Human Factors and Pilot Performance Section 2. Seeing, Hearing and Fitness.

Human Factors and Pilot Performance

Section 2. Seeing, Hearing and Fitness


• Section 2. Seeing, Hearing and Fitness• 2.1 Seeing

• Eyes and Eyesight• Most important (but not only) sensory input to brain• Light is focussed on light sensitive cells at back of eyeball (retina) by lens.• Optic nerve carries signals to posterior lobe of brain where they are interpreted. (Thom

2.1)• Each eyeball can be rotated in socket by muscles, so eye can follow moving object even

when the head is also moving. • At rest (not looking at anything in particular) eyes are focussed on • infinity (in fact a point about 2 m away)• This is known as empty field myopia• Otherwise eyes are coordinated to focus on close or distant object (Thom 2.2).• This is Binocular Vision – gives a slightly different view of an object from each eye,

producing a 3D combined image.


• Structure of the eye (Thom 2-5)• • Cornea. Transparent protective outer covering of eyeball• Iris Coloured zone, acts like camera shutter – aperture in middle (pupil) becomes smaller in bright light and

vice versa.• Lens Focusses image on Retina. • The shape of the lens can be altered by ciliary muscles, changing its curvature and enabling the focussing of

images of near or far objects on the retina • This is known as Accomodation• Retina Layer of light sensitive cells round back of eyeball onto which visual image is projected. Cells are really

nerve endings of optic nerve.• Central part (Fovea) contains cone-shaped cells (cones) which are sensitive to colour, small details, distant

objects. Need good light intensity (daylight).• Lateral parts contain rods – sensitive to movement but not colour (black, white and grey) or detail. Effective in

high or low light intensity (even night).• Provides Peripheral Vision. • Blind spot. This is where optic nerve passes through retina• No light sensitive cells, so no image. • Since binocular vision gives slightly different view from each eye, unlikely that both images will fall on the blind

spot – so an image will still be projected (seen)


• Visual Acuity is the ability to see clearly and sharply. • Acuity is best when images are focussed precisely on the foveal

(cones) region of the retina• It is defined as how clearly each eye can see images of particular size at

6m. • The pilot standard is clear vision with both eyes at 6m or 6/6 vision.• 6/9 vision is where one eye can only see at 6m what the normal eye

can see clearly at 9m (Thom 2.7).


• Eyesight problems• General fitness important. Eyes are an extension of the brain so anything that affects the

brain may affect eyesight also e.g. • fatigue, alcohol, hypoxia. Excessive “g” loads may do it too – if it restricts the blood supply to

the head.• Medical conditions. • With perfect eyesight, images close to the eye or faraway are both focussed exactly on the retina by the

lens.• Myopia (shortsightedness) is when an image is focussed in front of the retina. A concave lens will correct

this. (Thom 2.31 – 2.33)• Hyperopia (hypermetropia) is the opposite - the image is focussed behind the retina. A convex lens will

correct this. (Thom 2.34- 2.35)• Presbyopia is longsightedness due to weakening of lens muscles with age (loss of accommodation).

Distant objects are clear, close ones are fuzzy. • Half glasses correct close-up vision (e.g. for reading), but eye can see over the • top so long vision is not affected.


• Eyesight medical conditions (cont)• Astigmatism is distortion of the image due to imperfect curvature of the cornea or

lens. A special lens that compensates for this is needed to make correction• Colour blindness is the inability to distinguish colours (reds and greens especially).

More frequent in men than women.

• Other optical (environmental) conditions • Glare occurs when the the light intensity is too much for eyes to cope with (pupil

cannot keep enough light out). Dark glasses are used to reduce light entering the eye• Flickering lights. (strobing). Due to light flashesreflecting from rotating props at

particular frequencies ( 8 – 20 Hz). This can cause acute discomfort and sometimes an epileptic fits. Wearing sunglasses reduces the sensation


Seeing while flying • Scanning. The foveal area is most sensitive to small and distant objects (area

of retina with cones). Should use this area when keeping lookout for other aircraft by day. Scan systematically (Thom 2.9). Remember to be very aware of other aircraft – especially if relative motion between you is small (likely collision course) (Thom 2.10).

