Human Factors

Instrument Flying

Human factors

Human factors

  • Spatial disorientation.
  • Hypoxia.
  • Hyperventilation.       
  • Motion sickness.
  • Carbon Monoxide.
  • Fatigue and stress.
  • Dehydration.
  • Alcohol and drugs.
  • Scuba diving.
  • Middle ear and sinus problems.

Spacial disorientation

  • Brain receives messages that contradict what the body perceives.
  • An incorrect mental image of your position in relation to what is actually happening to the airplane.
  • 3 body sensory organs:
    • Visual (eyes)
    • vestibular (inner ear)
    • Kinesthetic (nerves in the skin, joints and muscles).
  • Conflicting information from the three areas may result in disorientation if not overcome.
  • The best things to do is to be confident on your flight instruments, more than your feeling.
Vestibular Illusion
  • The sensation of bank in the opposite direction:
    • May occur when a banked attitude is entered too slowly to set the fluid in the vestibular system in motion but an abrupt correction is used to level the aircraft.
  • Coriolis Illusion:
    • An abrupt head movement in a prolonged constant-rate turn can create the illusion of rotation or movement in an entirely different axis
  • Graveyard spin :
    • Recovery from a spin and create the illusion of spinning in the opposite direction. The disoriented pilot returns the aircraft to its original spin.
  • Graveyard spiral:
    • Losing altitude in a constant rate turn creates the illusion of being in a descent with the wings level.The disoriented pilot will pull back on the controls, tightening the spiral and increasing loss of altitude.

Hypoxia

  • Hypoxia means « not enough oxygen ». It can severely impair the function of the brain and other organs. Judgment, perception and mental ability, amongst others are affected.
  • Symptoms:
    • Impaired judgment
    • Euphoria.
    • Blue fingernails and lips (Cyanosis).
    • Headache.
    • Visual impairment (tunnel vision, impaired night vision).
    • Drowsiness .
    • Dizzyness.
    • Tingling and numbness in fingers and toes.
  • Night vision starts becoming deteriorated already at 5000 ft cabin altitude.
  • Descend to a lower altitude or using supplemental oxygen.

Hyperventilation

  • Can occur as a reaction to:
    • emotional stress.
    • Fright.
    • Pain…
  • Symptoms:
    • Are nearly the same as for hypoxia, but instead of cyanosis, and limp muscles, the person experiencing hyperventilation will have get a pale appearance, and possibly muscle spasms.
  • Corrective actions:
    • Control breathing rate. Try restoring CO2 levels by breathing in a paper bag.
    • If unsure whether it’s hypoxia or hyperventilation – treat for hypoxia!

Motion Sickness

  • Brain receiving conflicting messages about the state of the body.
  • Common among passengers and some inexperienced pilots.
  • If prone to motion sickness:
    • Avoid turbulence.
    • Open air vents
    • Focus outside
    • Avoid head movements.
    • Start with short lessons, gradually longer.
    • Medication is not recommended while piloting.
  • Symptoms:
    • General discomfort, nausea, dizziness, paleness, sweating, and vomiting.

Carbon Monoxide Poisoning

  • Colorless and odorless gas produced by all internal combustion engines.
  • Attaches itself to the hemoglobin in the blood about 200 times more easily than oxygen.
  • Aircraft heater vents and defrost vents.
  • Symptoms:
    • Red lips, nails.
    • Headaches.
    • Blurred vision.
    • Dizziness.
    • Drowsiness, and/or loss of muscle power.
    • Can result in death
    • Inexpensive carbon monoxide detectors. Turns black when exposed.
  • Corrective actions:
    • Turn off the heater
    • Open fresh air vents and windows.
    • Use supplemental oxygen, if available.
    • Tobacco smoke also causes carbon monoxide poisoning. Effects similar to flying at 8,000 feet.

Stress

  • The body’s response to physical and psychological demands placed upon it.
  • Release chemical hormones (such as adrenaline) into the blood.
  • The blood sugar, heart rate, respiration, blood pressure, and perspiration (transpiration) all increase.
  • Stressors:
    • Physical stress (noise or vibration).
    • Physiological stress (fatigue).
    • Psychological stress.
    • Acute (grave,aigu) stress (short term).
    • Chronic stress (long term).
  • A certain amount of stress increases performance until it exceeds a specific level.

Fatigue

  • Frequently associated with pilot error.
  • Degradation of attention and concentration, impaired coordination, and decreased ability to communicate.
  • Physical (sleep loss, exercise, or physical work) and mental fatigue (stress)
  • Acute and chronic.

Dehydration

  • Critical loss of water from the body.
  • The first effect of dehydration is fatigue.
  • Increased risk at hot summer days and/or high altitudes.
  • If this fluid is not replaced, fatigue progresses dizziness, weakness, nausea, tingling of hands and feet, abdominal cramps, and extreme thirst.

Alcohol:

  • Drinking and performance deterioration are closely linked.
  • Alcohol drastically reduces the chances of completing a flight without incident.
  • Even in small amounts alcohol can:
    • Impair judgment.
    • Decrease sense of responsibility.
    • Affect coordination.
    • Constrict visual field.
    • Diminish memory.
    • Reduce reasoning power.
    • Lower attention span.
  • With a hangover a pilot is still under the influence of alcohol.
  • Alcohol interferes with the brain’s ability to utilize oxygen, producing a form of
  • Don’t drink before a minimum of 8 hours pass between drinking alcohol and piloting an airplane. Good idea to be more restrictive than that.

Drugs

  • Performance seriously degraded by both prescribed and over-the-counter medications, as well as by the medical condition they are taken.
  • May impair judgment, memory, alertness, coordination, vision, and the ability to make calculations.
  • If there is any doubt regarding the effects of any medication, consult an aviation medical examiner before flying.

SCUBA Diving

  • Scuba diving then flying can lead to decompression sickness
  • The bends can be experienced from as low as 8000 feet MSL.
  • Minimum time before flying up to an actual altitude of 8000 feet:
    • 12 hrs after dives which has not required a controlled ascent.
    • 24 hrs after dives with controlled ascent.
  • Flying above 8000 feet:
    • Should be at least 24hrs after any scuba dive.

Blood Donations

  • Because it takes several weeks for the blood circulation to return to normal after a blood donation, it’s recommended that pilot who are actively flying to refrain from volunteering as blood donors.
  • It’s recommended that you should wait at least 48 hours.

Eating

  • The stress of flying, or indeed of any activity, consume energy.
  • This energy is derived from oxygen and from blood sugar.
  • The pilot is unwise to fly for too long without eating.
  • His blood sugar will be low (hypoglycemia), that is, his energy reserve will be low.
  • Reaction will be sluggish (lente) and efficiency will be impaired.
  • It’s good precaution to carry a nutritious snack on long flight.

Middle ear and sinus problems

  • Differences in pressure due to climbs/descends between the outside air, and the air in the middle ear, or in the nasal sinuses may cause discomfort and pain. Worst during descent.
  • Pressure equalized through Eustachian tube, which can be opened through chewing, yawning or valsalva maneuver.
  • Can also affect teeth.
  • During a cold, sinuses and the Eustachian tube may be swollen, equalizing will be harder.
  • Symptoms:
    • Pain and discomfort in sinuses, ears, teeth.
  • Corrective actions:
    • Attempt to equalize. Reduce rate of descent/climb.

Review questions

  • What can be the causes of hyperventilation ?
  • How long is the minimum time required after drinking alcohol before flying?
  • What do you have to do to counteract the effect of spatial disorientation and illusion?