2. Human Limitations
Estimate the noise intensity at which temporary and permanent hearing damage likely to occur.
85 dB average over a range of 8 hours and a peak of 140 dB
Describe how the three divisions of the ear function to detect sound.
OUTER EAR: Directs sound down the auditory panel and onto the eardrum. The sound waves cause the eardrum to vibrate. MIDDLES EAR: Transmits Vibrations from the eardrum by way of three small bones to the fluid of the inner ear. INNER EAR: The inner ear is filled with fluid. It has small hair-like cells which detect movement. Any movement is sent to the brain.
Describe the changes that take place as the intensity of light decreases.
The amount of light available affects the visual acuity of the eye. as light decreases so does the acuity of vision
Describe the performance of the ear when associated with the range of sounds that can be heard, particularly in respect to pitch (frequency) and volume.
The audible frequency range that a young person can hear is typically between 20 and 20000 cycles per second (or hertz)
Outline how the ear protects itself from high levels of noise and the limitations on this "self protection" in a hangar environment.
The middle ear has two muscles which helps protect the ear from sounds above 80 DB by means of acoustic or aural reflex reducing the noise level by up to 20 dB. This protection can only last up to 15 minutes. It also does not provide protection against sudden noises.
Explain the meaning of perception and give practical examples.
The organisation and interoperation of sensory data in order to make it meaningful, discarding non relevant information / assembling sensatation info and usable mental representation of words, ( e.g. the image formed on the retina is inverted and 2 dimensional yet we see the world the right way up) (
Describe the effects that advancing age has on hearing and indicate the signs that show hearing loss may be occurring.
hearing deteriorates naturally as one grows older. this affects the ability to hear high pitch first and may accure gradually from the 30's onwards
State the noise intensity level, above which, hearing protection is required.
hearing protection should always be used for noise, of any duration above 115 dB
Describe the adverse effects of each type of noise in respect of errors, variability and work rate.
high frequency noise has more adverse affects on performance than lower frequency noise. Noise increases error and variability rather than directly affecting the work rate.
Outline precautions that should be taken to avoid the onset of claustrophobia.
if an engineer suffers from an attack they should let the colluege and supervisors swear. work as a team / guid each other and take turns
Explain the importance of manuals and temporary aides-memoires in overcoming problems associated with memory.
if you don't write something down you will likely forget it, e.g. an engineer looking in the manual for torque values, thinks he remembers it then walks to the aircraft and forgets it. NEVER GO OFF MEMORY
Describe the causes and effects of noise-induced hearing loss.
short exposure to loud sound may cause temporary hearing loss. with longer exposure hearing will gradually decrease and become permanent. regular exposure to high levels of noise over a long period of time may lead to irreversible hearing damage
Explain situational awareness, the factors that lead to situational awareness and its importance in the course of an engineer's work activities.
situation awareness is understanding your environment and personal situation, and the ability to use this to make predictions of possible future situations. (1) the perception of important elements ( e.g. seeing a loose bolt or missing part, having information passed verbally (2) the comprehension of there meaning ( e.g. why is it like this ? is this how it should be ? (3) the projection of there status into the future ( e.g. future effects on safety, schedule, airworthiness
Identify the human senses that gather information for processing into decisions and actions.
smell, sensitation, sound, taste, sight
Distinguish between types of noise, such as: a. Sudden b. Continuous c. High frequency d. Low frequency
sudden noise is more disturbing than continues noise at the same level. high frequency noise generally is more adverse than lower frequency
Describe in a practical sense, how the condition of a person's hearing may be subjectively assessed.
the ability to hear an average conversation in a quiet room at a distance of 2m
Describe deficiencies that may arise if an engineer carries out inspection functions while at the same time fearing heights.
they are more worried about the height than the task at hand
Explain the importance of feedback during the decision making process.
this helps to improve knowledge and refine future judgement by learning from experiences
Outline how the fear of heights may be alleviated while working on the external surfaces of aircraft.
use safety harness and safety rope, this will not remove the fear but reassure the engineer allowing him to work on the task at hand
Identify measures that may be taken to reduce the feelings of discomfort when working in confined spaces.
work as a team / guid each other and take turns
Describe the reason why it is common for people over the age of 40 to require spectacles for reading and other close-up work.
A person over 40 will likely develop presbyopia which is a form of long sightedness. Consequently spectacles may be required to see close up objects especially in poor light conditions.
