Colour Vision Flight Testing

Transcription

1 Colour Vision Flight Testing SAAsMA African Aerospace Medicine Conference 12 June 2014 Dr Kobus Kotzé Senior AME and Occupational Health Practitioner, Com Pilot 1

2 1. What is Colour and the Perception of Colour? 2. Types of Colour Deficiencies 3. Why is Colour important in Aviation? 4. Current ICAO rules 5. International Ruling on Pilots with Colour Deficiencies for Class I Medical 6. Colour Vision Screening and Diagnostic Testing in Pilots 7. Medical Practical Flight Testing to determine flight safety 8. South African Practical Medical Flight Test 9. Video 10.Discussion African Aerospace Medical Conference 12 June Dr Kobus Kotzé 2

3 What is Colour? African Aerospace Medical Conference 12 June Dr Kobus Kotzé 3

4 African Aerospace Medical Conference 12 June Dr Kobus Kotzé A representation of the retinal photoreceptor mosaic artificially colored to represent the relative proportions of L (red), M (green), and S (blue) cones in the human retina. Modeled after Williams et al. (1991) 4

5 Illustration of the spatial properties of color vision: (a) original image, (b) luminance information only, more spatial detail can be visually obtained from the luminance image than from the chromatic residual image. (c) chromatic information only, (d) reconstruction with full resolution luminance information combined with chromatic information sub-sampled by a factor of four produces no noticeable degradation in perceived resolution or color. Original motorcycles image from Kodak Photo Sampler PhotoCD African Aerospace Medical Conference 12 June Dr Kobus Kotzé 5

6 Are the colours that we see the real colours? An example of afterimages produced by local retinal adaptation during low light intensities since pupil dilatation could only explain light and dark adaptation over a 5 range of luminance's. Fixate the black spot in the colored pattern for about 30 seconds and then move your gaze to a uniform white area. Note the colors of the afterimages with respect to the original colors of the pattern. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 6

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8 Chromatic Adaptation Mechanisms 1. SENSORY: Kries coefficient of law How the cones respond to colour stimuli 2. COGNITIVE: Because of the difficulty in quantifying the cognitive interpretation of colour recognition it is better to quote a few people: i. Helmotz (1866): We learn to judge how such an object would look in white light, and since our interest lies entirely in the object color, we become unconscious of the sensations on which the judgment rests. ii. Hering (1920): All objects that are already known to us from experience, or that we regard as familiar by their color, we see through the spectacles of memory color. iii. Evans (1943):... in everyday life we are accustomed to thinking of most colors as not changing at all. This is in large part due to the tendency to remember colors rather than to look at them closely. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 8

9 TYPES OF COLOUR DEFICIENCIES Normal TRICHOMAT Red M F Protanopia Protanomaly Green M F Deutranopia Deutranomaly Blue M F Original birds image from Kodak Photo Sampler PhotoCD. Tritanopia Tritanomaly M F Total: African Aerospace Medical Conference 12 June Dr Kobus Kotzé 9

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11 1. ICAO Current Colour Vision Regulation 2. JAA The International Civil Aviation Organisation (ICAO) requires member nations to maintain a colour vision standard to ensure pilots can recognize correctly the colours of signal lights used in aviation: The applicant shall be required to demonstrate the ability to perceive readily those colours the perception of which is necessary for the safe performance of duties (ICAO, 2001b). Many ICAO member states have different requirements for colour vision assessment and employ different tests as the standard. In, Europe, there is agreement among the 38 members of the JAA to apply the same standard, at least in terms of primary tests. The current JAA colour vision requirements (Section 1; JAR-FCL 3, 2002) use the first 15 plates of the 24-plate version of the Ishihara plates as a screening test for colour vision with no errors as the pass criteria. If applicant fails then either a Lantern or Nagel anomaloscope test with no errors allowed. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 11

