January 1, 2013
By Jonathan Sackier
Vertigo is a false sense of movement, causing confusion, disorientation—and, eventually, incapacitation. According to the FAA, vertigo and spatial disorientation (SD) contribute to 15 percent of accidents, typically at night or in instrument meteorological conditions (IMC). Most are fatal, and experienced pilots are not immune. The U.S. Air Force investigated 633 crashes between 1980 and 1989 and referenced SD in 13 percent. Non-instrument-rated pilots have a life expectancy of less than three minutes in IMC, probably because of SD.
Positional sense in space occurs from combining visual and gravitational input, a properly functioning inner ear, and proprioception—brain feedback from nerve receptors. Ever induced a “dead arm” from lying on it? Other than looking, you have no idea where it is. That is failure of proprioception. Your inner ear plays a big role in vertigo. Inboard of your ears is a complex system of three semicircular canals oriented in pitch, roll, and yaw planes. Specialized cells sense movement of fluid inside the tubes and transmit information to your brain. That’s how theme park simulators trick you into believing you are upside down, or, when aboard a stationary train and another train beside you starts to move, why it creates confusion.
Initially pilots experiencing vertigo/SD acknowledge conflict between sensations and instruments; the disconnect then blurs—and finally, incapacitation follows with nausea, visual disturbances, muscle spasms, and panic. Different flying maneuvers provoke insidious, yet compelling and specific, forms of disorientation. Unlike other in-flight emergencies such as cockpit fire or catastrophic engine failure, the spatially disoriented pilot does not perceive there is anything wrong. The aptly named graveyard spiral occurs after a bank; feeling the nose drop, the pilot pulls back to initiate a climb or reduce perceived rate of descent. A tighter turn ensues that magnifies the effect and leads to a stall, overstressing the aircraft or flying into the ground.
The leans occurs after a routine turn with sudden transition to level flight provoking a feeling that one is turning the opposite way. The pilot therefore turns back to the original bank, attempting to correct to a perceived proper orientation. If a pilot turns his head out of the plane of rotation while executing a turn, perhaps looking down at a chart, a rolling sensation may occur and, depending on orientation, erroneous pitch, yaw, or roll inputs may result.
Another illusion convinces pilots they are inverted after a high-performance climb. After leveling off, a lightness in one’s seat is felt while contemporaneous seat-back pressure, caused by continued acceleration, induces continued pitch increase, eventually transitioning to the sensation of inversion.
On terra firma several problems can cause vertigo and merit medical attention. Commonly, benign paroxysmal positional vertigo (BPPV) presents with vertigo precipitated by sudden head movements and may be transitory, recurrent, or incapacitating. It may be because of an inner ear infection (vestibular neuritis or labyrinthitis) and hearing loss also may be present. Ménière’s disease may develop suddenly, be longer lasting, and have associated tinnitus (ringing in the ears) associated with vertigo and hearing loss. Abnormal eye movements may occur. Certain medical conditions can mimic vertigo; multiple sclerosis might present in this way. Impaired blood supply to the brain, acoustic nerve tumors, head trauma, migraine, and diabetes can all cause this troubling symptom.
After a careful review of your medical history and thorough examination, various investigations may be necessary to rule out serious causes. Physicians may recommend Epley or Sermont exercises to suppress symptoms. A variety of home remedies has been proposed but scientific evidence of efficacy is lacking.
Several medications control vertigo symptoms but none are FAA approved, so complete and well-documented recovery with no drug use is mandated before flying as PIC. Interestingly, one of the drugs often prescribed for vertigo, diphenhydramine, is often implicated in fatal accidents. Steroids or anti-infective medicines may have a role to play.
Someday, assistive technologies such as Automatic Ground Collision Avoidance Systems (A-GCAS) may help pilots in trouble and correct an unusual attitude induced by spatial disorientation. Until then recall that Alfred Hitchcock’s classic movie Vertigo was based on a French novel The Living and the Dead; boning up on vertigo can help you remain among the former.
Dr. Jonathan Sackier is an expert in aviation medical concerns and helps members with their needs through the AOPA Pilot Protection Services plan. Email the author at [email protected].
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