HUMAN PERFORMANCE AND LIMITATIONS I

1. HUMAN PERFORMANCE AND LIMITATIONS I

2. LECTURE ONE: EVERYTHING YOU NEED TO KNOW! 1. Basic Concepts 2. Hypoxia & Hyperventilation 3. Vision & the Eyes 4. Hearing & the Ears 5. Spatial Disorientation & Motion Sickness 6. Flying & Health 7. Information Processes 8. Central Decision Channel 9. Stress 10. Judgement & Decision Making

3. THE ATMOSPHERE: COMPOSITION 1% OTHER GASES (including water vapour) 21% OXYGEN Knowledge of the atmosphere is important to pilots and aircraft designers because it is the medium we fly in and the air we breathe! 78% NITROGEN

4. THE ATMOSPHERE: THE GAS LAWS BOYLE’S LAW ƥV = k For a given mass at a constant temperature, pressure multiplied by volume is a constant figure T denotes temperature V denotes volume K is a constant

5. THE ATMOSPHERE: THE GAS LAWS CHARLES’ LAW V = kT T denotes temperature V denotes volume K is a constant For a given mass at a constant temperature, volume is directly proportional to temperature

6. THE ATMOSPHERE: THE GAS LAWS COMBINED GAS LAW The pressure and volume of a gas are inversely proportional to each other but directly proportional to the temperature of that gas If pressure is increased, the volume will decrease and the temperature increases If pressure is decreased, the volume will increase and the temperature decreases

7. RESPIRATION – HOW WE BREATHE When we breathe in (INHALATION) the diaphragm moves downwards which increases the volume of the lungs. The pressure inside the lungs decreases and air is pulled in down the windpipe

8. RESPIRATION – HOW WE BREATHE The opposite occurs during EXHALATION (breathing out) The diaphragm moves upwards, decreasing the volume of the lungs, the pressure inside the lungs increases and air is expelled up the windpipe.

9. THE CIRCULATORY SYSTEM The CIRCULATORY SYSTEM transports blood around the body ARTERIES transport oxygenated blood from the heart to the tissues and organs VEINS transport de-oxygenated blood from the tissues and organs back to the heart

10. RESPIRATION – HOW WE BREATHE The oxygen in the lungs enters the bloodstream via CAPILLARIES through a process called diffusion where a high oxygen content tries to equalise with a lower oxygen content The oxygenated blood is then moved around the body via the CIRCULATORY system and the oxygen then enters the body tissues

11. PARTIAL PRESSURE PARTIAL PRESSURE is the measure of how readily DIFFUSION takes place With a gain in altitude, the partial pressure of air decreases. This means that diffusion does not take place so readily Therefore, although the percentage of oxygen stays the same with altitude, it is more difficult for the body to use

12. PARTIAL PRESSURE As anyone who has climbed a mountain recently will know, it is more difficult to breathe at higher altitudes! At 18,000 feet the partial pressure of oxygen is only 50% of that at sea level. At the summit of Everest (29,000 ft) it is only 30% Therefore, at 29,000 feet the driving force behind the lungs’ gas exchange is reduced to 30% of that we are used to Airliners are PRESSURISED to maintain an altitude of approximately 8,000 feet so that passengers and crew remain conscious!

13. PRACTICE QUESTION! “Which system moves blood around the body?” The Circulatory System

14. TIME OF USEFUL CONSCIOUSNESS The time of useful consciousness is the amount of time that a member of flight crew will be able to perform flying duties efficiently without an external oxygen supply In the event of no external oxygen being available or, in the case of an airliner, a depressurisation of the cabin, these times are how long all on board have before an unconscious state prevails The CAA recommend the use of an additional oxygen supply at altitudes above 10,000 feet

15. HYPOXIA Hypoxia occurs when the body does not receive an adequate supply of oxygen The body tissues, muscles and brain are starved of oxygen and cannot work properly In the aviation environment, Hypoxia is generally caused due to HIGH ALTITUDE (above 10,000 feet amsl) or CARBON MONOXIDE POISONING. It can be worse in people who smoke As pilot’s it is VITAL that we recognise the symptoms of hypoxia and how to deal with them

16. HYPOXIA: SYMPTOMS Hypoxic symptoms include: Rapid breathing Cyanosis (blue lips and nails) Poor co-ordination Rosy cheeks Poor judgement Muscle and mental fatigue Headache Dizziness Visual impairment Tingling Euphoria Seizures DEATH!

