Unusual Attitudes and Spatial Disorientation

Spatial disorientation is the loss of a correct sense of the airplane's position, attitude, or motion. The handbook says the body "uses three integrated systems that work together to ascertain orientation and movement in space" 1:

• the vestibular system, "organs found in the inner ear that sense position by the way we are balanced"
• the somatosensory system, "nerves in the skin, muscles, and joints that, along with hearing, sense position based on gravity, feeling, and sound"
• the visual system, the eyes.

With a horizon in view, the eyes correct the other two. In cloud or in darkness the eyes have no horizon to use. The pilot then senses attitude only through the inner ear and the body, and in an airplane those senses are often wrong. A pilot without a horizon cannot trust the inner ear at all.

Why the inner ear is wrong in an airplane

The semicircular canals sense rotation by the movement of fluid in them. A slow, steady turn does not move the fluid enough for the canals to sense it. The handbook says "human exposure to a rotational acceleration of 2 degrees per second or lower is below the detection threshold of the semicircular canals" 2. A turn that starts slowly is not felt at all. A turn held long enough is felt as no turn, because the fluid reaches the same speed as the canal.

The leans

The leans is the most common illusion in flight. The handbook says it "is caused by a sudden return to level flight following a gradual and prolonged turn that went unnoticed by the pilot," and that "leveling the wings after such a turn may cause an illusion that the aircraft is banking in the opposite direction" 2. The pilot who believes the sensation rolls back into the original bank. The pilot who does not believe it sits wings level, leaning in the seat, until the sensation passes. The AIM's description is the same: "the disoriented pilot will roll the aircraft back into its original dangerous attitude, or if level flight is maintained, will feel compelled to lean in the perceived vertical plane" 3.

The graveyard spiral

After a prolonged banked descent the pilot no longer feels the turn. The handbook describes the graveyard spiral: a pilot in a constant-rate turn "will have the illusion of not turning," and on recovering to level flight "will experience the sensation of turning in the opposite direction" 4. The disoriented pilot rolls back into the original turn. The altimeter shows a descent, and the pilot pulls to stop it. With the wings still banked, the pull tightens the turn and steepens the spiral. The only recovery is to level the wings first, by the instruments, and then raise the nose.

The Coriolis illusion

A sharp head movement during a prolonged turn produces a strong false sensation of rotation. The handbook says the illusion "occurs when a pilot has been in a turn long enough for the fluid in the ear canal to move at the same speed as the canal. A movement of the head in a different plane, such as looking at something in a different part of the flight deck, may set the fluid moving, creating the illusion of turning or accelerating on an entirely different axis" 5. The sensation is violent and the pilot can maneuver against it. On instruments the head stays still. The eyes move instead. A chart that fell on the floor stays on the floor.

The somatogravic illusion

Acceleration feels like pitching up. The handbook says "a rapid acceleration, such as experienced during takeoff, stimulates the otolith organs in the same way as tilting the head backwards," creating "the 'somatogravic illusion' of being in a nose-up attitude, especially in conditions with poor visual references. The disoriented pilot may push the aircraft into a nose-low or dive attitude" 6. Deceleration feels like pitching down, and the pilot pulls. The fatal case is a push after a night or instrument takeoff, with full power, no horizon, and the ground a few hundred feet below. The attitude indicator shows the actual pitch. The body senses a higher nose.

Recovery is a procedure

Recovery from disorientation is a procedure, not a sensation. No amount of attention to the sensation corrects it. The handbook's list for coping with disorientation begins with three items 7:

• understand the illusions
• obtain a weather briefing
• rely on the instruments and disregard the senses when no horizon is visible.

The pilot reads the instruments, believes them, and flies them until the conflict passes. The false sensation of bank fades in seconds to a minute once the airplane is level.

The flight of N7806W

On November 14, 2023, a 21-year-old private pilot with 66 hours and no instrument rating took off from Kissimmee, Florida, for Keystone Heights. He flew a Cherokee 180 he had bought two weeks earlier, and he had no weather briefing. Twenty miles short of his destination he flew into cloud. For 34 minutes he circled, climbed, and descended between 500 and 6,900 feet. He told the controller he was lost in weather and thought he was upside down. He then spiraled into the woods near Micanopy at more than 5,000 feet per minute and died 8.

