3. On 15 June 1988 the Civil Aviation Act 1988 came into force. It amended Schedule 1 to the AAT Act by omitting Part III. Although provision is included in the Civil Aviation Act for review by the Administrative Appeals Tribunal of decisions relating to air crew licences made under that Act, it is doubtful whether the transitional provisions extend to proceedings commenced under section 26 of the AAT Act, such as the application for review made by the applicant, before the Civil Aviation Act came into force. Consequently it was agreed by the parties that a new request under regulation 63 should be made to the Authority by the applicant for the grant of a licence not subject to a condition prohibiting night flying, that, if it were refused, a new application for review of that new decision would be made to the Administrative Appeals Tribunal under section 31(2) of the Civil Aviation Act, that the original application for review would be withdrawn but that the evidence adduced in the proceedings of the Tribunal in respect of that application should be treated as evidence in the proceedings on the new application. In the event a new application was lodged with the Tribunal on the last day of the hearing and the original application was withdrawn. Accordingly, the decision of the Tribunal relates to the new application.

4. At the hearing of the application the applicant was represented by Mr K. H. Bell, of Counsel, and the respondent by Mr P. N. Rose, of Counsel. A great many documents were tendered in evidence. A considerable number of witnesses gave evidence. Demonstrations were arranged so that we might better understand the nature of various types and degrees of defective colour vision and so that we could observe simulated flight in a Boeing 767 aircraft from the perspective of the pilot in the cockpit, including observation of the aircraft's instruments.

5. Regulation 63(1) of the Civil Aviation Regulations is as follows:-

"63. (1) Where:

(a) the Authority refuses to grant a licence to

which regulation 62 applies on the ground

only that the applicant for the grant of

the licence has failed to meet the medical

standards referred to in paragraph

62(2)(e); and

(b) the applicant, within 21 days after the

date on which he or she receives

notification of the refusal, makes a

written request to the Authority for the

grant of the licence under this regulation

and specifies therein the reasons why, in

his or her opinion, the grant of the

licence would not be likely to affect the

safety of air navigation;

the Authority may grant the licence to the applicant

subject to such conditions or limitations as the

Authority, having regard to the medical condition,

experience and ability of the applicant, considers

necessary in the interests of the safety of air

navigation."

Although the regulation does not expressly state any criteria to govern the exercise of the discretion vested in the Authority by it, the provision of paragraph (b) that the applicant is to state why the grant of the licence would not be likely to affect the safety of air navigation implicitly makes that the criterion.

6. In a number of cases the Tribunal has been required to consider the meaning of the phrase "which is likely to interfere with the safe operation of an aircraft" (see Re Waddy and Delegate of the Secretary, Department of Transport (1978) 1 ALN N3 and Re Chryssanthou and Department of Aviation (1985) 7 ALD 534). The Tribunal noted in those cases that the word "likely" is capable of bearing a broad range of meanings from, at one end of the scale, more probable than not, to, at the other end, less than probable but more than a mere fanciful possibility. In the same way, we are satisfied, the expression "not be likely to" is capable of bearing a wide range of meanings. It may mean that it is simply less than probable or that it almost certainly will not. The context in which the expression is used in regulation 63 requires that the expression bear a meaning at the latter end of the scale. The provisions of Part V of the Civil Aviation Regulations are clearly intended to ensure that aircraft are not flown by persons who, because of incompetence or a physical or mental condition, pose any significant and unacceptable risk to public safety. We are satisfied that in these proceedings the decision under review has to be affirmed if we find that a pilot with defective colour vision piloting an aircraft at night poses any significant and unacceptable risk to the safety of the public; we should set it aside only if we find that he will not pose any significant and unacceptable risk to the safety of the public. In deciding whether or not a risk is unacceptable, we must have regard to any risks which particular provisions of the medical standards show are regarded as acceptable (see Re Chryssanthou (supra)).

