Spatial Orientation PDF

SPATIAL ORIENTATION Date: 18 Jan 2022 Revision no. 01 The Aeromedical professional must be familiar with the physiologic bases & operational limitations of the flyer’s orientational mechanisms to contribute significantly to investigation of A/C mishaps in which spatial disorientation may be impli...

SPATIAL ORIENTATION Date: 18 Jan 2022 Revision no. 01 The Aeromedical professional must be familiar with the physiologic bases & operational limitations of the flyer’s orientational mechanisms to contribute significantly to investigation of A/C mishaps in which spatial disorientation may be implicated. Linear Motion is Motion in straight line & Angular Motion is Motion in a curved path Parameters of motion - Displacement - Velocity - Acceleration - Jerk Displacement (X) is the distance & Direction of the object. Linear Motions in space are described by reference to 3 linear axes. Angular Motions in space are described by reference to 3 angular axes. In aviation, the Linear Axes are: - The Longitudinal (fore-aft) X axes - The Lateral (right-left) Y axes - The Vertical (up-down) Z axes The Angular axes are: - The Roll - The Pitch - The Yaw Linear Acceleration - Change of velocity/ time Angular Acceleration - Change of Direction/ time An orientational percept is a sense of one’s position & motion relative to the plane of the earth’s surface. *It can be Primary (Natural), meaning that it is based on ambient visual, vestibular, or other sensations that normally contribute to our orientation in our Natural environment, or *It can be secondary (synthetic), meaning that it is intellectually constructed from visual or verbal data (flight instruments & maps). Spatial Orientation 3 Sensory Systems provides the orientation information: 1. Visual Orientation Is the most important sensory modality that serving the spatial orientation. * 2 Distinct functions: i. Object recognition ii. Spatial orientation – Focal vision & - Ambient vision * The Focal vision mode is concerned with object recognition & identification & in general, answers the question … What * The Ambient visual mode subserves spatial localization & orientation & is in general, concerned with the question of … Where 2. Vestibular Orientation Semicircular canals can percept movement in all the directions, however, there is a threshold of this perception. 3. Proprioceptors • Muscle & tendon senses • Joint sensation An other systems might contribute in orientation but in a lesser extent: 4. Auditory Orientation 5. Cutaneous Exteroceptors SPATIAL DISORIENTATION In aviation the mankind has been subjected for the first time to many different varieties of transient motions & sustained linear & angular accelerations which are commonly experienced in Aviation. As a result, human’s sensory systems found to be poorly suited for flying environment. *A mismatch between the orientational demands of the new environment & our innate ability to orient. THE MANIFESTATION of this MISMATCH IS SPATIAL DISORIENTATION. Spatial Disorientation is a state characterized by an erroneous orientational percept (An erroneous sense of one’s position & motion relative to the plane of the earth’s surface). Should be differentiated from erroneous location percept which is the Geographic disorientation or “being lost”. Types of Spatial Disorientation  Unrecognized  Recognized  Incapacitating Illusion in flight Illusion is a false percept Orientational Illusion is a false percept of position or motion. Great number of these illusions occur during flight. They are categorized into: - Those resulted primarily from visual misperceptions. - Those involving primarily vestibular error. ERRORS OF VISUAL PERCEPTION Occurs when the visual cues are either: - Atypical • Modification of atmospheric conditions, such as, fog, rain, haze, smoke, or snow which reduce visibility leads to Overestimation of Distance.  The runway may appear to be further away than its true distance. And the height thought it is greater than it is → Pilot may fly a higher approach & have to overshoot. - Degraded • Darkness degrades the external visual cues that employed in the day-time approach & the pilot may think that he is flying higher than his true altitude, & hence make a low approach. Conversely, bright runway lights & good visibility lead to underestimation of distance. Visual Illusions Some involving focal vision & some involving ambient vision. Examples of Factors causes visual illusions:  Loss of shape constancy  Loss of size constancy  Absence of Ambient cues  Absence of Focal cues  Aerial perspective *The constancy of shape & size is important in judging the distance. *False cues are frequently responsible for A/C mishaps due to illusions of focal visual origin. *The runaway width illusion is an example. A runway that is narrow than to which a pilot is accustomed can create a hazardous illusion on the approach to landing. The pilot will perceive the narrow runway to be farther away than is actually the case. The pilot may flare too late & touch down sooner than he expects. • Runways at commercial airports are 45m wide & 2000 – 3000 meter long. If the runway is unusually wider, the pilot will underestimate distance. Conversely, a narrow runway can lead to an over-estimation of distance from the threshold & will land long (overshoot). • Feature less terrain, snow-covered ground or a smooth sea are examples of situations where there is a lack of Visual cues to allow any reliable perception of height. • Effect of runway slope on final approach, also is an example of false ambient cues. Analysis of accidents occurred during approach & landing has indicated that, Dimensions & Topography of the runways have also led to perceptual error. • If the runway slopes up, the pilot overestimate the A/C height distance from touch down, he will make a low approach & has tendency to land short. • Conversely, a runway sloping downwards, the pilot is more likely will have a high approach & lands beyond the threshold. Examples of False Ambient cues: Autokinesis • A puzzling illusion that occurs when ambient visual orientation cues are minimal. Vection Illusion • False Horizons & surface planes VESTIBULAR ILLUSIONS:  Somatogyral Illusion  Ocalogyral Illusion  Coriolis  Somatogravic Illusion  Inversion Illusion  G. Excess Effect  Oculogravic Illusion  The Leans Errors of Vestibular Perception The Leans  The most common form of spatial disorientation.  