Explain the following factors relating to colour vision. a. The normal causes of defective color vision b. Colours that are affected by the common, and less common, types of colour-defective vision c. The colour of objects as seen by a person with color-defective vision d. The degrees of color-defective vision in relation to viewing objects in variable lighting conditions e. The effects of aging on colour vision
A. THE NORMAL CAUSES OF DEFECTIVE COLOR VISION: Normally Hereditary or temporary condition due to illness. B. COLOURS THAT ARE AFFECTED BY THE COMMON, AND LESS COMMON, TYPES OF COLOR-DEFECTIVE VISION: It is most common between red and green, or more rarely between yellow and blue. C. THE COLOUR OF OBJECTS AS SEEN BY A PERSON WITH COLOR-DEFECTIVE VISION: Color they have problems with are usually seen has a neutral gray. D. THE DEGREES OF COLOR-DEFECTIVE VISION IN RELATION TO VIEWING OBJECTS IN VARIABLE LIGHTING CONDITIONS: Some individuals may be able to distinguish between Red and Green. E. THE EFFECTS OF AGING ON COLOUR VISION: Aging can cause changes in the color vision particularly between Yellow and Blue.
Describe the importance of colour vision to the aircraft maintenance engineer and give examples of why good colour vision is required.
Although not directly affecting visual acuity, inability to see particular colours can be a problem for the aircraft maintenance engineer. Amongst other things, good colour vision for maintenance engineers is important for: - Recognising components; - Distinguishing between wires; - Using various diagnostic tools; - Recognising various lights on the airfield (e.g. warning lights).
Outline the importance of regular eye tests in identifying visual deterioration that may cause work-related problems.
It is important for an AME to have regular vision tests as an AME may not his vision deteriorating.
Outline how the eye functions to convert light into a perceived image in the brain.
Light enters the eye through the cornea, then passes through the iris and the lens and falls on the retina. Here the light stimulates the light-sensitive cells on the retina (rods and cones) and these pass small electrical impulses by way of the optic nerve to the visual cortex in the brain. Here, the electrical impulses are interpreted and an image is perceived.
Describe what is meant by the term "peripheral vision" and how this is achieved in the eye.
Peripheral vision is a part of vision that occurs outside the very centre of gaze. There is a broad set of non-central points in the field of view that is included in the notion of peripheral vision.
Explain the three processes associated with memory.
REGISTRATION = the input of information into memory STORAGE = the retention of information RETRIEVAL = the recovery of stored information
Outline how colour sensitivity is achieved.
The Cones are responsible for colour sensitivity.
Describe visual acuity and how it is measured and expressed.
Visual acuity is the ability of the eye to discriminate sharp detail at varying distances. An individual with an acuity of 20/20 vision should be able to see at 20 feet that which the so-called 'normal' person is capable of seeing at this range. It may be expressed in metres as 6/6 vision. The figures 20/40 mean that the observer can read at 20 feet what a 'normal' person can read at 40 feet.
Explain the meaning of "visual cues" and provide examples relating to the detailed inspection of objects.
Visual cues often refer to the comparison of objects of known size to unknown objects. An example of this is that we associate small objects with being further away. Similarly, if an object does not stand out well from its background (i.e. it has poor contrast with its surroundings), it is harder to distinguish its edges and hence its shape.
Describe how vision may be improved or impaired in respect of the following factors. a. The adverse effects of glare b. Moving from brightly lit to dimly lit areas c. Light adapted and dark adapted vision d. Eye focussing techniques for dimly lit areas e. The effects of airborne substances on vision f. Limitations and adverse effects of wearing contact lenses g. Eye protection requirements
a. The adverse effects of glare VISON IS REDUCED AS IT IS HARD TO FOCUS ON AN OBJECT b. Moving from brightly lit to dimly lit areas c. Light adapted and dark adapted vision d. Eye focussing techniques for dimly lit areas e. The effects of airborne substances on vision f. Limitations and adverse effects of wearing contact lenses g. Eye protection requirements
Describe physical factors that can affect the visual acuity of the eye, such as: a. long sight b. short sight c. cataracts d. migraine headaches e. tiredness and fatigue
a. long sight - Known as Hypermetropia. Blurred vision when looking at close objects. Caused by shorter than normal eyeball. b. short sight - Known as Myopia Blurred vision when looking at distant objects. Cause by longer than normal eyeball. c. cataracts - Clouding of the lens usually associated with ageing. d. migraine headaches - severe headaches that can cause visual disturbances. e. tiredness and fatigue - results in a less sharp vision
Outline the intensity levels of sound that certain aviation related activities may produce around an airport.
conversation at 2 metres = 20 décibels car at 15m = 70 propellor at 300m = 100 jet at 300m = 110 standing near propellor = 120 threshold of pain = 140 immediate hearing damage = 150
Explain the decision-making process.
decision making is the generation of alternative courses of action based on the available information, knowledge, prior experiences, context, goals, ect and selecting one preferred option. it is described as thinking, problem solving and judgement.