7. In these proceedings we are concerned principally with whether, although the applicant has not met the colour vision standard, a licence should be granted to him which is not subject to the condition totally prohibiting him from piloting an aircraft at night which is currently considered by the Authority to be necessary in the interests of safety of air navigation. However, we must also consider whether any other conditions or limitations should be imposed either instead of or in addition to that condition.

8. The Tribunal has no power to review any decision of the Authority to make or vary Air Navigation Orders notifying medical standards. Nevertheless, in order to decide the issues in these proceedings, it is necessary for us to consider why the colour vision standard has been set, whether the safe navigation of aircraft depends generally on pilots meeting that standard and, if it does, whether there are particular circumstances in which it does not depend on that. In October 1987 we carried out a review of a similar decision that had been made in respect of Dr A. M. Pape, but only in respect of his private pilot licence. We understand that there are a considerable number of other pilots with defective colour vision who have requested the granting of licences which do not contain a condition prohibiting their piloting aircraft at night. For that reason the respondent indicated that it wished to conduct this case as a test case. Mr Rose, therefore, informed the Tribunal that the respondent intended to present its case in a manner which would encompass not only the applicant's situation but also broader issues relating generally to defective colour vision. At the request of the respondent the Attorney-General granted legal aid to the applicant to ensure that he was not disadvantaged by the respondent presenting his case in that manner. The matters which we have to consider in these proceedings have consequently been extended well beyond those which the applicant originally sought to raise, that is to say whether his defective colour vision made it unsafe for him personally to pilot an aircraft at night. The proceedings have taken 28 hearing days. In order to reach conclusions on those matters raised it is necessary for us to address a number of questions. Because of the amount of evidence given we cannot set all of it out in detail; however, we have taken the whole of it into account in making our decision and in expressing conclusions on the various matters raised for our consideration.

9. Australia, as a party to the Chicago Convention on Civil Aviation, is required to set medical standards for air crew. In respect of colour vision the standard must be such as to ensure that a pilot has the ability to distinguish readily those colours used in aviation the perception of which is necessary for the safe performance of his duties. Implicit in that requirement is a presumption that some type or degree of defective colour vision may on its own impair the ability of some pilots to perform those functions safely. The requirement and the reasons for it are not expressed in any more detail. The questions which have to be addressed in these proceedings, therefore, include the fundamental one why, if at all, a pilot's defective colour vision may, either at all times or at some time, impair his ability to pilot an aircraft safely. It is convenient to break down that question into a number of subsidiary questions. Only when that fundamental question has been answered and the type and degree of the applicant's colour vision defect has been ascertained is it possible to address the question whether a licence to pilot an aircraft can be granted to him and, if so, to what conditions and limitations it should be subject.

10. The following are the questions which we consider have to be addressed. The final question must be answered strictly in terms of the applicant. However, as these proceedings have been conducted as a test case, we shall try to answer all the questions in as full and broad a manner as possible.

1. What is the nature of the following types of

defective colour vision -

(a) protanopia and protanomaly,

(b) deuteranopia and deuteranomaly,

(c) tritanopia and tritanomaly,

(d) other?

2. How is colour used -

(a) outside aircraft,

(b) in the cockpit of an aircraft,

relevantly to the safe piloting of an aircraft?

3. Does defective colour vision of any type or

degree make it unsafe for a person to pilot an

aircraft -

(a) at night,

(b) by day,

so that there is a significant and unacceptable

risk to the safety of the public?

If so, why?

4. If an unacceptable risk is found to exist, can

the risk be eliminated, or reduced to an acceptable

level, by the imposition of conditions or limitations

on the pilot's licence?

5. Are the answers to any of questions 2, 3 and 4

different depending on whether the aircraft is fixed

wing or rotary wing?

The witnesses fell into four classes but with some

(1) Witnesses who gave evidence relating to the

validity of demonstrations, by use of specially

adapted television receivers, of colours as seen

by persons with defective colour vision. The

principal witnesses in this class were Dr B. A.

