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Human Factors

Objective​

To become familiar with human and aeromedical factors that can affect flight safety, and apply corrective actions to mitigate them.

Motivation​

Understand the risks and mitigations for aeromedical factors that can affect flight safety, as they may happen to you, another pilot, or your passengers.

Timing​

45 minutes

Format​

Elements​

Hypoxia​

  • Cause: Hypoxia is a state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs
  • Symptoms: Cyanosis, headache, dizziness, euphoria, impaired vision, drowsiness
  • Corrective Actions
    • Use supplemental Oxygen
    • Fly lower
    • Address any pollution in the air
  • Time of useful consciousness
    • From AC 61-107B
  • Types of Hypoxia
    • Hypoxic: Caused by the reduction in partial pressure of oxygen at high altitude
    • Hypemic: Caused by the blood not being able to take up and transport a sufficient amount of oxygen; CO poisoning
    • Stagnant: Caused by a lack of circulation of oxygenated blood in the body; can occur during high-G maneuvers

Hyperventilation​

  • Cause: Excessive rate and depth of respiration leading to abnormal loss of carbon dioxide
  • Symptoms: Rapid breathing, visual impairment, sweaty skin, dizziness
    • Often occurs with stress or anxiety
  • Corrective Actions
    • Breathe slowly
    • Speak something slowly
    • Breathe into a bag

Middle ear and sinus problems​

  • Cause: Blockage of the Eustachian tube which equalizes pressure between both sides of your ear drum. Often happens with inflammation
  • Symptoms:
    • Ear pain and pressure
    • Muffled hearing
  • Corrective Actions
    • Valsalva method
    • Descend slowly
    • Avoid flying with any sinus blockage
    • Decongestants can be helpful (for passengers)

Spatial disorientation​

  • Cause: Disagreement or confusion between your sensory systems about the aircraft's position, attitude, or movement
  • Symptoms:
    • Confusion
    • Loss of airplane control
  • Corrective Actions
    • Trust flight instruments
    • Limit maneuvering
    • Limit rapid head movements

Illusions that contribute to spatial disorientation​

  • The "leans"
    • After a long gradual turn, the airplane is returned to level
    • The plane may feel as though it's banking in the opposite direction
  • Coriolis illusion
    • Rapid head movement during a turn
    • The plane may feel as though it's banking in the opposite direction
  • Graveyard spiral
    • After entering a prolonged, coordinated, constant-rate turn without visual references, the pilot's inner ear no longer senses the turn, leading to the false impression of straight-and-level flight.
    • When the pilot levels the wings, it feels as though the aircraft is turning in the opposite direction, so the pilot may erroneously bank back into the original turn.
    • The airplane will tend to lose altitude in the turn, so the pilot pulls back on the elevator, tightening the spiral.
    • The result is a nose-low, descending, high-G turn.
  • Somatogravic illusion
    • Acceleration may feel like a pitching-up movement
    • Especially true with limited visual reference, like at night
    • Pilot may consequently push into a nose-low attitude
    • Likewise, deceleration may cause the sensation of pitching down
  • Inversion illusion
    • Abrupt change from climbing to straight-and-level flight can create the illusion of tumbling backwards
    • Pilots may then push the aircraft into a nose-low attitude
  • Elevator illusion
    • Upward vertical acceleration like an updraft can create the illusion of being in a climb
    • Pilots may push the aircraft into a nose-low attitude
    • Likewise a downward acceleration can create the illusion of being in a descent

Overcoming disorienting illusions​

  • Trust flight instruments
  • Instrument training and proficiency
  • Limit maneuvering, especially high-load factor maneuvers
  • Limit rapid head movements
  • Use autopilot if needed

Motion sickness​

  • Cause: The brain receiving conflicting messages about the state of the body's position in space.
  • Symptoms:
    • Nausea
    • Dizziness
    • Paleness, sweaty, clammy skin
    • Vomiting
  • Corrective Actions
    • Fresh air
    • Focus on objects outside the airplane
    • Avoid unnecessary head movements
    • Always have a bag

Carbon monoxide poisoning​

  • Cause: Hypemic hypoxia caused by the presence of CO in the air, which attaches to hemoglobin in the blood.
  • Symptoms:
    • Headache
    • Drowsiness
    • Blurred vision
    • Loss of muscle power
  • Corrective Actions
    • Close heater vent
    • Land and ventilate the cabin
    • Open fresh air vents

Stress​

  • Cause: The body's response to physical and psychological demands placed upon it. Stress can be chronic or acute.
  • Symptoms:
    • Agitation
    • Not thinking well
    • Fatigue
  • Corrective Actions
    • Correct underlying stressors, which may require medical treatment for chronic stress

Fatigue​

  • Cause: Acute fatigue is caused by lack of sleep. Chronic fatigue usually has medical underpinnings.
  • Symptoms:
    • Drowsiness
    • Errors in judgment, timing, computation
    • Loss of muscle control
  • Corrective Actions
    • Chronic fatigue: correct underlying issues, which may require medical attention
    • Acute fatigue: Rest

