408 Human Factors

408.01 Aeromedical 1

Hypoxia

  • Hypoxia: condition where cells of body do not get sufficient oxygen to function properly

    • Hypoxic Hypoxia: inability of lungs to transfer oxygen to bloodstream, caused by reduced partial pressure of atmospheric oxygen at high altitudes

    • Anemic Hypoxia: inability of blood to absorb oxygen, caused by anemia/low blood volume/carbon monoxide poisoning

    • Stagnant Hypoxia: reduced oxygenation of cells due to circulatory impairment, caused by cardiovascular disease/tight clothing

    • Histotoxic Hypoxia: inability of cells to absorb oxygen due to chemical interference at cellular level, caused by drugs

  • Central nervous system, eyes, and brain are sensitive to hypoxia

  • Effects of hypoxia: reduced visual acuity, impaired night vision, impaired judgment, impaired physical performance, eventually loss of consciousness, death (extreme cases)

  • What you feel: euphoria, dizziness, nausea, headaches, hot + cold flashes, tingling in extremities numbness (bilateral)

  • What others see: poor performance, impaired judgment, belligerence, cyanosis (fingers/toes and mouth)

  • Time of Useful Consciousness: time available to you to recognize the onset of hypoxia and take action before incapacitation

    • <10000ft = indefinite

    • 15000ft = 30mins

    • 20000ft = 5-12mins

    • 30000ft = 45-60secs

    • >45000 = <10secs

  • Physical Fitness: individuals with greater aerodbic fitness will have a greater TUC

  • Physical Activity: the more active you are at altitude, the shorter your TUC

  • Smokers: have shorter TUC (anemic hypoxia)

  • Hypoxia is insidious + associated with an overwhelming sense of well-being and bliss

  • What to do if someone is becoming hypoxic: go on oxygen, reduce altitude, land ASAP

  • Altitude restrictions for flight without oxygen = max.  30mins from 10000ft to 13000ft ASL (not authorized above 13000ft)

  • Supplemental breathing oxygen required for crew + passengers when flying above 13000ft

Hyperventilation

  • Hyperventilation: breathing at rate + depth in excess of current bodily demand for oxygen



  • Causes:

    • Fear

    • Anxiety

    • Apprehension

    • Temperature extremes

  • Onset of hyperventilation

    • Rapid elimination of CO2 (imbalance of O2 and CO2)

  • Reduced blood flow to brain

  • Eventual loss of consciousness

    • After passing out, autonomic system takes over and restores normal breathing rate until recovered

  • Symptoms:

    • Increased breathing rate

    • Shallow breathing

    • Cold, clammy skin

    • Dizziness

    • Lightheadedness

    • Hot + cold flashes

    • Vision disturbances

    • Numbness/tingling in extremities

  • Treat:

    • Assume worst case scenario, treat for hypoxia + hyperventilation

    • Control breathing: slow down, deep breaths, in and out for 3secs each

    • In through nose, out through mouth

Gas Expansion Effects

  • Boyle's Law: volume of a gas is inversely proportional to its pressure. If gas is subjected to lower pressure, it will expand

  • As we fly at higher altitudes, atmospheric pressure drops at a know rate, and gases trapped in various cavities in body will expand

    • Expansion can result in discomfort or pain

    • Body cavities to consider: ears, sinuses, teeth, gastro-intestinal tract

  • Symptoms of ear blockage:

    • Eardrum bulging inwards

    • Dulled hearing

    • Sense of “fullness”

    • PAIN

    • Rupture of eardrum

  • Preventative measures: don’t fly when congested and don’t self-medicate

  • Relief measures: chewing, sucking, swallowing, yawning, altitude control, and valsalva maneuver

  • Suggestion:demonstrate the valsalva maneuver and have candidates practice it carefully 

  • Gases trapped in sinus cavities can expand and cause severe pain

  • Causes for sinus blockages include genetics, illness (cold/flu) or allergies

  • Preventive measures: don’t fly until congestion clears up and don’t self medicate

  • Sinus relief measures:

    • On ascent: vigorous nose blowing

    • On descent: valsalva maneuver

  • Gas trapped within teeth

    • Decay: resulting in gas formation

    • Air trapped under filling during dental work

    • Effect can be excruciating tooth pain

    • Relief: there are non, just don’t fly and get it fixed by a dentist

  • Gastrointestinal Tract

    • Digestive process generates gases in stomach and intestines 

    • Gas expands during ascent, results in discomfort or pain

    • Preventative measures: don’t eat gassy foods, don’t consume gassy/carbonated drinks, don’t eat too fast (swallow air when you eat fast)