J. Clark, who had devised the system of

adaptation of the television receivers, and Dr P.

R. Flanagan. Useful observations relating to

what was demonstrated by the adapted television

receivers to what a deuteranope actually saw were

made by Dr A. M. Pape, who is a deuteranope.

(2) Witness who gave expert evidence relating to

the practical effects of defective colour vision,

particularly in respect of flying an aircraft.

They included optometrists, an ophthalmologist

and psychologists. The principal witnesses in

this class were Professor B. L. Cole, Dr A. J.

Vingrys, Dr W.A. Macdonald, Dr M. V. Samuel,

Professor T. J. Triggs and Professor B. U.

Crassini.

(3) Witnesses who gave evidence of their practical

experience as pilots, particularly in relation to

the role played by colour in assisting a pilot to

fly an aircraft safely.

(4) Witnesses who gave an overview of the expert

evidence, setting it in the context of the

obligation imposed on Australia, as a result of

its being a party to the International Convention

on Civil Aviation, to set a standard of colour

vision which persons must attain before being

granted a licence to pilot aircraft. The

principal witnesses in this class were Dr A. B.

Zentner and Dr A. M. Pape.

11. Before discussing the contentious parts of the evidence, it is desirable that we set out some facts regarding which there was broad agreement among the witnesses expert in the nature of defective colour vision.

12. Within the retina of the human eye there are nerve end cells, usually referred to as cones, which are sensitive to colour. The cones are situated in the very centre of the retina. They "pick up" colour, that is to say colours are stimuli to which they react, in objects at which the person is looking directly. Away from the centre of the retina there are also nerve end cells, usually referred to as rods, which are stimulated by light but appear to be almost insensitive to colour.

13. Colour is dependent on the wavelength of light; each different colour and each different shade of colour has a different wavelength. That can be readily displayed by means of a chromaticity chart. The chart discloses a shape roughly triangular in form with three primary colours, deep red, deep green and deep blue, in the respective corners; within the triangle are all the different colours and shades of colour. Each colour and shade of colour is either one of those primary colours or a combination of them. In the retina of a human with normal colour vision there are cones of three types. Each type is sensitive principally to one of the primary colours; for that reason persons with normal colour vision are referred to as trichromats. Where a person has defective colour vision, his cones either totally lack sensitivity to one or more of the primary colours or are not fully sensitive to one of those colours. A person whose cones totally lack sensitivity to one of the primary colours, that is to say who has sensitivity to only two of the primary colours, is referred to as a dichromat. A person whose cones totally lack sensitivity to two of the primary colours, that is to say who has sensitivity to only one of the primary colours, is referred to as a monochromat. A person who has cones which are not fully sensitive to one primary colour is described as an anomalous trichromat.

14. Where a dichromat lacks cones sensitive to red, he is referred to as a protanope. Deuteranopes and tritanopes are those dichromats who lack, respectively, cones sensitive to green and blue. Anomalous trichromats who have cones not fully sensitive to red are referred to as protanomals. Those with cones not fully sensitive to green and blue are respectively referred to as deuteranomals and tritanomals. A person is described as suffering from mild, moderate or severe protanomaly, deuteranomaly or tritanomaly depending on how nearly his cones are to being, at one end of the scale, fully sensitive and, at the other, totally insensitive to the particular primary colour. Protanopes and protanomals are referred to compendiously as protans; deuteranopes and deuteranomals, and tritanopes and tritanomals, are likewise referred to as deutans and tritans respectively.

