When the subject of disorientation comes up in any discussion, especially among pilots, the perception is that it relates to dizziness. It does, but it goes way beyond a simple definition. Aviation disorientation has many forms, each one different, yet all can be occurring at the same time.
Postural (proprioceptive) disorientation
A constant source of sensory input comes from the body’s interpretation of the direction of gravitational force through proprioceptive signals, which are signals from various muscles in the body. Our minds are programmed to interpret these signals as being up or down, relative to the Earth and its gravitational pull. This in turn determines our posture (our position relative to the ground). Concurrently, there are proprioceptive sensors within our skin, muscles, tendons, and joints that detect changes in relative position, pressure, and changes from that of up or down posture.
Every time a muscle contracts or relaxes, tendons are pulled or released and joints move. Proprioceptive signals are those generated by these changes. All these inputs, which are continuously coming to the brain, tell the pilot what position he or she is in, usually relative to the foundation of gravity. It’s simi- lar to inertial navigation, where cockpit devices determine a plane’s current position relative to where it started moving. We learned how to walk upright not because we were taught but by trial and error and our proprioceptive sig- nals. These signals were processed by our brain over time until all muscles were working together to keep us from falling.
Another source of signals defining posture is part of the vestibular system, the otolith organs (utricle and saccule), located in the inner ear. They play a role, along with proprioception, when the body is subjected to changes rela- tive to gravitational force and when subjected to linear accelerations. They will be discussed under vestibular orientation.
Because gravity is “down” to the mind, any input from proprioception or the otolith organs sensing this position is interpreted as either being “down” or a variation from that position. Our largest source of such information is when we are sitting down: “seat of the pants” flying. By being seated in flight, the positional forces acting on the pilot can tell the brain about the quite distinc- tive motions of the aircraft and body, both acting as one.
Because these senses are associated with the vestibular system’s signals (including otolith organ signals), there is, under conditions other than flying, a comprehensive resource of a variety of information the mind uses to orient
Types of disorientation 129 itself, much like a computer data bank. In flight, these signals can conflict and be confusing to the mind, giving false interpretations and leading to dis- orientation; however, they are somewhat predictable and one can train the mind and body to cope with these misleading cues, especially through experi- ence and periodic practice in unusual attitudes of flight maneuvers.
Proper postural orientation in flight is noticeable in a well-coordinated turn, where all postural signals are equal to that noted when sitting upright on the ground and directly related to gravity. If the turn is coordinated and doesn’t disrupt the vestibular system and the position is confirmed visually, there is no impairment to the pilot’s performance. Postural orientation is particularly important in erratic and unfamiliar airplane movements such as aerobatics and high G-force maneuvers that conflict with the pull of natural gravity by duplicating that sense artificially.
However, in an improperly executed turn, especially during a climb, these signals become very confusing to the brain, giving false illusions as to one’s true posture (plus other disorienting feelings to be discussed). Rather than being pushed directly into the seat, the body is being pushed sideways as in a skid or slip, giving the impression of tilting. In the absence of visual refer- ence, the only sensation will be from the body being pressed into the seat, but not necessarily toward the ground. The vestibular system will also be sending signals, some being opposite to the proprioceptive signals. Recovering from such a situation in a climb gives the illusion of descending, causing the pilot to pull back on the stick.
To the physiologically impaired pilot (fatigued, dehydrated, hypoglycemic, etc.), these expected signals become illusions that lead to subtle incapaci- tation and potentially eroded performance in spite of the pilot’s being well- trained and current. Also, as we get older, these proprioceptive sensors become less sensitive and provide a less reliable source of postural informa- tion. Sitting for long periods of time also dulls these sensory signals, again providing inaccurate and unreliable data to the brain.
FOLKS, WE HAVE A SURPRISE FOR YOU!
In March 1997, the crew of a chartered jet carrying the University of Arkansas men’s basketball team landed in Springdale, Arkansas, 12 miles from the Fayetteville destination.
In May 1997, the crew of a Continental Airlines B737 landed their scheduled flight at Corpus Christi at a WWII airfield, Cabaniss Field, 4.5 miles south of their anticipated destination.
These are not rare occurrences!
GOTCHA!
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Positional disorientation
Positional disorientation basically means the pilot is lost, if even for a brief moment, and doesn’t know her position. Realizing for a short period of time that she doesn’t really know where she is, the pilot becomes disoriented until she resolves her position or lands at the wrong airport. In other words, the pilot doesn’t know what to do: keep going, go back, call for directions, or what. Positional disorientation is also referred to as geographic or directional disorientation. They all mean the same thing; the pilot is temporarily lost and unable to take effective corrective action until she locates her position.
All animals are creatures of habit, especially humans. Much of what we do during a typical day is a routine that we do the same way, day after day, and usually without too much thought. Interrupt or change that routine and one is disoriented, not knowing how to continue without having to think about it and then figure out the next step. Take for example how you take a shower or bath. Most people wash in the same way, each time starting at one part of the body and ending up at another. If you start with the front of your left shoul- der, for example, that’s how you start every time. The next time you shower, change the sequence. Start with your right foot. Now you have to think about what to wash next. This is no longer your routine and for a moment you are lost on your own body. You are briefly disoriented.
