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Information about SpatialDisorientation

Published on January 14, 2008

Author: Dario


Spatial Disorientation:  Spatial Disorientation USAF SD Data:  USAF SD Data Spatial Disorientation:  Spatial Disorientation SD causes sizable annual attrition rate in the military, GA, and to a lesser extent transport category fleet. SD crashes are usually fatal because they occur from unusual attitudes. The most severe incidence of SD is under IMC (no surprise) on conventional “steam gage” style instruments SD is most often triggered by a premature attempt to transition from heads-down to heads-up when flying from IMC to (partial) VMC Pilots on “steam gages” or conventional EFIS are so compelled to seek natural horizon references, that they tend to go heads-up at the earliest possible time This is done to reduce workload Spatial Disorientation:  Spatial Disorientation All pilots, regardless of flight experience, can fall victim to the dangers of SD. Human vestibular system is designed to detect accelerations related to pedestrian motions relative to the surface of the earth Correlation of the vestibular sense with the visual sense is optimized for ground based existence In aircraft, the visual, vestibular, and proprioceptive systems may receive conflicting information, refer to different origins (earth horizon, cockpit), and may be operating outside the expected parameters. SD is said to occur if a person loses the ability to determine orientation relative to the surface of the earth and objects. Spatial Disorientation:  Spatial Disorientation Type I: Unrecognized SD Most dangerous type of SD because the aviator is unaware of the deviation in perceived and actual aircraft state Outcome of type I SD is usually fatal May be induced by a gradually failing gyroscope, a situation for which pilots receive little or no training. Type II SD Pilot actually perceives problem related to orientation or attitude Pilot may not be able to generate the correct control response, because the vestibular cues of perceived straight and level flight are so strong E.g. graveyard spiral is a type of unusual attitude, where the plane is in a steep banking descending turn with decreasing radius and increasing angle of bank Type III SD: Pilot overwhelmed by the sensation of movement induced by the vestibular system that aircraft control cannot be regained, unless a second crew member can take over the controls. It is said that about 80 percent of a pilot’s ability to orient comes from the visual sense First “Blind” Sortie From Bill Ercoline:  First “Blind” Sortie From Bill Ercoline Sep 1929 under direction of Guggenheim in NY (Mitchell Field) First use of artificial horizon, Kollsman altimeter, and directional gyro Other Significant Work* From Bill Ercoline:  Other Significant Work* From Bill Ercoline Fully Automated Landing Project Carl Crane and George Holloman Wright Field, 1936-37 Low Visibility Landing Investigation Instrument Pilot Instructor School & FDL Randolph AFB, 1967-70 Crane Flitegage Patent 1982 Integrated Information *All Fixed Wing Aircraft Slide8:  FORMAL DEFINITION OF SD From Bill Ercoline “A failure to sense correctly the position, motion or attitude of his aircraft or of himself [herself] within the fixed coordinate system provided by the surface of the earth and the gravitational vertical.” “In addition, errors in perception by the aviator of his position, motion or attitude with respect to his aircraft, or of his own aircraft relative to other aircraft, may also be embraced within a broader definition of spatial disorientation in flight.” -- Alan Benson (1978) The Human Inner Ear:  The Human Inner Ear Coiled Canals of the Human Cochlea:  Coiled Canals of the Human Cochlea Three tubular canals running parallel to one another called the scala vestibule, scala media, scala tympani Within lies the actual sensory apparatus Organ of Corti Within the organ of Corti are the receptor cells: the outer and inner hair cells. Vestibular System:  Vestibular System The vestibular system is located in the inner ear Consists of vestibular organs that measure accelerations Each vestibular has what is referred to as the semicircular canals and the otolith organs The semicircular canals measure acceleration and deceleration in three rotational axes. The otolith organs measure linear acceleration/dceleration by virtue of sensory hairs that are in contact with an overlaying gelatenous membrane Semi-circular canals are filled with a fluid called endolymph Mapping of Semicircular Canals:  Mapping of Semicircular Canals Depends on head position G Excess Illusion:  G Excess Illusion Human Thresholds for the Detection of Linear Acceleration:  Human Thresholds for the Detection of Linear Acceleration Boff, Kaufmann, & Thomas (1986) Human Thresholds for the Detection of Rotary Accelerationn:  Human Thresholds for the Detection of Rotary Accelerationn Boff, Kaufmann, & Thomas (1986) SOMATOGYRAL ILLUSIONS:  SOMATOGYRAL ILLUSIONS Caused when angular accelerations and decelerations stimulate the semicircular canals Those that may be encountered in flight are the leans, graveyard spin, and Coriolis illusions The Leans Graveyard Spiral Coriolis Illusion SOMATOGRAVIC ILLUSIONS:  SOMATOGRAVIC ILLUSIONS Caused by changes in linear accelerations and decelerations or gravity that stimulate the otolith organs The three types of somatogravic illusions that can be encountered in flight are oculogravic, elevator, and oculoagravic. Oculogravic Illusion Occurs when an aircraft accelerates and decelerates Pilot falsely perceives that the aircraft is in a nose-high attitude Elevator Illusion Occurs during upward acceleration. Because of the inertia encountered, the pilot’s eyes will track downward as his