15. The perception of colour is not by the retina but by the brain through the medium of the retina and the nerves leading from it to the brain. At some stage in the process of perceiving colour the stimuli received by the cones from light of varying wavelengths are combined to produce perception of colour of a particular wavelength. It is impossible to be sure that all persons with normal colour vision perceive identically colour of the same wavelength; but the perception of each from time to time is generally consistent, so that what is perceived each time is colour of that wavelength. In persons with defective colour vision the effect of the absence or the reduced sensitivity of cones of a particular type leads to the combination of the stimuli resulting in perception of colour of a wavelength different from that perceived by persons with normal colour. However, as in persons with normal colour vision, the colour perceived by any person as the result of the combination of particular stimuli of the cones alone is generally consistent. That generalisation is subject to the qualifications that perception of colour may be temporarily affected by such factors as hypoxia, which usually occurs at altitudes of over about 10,000 ft, or by bright light or striking images seen shortly before. There is also some divergence of views in respect of instability of colour vision in those suffering from severe deuteranomaly, a matter which we discuss in some detail later in this statement. Further, where colour stimuli are received in large quantities from a bright light source, the colour perceived approaches to a greater or lesser extent that seen by a person with normal colour vision. The mechanism of this is not entirely clear. Possible explanations are that in that situation some cones respond to stimuli other than those to which they are principally sensitive, or that the rods have some minimal colour sensitivity.

16. Not only do persons with defective colour vision perceive the wavelength of colours differently from persons with normal colour vision, but also there are zones of wavelengths of colour, 27 in the case of deuteranopes and 16 in the case of protanopes, within which the colours, although of different wavelengths, are all seen as the same. They are commonly referred to as confusion zones. Such persons will usually confuse colours whose wavelengths lie within the same confusion zone. In the case of both protans and deutans the confusion zones run in the shape of a fan from the red segment of the chromaticity chart to the blue/green boundary.

17. Among the documents included in those lodged with the Tribunal pursuant to section 37 of the AAT Act there were the records of the applicant's Farnsworth lantern tests. We noted, as we had done in Re Pape and Secretary, Department of Aviation (Decision No. 3821: 9 October 1987) in respect of Dr Pape, that he had made very few errors of identification of red lights. Most of his errors showed confusion of green and white lights with one another. When Dr Vingrys gave evidence, this aspect of the results of the tests was put to him. He accepted that, in the case of deutans, the main problem was confusion of green and white lights and that generally their identification of red lights was considerably better. We did not receive any evidence whether in the case of protans there was a similar greater confusion of certain colours than of others. So far as deutans are concerned, the nature of the confusion is of some significance in relation to the safe flying of an aircraft.

18. Light, whether direct or reflected from the surface of any object, comprises colour, i.e. wavelength, and intensity, i.e. energy. Although a deutan or a tritan may perceive incorrectly the wavelength of the colour of any light, his perception of its intensity is practically the same as that of a person with normal colour vision. That means, in effect, that he sees lights of the same intensity from the same distance. Except for red lights, a protan similarly perceives the intensity of any light as practically the same as that perceived by a person with normal colour vision. However, it is generally accepted by optometrists and ophthalmologists that the intensity of a red light perceived by a protan is considerably reduced. This is a matter of considerable significance in relation to the ability of pilots who are protans to become aware of the existence of red obstruction lights. Nevertheless, we received evidence from Dr Samuel which cast doubt on whether all protanomals suffer that reduction. At present the colour vision standard in ANO 47.3 cannot be attained by any protan. As a matter of policy, when protans are granted pilot licences pursuant to regulation 63, a condition is imposed prohibiting them from piloting an aircraft at night. We discuss the question of reduced perception of intensity of red light by protans, and its consequences, at length later in this statement.

Simulation of Defective Colour Vision by TV Receivers

19. At the commencement of the proceedings Mr Rose informed the Tribunal that at the respondent's request Dr Clark had undertaken research to try to demonstrate visually to persons with normal colour vision the colours perceived by persons with defective colour vision. He referred to those colours, when contrasted with those perceived by persons with normal colour vision, as degraded. It should, we consider, be made clear that we understand that as describing the smaller number of colours perceived and the reduction in the perceived dissimilarity of colours within the same or adjacent colour zones.