Dehydration​

  • Cause: Critical loss of water or electrolytes from the body
  • Symptoms:
    • Headache
    • Fatigue
    • Drowsiness
    • Cramps
  • Corrective Actions
    • Drink plenty of fluids and electrolytes
    • Drink before you become thirsty
    • Your thirst response may work too slowly to warn of the onset of dehydration

Hypothermia​

  • Cause: Exposure to cold temperature for extended periods.
  • Symptoms:
    • Coldness
    • Shivering
    • Drowsiness
    • Loss of consciousness
  • Corrective Actions
    • Move to a warmer environment
    • Add clothing, blankets, or coats
    • Cover exposed areas

Alcohol​

  • Symptoms:
    • Symptoms similar to that of hypoxia
    • Impaired judgement, coordination, reaction time
  • Regulations
    • Alcohol, 14 CFR Part 91.17:
      • 8 hours single last alcoholic drink before acting a crew member ("bottle to throttle")
      • 0.04% BAC limit
      • Cannot carry drunk passengers, except in an emergency or under the supervision of a doctor

Drugs​

  • Regulations
    • Part 61.53:
      • A pilot cannot act as PIC if:
        • They have any known condition that would make them ineligible for a medical
        • Are receiving treatment or taking medication that would make them ineligible for a medical
  • AOPA Drug Database
  • FAA Over-the-Counter (OTC) Drug List
  • Check the half-life of any drug you intend to take
  • Substances to Avoid
    • Nicotine: Impaired night vision, CO poisoning
    • Amphetamines: Impaired vision, impaired judgement
    • Caffeine: Impaired judgement, dehydration, headaches
    • Antacids: Release CO2 at altitude
    • Antihistamines: Drowsiness, dizziness
    • Aspirin: Contribute to hypoxia
    • Prescription pain killers
    • Illicit drugs

Dissolved nitrogen in the bloodstream after SCUBA dives​

  • Cause: Dissolved nitrogen in the blood being forced out of body
  • Corrective Actions
    • For flights below 8,0000' MSL:
      • At least 12 hours after diving that does not require controlled ascent (non-decompression stop diving)
      • At least 24 hours after diving that does require controlled ascent (decompression stop diving)
    • For flights above 8,000' MSL: At least 24 hours

IMSAFE checklist​

  • Preflight self-evaluation:
    1. Illness
    2. Medication
    3. Stress
    4. Alcohol
    5. Fatigue
    6. Emotion

Hazardous attitudes​

  • Attitudes
    • Anti-authority: "Don't tell me what to do"
    • Impulsivity: "I can do it quickly"
    • Invulnerability: "It won't happen to me"
    • Macho: "I can do it"
    • Resignation: "What's the use?"
  • Antidotes
    • Anti-authority: Follow the rules, they are usually right.
    • Impulsivity: Not so fast, think first.
    • Invulnerability: It could happen to me.
    • Macho: Taking chances is foolish.
    • Resignation: I am not helpless, I can make a difference.
    • Stress: I can manage stress.
  • Learn to recognize these attitudes when they occur. Slow down and state the antidote to yourself

Get-There-itis​

  • The desire to get to a destination, complete the mission, or meet a schedule
  • Pilots can feel pressured to continue, even when conditions are unsafe
  • Consequences of not getting there are immediate and specific
  • Consequences of an accident are vague and hypothetical

Combatting Get-There-itis​

  • Recognize the symptoms
  • Avoid situations where you feel pressured to continue
  • Avoid situations where peer pressure would be strong

Optical Landing illusions​

  • False Horizon
  • Runway Width Illusion
  • Sloping Runway Illusion
  • Other Illusions
    • Featureless terrain
      • Over water at night
      • Aircraft may appear higher than it actually is
      • "Black hole" approaches
    • Water on windscreen
      • The aircraft seems higher than it actually is
    • Haze
      • Aircraft may appear to be further away
    • Fog
      • Flying into fog: Illusion of pitching up
    • Mistaking city lights for runway lights

Questions​

  • You are flying at 7,500 feet and your passenger complains of fatigue and a headache.
    • Suspect some form of hypoxia
    • Check CO detector, if installed
    • Use a pulse-oximeter if you have one
    • Descend if possible
  • You are flying at 9,500 feet and your passenger is become abnormally euphoric and giddy.
    • Suspect hypoxia
    • Use a pulse-oximeter if you have one
    • Descend if possible
    • Use supplemental oxygen if available
    • Suspect that you may also be hypoxic
  • You want to take your three friends flying shortly after you receive your private pilot certificate. You're flying a Cessna 172, and from your weight and balance calculations, you know that the aircraft will be above gross weight with the four of them.

References​

Pilot's Handbook of Aeronautical Knowledge pg. 17-1