    • Relief: altitude control, “use flapper valve” and “pass the gas” 

Decompression Effects

  • Blood contains nitrogen

  • While at sea level, nitrogen remains in solution, but if we’re exposed to reduced atmospheric pressure (at high altitudes) the nitrogen starts to “bubble off” or come out of solution

  • Slow off-gassing can be handled by the body, but rapid decompression/very significant decompression can result in nitrogen forming bubbles in bloodstream (analogy to shaking a bottle of pop)

  • Nitrogen bubbles in bloodstream can cause decompression sickness

Types of Decompression Sickness

  • The Bends

    • Bubble location: mostly large joints of body

    • Signs + symptoms: 

      • Deep pain (mild to excruciating, rarely a sharp pain)

      • Motion of join can aggravate pain

      • Main occurring at altitude during descent or many horus later

  • The Chokes

    • Bubble location: lungs

    • Signs + symptoms:

      • Burning deep chest pain

      • Pain aggravated by breathing

      • Shortness of breath

      • Constant dry cough

  • The Creeps (panesthesia) 

    • Bubble location: skin

    • Signs + symptoms:

      • Itchy around ears, face, neck, arms, upper torso

      • Sensation of tiny insects crawling on skin

      • Marbled skin (usually around shoulders, upper chest, abdomen)

      • Swelling skin

  • Central Nervous System Disturbances

    • Bubble location: central nervous system

    • Signs + symptoms:

      • Similar symptoms to stroke (headache, vision disturbances, balance disturbances, loss of motor function)

  • Nitrogen Narcosis 

    • Bubble location: brain

    • Signs + symptoms:

      • Effects vary like hypoxia: sense of bliss, impaired judgment and performance

  • Type of decompression sickness is characterized by where nitrogen bubbles migrate/congregate

    • Can be fatal in extreme cases 

Decompression Sickness

  • Decompression sickness - Aviation Hazards

    • Rapid climbs put you at elevated risk for DCS

    • Explosive decompressions (in pressurized cabin) put you at elevated risk for DCS

  • Avoidance of DCS

    • If conducting dive where decompression stops aren’t required, don’t fly for 12hrs unless flight is above 8000 ASL, then wait 24hrs

    • If conducting dive with decompression stops, don’t fly for 24hrs regardless of altitude



408.02 Aeromedical 2

Orientation and Disorientation

  • Orientation: determination of relative position of something or someone (especially oneself)

    • Process of disorientation is dominated by visual cues/references

  • Disorientation: false sense of one’s position and motion relative to surface of earth (two classes)

    • Recognized Disorientation: conscious recognition that we are disoriented + can compensate for it

    • Unrecognized disorientation: no conscious recognition we are disoriented, no corrective action can be taken, can result in loss of control, leading cause of aviation accidents

  • Sensory Illusion

    • Brain incorrectly interprets sensory information + tells us body is moving in ways it is not

    • Usually occurs when visual cues are reduced (flying in bad weather, in cloud [IFR], at night)

    • Can be very powerful →if unaware of illusions, you can become disoriented

  • Somatogravic Illusions

    • Acceleration/deceleration illusion resulting from brain responding to sensory input from otoliths reacting to acceleration forces (but with reduced visual cues which cause disorientation

      • Level acceleration = pitch up illusion

      • Level deceleration = pitch down illusion

  • Vestibular Illusions (“The Leans”)

    • Caused by contradictory inputs from vestibular apparatus, specifically the semicircular canals

    • During prolonged coordinated turn under reduced visual references, fluid in canals stabilize →brain interprets this as being in stable wings-level attitude

    • When banking to level wings, vestibular apparatus are upset and brain interprets this as moving/LEANING into banked attitude in opposite direction (opposite turning illusion)

    • If succumb to illusion, will incorrectly compensate by rolling to what you BELIEVE to be wings level, but is actually original banked attitude →spiraling into ground

  • Coreolis Illusions

    • Misinterpretation of body orientation and induced nausea

    • Happens when head is moved in contrary/similar motion with body during spin

    • Most power + violent of sensory illusions

    • Causes sense of violent, rapid tumbling (spinning on office chair/merry-go-round)

  • Visual Illusions (refer to slide 10 of 408.02 for picture)

    • Our eyes pick up contradictory information, or when we expect to see one thing and our brain cannot accept what we actually see