12 3. FAA Federal Aviation Administration guidelines are more liberal and the 15 approved primary tests include Ishihara, Dvorine, AOC-HRR, Richmond, etc. The pass limits are also more relaxed which favours some applicants with mild colour deficiency. Other tests include the Farnsworth Lantern, Keystone Orthoscope, etc. Unlimited attempts. Any pass allowed unrestricted licence. Failure of any screening test can then be followed by the more practical Signal Light Gun Test (SLGT) and MAP reading, usually carried out in an aircraft or on ground. Failure of SLGT Not valid for Night flying or under colour signal control. 4. CASA Visual Requirements Standard CASR Part 67 sub-regulation (6) and item 1.39 of table If the applicant should incorrectly identify more than two of the 24 Ishihara plates, a test on a Farnsworth lantern is needed to determine whether or not he or she meets the colour perception standard. Class 1 and class 2 applicants who are unable to pass either the Ishihara Plate Test or Farnsworth Lantern Test may be further assessed by means of Practical Signal Light Test. An applicant who fails to meet the colour perception standards above but who meets all other standards, is eligible for issue of an operationally restricted student pilot, private pilot or commercial pilot license to operate at night in a suitably radio-equipped aircraft. This dispensation applies to Australian airspace only. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 12

13 5. SA CAA [Current] The use of tinted lenses to obtain adequate colour perception is not permitted. Use the first 15 plates of the 24-plate version of the Ishihara plates as a screening test for colour vision with no errors as the pass criteria. Applicants who fail to obtain a satisfactory score in the Ishihara test may nevertheless be assessed as fit (Class II Safe) if the applicants are able to readily and correctly identify aviation coloured lights displayed by means of a recognised colour perception lantern. Class 1 and class 2 applicants who are unable to pass either the Ishihara Plate Test or Farnsworth Lantern Test may be further assessed by means of a Practical Medical Flight Test [PMFT] in accordance with Schedule 25 of the Colour Vision Protocol. Applicants who fail to obtain a satisfactory score in any of the above may nevertheless be assessed as fit (Class II Safe), provided the following criteria are met: a. Applicants with any abnormality of colour perception other than deuteranomaly shall be assessed as unfit; b. Applicants must undergo a practical flight test with an instructor designated by the Commissioner; c. A satisfactory report declaring that the applicant can safely identify all the aviation lights necessary for the safe performance of duties must be submitted; d. Applicants must submit a satisfactory report from an ophthalmologist declaring the applicant is deuteranomalous and have normal visual acuity ( 6/6), depth perception and peripheral vision. e. Must submit an annual ophthalmologist report to verify that there has been no change in vision standards. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 13

14 Applicants with any abnormality of colour perception other than deuteranomaly or a deuteranope that has failed the PMFT shall be assessed as Grade III colour-unsafe and unfit for a Class I medical. The licence will be endorsed with the following restrictions: i. For private pilot license privileges only ; ii. iii. iv. Not valid for flight in the vicinity of a controlled aerodrome (unless the aircraft is in radio contact with aerodrome control) ; Not valid for night flying, IFR flying or flying of EFIS equipped aircraft ; The applicant shall submit a satisfactory {visual acuity and peripheral vision} report from an ophthalmologist on an annual basis; African Aerospace Medical Conference 12 June Dr Kobus Kotzé 14

15 Schedule 25: Procedure for practical flight testing in colour vision deficiency Applicants who fail to obtain a satisfactory score in the Farnsworth lantern, Beyenne, Holme-Wright type A or Spectrolux colour perception lanterns, as the case may be, shall undergo a practical flight test with an instructor designated by the Commissioner in accordance with the following requirements: 1. The test may be conducted in a simulator or aircraft; 2. If conducted in a simulator, the simulator shall be of the same Class as the aircraft to be flown by the applicant; 3. All tests shall be conducted in an EFIS-equipped aircraft, or EFIS cockpit simulator; 4. The procedure and environmental requirements detailed below shall be approximated as far as is practicable in a simulator test; 5. The test shall be undertaken by two (2) instructors, one of whom shall be an instructor designated by the Commissioner for the assessment of applicants during a practical flight test for colour perception purposes; 6. An instructor designated by the Commissioner for the assessment of applicants during a practical flight test for colour perception purposes shall have normal colour vision; 7. The instructor designated by the Commissioner shall administer the test to the applicant, while the second instructor shall pilot the aircraft during the test; 8. The test shall be conducted at dusk; 9. The test shall be conducted in a small airfield with minimal lighting; 10. The instructors shall communicate with tower operators prior to undertaking the test; 11. On the ground, the applicant shall be requested to identify ground lights, taxi lights etc; The tower shall be requested to flash lights at the aircraft; 12. Red, Green and White lights shall be flashed by the tower in a random manner, and the applicant shall be requested to identify the lights as they are being flashed by the tower; 13. Lights shall be flashed a minimum of eighteen (18) times, and the applicant shall be requested to provide a correct answer within three (3) seconds of any light being flashed; African Aerospace Medical Conference 12 June Dr Kobus Kotzé 15