• Adapting to darkness. Mainly use rods for night vision (peripheral vision more sensitive). Slower to adapt to light intensity changes than Cones. May need 30 mins to adapt to darkness – so no bright lights in the cockpit when flying at night.

• At night, more likely to spot movement (rods) so most likely to notice object looking 10-20 degrees to the left or right rather than right at it. Scan more slowly. Look for nav. lights to indicate relative orientation (Thom 2.11)


• Visual illusions• • On Approach • • Upsloping runway – plane may appear to be too high (Thom 2.23)• Downsloping runway - plane may appear to be too low (Thom 2.24) • Need to adjust flare in either case• Narrow and wide runways. Thom 2.25, 2.26. May give the impression of being closer (too high) or

further away (too low) than you really are • Haze . Plane may appear closer to the runway than it really is – liable to flare too high• • Others• • Autokinesis. Light against dark background can appear to move if focus on it long enough. Keep eyes

moving!• Pattern interpretation. e.g. Water on windscreen – runway appears closer than in reality (Thom

2.19)• False horizons (Thom 2.20,2.21)


2.2 Hearing and Balance

• Ears• Used for hearing (detection of sound i.e. pressure waves) and balance (detection of relative movement) • Structure (Thom 3.1)• • Outer ear• Auricle. Gathers sound• Outer canal. Conducts pressure waves• Eardrum. Pressure waves cause it to vibrate• • Middle Ear• Ossicles. 3 linked bones which amplify and pass on vibrations registered by the eardrum• Eustachian Tube. Keeps pressure in middle ear constant (i.e. at atmospheric pressure) – links to back of

nose/throat• When blocked (cold etc.) air is trapped in middle ear. • Special case of barotrauma – barotitis


• Ear structure (cont)

Inner Ear • Hearing• Cochlea. Mechanical energy of Ossicles sensed by hairs

Converted to electrical signals that are transmitted by auditory nerve to the brain

• Orientation and Balance

• Vestibular apparatus• Static organ and semicircular canals. • 3 semicircular canals mutually at right angles,

Contain fluid and small hairs, convert gravity and acceleration forces into electrical signals, interpreted by brain


• Sound. Two components• Frequency (wavelength) Measured in Hz. Normal range in humans 20 – 20,000 (speaking range is 500 -

3000 Hz)• Intensity (loudness). Measured in Decibels (dB). • This is a Logarithmic scale. 2dB is 10x louder than 1dB• • Typical sound levels (at a distance of 1-2m from source)

20 dB Whispering • 30 dB Quiet conversation• 40 dB Office conversation• 50 dB Factory with plant running• 60 dB Street noise with traffic• 80 dB Near heavy machinery (tractor, digger)*• 90 dB Maximum recommended average sound for 8 hr day*• 100 dB Maximum recommended for 2h exposure*• 110 dB Maximum recommended for ½h exposure*• 120 dB Near piston-engine plane. Noise uncomfortable*• 130 dB Near jet plane. Noise painful*


Damage to hearing . • Unwanted sound = Noise = other sounds that interfere with what you are trying to hear. Turn

up the volume?? Hearing Loss • The longer the exposure to Noise, the more likely you are to suffer damage to your hearing

(noise-induced hearing loss)Sudden very loud noises (e.g. explosions) may do this anyway ( burst eardrums, damaged ossicle connections)

• Poor conduction of sound (ear wax in outer ear, pressure problems in middle ear can lead to conductive hearing loss

• loss of sensitivity of hair cells in cochlea due to noise, infection can lead to sensory hearing loss

• Prebycusis. Gradual loss of ability to hear with age, especially higher frequencies (5% loss by age 60, 10% by age 70)


• Preventing/minimising hearing loss• may develop unnoticed (so be aware of this and always minimise noise as much as

possible• wear ear muffs in noisy environments (apron) • reduce background noise to minimum (squelch control on radio) or• use noise cancelling headset when flying (cockpit)• these procedures will reduce noise by 20 – 40%


• Balance • Balance organ (Semicircular canals and vestibular apparatus) sense

angular acceleration and direction (only - does not react to steady speed i.e. no acceleration).

