a sustained turn.
After ± 30s, the canals stop responding and the brain has no sense of turning any more.
If the trajectory of the aircraft is now straightened, the brain senses a turn in the opposite direction due to the angular deceleration.
The pilot perceives a turn in the opposite direction
He may erroneously correct for this illusory spin, and reenter the original turn to compensate, so that he perceives stable flight.
Additionally, his gaze may be disturbed by the nystagmus of his eyes (eyes flickering sideways), that disables clear reading of the instruments.
With thanks to Prof Floris L Wuyts, Head of the Vestibular Function Lab, University of Antwerp, Belgium
Graphic credit Airbus

14. Turning illusion The aircraft makes a sustained turn.
After approx 30 seconds, the brain has no sense of turning any more.
With thanks to Prof Floris L Wuyts, Head of the Vestibular Function Lab, University of Antwerp, Belgium

15. Turning illusion
If the trajectory of the aircraft is now straightened, the brain senses a turn in the opposite direction.
The pilot perceives a turn in the opposite direction.
He may erroneously correct for this illusory turn by re-entering the original turn and overbanking to compensate, so that he perceives stable flight.
With thanks to Prof Floris L Wuyts, Head of the Vestibular Function Lab, University of Antwerp, Belgium

16. Turning illusions - defenses
‘Make the instruments read right!’
Rely on the flight instruments
– never on your perception.
Ignore your internal instruments.
Rely on the flight instruments – never on your perception (or your internal instruments)
Make the instruments read right !
Remember that sustained rotations are misperceived by the equilibrium system.
If your vision is disturbed – look at and concentrate on a nearby fixed point on the instrument panel.
Remember that sustained rotations are misperceived by the equilibrium system as a false turn.

17. False Climb illusion (Somatogravic illusion)
This illusion is a false sensation that the body has tilted due to a longitudinal acceleration.
The pilot thinks the aircraft is climbing, but the aircraft pitch attitude is level or at a lower attitude than perceived.
Gravity (1g)
Acceleration
Vertical as sensed by gravity
False vertical due to acceleration; give apparent climb

18. False Climb illusion
During an acceleration, the pilot thinks the aircraft is climbing, but the aircraft pitch attitude is at a lower attitude than perceived.
False vertical due to acceleration; gives apparent climb
Acceleration
Avoid the tendency to push forward. Concentrate on the attitude indicator.

19. False Climb illusion during Go Around
The false climb illusion of a ‘nose-up’ sensation during an acceleration may occur during go around or after takeoff; any erroneous correction by the pilot to push the controls forward could lead to a hazardous situation.
An aircraft accelerating from 170 to 200 knots over a period of 10 seconds just after takeoff generates G acceleration on the pilot. This corresponds to a sensation of 9 degrees ‘nose up’ attitude change.
When no visual cues are present, follow the INSTRUMENTS,
and do not push the nose down.
Scan all instruments and believe their readings.
Do not make control inputs based on your ‘feelings.’

20. Simulators cannot mimic all illusions
Flying in the simulator can provoke ‘some’ of these illusions, but the accelerated ‘g’ never exceeds 1g. Thus simulators cannot mimic the false climb illusion (false ‘nose up’ sensation due to acceleration or nose down due to deceleration).
Simulators have tilt but no acceleration.

21. False ‘attitude’ illusion on approach
Deceleration due to lowering the flaps/use of airbrake is perceived as a nose down sensation
On the runway, before the nose wheel touches down, the deceleration from spoilers may be perceived falsely as a too-low pitch attitude.
False vertical due to deceleration; gives apparent nose down pitch
Vertical as sensed by gravity
Deceleration
Gravity (1g)

22. Scan your flight instruments
Scan all instruments and believe their readings.
Do not make control inputs based on your ‘feelings.’

23. Recovery from Spatial Disorientation
Recover from disorientation by scanning the instruments:
Use the instrument reading, regardless of your sensation.
Don't trust your equilibrium organs, particularly in low-visibility conditions.
In moments of stress, make decisions based on the instruments, and don’t use your ‘instinct,’ i.e. perception.
RECOVERY FROM SPATIAL DISORIENTATION
Spatial disorientation can easily occur in the aviation environment. If disorientation occurs, aviators should—
Refer to the instruments and develop a good cross-check.
Delay intuitive actions long enough to check both visual references and instruments.
Transfer control to the other pilot if two pilots are in the aircraft, rarely will both experience disorientation at the same time.
Debrief on your erroneous perception and realize that it is a perfectly ‘human’ and ‘normal’ sensation (humans can’t help it). BUT, it is ‘not suitable’ for flying.
FAA Instrument Flying Handbook, Advisory Circular 61-27C (AC) (Section II, "Instrument Flying: Coping
with Illusions in Flight"),
FSF Human Factors and Aviation Medicine Nov-Dec 1997
US Army

24. Preventing Spatial Disorientation
Having confidence, competence and currency in instrument flying reduces the risk of disorientation
Use an instrument scan - practice
Prioritize the workload
First fly the aircraft, then consider other things
Build up experience in controlling the aircraft in an environment of conflicting orientation cues
Practice go-arounds in the aircraft
Avoid disorientation by making frequent instrument cross-checks, even when the autopilot is engaged
PREVENTION OF SPATIAL DISORIENTATION
Spatial disorientation cannot be totally eliminated. However, aircrew members need to remember that misleading sensations from sensory systems are predictable. These sensations can happen to anyone because they are due to the normal functions and limitations of the senses. It is ‘normal’ that the vestibular system gives misleading input to the brain under special conditions of accelerations and turns. However, training is essential to redirect the pilots attention to the instruments. Training, instrument proficiency, good health, and aircraft design minimize spatial disorientation. A high level of attention will contribute to limit spatial disorientation because the brain will focus and interpret immediately the right instruments. Fatigue will enhance spatial disorientation because of the prevailing basic instinct to rely on the senses and the lack of focus on the instruments. Spatial disorientation becomes dangerous when pilots become incapable of making their instruments read right. All pilots, regardless of experience level, can experience spatial disorientation. For that reason, they should be aware of the potential hazards, understand their significance, and learn to overcome them.
To prevent disorientation, aviators should—
Never fly without visual reference points (either the actual horizon or the artificial horizon provided by the instruments).
Trust the instruments.
Avoid fatigue, smoking, hypoglycaemia, hypoxia, and anxiety, which all heighten illusions.
Never try to fly VMC and IMC at the same time.
21% of Approach and landing accidents involved disorientation/visual illusion.

25. Scan your flight instruments
Understand Spatial Disorientation
Scan your flight instruments
Graphics DJG
Scan your flight instruments