He held a private pilot certificate with an airplane single-engine land rating, a third-class medical from 2020, and a flight review from September 2023. His logbook showed 66.3 hours, 30.9 of them as pilot in command. It showed 2.2 hours of simulated instrument time and 1 hour in actual instrument conditions, the most recent in January 2021. None of his logged time was in the accident airplane. He had bought it on October 31, 2023. A mechanic's pre-buy inspection in May found the attitude indicator inoperative, and no logbook entry showed it repaired or replaced.

Before he taxied, the ground controller at Kissimmee told him the weather was "IFR," with a broken ceiling at 800 feet. A minute later the controller said the observation now showed few clouds at 800. The forecasts along his route showed marginal VFR with rain, and a graphical AIRMET for IFR conditions covered part of it. He had a ForeFlight account with the route entered. He did not look at the weather in it, file a flight plan, or call Flight Service.

He departed at 12:45 and flew north at 3,500 feet. At 1:14 he descended to 2,000 feet. At 1:22 he descended to 800 feet above sea level. At 1:31 he turned briefly east, then back north. From 1:35 the ADS-B track showed erratic 360-degree turns and climbs and descents between 500 and 6,900 feet.

He called mayday and said he "was lost in weather." He said he had "mistakenly flew into weather," that "it's completely white," and that he could not see anything outside. He reported that his vacuum-driven attitude indicator and his electric turn and bank indicator both failed. The controller gave him vectors toward better weather and told him when he drifted off heading or began a climb or descent. At one point he told the controller he thought he was "upside down."

The last ADS-B data showed two tight left 360-degree turns in a descent of more than 5,000 feet per minute. The wreckage was 650 feet from the last data point, in a 4-foot crater in heavy woods. Investigators found rotational scoring on the gyros of both the attitude indicator and the turn and bank indicator, which showed both spun at impact. The nearest weather station reported 2 miles in rain and mist. A model of the atmosphere over the site showed stratus at 600 feet and overcast at 1,000 feet with tops near 16,200. The probable cause is "the non-instrument-rated pilot's improper inflight decision making and his flight into instrument meteorological conditions, which resulted in spatial disorientation and subsequent loss of airplane control. Contributing to the accident were the pilot's inadequate preflight weather planning" 8.

Where the accident chain could have been broken

The accident was five decisions. Each is listed below with its PAVE category and the decision that would have ended the flight safely at that point. Four of the five were made on the ground or with the ground in sight.

Runway width and slope

A runway that is narrower than usual makes the airplane look higher than it is. The handbook says a narrow runway "can create an illusion that the aircraft is at a higher altitude than it actually is," and "the pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects along the approach path or landing short" 9. A wider runway has the opposite effect, and the pilot flares high. An upsloping runway also looks like a high approach, and the pilot flies low to correct it. The defense is the glidepath: the VASI or PAPI, the known power and pitch for the approach, and the altimeter against the field elevation.

The black hole

A featureless dark approach produces a low descent. The handbook says "an absence of surrounding ground features, as in an overwater approach over darkened areas or terrain made featureless by snow, can create an illusion that the aircraft is at a higher altitude than it actually is," an illusion "sometimes referred to as the 'black hole approach'" 9. The pilot sees the runway lights across a dark gap and descends toward them along a line that reaches the ground before the runway. The defense is the same: fly the glidepath aids and the known power and pitch, not the view outside.

Autokinesis and false horizons

A single light stared at in the dark appears to move. The handbook says "when flying in the dark, a stationary light may appear to move if it is stared at for many seconds" 10. A pilot who fixes on one light can steer after its apparent movement. The defense is to scan and not stare.

A false horizon is a line that looks level and is not. The handbook lists "a sloping cloud formation, an obscured horizon, an aurora borealis, a dark scene spread with ground lights and stars, and certain geometric patterns of ground lights" 10. A lit shoreline at night, a sloping cloud deck, and a road of lights that runs uphill all look like a horizon and are not. The defense is the attitude indicator.