20. Dr Clark is the group leader of the Human Factors Group in the Aircraft Systems Division of the Commonwealth's Aeronautical Research Laboratories. He holds a Diploma of Mechanical Engineering, and the degrees of B.Sc. in Physics, and of Master of Applied Science and Ph.D. in Physiological Optics. He obtained his degrees at Melbourne University, the Ph.D. in 1971. At various times he has been a Member of the Victorian College of Optometry, a Member of the Australian Optical Society and a Member of the Colour Society of Australia. He gave evidence that he had published about 100 scientific publications, several of them in areas involving colour vision. He said that the main function of the Human Factors Group was to provide technological and scientific assistance to the Australian Defence Forces, particularly in the field of the interaction between air crew and aircraft. In carrying out that work he had studied the role of colour in aviation.

21. In response to the respondent's request referred to above, Dr Clark adapted two commercial colour television receivers so that they could be adjusted to demonstrate approximately what persons with defective colour vision perceived. He pointed out that, just as the basis of colour vision in the human being was, in effect, three colour receptive systems, with the signals received in each of them combined in an appropriate way by the brain to produce a sensation of colour, so colour displayed by colour television receivers was the result of three separate colour signals being received by the sensors in the receiver and being combined so as to present coloured images on the screen. He said that that process mimicked to some extent the process which went on in the human visual system. The manner in which he adapted the television receivers to simulate defective colour vision was to reduce or eliminate the signals received by the red or the green sensors. In making the adaptations he utilized the knowledge of the confusion zones in order to mix the colours in such a way as to simulate the colours seen by protans and deutans. In order to simulate the colour vision of a protanope he removed the red signal entirely. In order to simulate the colour vision of a deuteranope he reduced the green signal and combined the channels of the red and green signals. By adjusting the amount of the red and green signals respectively which were removed, he was able to simulate the colour vision of protanomals and deuteranomals.

22. However, he acknowledged that the simulation was not perfect. There were a number of reasons for that. First, the colours on the outer part of the chromaticity chart of colours seen by persons with normal colour vision were not reproduced properly by colour television receivers; the colour frequency range of the phosphors of a television set was considerably more limited than the colour frequency range of the detectors in the human eye. There was also a degree of overlap in perception of the three primary colours by the detectors in the human eye which was not present in the phosphors of the colour television set. That was partly because of the shape of the spectral pigments in the retina of the human eye; but also a good deal of processing of the perception of colour took place in the higher visual pathways between the retina and the visual centre of the occipital area of the brain. Consequently, the way that the human visual system responded to colour was not solely determined by the photo pigments in the cones of the retina. Nevertheless, he demonstrated by diagrams relating to the television protanope and the television deuteranope that the colour mixtures lay along straight lines on the chromaticity chart radiating from the deep red sector. He said that the consistency of the whole system which he had devised was demonstrated by the fact that the points which had been plotted in respect of various colour mixtures lay on those straight lines. Further, he had carried out computer checks to show that his calculations were correct. He stressed, therefore, that the system which he had devised was as accurate as the limitations imposed by the equipment permitted and described it as "an aid to understanding what is going on for anybody who is interested in wishing to know and provided that they have normal colour vision".

23. That evaluation of the system was expressed also by Dr Vingrys and Professor Cole. They considered that the colours displayed by the adapted television receivers could not be taken to be precisely what was seen by a person with colour defective vision but they believed that it gave a very fair idea of what was seen by such persons.

24. Dr Pape, who is a deuteranope, was shown the television receivers displaying on their screens the series of vertical columns of colour transmitted by television stations to enable viewers to adjust their sets. He was able to distinguish the colours as displayed when the sets were in the colour normal mode. Although the width of the vertical columns was not measured, it was almost certainly in excess of two centimetres. That demonstrated, we consider, the situation where colour, because of its size and brightness, is perceived through the retina by some mechanism, as referred to above.