The same thing happens on familiar routes. You fly the same airways, talk to the same controllers, and make the same approaches on all the legs of the trip. Initially, when you fly the route for the first time, you concentrate on maintaining your awareness of where you are. Then the trip truly becomes routine because there is nothing to break the monotony of the hundredth trip. It now becomes easy to fall into the trap of flying past a checkpoint with- out knowing it. If ATC gives you a revised flight plan or changes your heading for traffic, you might miss the new instructions or clearance or continue on the same flight path you have always flown before.
The pilot becomes more susceptible to positional disorientation if he becomes distracted. He might be thinking about problems at home or concentrating on some activity in the cockpit unrelated to flying, such as reading a manual, listening to a commercial radio station, or playing with the computers in a
“glass cockpit.” Or he becomes involved with a political conversation with a crewmate. Now both pilots are out of the loop of maintaining positional awareness.
Another trap is the last flight of the day, or “get-homeitis.” This becomes more risky than the initial leg because there is the added distraction of anticipat- ing what needs to be done at home. In any case, checklists read many times before become superficially reviewed. Distances, checkpoints, and waypoints become committed to memory (or so you think). Even familiar frequencies are part of this virtually automatic flight.
Now throw in any deviation from the expected routine or a malfunction of the aircraft, and the pilot is easily distracted and becomes disoriented regarding his position. He has to spend time reasoning out what needs to be done to correct the problem and get back on course.
Types of disorientation 131 Pride often gets in the way of taking corrective action during these situations, with the pilot thinking that she can get out of this fix without having to refer to manuals or maps. Certainly she is reluctant to admit to ATC or even a crew- mate that she is lost or forgot the controlling center’s frequency and name.
Consider how this situation can be amplified if it happens at the same time you enter actual instrument conditions. This combination of positional and poten- tial vestibular disorientation is an incident or accident waiting to happen.
Listen to other pilots talk about their episodes and read accounts of honest and candid pilots who are willing to share experiences of being lost or tempo- rarily out of touch with their surroundings or their situation, which are other examples of impaired situation awareness. Then consider the fact that this positional disorientation is another form of an incapacitating human factor.
Even if only for a brief moment, the pilot is technically impaired, unable to function in a timely manner.
Temporal disorientation
Disorientation relative to time (also called temporal disorientation) is very subjective and is a direct function of how fast the brain is processing infor- mation. How long any given activity exists in the mind of a pilot depends on the level of activity and motivation occurring at that time.
During periods of high activity, time can be perceived as being expanded.
That is, the pilot thinks he has more time than is actually available to accom- plish some action because the mind is working in high gear, probably second- ary to an increased flow of adrenaline. On the other hand, time might appear compressed, with the pilot feeling that less time has passed than actually has, while at the same time realizing that it seems to take forever to get to the next checkpoint. This is common in monotonous, slow, and uninterest- ing activities.
Little is known about why this happens in the mind. There is some evidence that the amount of adrenaline flowing through the body during periods of high and exciting activity will increase all metabolism, especially the brain.
The hormonal chemical adrenaline is instantaneously released into the blood stream in fight-or-flight situations, allowing the body to respond to unex- pected and emergency situations. With extra “emergency” adrenaline, pulse rate and blood pressure go up; blood flow is diverted to crucial organs such as muscles, the heart, and the brain. More energy from blood sugar stored in the body is made available for metabolism. Sweating is increased to cool the body. Changes occur in the ear to intensify its ability to hear, and the threshold for pain and endurance increases. The brain therefore becomes more intensely alert and processes information at an accelerated rate.
Frequent stories from people in sudden emergency situations later revealed that events seemed to happen in slow motion. They vividly recall past events in their lives. Everyone has felt that “adrenaline rush” instantly after a near- miss at a street intersection, or upon realizing that the airplane engine has lost power.
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It’s the reason some pilots leave training simulators soaking wet from sweat- ing due to the stress of the exercises. Professional athletes will know when they are having a good day because mentally the baseball or tennis ball appears extra large and very slow, allowing them to react quicker and more accurately with winning swings. Their adrenaline is helping their athletic performance.
Whatever the reason, the perception of expanded time, for example, is real in the mind of the pilot during the crucial event. It becomes a concern because the pilot, in an emergency situation, might take too long to react, thinking that there is plenty of time available to try some other course of action. In the military, it is a major concern with fighter pilots. In an emergency, the activ- ity level is high, and in the pilot’s mind, there appears to be plenty of time to recover, and he or she does not eject in time. It’s interesting to note that if the fighter pilot does eject and then is asked how long he felt that it took from the time he pulled the handle, the canopy released, he punched out, and the parachute opened, he will probably say at least a minute or two before he was hanging from the parachute. In fact, it takes but a few seconds. But he will swear that it takes longer. Furthermore, the pilot will be able to recall, in detail, every position of the instruments and controls, what was happen- ing in the aircraft, and what he was doing during the ejection, all in those few seconds.