Haze, rain, and flicker

Haze makes lights and terrain look farther away. The handbook says "atmospheric haze can create an illusion of being at a greater distance and height from the runway. As a result, the pilot has a tendency to be low on the approach" 9. Rain on the windshield makes the horizon appear lower, and the pilot feels high and flies low.

Flicker vertigo is rare and real: "a light flickering at a rate between 4 and 20 cycles per second can produce unpleasant and dangerous reactions," including nausea and vertigo, and the source can be sunlight through a propeller or a rotating beacon 11. The fix is to change the rpm or look away.

Not enough oxygen

Hypoxia is oxygen starvation. The handbook says the word means "reduced oxygen" or "not enough oxygen," and that "the greatest concern regarding hypoxia during flight is lack of oxygen to the brain, since it is particularly vulnerable to oxygen deprivation" 12. The first symptoms are the dangerous ones. "The first symptoms of hypoxia can include euphoria and a carefree feeling." The victim feels fine, and judgment fails first. Other symptoms follow: headache, blue fingernails and lips, tingling, drowsiness, and a narrowing of vision.

Four kinds

The handbook names four forms of hypoxia by their cause 13:

• hypoxic: "insufficient oxygen available to the body as a whole," from the fall in the partial pressure of oxygen with altitude
• hypemic: "the blood is not able to take up and transport a sufficient amount of oxygen," from carbon monoxide, anemia, or blood loss
• stagnant: "the oxygen-rich blood in the lungs is not moving," as under G-loads or in shock
• histotoxic: "the inability of the cells to effectively use oxygen," from alcohol, narcotics, and poisons.

The handbook adds that "drinking one ounce of alcohol can equate to an additional 2,000 feet of physiological altitude."

The response

The treatment for hypoxia "includes flying at lower altitudes and/or using supplemental oxygen" 14. Oxygen on if the airplane has it, and descend. The AIM adds the threshold that matters at night: "a deterioration in night vision occurs at a cabin pressure altitude as low as 5,000 feet," and "other significant effects of altitude hypoxia usually do not occur in the normal healthy pilot below 12,000 feet" 15. The pilot of a Warrior at 5,500 feet at night already has degraded night vision. The pilot of a Warrior at 12,000 feet has degraded judgment.

Hyperventilation

Hyperventilation is over-breathing. The handbook defines it as "the excessive rate and depth of respiration leading to abnormal loss of carbon dioxide from the blood," and says it "occurs more often among pilots than is generally recognized" 16. Stress starts it. The symptoms, lightheadedness, tingling in the extremities, and a sense of suffocation, look like hypoxia and cause more anxiety and faster breathing. The fix is to slow the breathing on purpose. The AIM says "the symptoms of hyperventilation subside within a few minutes after the rate and depth of breathing are consciously brought back under control" 17.

Hypoxia or hyperventilation

Hypoxia and hyperventilation share symptoms, and they can occur together. The AIM gives the test: "if a pilot is using an oxygen system when symptoms are experienced, the oxygen regulator should immediately be set to deliver 100 percent oxygen," and if the symptoms continue on oxygen, the cause is hyperventilation 17. A pilot in doubt treats both at once: oxygen on if available, breathing slowed, and a descent.

Ear and sinus blocks

Air in the middle ear and the sinuses must equalize with the cabin as the pressure changes. On descent the pressure outside rises faster than the air inside can equalize, and a cold or congestion closes the passages. The AIM says that during descent "the pilot must periodically open the eustachian tube to equalize pressure. This can be accomplished by swallowing, yawning, tensing muscles in the throat, or if these do not work, by a combination of closing the mouth, pinching the nose closed, and attempting to blow through the nostrils (Valsalva maneuver)" 18. A sinus block "occurs most frequently during descent" and "usually produces excruciating pain over the sinus area" 19. The handbook's prevention is one sentence: "Sinus block can be avoided by not flying with an upper respiratory infection or nasal allergic condition."