17. HYPOXIA: TREATMENT Oxygen must be increased either by the use of an oxygen mask or, in the case of flying, by reducing altitude as the first step If you are flying you need to descend immediately and land at the earliest opportunity If you suspect that you or any of your passengers have experienced hypoxia, it is recommended to get medical attention once on the ground again The best treatment is PREVENTION – always use oxygen above 10,000 feet and guard against carbon monoxide poisoning

18. CARBON MONOXIDE POISONING Carbon monoxide is produced when there is not enough oxygen to produce carbon dioxide during burning (such as in internal combustion engines operating in enclosed spaces) In aircraft, this can be made worse because the cabin air intake is usually from inside the cowling. Any small holes in the exhaust system may lead to CO entering the cabin CO is ODOURLESS, COLOURLESS and TASTELESS making it almost impossible to detect

19. CARBON MONOXIDE POISONING The body’s red blood cells have a greater affinity for carbon monoxide (CO) than for oxygen (O2) If CO is breathed in, the red blood cells will absorb it in preference to oxygen. This starves the body of O2 This leads to HYPOXIA

20. CARBON MONOXIDE POISONING Very small concentrations of CO can have an effect – you need to be vigilant of any symptoms and have the cause investigated Know the symptoms of hypoxia. In a light aircraft below 10,000 feet, hypoxic symptoms may be caused by carbon monoxide poisoning

21. CARBON MONOXIDE POISONING Remember that CO poisoning kills! Always check that there is a detector in your aircraft. “Dead Stop Detectors” are found in most aircraft but you can also buy electronic detectors that are designed for use in an aviation environment In a Cessna, ALWAYS select “Cabin Air” when selecting “Cabin Heat” as the heat comes from air being passed around the exhaust manifold If you suspect CO has entered the cabin: SHUT OFF cabin air and cabin heat selections OPEN all windows (no matter how cold it is!) LAND as soon as is practicable

22. PRACTICE QUESTION! “How is carbon monoxide most likely produced in an aircraft?” From the engine and then this is introduced into the cabin by use of a cabin heater which warms air via the air around the exhaust system

23. HYPERVENTILATION Hyperventilation or OVER-BREATHING is a state where breathing is faster and/or deeper than usual It is usually caused by panic or extreme nervousness but can be due to illness or brought about voluntarily Hyperventilation leads to an excess of oxygen in the blood which reduces the body’s cues to continue to breathe It may also raise the blood pH which constricts the blood vessels and inhibits the transport of oxygen to the brain

24. HYPERVENTILATION: SYMPTOMS Hyperventilation symptoms include: Rapid Breathing Cyanosis (blue lips and nails) Poor co-ordination Nervous laughter Panic Muscle and mental fatigue Headache Dizziness Visual impairment Tingling Do these symptoms look familiar?

25. PRACTICE QUESTION! “When operating below 10,000 feet you notice you are feeling dizzy and have tingling in your fingers and lips. What is likely to be the problem?” Hyperventilation (hypoxia is generally only above FL100)

26. VISION: THE EYE The eye is like a camera – taking in images and focussing them so that they are understood by the brain LIGHT enters the eye through the PUPIL and is focussed on the RETINA The information is then passed to the brain via the OPTIC NERVE The image received by the brain is upside down

27. HYPERVENTILATION: TREATMENT The classic remedy : ask the sufferer to breathe into a paper bag. This ensures CO2 is re-breathed, restoring the correct mixture in the lungs This method is now frowned upon medically as its effectiveness is limited and may be dangerous if the diagnosis is incorrect and the sufferer is actually having an asthma attack or even a heart attack and may induce panic rather than correcting for it! The only way to cure hyperventilation is to breathe calmly, slowly and not too deeply. If the patient continues to hyperventilate they will pass out, thereby restoring normal breathing. Let’s hope it’s not you as the pilot! If you do not know if it is hypoxia or hyperventilation, consider your altitude – if above 10,000 feet treat as hypoxia, if below 10,000 feet it is more likely to be hyperventilation but monitor the situation closely

28. VISION: THE EYE The human eye changes over time, tending to become more far-sighted with age as the lens gets harder and the muscles get weaker making changes of focus more difficult Eyesight tends to stabilise after the age of 25 until about the age of 40 when it will change Most eyesight defects can be corrected for with glasses or contact lenses (or with surgery)

29. PRACTICE QUESTION! “Which part of the eye is sensitive to light?” The retina

30. VISION: VISUAL DEFECTS - MYOPIA MYOPIA, or SHORT-SIGHT, is caused when the lens focuses the image in front of the retina It can be corrected by glasses or contact lenses which cause the image to be focussed correctly

31. VISION: VISUAL DEFECTS - HYPEROPIA HYPEROPIA, or LONG-SIGHT, is caused when the lens focuses the image behind the retina It can be corrected by glasses or contact lenses which cause the image to be focussed correctly

32. VISION: VISUAL DEFECTS - ASTIGMATISM With normal eyesight, the image is focussed on the retina where it can be transmitted as a clear picture via the optic nerve An eye with an astigmatism fails to focus the image completely leading to a blurred picture being transmitted

33. VISION: JAA MEDICAL REQUIREMENTS The initial JAA Class 2 medical eyesight standard is to be able to read a letter chart at 6 metres to a level of 6/6 (equivalent of “20/20 vision”) with both eyes and 6/12 with each individual eye with or without correction Near vision: to be able to read N5 print at 30-50cm and N14 print at 100cm with or without correction Correction of vision must not be greater than +5 to -8 dioptres and any astigmatism must not exceed 3 dioptres No double vision, no squints and “lazy eye” can be assessed for at the initial medical examination

