Aviation Safety Letter 3/2004
I Have Seen The Eyes of Death — Part 2
by Dr. John Albrecht. Continued from "I Have Seen The Eyes of Death — Part 1," published in Aviation Safety Letter 2/2004.
Understanding spatial disorientation and the human frailties that contribute to this seductive siren are essential to a pilot's longevity. Three senses interact to keep us upright, feet firmly planted on terra firma: vision, proprioception (pressure sensing organs in the skin and joints), and vestibular (balance apparatus in the inner ear called the semicircular canals). Once airborne, the rules change dramatically with the two fallible senses, proprioception and vestibular, being negated. Vision rules supreme as the only reliable orientation sense once the aircraft abandons the earth's surface. Remove the natural horizon, ignore attitude instruments and your lifespan is reduced to an average of three terror-filled minutes!
There are certain natural phenomena and emergency situations that may deprive a pilot of their vision. The brilliance of the low setting sun can temporarily blind a pilot as they flare to land. A windscreen covered with ice or oil from a failed engine can severely restrict visibility. Smoke in the cockpit can have serious consequences. Even sweat and suntan lotion can lead to temporary visual loss. A direct bird strike on the windscreen can result in catastrophic visual impairment with plexiglass fragments, blood and feathers. Vision and aircraft control go hand in hand.
Pilots should be aware that spatial disorientation may occur in three distinct forms — each just as seductive and deadly. Unrecognized spatial disorientation (Type I) describes a situation wherein the pilot is disoriented, but is unaware and controls his aircraft using false sensory information. This may occur in visual or instrument conditions. Visual illusions are the most common factor contributing to Type I accidents. The pilot misinterprets what his eyes see, often with deadly consequences. Many of us have experienced visual illusions in our automobiles, such as jamming the brakes at an intersection as our vehicle starts to roll backward. The reality is the adjacent car is edging forward. Our interpretation and reaction are in error. In a carwash, the sensation is one of a stationary vehicle and moving brushes, when the reverse is true.
Visual illusions encountered in flight deserve special consideration to increase awareness and avoidance. Heavy rain causes light refraction. This can lead to approaching obstacles appearing lower than they actually are. The potential risk is a controlled flight into terrain (CFIT) accident or undershooting the approach in a heavy rain shower. Night flying has its perks, but the risk of disorientation with these illusions is much greater.
Float flying can be a risky business, and one of the reasons for this is the alluring tranquillity of glassy water conditions. Float planes frequently approach to land, fail to flare, dig a float or the nose and flip inverted. The reason is spatial disorientation due to visual illusion. If you have ever walked nose-first into a spotless plate glass door or window, you have experienced the shock and unpredictability of glassy water.
Under certain conditions of diverse light refraction and terrain absorption, IFR conditions prevail even though ceiling and visibilities are well in the VFR domain. The result is an indiscernible horizon and/or lack of ground shadows or contrast, known as whiteout. Accidents are often of the CFIT variety, and can involve highly experienced crews.
Example of sector whiteout conditions
Type II, or recognized spatial disorientation, is when the pilot is disoriented and aware of the fact, but for reason of lack of instrument proficiency or vestibular (inner ear) or proprioceptive (seat of the pants) illusions, is unable to believe the attitude instruments. Once in instrument conditions, the VFR pilot does not have the training or discipline to cope with loss of the natural horizon, and smooth transition to instrument flight is most unlikely.
Acceleration without monitoring the attitude instruments gives an illusion of the nose pitching up. The pilot compensates by pitching the nose down, a very dangerous reaction when taking off on a dark featureless night. The end result can be an aircraft impacting terrain on takeoff for no apparent reason. With deceleration, the process is reversed with the illusion of the nose pitching down and the pilot reacting by raising the nose of an already slowing aircraft; a setup for a stall and spin in instrument meteorological conditions (IMC).
Type III spatial disorientation, or vestibulo-ocular disorganization, is fortunately a rare variation. In this type, the pilot is aware of the disorientation, but is unable to control the aircraft because reflex eye movements prevent instrument interpretation. Chances of survival are remote. The sensations of this type can be mimicked by rolling down a grassy hill. The resulting intense vertigo (spinning) makes walking a straight line impossible. Controlling an aircraft would be out of the question!