Decongestants

A decongestant taken before a flight does not remove the risk of a block and adds side effects. The handbook says "adequate protection is usually not provided by decongestant sprays or drops to reduce congestion around the sinus openings. Oral decongestants have side effects that can impair pilot performance" 19. The side effects include drowsiness, and the congestion returns at altitude when the drug's effect ends. The pilot checks the medication with an AME, not only the symptom. The rule that requires the check is 61.53.

Motion sickness

Motion sickness is a conflict between the senses. The handbook says it "is caused by the brain receiving conflicting messages about the state of the body," that a pilot "may experience motion sickness during initial flights, but it generally goes away within the first few lessons," and that anxiety contributes 20. The responses are eyes on the horizon, cool air from the vents, gentle maneuvers, and a landing if it progresses. An airsick pilot flies badly. An airsick passenger distracts the pilot, and the brief before the flight includes the vent and the bag.

Carbon monoxide

Carbon monoxide is in the exhaust, and the cabin heater is a shroud around the exhaust. The AIM says "most heaters in light aircraft work by air flowing over the manifold. Use of these heaters while exhaust fumes are escaping through manifold cracks and seals is responsible every year for several nonfatal and fatal aircraft accidents from carbon monoxide poisoning" 21. The gas is "colorless, odorless, and tasteless." The headache, drowsiness, and dizziness build slowly. A pilot who smells exhaust in the cabin assumes carbon monoxide is present.

The response

The AIM's response is direct: "a pilot who detects the odor of exhaust or experiences symptoms of headache, drowsiness, or dizziness while using the heater should suspect carbon monoxide poisoning, and immediately shut off the heater and open air vents" 21. Heat off, vents and windows open, land as soon as practicable, oxygen if the airplane has it. A carbon monoxide detector on the panel or the glareshield gives the warning before the headache.

Why it lingers

Carbon monoxide binds to hemoglobin in place of oxygen. The handbook says it attaches "about 200 times more easily than oxygen," so it "prevents the hemoglobin from carrying oxygen to the cells, resulting in hypemic hypoxia. The body requires up to 48 hours to dispose of CO" 22. A pilot poisoned on the morning flight is still poisoned on the afternoon one. Landing stops the exposure and not the effect.

Stress

Stress comes in two forms. The handbook says "acute stress involves an immediate threat that is perceived as danger," and that "chronic stress can be defined as a level of stress that presents an intolerable burden, exceeds the ability of an individual to cope, and causes individual performance to fall sharply" 23. Acute stress narrows attention to the threat. Chronic stress reduces attention to everything. A pilot under chronic stress fails the S item of IMSAFE on the ground, before the engine starts.

Fatigue

Fatigue also comes in two forms. The handbook says "acute fatigue is short term and is a normal occurrence in everyday living," the tiredness after "strenuous effort, excitement, or lack of sleep," and that "rest after exertion and 8 hours of sound sleep ordinarily cures this condition" 24. Chronic fatigue "extending over a long period of time" is "not relieved by proper diet and adequate rest and sleep and usually requires treatment by a physician." Fatigue degrades judgment before it degrades control of the airplane. A tired pilot flies the airplane and misjudges the weather.

Water and food

Dehydration is "a critical loss of water from the body," and its causes are "hot flight decks and flight lines, wind, humidity, and diuretic drinks—coffee, tea, alcohol, and caffeinated soft drinks" 25. The first effect "is fatigue, which in turn makes top physical and mental performance difficult, if not impossible." The cabin of a Warrior in summer is hot and dry, and the loss is faster than on the ground. The pilot carries water and drinks it, and eats before flying. A skipped meal causes a headache at altitude.

Cold

Hypothermia is a survival risk after any off-field landing, in any season. A pilot who lands in a field in a light shirt in April has a long cold night if no one comes before dark. Clothing for the terrain under the route, not for the cabin, is part of the preflight.

Diving

Flying after scuba diving can bring nitrogen out of solution in the blood. The AIM gives the waiting times: "at least 12 hours after diving that did not require a controlled ascent (i.e., non-decompression stop diving), and at least 24 hours after diving that required a controlled ascent (i.e., decompression stop diving)" before flying to altitudes up to 8,000 feet, and "at least 24 hours" before flying above 8,000 feet 26. The handbook says the diver "should allow the body sufficient time to rid itself of excess nitrogen absorbed during diving" 27. A morning dive followed by an afternoon flight can cause decompression sickness.