False sensation of bank when the A/C is in level flight”  “It is the consequence of an unperceived error in roll attitude”. Mechanism: Allowing one wing of the A/C to drop at a rate below the threshold for detection of angular velocity (0.5-5.0°/sec) so the pilot will be unaware of the change in roll attitude. → No adequate stimulation of the receptors in the vestibule. *The A/C, now, flying one wing low, but the pilot thinks that his wings are level. *Control should be maintained by instrument reference. G EXCESS ILLUSION When head movements are made in a turning A/C → cross → coupled stimulation of the semicircular canals → induce a false sensation of the A/C attitude (climb or dive). SOMATOGRAPHIC ILLUSION Error in perception of pitch attitude due to exposure to a force vector that differs in direction or magnitude from the normal gravitational force. CORIOLIS  Angular movement of the head in an A/C which is turning.  →cross-coupled responses due to stimulation of the semicircular canals by the interaction of angular motion in 2 planes → inflight perceptual error, the pilot will have false vestibular sensations produced by head movements. 2. Vestibular Orientation Prevention of Disorientation Mishaps Doing some specific counter measures like:  Modifying flying procedures to avoid those visual or vestibular motion & position stimuli that tend to create illusions inflight.  Improving the capacity of flight instruments to translate A/C position & motion information into readily assimilable orientation cues.  Training on Instrument flight  Use of Autopilot cannot only help to prevent disorientation, but it can do also help the pilot recover from it. (Bring back the A/C to wings level attitude).  Recognizing disorientation is not easy. If the pilot became aware that he is having a problem holding altitude or heading, he is well along the road to recovery.  Education & training • Physiologic Training • Monitoring bank, pitch, vertical velocity, altitude, frequently the displayed by flight instruments. • When disorientation dues occur & recognized, The standard advice “Believe the instruments” • Simulation of disorientation using the Gyrolab & try to familiar with it. PROPHYLAXIS As the spatial disorientation is the most threatening factor to the safety of flight operation, efforts, should be made to prevent the occurrence of perceptual errors. The following method, techniques, & procedures should be employed to minimize disorientation. I. AIRCRAFT FACTORS i. Instrumentation  Every effort should be made to provide the pilots with instruments that can be read quickly & unambiguously at day or night; Head up display will assist in transfer from external visual to instrument cues.  Instrument reliability is of prime importance. ii. Cockpit Ergonomics  Instrument & controls should be placed in the cockpit so that the pilot does not have to make head movement, during critical phases of flight.  The configuration of the cockpit canopy is significant. It will assist the pilot to maintain a level attitude when flying on external visual references. II. i. ii. OPERATIONAL FACTORS Training & Experience of Aircrews. (Instrument flying training & experience) Instrument flying is required when flying in cloud or other poor visibility condition. ***Objectives of training iii. Pilots should be aware of  His own limitation  Flight conditions &  A/C maneuvers likely to induce S.D. Environmental Factors of Flight maneuvers likely produce disorientation. Flight Environment iv. Night v. High Altitude vi. Flight over featureless terrain (sea) vii. Flight in IMC Instrument Meteorological Conditions viii. It is a flight category that describes weather condition that requires pilots to fly primarily by reference to instruments & therefore, under Instrument Flight Rules (IFR) rather than outside visual reference under Visual Flight Rules (VFR). Flight Maneuver ix. Prolonged Linear Acceleration x. Prolonged Angular motion xi. Sub-threshold changes in altitude xii. Workload xiii. Ascent xiv. Cloud penetration III. AIRCREW FACTORS i. Selection (Individual variation) To exclude disorientation prone aviator who are more susceptible. Example, those with gross disturbances of vestibular function (Meniere’s diseases, Central Lesion……etc) To exclude ones with low tolerance to the vestibular stimulation. ii. Any trained pilot who suffers a disorder affecting the vestibular & visual sensory systems, should not be permitted to fly. iii. Drugs – Susceptibility to S.D. is increased by many drugs like barbiturates & antihistamine & hyoscine. Pilots should not be permitted to fly when receiving drugs that are central depressants. iv. Alcohol OBJECTIVES OF TRAINING 1. To inform aircrew about factors that contributes to the effective spatial orientation in the flight environment. 2. To familiarize them with the various conditions & flight operations this may lead to spatial disorientation. 3. To inform about the manifestation of S.D. & how to detect the onset of existence of S.D. 4. To explain the mechanisms by which S.D. is produced, & to discuss Normal limitations of sensory functions. 5. To inform how S.D. can be overcome & to develop skills so that Aircrews can cope with it. Thank you