The opposite is true in minimal mental- and physical-activity situations.
Here time drags on although the pilot feels it is moving faster. This is less crucial than time expansion because, although the actual prolonged time makes the trip even more boring, it doesn’t affect performance other than increasing the likelihood of positional disorientation and easy dis- traction.
Temporal disorientation, therefore, is not clearly understood from a sci- entific perspective, but we know it happens. And it can be an unbeliev- able experience when shared with others. There is no way to prevent the body’s automatic response to emergency situations. How and when the pilot responds to that situation, despite his or her perception of mislead- ing available time, is a result of the level of training and respect for known responses.
This might become a factor in the transition from traditional flying to that found in the glass cockpit. How will a pilot, experienced in stick-and-rudder
MENIERE’S SYNDROME
This is a disorder that has unpredictable sudden and episodic attacks of dizziness (vertigo) along with tinnitus and progressive deafness, often accompanied by nausea and vomiting, all persisting for several minutes to hours. This combination of symptoms requires further medical evaluation.
Types of disorientation 133 controls and conventional instrumentation, react to an emergency in a high- tech airplane? Will the time distortion prevent him or her from following new techniques, or will he or she revert to old methods?
Vestibular disorientation
Recall that vestibular disorientation is the term commonly used for spatial disorientation and is also compared to the feeling of vertigo. While they are similar and often occur with each other, they are separate entities. Spatial disorientation will be discussed after vestibular.
Vertigo, to the pilot, is the feeling recognized when actually experiencing vestibular disorientation. To the medical profession, vertigo has a dif- ferent meaning. The symptoms might be similar: lightheadedness, diz- ziness, the sensation of either the room or the person spinning, and a feeling of instability; however, to the doctor, vertigo might be caused by a variety of abnormal situations. Certain abnormalities might be neuro- logically significant (such as tumors); others might be related to infec- tions of the inner ear or central nervous system. Consequently, when you tell a doctor about these symptoms, she or he will probably pursue additional testing to rule out any medical pathology. For aviation, it is better to keep with the term vestibular disorientation and leave vertigo to other medical problems. Vertigo from any source does cause vestibular disorientation.
Disorientation from dysfunction of the vestibular system (or apparatus) is probably the most severe and intense feeling of instability or unbalance.
It is thought that this is the source of most motion sickness problems. In fact, even experienced pilots can get airsick under conditions of flight that interrupt the vestibular system. Although vision is still the most impor- tant source of orientation signals, disturbances of the vestibular source of signals are the most difficult to cope with and the hardest from which to recover.
The vestibular system is located in the inner ear (Fig. 8-1). There are two dis- tinct structures—the semicircular canals, which sense angular acceleration, and the otolith organs (Fig. 8-2), which sense linear acceleration and gravity (Fig. 8-3).
Semicircular canal
This organ is similar to three gyros in three geometric planes that are perpen- dicular to each other (Fig. 8-4). It is a series of three closed tubes filled with a fluid called endolymph (Fig. 8-5). This fluid is put into motion as a result of angular acceleration in the plane of the canal. Motion of the fluid exerts a force upon a gelatinous structure called the cupula. Bending of the cupula results in movement of the hair cells situated beneath the cupula. These hair cells move in the same way that sea grass moves with the currents and wheat fields move in the wind. As the currents and winds change, so does the movement of the blades of grass or wheat as a unit. This movement in turn
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stimulates the vestibular nerve, whose impulses are transmitted to the brain, where they are interpreted as rotation of the head.
When no acceleration takes place, the hair cells do not move but remain upright, and a sense of no turn is felt (Fig. 8-6A). When a semicircular canal is put into motion, as during the acceleration of a turn, the fluid within the canals moves (Figs. 8-6B, 8-6C, and 8-6D), but there is a lag in the response along the canal walls. This bends the hair cells in the direction opposite that of the acceleration. The brain interprets the movement of the hairs as motion, or a turn.
Figure 8-1
Figure 8-1 Anatomy of the ear.
Figure 8-2
Figure 8-2 Anatomy of the otolith organs.
Types of disorientation 135 Figure 8-3
Figure 8-3 Otolith organ in upright position.
Figure 8-4 The semicircular canal responds to roll, pitch, and yaw.
136 Orientation Otolith organs
Two components of the otolith organs are the utricle and the saccule. They are small “containers” located in the inner ear between the semicircular canal and the cochlea (refer back to Fig. 8-1 for approximate location). Lining both the bottom of the utricle and the wall of the saccule is a patch of small hairs called the macula (similar to what is found in the semicircular canal). What is different is that within the container’s endolymph and on the container’s wall there is an overlying gelatinous membrane containing chalklike crystals calledotoliths (refer back to Fig. 8-2).
Figure 8-5
Figure 8-5 Anatomy of the semicircular canal.
Figure 8-6
Figure 8-6 Hair cells change position during turns.