The alcohol rule

14 CFR 91.17(a) has four prohibitions 28. No person can act as a crewmember:

• within 8 hours after the consumption of any alcoholic beverage
• while under the influence of alcohol
• while using any drug that affects the person's faculties in any way contrary to safety
• while having an alcohol concentration of 0.04 or greater in a blood or breath specimen.

The four are separate. A pilot 9 hours from the last drink with a concentration of 0.05 violates the fourth. A pilot 9 hours from the last drink at 0.02 and impaired violates the second. The 8-hour limit is one test of four.

Eight hours is the minimum

Eight hours is the least the rule allows, not the number a careful pilot uses. The AIM says that "due to the slow destruction of alcohol, a pilot may still be under influence 8 hours after drinking a moderate amount of alcohol," and that "an excellent rule is to allow at least 12 to 24 hours between 'bottle and throttle,' depending on the amount of alcoholic beverage consumed" 29. A hangover is impairment with a blood alcohol concentration of zero. The school's guidance is the AIM's: 12 hours at the least, and 24 after heavy drinking. The handbook adds that one ounce of alcohol equates to about 2,000 feet of additional physiological altitude 13.

Testing, and the intoxicated passenger

Paragraph (c) of 91.17 requires a crewmember, "on request of a law enforcement officer," to "submit to a test to indicate the alcohol concentration in the blood or breath" when the officer is authorized to conduct it and is investigating a suspected violation 30.

Paragraph (b) governs passengers: "except in an emergency, no pilot of a civil aircraft may allow a person who appears to be intoxicated or who demonstrates by manner or physical indications that the individual is under the influence of drugs (except a medical patient under proper care) to be carried in that aircraft."

Medications

The rule for medication is 61.53. A pilot must not act as pilot in command while taking a medication, or a treatment for a condition, that fails the medical standard 31. The AIM's guidance is to check any medication with an AME. Its list of medications of concern is ordinary: "analgesics, tranquilizers, sedatives, antihistamines, some cough and cold remedies," and "any medication that depresses the nervous system, such as a sedative, tranquilizer or antihistamine, can make a pilot much more susceptible to hypoxia" 32. Sedating antihistamines are the most common case, because they are sold for the cold that also causes the ear block.

Five dosing intervals

The FAA's guidance for a new medication is to wait before flying. The over-the-counter guide says to wait at least five maximal dosing intervals after the last dose. The wait applies to any medication whose label warns about drowsiness or operating machinery 33. A drug taken each 6 hours means 30 hours on the ground. The wait lets the side effects appear on the ground.

Prevention

An unusual attitude is an attitude not required by the maneuver. The Instrument Flying Handbook says the common errors that lead to one begin with "failure to keep the airplane properly trimmed. A flight deck interruption when holding pressures can easily lead to inadvertent entry into unusual attitudes" 34. The same three things that fix an unusual attitude prevent it: a working scan, a trimmed airplane, and no distraction at low altitude.

Read the attitude first

Before recovering, the pilot reads the attitude from all the instruments together. The handbook says that "any time an instrument rate of movement or indication other than those associated with the basic instrument flight maneuvers is noted, assume an unusual attitude and increase the speed of cross-check to confirm the attitude, instrument error, or instrument malfunction" 35. The airspeed trend, the altimeter, the VSI, and the turn coordinator confirm the attitude indicator. A recovery from an attitude the airplane is not in is the cause of many upset accidents. A pilot who trusts a tumbled attitude indicator and "recovers" from a climb that is not there dives.

Nose high

The handbook gives the nose-high recovery: "if the airspeed is decreasing, or below the desired airspeed, increase power (as necessary in proportion to the observed deceleration), apply forward elevator pressure to lower the nose and prevent a stall, and correct the bank by applying coordinated aileron and rudder pressure" 36. Power, nose down, wings level, then return to level flight. The corrections "are made almost simultaneously, but in the sequence given above."