Type III spatial disorientation can also be induced by the pilot in-flight. This condition is called the coriolis effect. It results from simultaneous stimulation of two or more of the semicircular canals in the inner ear. This can occur in IMC when the pilot initiates a turn and simultaneously looks up or down with head movement. The stimuli to the brain are overpowering and produce a tumbling sensation. Rapid reflex movements of the eyes (nystagmus) make instrument interpretation and aircraft control impossible. Prevention comes with a disciplined instrument scan — eye movement only. By holding the head still, only one set of semicircular canals is stimulated by the rolling movement of the aircraft. Vertigo and nystagmus are averted.
It is quite possible that more than one type of disorientation come into play in an accident. A pilot suffering from unrecognized spatial disorientation (Type I) may receive an altitude alert from a vigilant air traffic controller. Distraction or fixation may result in progression to recognized (Type II) disorientation as instrument skill deteriorates. Over-controlling the aircraft and sudden head movement in search for the elusive runway environment may induce the coriolis effect (Type III). The odds of survival in this escalating scenario would be close to nil!
Several factors can contribute to the likelihood of a pilot becoming spatially disoriented. There is usually an element of surprise and unpreparedness as the VFR pilot stumbles into instrument conditions. Anxiety can rapidly escalate to a panic state when the outside world disappears. With panic goes any semblance of problem solving, which is key to survival.
VFR flight into IMC having such a high fatality rate, insight, avoidance and prevention are key to longevity in aviation as a recreational pastime or career. Weather smarts, with sound decision making, in the go/no go scenario are critical survival tools. A VFR pilot receiving a briefing of marginal VFR or IFR conditions for the intended route, or an en-route update of unforecast deterioration at destination, is well advised to stay on the ground or press plan B into action.
"Get-home-itis" is a term that often comes into play with spatial disorientation accidents. It refers to the psychological pressure perceived by the pilot, whenever there is a seemingly urgent need to complete a flight for personal or business reasons. The next link in the accident chain is this statement: "Let's take off and have a look, we can always come back to the airport." Once airborne, IMC may be encountered in the climb out and the safe sanctuary of the departure runway vanishes.
When I obtained my private pilot's licence, instrument flying was not included in the syllabus. Now it is, as well as with the night rating and commercial licence. This experience provides the pilot with the ability to fly straight and level, recover from unusual attitudes, turn 180° and perhaps penetrate a thin cloud layer — that's it! This skill is maximal at the time of the flight test and rapidly deteriorates thereafter if not practiced.
A current instrument rating is good insurance against a disorientation accident, but not a guarantee. Several scenarios come to mind of IFR drivers coming to grief. A typical example is a non-precision approach with circling procedure. During the circle to land, visual reference is lost but the pilot pushes on in low-level IMC rather than carrying out the missed approach procedure. On an IFR flight test, there are several critical safety checks which, if omitted, will result in automatic failure. In the real world of IMC, similar omissions can have dire consequences!
During my years as an Aviation Medical Examiner, I have heard some fascinating anecdotes. One private pilot en route to Tofino, British Columbia, inadvertently entered a band of cumulus clouds near Nanaimo, B.C. After a roller-coaster ride of terror lasting close to 45 min, he and his passengers were spit out near Courtenay, B.C., a little older and infinitely wiser!
The real champion was a student pilot flying out of Bellingham, Washington. He was climbing out on a solo VFR flight to Oregon. Just above circuit altitude, he entered cloud. Aware of the risk of adjacent hills, he elected to climb. At 4 000 ft, he broke out into brilliant sunshine, in an extreme banked attitude. After regaining control and his composure, he notified Bellingham Tower of his predicament. Cloud below as far as the eye could see! After orbiting for several minutes, he was handed off to Vancouver air traffic control (ATC). A calm voice provided radar vectors northward along the invisible coastline. At a break in the cloud, he transmitted his intention to descend, but was advised against this by ATC, as airliners were passing below cloaked in cloud. Eventually he was guided to a cloud break over the Strait of Georgia and authorized to shuttle down below the overcast. He then navigated VFR back to Bellingham for an uneventful landing. Survival is possible, as demonstrated by this fortunate young pilot. He did everything right and did not lose control of his aircraft, despite a prolonged climb in total instrument conditions.
Readers interested in the full, unedited version of Dr. Albrecht's article can e-mail the editor, or visit http://www.jalbrecht.ca/. — Ed.
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