State the engineer's responsibilities for ensuring that they are properly protected from hearing damage.
it is the individuals responsibility
Explain "motor programmes" and where they may be in effect during the performance of aircraft maintenance.
when you repeat a task often enough it becomes automatic and the required skills and actions are stored in the long term memory, ( e.g. having a conversation while driving)
Illustrate how the following forms of attention may be applied to the functions an engineer may perform in the workplace. a. Selective attention b. Divided attention c. Focussed attention d. Sustained attention
(a) Selective attention = when a person is loitering several sources of information / input at once and is focusing on one while sampling others in the background (b) Divided attention = one task suffers at the expense of another when focusing on more than one thing (c) Focused attention = focused on one thing without distraction (d) Sustained attention = to maintain attention and alertness over a long period of time
Describe the limitations associated with information processing including the following. a. Attention and perception errors b. Missing data c. Filling in the gaps with erroneous information d. Visual illusions e. Contextual error f. Expectation error g. Fallibility of human memory (forgetting)
(a) attention and perception error = failing to perceive something which someone has said to you as you are concentrating on something else (b) missing data = to perceive something even though something is missing ( this is dangerous as each individual fills this information with there own store and could result in the wrong conclusion (c) same as above (d) visual illusion ( e.g. seeing one line longer than the other when in reality they are the same (e) it is important to know the context of the information you are processing, otherwise you could perceive the same thing quite different
Explain the following three forms of memory: a. Ultra short-term. b. Short-term. c. Long-term
(a) ultra short term memory has the duration of unto 2 seconds, used as a buffer, giving us time to attend the sensory input (b) short term memory stores info only long enough for us to use it. receives a proportion of information into the sensory stores (c) long term memory is unlimited, it is used to store information that is currently not being used ( e.g. personal experiences, problem solving skills ect)
Describe, with examples, internationally accepted requirements that place responsibility on employers to take action to mitigate the adverse effects of noise in the workplace.
1) 85 decibels (if normal speech cannot be heard at 2m) the employer must assess the risk to hearing damage, tell the employees of the risk and the precautions to take and provide their employees with personal ear protection. 2) 90 decibles (if normal hearing at 1m cannot be heard) the employee must do all that is possible to reduce exposure to noise other means than PPE and mark zones which are to loud and provide signs to restrict entry. 3) 140 noise will cause pain
Illustrate the various negative effects of noise in the workplace.
1) Be annoying 2) interfere with verbal communication between individuals 3) cause accidents by masking warning signals or messages 4) Be fatiguing and affect concentration 5) damage workers hearing
State the two functions that the ear performs and how each function is achieved.
1. Detects sounds by receiving vibration to the air 2. Detects balance and Acceleration
Describe the cause and symptoms of claustrophobia.
Defined as abnormal fear of being in a confined space, this may be because of an incident
Describe what is meant by a blind spot and how it occurs.
Blind spot occurs at the point where the optic nerve joins the back of the eye. The blind spot may result in something not being seen. Though this does not usually happen due to the rapid movement of the eye.
Describe "noise dose" and the parameters against which it is measured.
the combination of duration and intensity of noise. any sound over 85 dB constitutes a noise dose and can be measured over the day as an 8 hour time weighted average sound level (TWA)
Describe the importance of human senses as people interact with the environment.
the senses receive information about the environment
Describe memory and its importance when performing aircraft maintenance activities.
the storage and retention of information, experiences and knowledge as well as the ability to retrieve this information. without memory we could not draw on the past experiences and knowledge
Describe how certain drugs, medications, alcohol and smoking may adversely affect vision.
Allows carbon monoxide to build up in the blood stream which allows less oxygen to flow to the eyes. It IPAIRS THE SENSITIVITY OF THE RODS.
Describe the active listening process and how to achieve active listening.
Its a way of listening and responding which improves mutual understanding
Identify the "arc of accurate" vision when associated with performing an inspection function.
The "Arc of accurate vision" refers to humans having a bout a 20 degree arc of accurate vision.
Identify the frequency of sound at which the ear achieves its greatest sensitivity.
The greatest sensitivity is at about 3000 Hz
Describe "attention" as it may apply to functions performed by the maintenance engineer.
having detected information, our mental resources are concentrated on specific elements