Visual Scanning Techniques

  • Vision: primary sense for orientation, very accurate + real-time + gives us “picture” of our orientation that is extremely comprehensive

    • Orientation by vision is dependent on outside references we can see

    • Visible horizon for attitude control

    • Ground references to determine altitude, distance, and navigation

    • Obscuration of visual references can cause confusion and possibly disorientation

      • Smoke/haze/fog/cloud/precipitation

      • Lack of daylight/hard to see in dark

  • Glare: vision is primary sense of orientation in flight, we need to optimize our ability to see

    • Bright sunlight causes glare, can reduce visual acuity and cause pain (causes you to squint or look away), wear proper sunglasses to enhance visual acuity, enhance ability to see clouds, protect eyes from damage

    • Long-term unprotected exposure to bright sunlight can cause long-term damage to eyes and can cost you your medical certificate

  • Collision avoidance based entirely on principle of “see and be seen”

  • Spotting small aircraft can be very difficult task because you have to watch for other things besides just other aircraft

  • Empty Field Myopia: when you are just looking outside aircraft with nothing to focus on 

    • Eyes naturally/automatically focus to close distances and it’s difficult to see objects more than 1-2 miles away

  • Kinetic Response: if there is a small object moving, greater chance you will be able to see it if scanning large area

    • More likely to see an object when it’s relative to horizon/ground reference/giving off reflection

  • Expectancy: psychological effect →if you don’t expect to see another aircraft, your brain won’t register that it sees one even if your eyes see/sense it

  1. Organize your scan (left to right, up and down)

    1. Don’t be random

    2. Don’t rush

  2. Look at a block of sky

    1. Stop, focus on that area, then move to next section of sky

  3. Focus on areas of sky where aircraft would be greatest collision for you

    1. Slightly above and below horizon

Fatigue - loss of energy/strength/weariness

  • Acute

    • Acute Fatigue: short term fatigue, result of working hard/high stress levels/poor sleep the night before

      • Easily corrected by a good night's sleep, cat-napping can help, caffeine can also ease short term effects

  • Chronic

    • Chronic Fatigue: longer term fatigue, typically result of sleep deprivation over extended period

      • Can only be addressed through several consecutive nights of long, effective sleep

  • Effects of Fatigue

    • Disorganized thinking

    • Slower reactions, longer reaction time

    • Loss of situational awareness

    • Fixation

    • Falling asleep

  • Ways to combat fatigue

    • Maintain high level of physical fitness →less susceptible to effects of fatigue when you’re fit

    • Maintain healthy mental attitude →less susceptible to fatigue when you’re in a good mood

    • Maintain proper diet →proper hydration + nutrition will improve resistance to fatigue

    • Adequate rest →take regular breaks during the day

    • Adequate sleep (CRITICAL) →everyone needs regular sleep (adults = 7-8hrs, teenagers = 8-9hrs)

Situational Awareness

  • Definition: the perception of the environment within a volume of time and space, comprehension of their meaning, projection of their effect in the near future

  • Good situational awareness is critical to good decision making

    • Maintaining good situational awareness requires a lot of work by pilot →doesn’t just happen

    • Situational awareness is observing what’s going on round you and knowing how it may affect your flight

    • Sometimes referred to as maintaining your “Air Picture”

  • Three levels:

    • Perception: what you see and hear

    • Comprehension: you understand significance of a situation/circumstance to your flight

    • Projection: you think ahead and anticipate what effect it may have on you in near future

  • Geographical Situational Awareness: where you are in relation to airport, terrain, landmarks, etc

  • Spatial Situational Awareness: altitude, attitude, speed, VSI, flight path, etc

  • System Situational Awareness: status of aircraft and systems

  • Environmental Situational Awareness: weather, winds, etc

  • Operational Situational Awareness: other aircraft, other gliders, what’s happening

  • Factors that can result in loss of Situational Awareness:

    • Poor situational awareness management (look, listen, update)

    • Poor maintenance of priorities

    • Misdirected/fixated attention

    • Distraction by irrelevant stimuli

    • Low workload, complacency

    • High workload, task saturation

408.03 Aeromedical 3

Hypothermia/Hyperthermia

  • Hypothermia: lowering of core body temperatures caused by exposure to extremely cold temperatures/prolonged exposure to cold temperatures 

    • Typically associated with survival situations after forced landing in cold climate/ditching in cold water

    • Hazards include impaired physical + mental function, progressive organ failure, loss of consciousness, and death (eventually)

    • Initial Symptoms:

      • Sense of extreme cold

      • Pale, waxy skin

      • Fatigue

      • Uncontrollable, intense shivering

    • Advanced Symptoms:

      • Clumsiness

      • Apathy + mental confusion

      • Slowed respiratory rate

      • Loss of consciousness

    • Prevention:

      • Dress for weather and carry appropriate survival equipment if flying in remote/uninhabitable terrain

      • Dress in layers that are warm and will stay dry

      • Wear a toque and gloves

      • Seek shelter (out of wind and in an area to stay dry)

      • Build fire

  • Heat Injuries

    • Exposure to high temperatures/continuous sun exposure (will be exposed to every day on course

    • Steps: heat rash, sunburn, heat cramps, heat exhaustion, heat stroke (hyperthermia)

  • Hyperthermia: uncontrolled rise of core body temperature caused by exposure to high temperatures or prolonged exposure to hot sunlight conditions

    • Hazards: discomfort/pain, confusion, irrational behaviour, organ damage, possibly death

    • Hypothermia Symptoms: gradually develop over time



  • Heat Exhaustion

    • Muscle cramps (large muscles especially)

    • Headache

    • Muscle weakness

    • Nausea, vomiting, stomach cramps

    • Fainting

  • Heat Stroke

    • Body stops sweating to preserve remaining fluid

    • Hot + dry skin

    • Confusion, irrational behaviour

    • Convulsions/seizures

    • Loss of consciousness

  • Control Measures

    • Know symptoms and monitor

    • Keep an eye out for symptoms in others

    • Drink lots of water

    • Take periodic breaks out of sun

    • Watch urine output (should need to pee every couple of hours, urine should be pale yellow, dark yellow/amber pee is sign of significant dehydration)

Alcohol, Drugs, and Medication

  • Pilots who fly drunk suffer from variety of impairments

    • Impaired judgment

    • Impaired balance

    • Impaired coordination

    • Spatial disorientation

    • Increased reaction time

    • Channelized attention

    • Euphoria and false senses of performance

  • Shall not fly as crew member if:

    • Under influence of alcohol (tolerance for blood alcohol level is zero)

    • You’ve consumed any alcohol in previous 12hrs

  • Medications

    • Illegal to act as crew member when under influence of medication (prescription of over the counter) that may impair your flying abilities

  • General rules (medications and OTCs)

    • Watch out for medications ending in “...amine”

    • Never mix medications

    • Never mix medications with alcohol

    • If the bottle says “don’t operate heavy machinery” you shouldn’t be flying

    • “Non-Drowsy” formulations of OTCs are not necessarily acceptable, as they typically have the same depressive effect only mitigated through the use of caffeine

    • If you “self-medicate” with an OTC, don’t fly for 48hrs after you stop taking the medication

    • DON’T SELF-MEDICATE, check with your CAME

  • Immunizations

    • After receiving routine immunizations such as flu shots or tetanus shots, pilots should remain at the clinic for the amount of time recommended by health care provider

    • If pilot feels well and there is no evidence of an adverse reaction, they may resume flying immediately without restriction

      • If they feel unwell/experience adverse reaction, they should wait for 24hrs and be assessed by a health-care provider prior to flying

Anesthetics and Blood Donations

  • You are prohibited from flying for 24hrs after receiving a local anesthetic of any kind

  • Local Anesthetic: numbs local area (normally injection), commonly used by dentists, when getting stitches or minor surgery

  • General Anesthetic: puts you to sleep, typically only used for more complicated medical procedures 

    • After receiving general anesthetic, you are prohibited from flying until you are cleared to fly by your CAME or Flight Surgeon

  • Have to wait 48hrs after donating blood to fly

  • Blood Donations: puts you at higher risk for anemic hypoxia due to reduced blood volume (body regenerates blood volume quickly, within few hours) and reduced red blood cells

    • These are the components that carry oxygen in blood, regeneration of red blood cells by the body can take 24-48hrs

Effects of Smoking

  • Nicotine is inhaled into the lungs and absorbed into the blood, can have immediate adverse impact on your physiological performance in the cockpit

    • Reduced cardio-pulmonary efficiency, resulting in reduced oxygenation of body tissues (smoking/vaping any substance)

    • Increased risk for anemic + histotoxic hypoxia

    • Reduced visual acuity (especially at altitudes above 5000ft)

    • Significant impairment of your night vision

    • Smoking + vaping are also proven to have long term adverse effects on your health →increased risk of cardiovascular problems, heart attack, stroke, cancer

    • Consuming nicotine in any way will all have similar negative effects