• semicircular canals lie mutually at right angles, similar to roll, pitch and yaw axes in plane (Thom 3.2)

• they contain fluid and hairs set in jelly, each with nerve cell at base• when there is a change in acceleration or direction, fluids move, hairs

bend and electrical signals are sent to brain.• When change in acceleration/direction stops, fluid movement stops,

i.e. once established in a turn, (steady state) balance mechanism stable, turning motion no longer sensed (Thom 3.3)


• Gravity and Linear acceleration are sensed in similar way, but in the static organ at the base of the semicircular canals

• In central part (cupula) hairs protrude into jelly containing crystals (otoliths). When the head is up, hairs point straight up.

• When head tilts hairs bend and otoliths move under gravity to a new position which is sent as a signal to brain (Thom 3.4)

• Cupula only detects direction of g forces. Cannot tell difference between gravity pull or centripetal force (Thom 3.5) or force due to acceleration or deceleration SO

• once in a turn or reaction to a change of speed is complete, sense of “up” • returns to “normal” (Thom 3.5,3.6)


• This leads to a number of illusions (spatial disorientation, vestibular illusions):

• • level flight while in steady turn (Thom 3.7)• turning while wings level (“ the leans”) – levelling wings after being in a

steady turn. Plane is level, but feels like it is still in a banked turn (Thom 3.8)• Coriolis illusions – due to rotation out of normal\plane of rotation – keep

head upright at all times- confirm with eyes • Same with acceleration and g forces• Sense of ascending when making a turn ( 1 2g) (Thom 3.9)• Sense of descending after a turn (2g 1g)• Make be perceived as• Tumbling backwards (when strong linear acceleration(3.10))• Pitching forward (when strong linear deceleration (3.11)


MEDICAL CONDITIONS

• Vertigo • illusion of rotation (dizziness) • caused by disease or• acceleration that upsets balance of inner ear or sudden pressure changes in inner ear. • Most often caused by flashing lights (flicker vertigo) or following strong g loadings (steep turns, spins,

spiral dives)

• Motion sickness • Often caused by overstimulation of inner ear mechanisms and changes in orientation (acceleration,

g forces) due to• mismatch of what ears are sensing and eyes are seeing e.g. turns on fixed simulator when balance is

only saying straight and level flight• turbulence, steep turns, spins • made worse by worry/ fear • poor ventilation.


Avoiding/reducing chances of airsickness

• fly smoothly • minimise turbulence• avoid unusual manoeuvres• involve passenger in cockpit work (divert attention) • good cabin ventilation• land asap• always have sick bag handy

Human Factors and Pilot Performance• 2.3 FITNESS• • Get into habit of checking that you are able to handle the demands of a flight • prepare for it beforehand.• • What matters? - general health and physical fitness

-mental fitness • General Health• • Medical checks – regular medicals required for all pilots – eyesight, • Blood pressure and cardiac function, kidney function, hearing, respiratory • system etc • Check your medical cert is current• Illness must be reported to IAA (surgery, incapacitating illness lasting more than 10 days)• Colds,flu - upper respiratory tract problems - risk of barotraumas – DON’T FLY• Medication – can cause drowsiness• - Others have side effects that are dangerous for pilots• - List of banned drugs in JARs – brief list in Thom p 61.• Food poisoning – commonest cause of pilot incapacitation. Avoid ready to eat foods!