Nose low

The nose-low recovery reverses the first two steps and adds a warning. "If the airspeed is increasing, or is above the desired airspeed, reduce power to prevent excessive airspeed and loss of altitude. Correct the bank attitude with coordinated aileron and rudder pressure to straight flight by referring to the turn coordinator. Raise the nose to level flight attitude by applying smooth back elevator pressure" 37. Power off, wings level, then ease out of the dive. The handbook says "the instinctive reaction to a nose-down attitude is to pull back on the elevator control." A pull with the wings banked tightens the spiral and loads the wings. The wings come level first.

The escape

The escape from inadvertent flight into cloud is a procedure. The Airplane Flying Handbook's rules for the untrained instrument pilot are short 38:

• "trim the airplane with the elevator trim so that it maintains hands-off level flight at cruise airspeed"
• "resist the tendency to over-control the airplane. Fly the attitude indicator with fingertip control"
• "make use of any available aid in attitude control, such as autopilot or wing leveler."

The handbook says turns "are perhaps the most potentially dangerous maneuver for the untrained instrument pilot," because of over-control "leading to steep banks and the possibility of a 'graveyard spiral,'" and that "the smallest practical bank angle should be used—in any case no more than 10° bank angle" 39. The escape is a level, coordinated 180-degree turn at 10 degrees of bank, back to the air the airplane just left. The pilot climbs only if terrain requires it. "Combined maneuvers, such as climbing or descending turns, should be avoided if at all possible" 40.

The turn before the entry

VFR into instrument conditions is among the most lethal situations in general aviation. The turn that prevents the accident is the one made while the ground is still visible. A pilot who sees the ceiling lowering and the visibility falling, and turns around then, makes an easy turn in visual conditions. The same pilot two minutes later makes a 10-degree-bank turn in cloud while the inner ear produces the sensation of a spiral. The handbook's first two items for coping with disorientation are the ones that keep a pilot out of cloud: know the illusions, and "always obtain and understand preflight weather briefings" 7.

The autopilot

An autopilot or a wing leveler, if the airplane has one, is a legitimate escape tool. The handbook lists it among the aids to attitude control 38. Wings-level mode holds the airplane upright while the pilot breathes, talks to the controller, and plans. The pilot monitors it, watches the attitude indicator and the turn coordinator with it engaged, and knows how to disconnect it. A student in a Warrior without an autopilot has the trim and the turn coordinator, which is what the airplane at Micanopy had.

Confess

The AIM says an airplane "is in at least an urgency condition the moment the pilot becomes doubtful about position, fuel endurance, weather, or any other condition that could adversely affect flight safety. This is the time to ask for help, not after the situation has developed into a distress condition" 41. A pilot who is lost, in weather, or unsure tells the controller and accepts the help. The pilot declares an emergency when the situation is one. Help exists for that purpose, and using it is airmanship. The pilot at Micanopy called mayday after the airplane was already in cloud, and the controller answered.

What radar can do

A radar controller can give a VFR pilot vectors, position, and headings away from terrain. The AIM says "radar equipped FAA ATC facilities provide radar assistance and navigation service (vectors) to VFR aircraft provided the aircraft can communicate with the facility, are within radar coverage, and can be radar identified" 42. The guidance "is advisory in nature and the job of flying the aircraft safely, remains with the pilot," and the controller does not always know the weather ahead, so "pilots should keep controllers advised of the weather conditions in which they are operating." A pilot who requests flight following before the flight is in trouble is already in contact with that controller.

Fly the airplane while asking

The pilot's task is to fly the airplane while the controller works out the position and the heading. The pilot holds a heading and an altitude by the instruments. The controller's vectors or the navigation equipment provide the route. The Instrument Flying Handbook's method is control and performance: attitude and power produce performance, and the cross-check confirms it 43. The Airplane Flying Handbook says of the controller's prompting: "the pilot should not let this prompting lead to rushing into a maneuver that could result in loss of control. It's reasonable to ask the controller to slow down" 40. The controller's urgency is concern, and the pilot's job is to fly the airplane.