34. VISION: NPPL MEDICAL REQUIREMENTS Based on DVLA driving vision standards Group 2 standard (professional) allows pilots to carry passengers whereas Group 1 standard (private driving) allows only for solo flying or flying with a safety pilot Group 1 “the ability to read in good light (with the aid of corrective lenses if necessary) a registration mark fixed to a vehicle containing letters and figures 79.4mm high at a distance of 20.5 metres” Group 2 visual acuity of at least 6/9 or better in the best eye and not worse than 6/12 in the poorer eye. Uncorrected acuity must be at least 3/60 and correction must be tolerated by the driver

35. COLOUR VISION Tested using standardised Ishihara Test plates If you fail this test you can chose to have a Colour Assessment and Diagnosis (CAD) test at a CAA approved location (at your cost) If you fail this test you can get a medical restricted to daytime flight only If you see an “8” on the right plate you have normal red-green vision. If you see a “3” you have a red-green visual problem

36. VISION: PROTECTION Most airline pilots and flying instructors wear sunglasses all year round and more frequently than the average person whether flying or not They aren’t posing! (well, some may be!) – sunglasses are an important piece of protective equipment and can protect your vision in the long-term Look for a good manufacturer (Ray Ban, Oakley, Randolph etc) with up to 80% absorption. Generally reactive glasses do not work well with some cockpit windshields Polarised lenses are fine but be careful with glass cockpits – you may find information disappearing at certain angles! If you are squinting at all, you should be wearing sunglasses!

37. VISION: LOOKOUT The human eye is not very good at picking out moving objects if it is moving For an effective lookout, we must stop our eyes for a few seconds before moving on You must scan the horizon as well as above and below it (remembering behind you once in a while as well!) “EMPTY FIELD MYOPIA” occurs when the eye has no distant object to focus on and it will rest at about 2 metres On a clear day, occasionally focus on the wingtips to “pull-out” your focus

38. VISION: LOOKOUT Lookout is very important, especially in the case of a head-on aircraft as closing speeds are at their highest The next slides illustrates the problem – even between two light aircraft Remember also that this has a place in the Controlled Flight into Terrain (CFIT) statistics as well…

39. VISION: LOOKOUT 0.05 nm / 1 seconds 0.5 nm / 7 seconds 0.25 nm / 4 seconds 0.12 nm / 2 seconds 1nm / 14 seconds

40. NIGHT VISION The RETINA has two types of receptors – RODS and CONES In daylight the CONES are used and feed the brain visual information in COLOUR At night, the RODS are used but have no colour information – this is why we see in black and white at night When trying to focus on something at night it may be necessary to look slightly to one side of it because the CONES concentrated at the centre of the retina aren’t working

41. NIGHT VISION When flying at night it is best to have the cockpit as dark as possible to reduce the contrast between inside and outside It takes 30-45 Minutes for your eyesight to adapt to darkness Some people achieve this “ACCOMMODATION” faster and some will take longer

42. NIGHT VISION When attempting to fly at night, it is best to avoid bright lights when adjusting to the darkness If when taxiing or flying a bright light is likely but you can’t close BOTH eyes it is best to close one – then you have vision but will keep night vision in one eye And yes! Eating carrots can help your night vision because they contain vitamin A which helps eyesight!

43. EARS: ANATOMY

44. EARS: BALANCE INFORMATION The SEMI-CIRCULAR CANALS provide us with our balance information Each canal has otoliths and lots of little tiny hairs which move when our head experiences any type of acceleration The three canals give us information on PITCH, ROLL and YAW which is handy as they are the three axes around which the aircraft also moves!

45. EARS: BALANCE INFORMATION If the aircraft yaws to the left, the hairs in the semi-circular canal for yaw will be pushed to the right by the acceleration and the information is fed to the brain by the vestibular nerve

46. EARS: HEARING The normal range for human hearing is between 20Hz and 20 kHz (20,000Hz) Usually a person’s hearing range will decrease with age, normally losing the higher frequencies first Hearing loss can also be caused by excessive noise – either constant or by one loud occurrence Normal conversation occurs at 60dB and will not cause damage, an idling bulldozer is 85dB and will cause damage after 8 hours. A gunshot or a jet engine (up to 190dB can cause instant damage)

47. EARS: HEARING

48. EARS: MEDICAL REQUIREMENTS For a JAA Class 2 medical you are expected to be able to hear a normal-volume conversational voice from 2 metres behind you with each ear separately For a JAA Class 1 medical, or if you wish to add an Instrument Rating to your PPL, you will need to take an audiogram to test for hearing at the 500, 1000, 2000 and 3000 hertz frequencies

49. EARS: PROTECTION Headsets are VITAL protective equipment for the pilot to protect our hearing It is recommended that you purchase the best headset you can for your budget Wycombe Air Centre recommends the use of noise cancelling headsets if you can afford them. If not, a good quality headset such as a David Clarke 10-13 is a robust and good alternative

50. SPATIAL DISORIENTATION Spatial disorientation occurs when the eyes and ears send the brain conflicting advice It can also occur because humans have a tendency to see what we expect to see, or what we are used to seeing Being aware that our brains can be easily fooled is the starting point to avoiding disorientation Let’s look at visual illusions first…