body tries, through inputs supplied by the inner ear, to maintain visual fixation on the environment or instrument panel. With the eyes downward, the pilot will sense that the nose of the aircraft is rising. This illusion is common for aviators flying aircraft that encounter updrafts. Oculoagravic Illusion Opposite of the elevator illusion and results from the downward movement of the aircraft. Pilot senses aircraft is in a nose-low attitude. This illusion is commonly encountered as a helicopter enters autorotation. The pilot’s usual intuitive response is to add aft cyclic, which decreases airspeed below the desired level. Proprioceptive System:  Proprioceptive System Reacts to the sensation resulting from pressures on joints, muscles, and skin and from slight changes in the position of internal organs Closely associated with the vestibular system and, to a lesser degree, the visual system. Forces act upon the seated pilot in flight. With training and experience, the pilot can easily distinguish the most distinct movements of the aircraft by the pressures of the aircraft seat against the body. The recognition of these movements has led to the term "seat-of-the-pants" flying. False Horizon Illusion:  False Horizon Illusion Pilot subconsciously chooses a sloping cloud deck as the only reference point available for orientation Often insidious and goes undetected until the aviator recognizes it and makes the transition to the instruments and corrects it Can also occur at night when flying over sparely lit areas and only one half of the windshield has lights on ground Depth Perception Illusions:  Depth Perception Illusions HEIGHT-DEPTH PERCEPTION ILLUSION Due to a lack of sufficient visual cues Causes an aircrew member to lose depth perception Flying over an area devoid of visual references—such as desert, snow, or water—will deprive the aircrew member of his perception of height May fly the aircraft dangerously low in reference to the ground or other obstacles above the ground CRATER ILLUSION Occurs when aircrew members land at night, under NVG conditions, and the IR searchlight is directed too far under the nose of the aircraft. This will cause the illusion of landing with up-sloping terrain in all directions Misperceived up-sloping terrain will give the aviator the perception of landing into a crater Lulls the pilot into continuing to lower the collective Can result in the aircraft prematurely impacting the ground, causing damage to both aircraft and crew If observing another aircraft during hover taxi, the aviator may perceive that the crater actually appears to move with the aircraft being observed. Structural Illusion:  Structural Illusion Are caused by the effects of heat waves, rain, snow, sleet, or other visual obscurants Straight line may appear curved when it is viewed through the heat waves of the desert Single wing-tip light may appear as a double light or in a different location when it is viewed during a rain shower The curvature of the aircraft windscreen can also cause structural illusions Size-Distance Illusions:  Size-Distance Illusions False perception of distance from an object or the ground Crew member misinterprets an unfamiliar object’s size to be the same as an object that he is accustomed to viewing Approach to a larger, wider runway, may perceive that the aircraft is too low. Approach to a smaller, narrower runway, may perceive that the aircraft is too high. Trees in the State of Washington, where the average tree is 100 feet tall Aircraft being observed suddenly flies into smoke or haze, the aircraft will appear to be farther away than before. Fascination and Plane of Reference:  Fascination and Plane of Reference FASCINATION (FIXATION) IN FLYING Target fixation, target hypnosis Pilot so intent on hitting the target that he forgets to fly the aircraft, resulting in the aircraft striking the ground, the target, or the shrapnel created by hitting the target. ALTERED PLANES OF REFERENCE Pilot has an inaccurate sense of altitude, attitude, or flight-path position in relation to an object so great in size that the object becomes the new plane of reference rather than the correct plane of reference, the horizon. Approaching a line of mountains may feel the need to climb although the altitude of the aircraft is adequate. Autokinesis:  Autokinesis Primarily occurs at night when ambient visual cues are minimal and a small, dim light is seen against a dark background After about 6 to 12 seconds of visually fixating on the light, one perceives movement at up to 20 degrees in any particular direction or in several directions in succession, although there is no actual displacement of the object This illusion may allow an aviator to mistake the object fixated as another aircraft In addition, a pilot flying at night may perceive a relatively stable lead aircraft to be moving erratically, when in fact, it is not The unnecessary and undesirable control inputs that the pilot makes to compensate for the illusory movement of the aircraft represent increased work and wasted motion, at best, and an operational hazard at worst. Caused by eye movements Spatial-Temporal Description of Motion Terms for SO From Bill Ercoline:  . . . . . . .. .. .. .. .. .. * * Assumes head is fixed with aircraft. * Parameters for geographic orientation Spatial-Temporal Description of Motion Terms for SO From Bill Ercoline Flight Instrument Functional Categories (get the pilot to DH) From Bill Ercoline :  Flight Instrument Functional Categories (get the pilot to DH) From Bill Ercoline CONTROL Attitude Pitch Bank Power PERFORMANCE Airspeed Altitude Vertical Velocity Heading Turn Rate Slip/Skid AOA Flight Path NAVIGATION Latitude Longitude Course Bearing Range Time

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