Human Factors and Pilot PerformanceMENTAL FITNESS • May be defined as the ability to think and react clearly (pilot performance) The following may reduce mental finess: • medication/drugs (including alcohol and tobacco)• stress • personal/family problems• lack of sleep• poor nutrition• fatigue/overtired (see below) Note:• Recreational drugs should never be taken when flying • alcohol Standard view is that the body metabolises one unit of

alcohol (glass of wine, ½ pint beer) per hour but for safety- after a small amount, no flying for 8 hours, - longer for larger amounts (maybe 24 – 30h or nore)• Smoking reduces the amount of oxygen carried in blood – hence pilots performance. So does carbon monoxide

(exhaust fumes)• Fatigue/tiredness/sleep deprivation. Pilot has to decide if he/she is up to flight (flying hours restrictions)• Personal problems/worry/stress. May interfere with sleep patterns, as well as distracting pilot’s attention.


Stress and stress management • Stress is caused by pressure overloads – too much to do or think about.

Can threaten health if excessive. Stressors can be acute – last short time – or chronic – long lasting • Stress management = how to deal with pressure – to stop pilot becoming overwhelmed by pressures which can then

interfere with normal activities (like flying the plane) • Small amount of pressure is good – stimulates good performance. Too much = poor performance. Positive factors for keeping stress down:• comfortable with job (lifestyle)• happy with personal life (lifestyle)• sufficiently rested (lifestyle)• good general aptitude for flight (training)• well prepared for flight (training)

• If OK with all of these, well set up to fly. Note: pressures/stressors are perceptions. May not be as serious as they seem. Example: Bang may be a slamming door OR may be an explosion


Physical stressFight or flight.

• Emotional reaction. Primitive reaction to life or death stress - adrenalin shot.

Prepares body for action.• Environmental – e.g. uncomfortable cabin conditions, vibration, turbulence, noise,

feeling unwell, eyestrain, flashing lights, mental strain, lack of sleep. Drain body of energy

Nonphysical stress • (intellectual, psychological, emotional) – eg time pressure, difficult decisions, doubting

own ability, row with partner, loss of relative, anxiety (see symptoms p75) • Arousal. Best performance depends on a moderate level of arousal – too little

or too much and performance suffers (Thom 5.1)


Stress - Be prepared for it! DO the following: • be completely at home with task• know you can do all of it

comfortably• leave all personal considerations at

home• tackle problems as they arise. Don’t

long finger!• talk through any problems with

someone else• Keep your balance – don’t imagine

the worst

DON’T do the following: • evade problems• take medications/drugs to

minimise symptoms• go into denial• make excuses• pretend to be ill• daydream• give up• get angry


Specifically as a pilot:• make timely decisions (don’t delay them)• don’t allow ATC to lead you into bad decisions (pilot responsibility)• keep mind on job – don’t be distracted (by ATC, passengers)• keep your normal routines going (FREDA checks, e.g.)• be prepared for delays (gethomeitis)• Do not press on regardless• (Thom Fig 5.2 – work load vs. pilot capacity) Always keep margin

between two


Fatigue Symptoms include:

• Lack of awareness• Diminished performance/slow reactions/easily distracted/more mistakes/poor instrument use• Drooping posture• Difficulty focussing• Short term memory lapses• Mood swings Sleep Sleep revitalises the body and brain. • 8 hours restful sleep prepares for 16h of activity• Comfortable bed in quiet dark room• Keep regular schedule• Good general fitness, avoid overtiredness• Try to switch off brain


• Sleep disorders – insomnia. Usually due to worries/brain not switching off

Stages of sleep – cycles • REM sleep rejuvenates brain – alcohol interferes• non-REM sleep ( 4 levels) rejuvenates body.

Human Factors and Pilot Performance Section 2. Seeing, Hearing and Fitness.

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Transcript of Human Factors and Pilot Performance Section 2. Seeing, Hearing and Fitness.