16 14. After take-off, the aircraft shall conduct low-level flying circuits at a maximum height of 3 miles for a minimum period of thirty (30) minutes while the tower continues to flash lights at the aircraft; 15. A minimum of eighteen (18) lights shall be identified by the applicant during this period; 16. The applicant shall also be requested to identify landscape features at this stage; 17. The instructor piloting the aircraft shall then fly to a pre-determined point and do a turn-around; 18. The tower shall be requested to flash lights at the aircraft; 19. Red, Green and White lights shall be flashed by the tower in a random manner, and the applicant shall be requested to identify the lights as they are being flashed by the tower; 20. Lights shall be flashed a minimum of eighteen (18) times, and the applicant shall be requested to provide a correct answer within three (3) seconds of any light being flashed; 21. After take-off, the aircraft shall conduct low-level flying circuits at a maximum height of 3 miles for a minimum period of thirty (30) minutes while the tower continues to flash lights at the aircraft; 22. A minimum of eighteen (18) lights shall be identified by the applicant during this period; 23. The applicant shall also be requested to identify landscape features at this stage; 24. The instructor piloting the aircraft shall then fly to a pre-determined point and do a turn-around; 25. At 13 miles from the final destination, the applicant shall be requested to identify the runway; 26. At 11 miles from the final destination, on a long and high final approach, the applicant shall be requested to identify the PAPI lights; 27. At 7 miles from the final destination, the applicant shall be requested to identify the runway lights; 28. At 5 miles from the final destination, with White PAPI lights, a rapid descent shall be undertaken, and the applicant shall be requested to identify the PAPI lights as they change colour; 29. At all stages during the flight and on the ground, the applicant shall be requested identify various colours and shades on the EFIS screen, and all difficulties shall be noted; 30. The test shall be a minimum of one and a half (1 ½) hour duration; 31. An applicant shall be deemed to have performed satisfactorily in the test if they are able to identify all the parameters they are being tested on. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 16

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18 Problem with current screening tests: 1. None of the current screening test screen for Yellow- Blue deficiencies unless specifically added or take a variance in Luminance into consideration. 2. Colour deficiency Severity cannot be accurately determined 3. 20% of Trichomats fail the 38 Plate Ishihara test if No errors are allowed due to non-typical errors e.g. digit confusion (5 6 or 3 8) 4. Current colour vision requirements vary from country to country. 5. The correlation between the outcomes of different tests is poor and therefore it is not uncommon for pilot applicants to fail the colour vision assessment in one country and to pass in another (Squire et al, 2005). The lack of standardisation often causes confusion amongst applicants and provides the opportunity to attempt several tests in order to pass one of the many colour vision standards. [Ishihara 24 vs 38 plates or other] 6. Ishihara plates are available commercially and are memorised by candidates to pass the initial screening test. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 18

19 A visual task analysis was carried out (UK CAA, 2006a) to identify and characterise the most important safety-critical, colour-related tasks for flight crew. The PAPI and the Parking Signal Lights were found to be the most safetycritical, colour-related tasks when no redundant information is available to carry out the task. PAPI Lights Parking Signal Lights Photograph of the red and green parking lights that are used at airports to indicate to the pilot the correct line of approach for parking the aircraft at the stand. The pilot sees two green lights when the aircraft is positioned correctly for approach. A red-green combination (as shown in the photograph) signals that the aircraft has to veer slowly right (towards the green light) whereas a green on the left and a red on the right signals the need to veer slightly to the left (again towards the green light). This task description illustrates clearly that the pilot has to be able to discriminate between the red and green lights. The angular subtense of the parking lights is much larger than the PAPI and the retinal illuminance generated is also higher. This colour discrimination task is therefore likely to be less demanding. African Aerospace Medical Conference 12 June Dr Kobus Kotzé 19

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