25. Dr Pape was then asked to compare the colours displayed by one television set in the deuteranope mode with those displayed simultaneously by the other in the colour normal mode. He gave evidence that the decrease in the luminance of the colours was excessive, so that they did not appear to him as he would see the colours normally. He pointed out also that, when the television receiver was adapted to show colours as they would be seen by a protanope, red appeared as black. He said that in real life a protanope saw a red light as a fairly dark light but not as black. He acknowledged that Dr Clark's "idea had some merit" but pointed out that the colours displayed by a normal television receiver, although acceptable for entertainment purposes, were not in fact as perceived in real life by human beings with normal colour vision. The screen of a television receiver had only some thousands of pixels, whereas in the eye there were millions. Consequently, human vision could not be replicated through a display on a television receiver.

26. In order that the parties might be able to decide how to present their respective cases, the Tribunal was asked to state its conclusions with regard to the validity and value of the demonstration of colour defective vision by Dr Clark's adapted television receivers. We stated our conclusions on 25 November 1988 and now repeat what they were. We regard Dr Clark's experiment as valuable in giving a broad impression of the nature of the degradation of the perception of colour by protans and deutans; but it is clear that what is displayed on the adapted television screen is not exactly what a colour defective person actually perceives. Possibly, in the future a television receiver will be manufactured expressly for the purpose of replicating the colours seen by colour defective persons, although the replication will never be perfect because of the nature of the phosphors and the process of mixing them on a television screen, which is far less complex than even the retina of the human eye and cannot reproduce the processing which occurs in the higher visual pathways between the retina and the visual centre of the brain. At present the nature of the television phosphor, the limitation of the colour frequency range of a television receiver and the inaccuracies which arise in the multiple processing between the taking of a picture with a video camera and the display of the result on the television screen in combination have the effect that what is displayed by the adapted television receiver is only a broad approximation of what is seen by a colour defective person.

27. We were shown films taken from aircraft at night by a video camera; they were displayed on the screens of the television receivers. The films were taken in the Melbourne area. On the first occasion the film was taken by Dr Clark himself. He is not a professional cinematograph cameraman and the quality was not satisfactory. The second film was taken by a professional cine-photographer and was of very good quality. It was shown simultaneously on one television set in the colour normal mode and on the other in a colour defective mode. It was shown several times with the second set in various different colour defective modes, ranging from mild protanomaly to protanope and from mild deuteranomaly to deuteranope. Dr Clark told us what features had been filmed. As was to be expected, red and green lights shown on the set in the colour normal mode appeared degraded on the set in the colour defective mode, in the same way as when the columns of colours had been shown.

28. We noticed that what we perceived was only what the camera at any particular point in time was focused on. There was no peripheral vision; that was significant, because motion is the prime stimulus to perception in the periphery of the human eye. At night, as the iris of the eye is larger because of the darkness there is greater peripheral vision than in the day time. Furthermore, the direction of the eyes can be changed much more quickly than that of a video camera; even when concentrating on taking-off or landing, a pilot has to scan round constantly. Consequently, what was filmed by the video camera and displayed on the television screen was not all that a human being would have perceived in a similar situation. That was a matter of significance independent of the question whether the colour displayed was what would have been seen by a person on the aircraft with defective colour vision. In summary, therefore, we were of the view that the demonstration was extremely valuable insofar as it gave a broad impression of the nature of the colour degradation concerned; but that was the full extent of its value as a display of what a pilot with defective colour vision sees at night.

29. It was generally agreed by the parties, and we accept, that during day time the visual cues available outside the aircraft are so many and varied that correct perception of colour plays an insignificant role in the safe flying of an aircraft. At night, however, particularly on dark nights, the only cues outside the aircraft are often lights, which are of various colours and in some circumstances grouped in various shapes. The lights normally displayed on aircraft are the red, green and white navigation lights in prescribed positions, a white strobe light or a red rotating beacon or both. Obstruction lights are generally red, although a bright flashing white light may be used. However, although red lights are displayed on many obstructions, not all obstructions are so marked. Further, the display of red lights on the ground or on structures for other purposes than as warning lights is not generally prohibited. Instances of such red lights are rear lights on motor vehicles, traffic lights, red lights outside doctors' surgeries, decorative lights on buildings and advertising signs.

30. On an aerodrome signal lights may be displayed from the control tower to convey instructions from air traffic control to pilots. The runways are marked by white lights on each side of each runway; the thresholds of the runways are marked by green lights at the commencement of the runway and by a single line of either red or green lights at the end of the runway and at right angles to it; a taxiway is marked either by a line of blue lights on either side of it or by a single line of green lights running down the centre of it; holding points where aircraft must s before going onto or across a runway are marked with a line of amber lights at right angles across the taxiway. At some airports there is a line of lights along the centre of the runway; as the end of the runway is approached the lights grade from white to red to indicate that fact. At many aerodromes VASIS lights are displayed. They are situated on the ground beside the runway at the optimum touch-down point. They indicate to a pilot whether during the approach for landing his aircraft is maintaining the optimum approach slope. There are two types in use in Australasia, the T-VASIS and the Red/White VASIS. In Australia the T-VASIS is in use at present. It uses shape, in the form of a horizontal bar of white lights which changes to an upright or inverted T-shape depending on whether the aircraft is below or above the optimum slope. If the aircraft deviates dangerously below the optimum slope, the lights forming the upright T-shape turn red. The Red/White VASIS, which is used in New Zealand and some other countries in the Pacific region, consists of two pairs of wing-bars, positioned at approximately 200 metres and 400 metres from the threshold of the runway. Each of the light units projects a controlled beam of light towards the approaching aircraft. The lower portion of the beam is red and the upper portion white. When the aircraft is maintaining the optimum approach slope, the closer pair of wing-bars show a white light while the further pair show a red light. If the aircraft is below the optimum slope, the pilot sees both pairs of wing-bars as red. If it is above the optimum slope, both pairs show as white. A pink transition zone is produced by the merging of the edges of the red and white light boundaries from each of the wing-bars, where the aircraft is slightly too high or slightly too low. At larger airports the immediate approach to a runway may be marked by a distinctive pattern of lights on the ground under the approach path.

31. Signal lights are rarely used now because of the reliability of communication between air traffic control and pilots. They are used only where radio communication cannot be maintained. We consider that the possibility that a pilot with defective colour vision may not be able to identify signal lights is not a reason for prohibiting him from flying by night. If it were, it would be an even stronger reason for prohibiting him from flying by day as the colours of the signals are of lower contrast. Such a restriction has never been imposed and we consider it unnecessary. However, it is our view that he must be required to have on the aircraft adequate reliable radio equipment to ensure that, when the aircraft is in the vicinity of an aerodrome or landing, he will be able to maintain radio communication with air traffic control.

32. Over recent years the Department has provided funds for research into the use that can be made by a pilot of coloured lights displayed outside his aircraft. Initially, the research related to the information to be derived from perception of the air navigation lights of other aircraft. Subsequently, there was research into the use of colour at airports. Accounts of that research were given in the proceedings in Re Pape (supra). In these proceedings it was agreed that the Tribunal, which was constituted by the same members as in those proceedings, should take into account the evidence which had been presented to it in Re Pape. Evidence was given in both cases by a number of pilots regarding the use which they made of perception of the air navigation lights of other aircraft and generally with regard to the use of information to be derived from the perception of coloured lights displayed on the ground or on structures.

33. The research into the use which could be made of the perception of air navigation lights was conducted by Professor Cole at the Victorian College of Optometry. The persons used as subjects in the research were without training or experience as pilots. Essentially, the research took the form of first instructing them on the position and colours of the navigation lights required to be displayed by aircraft. They were then told the directions from which each of the lights, either alone or in combination with another of the lights, was visible to observers outside the aircraft, and how the direction in which an aircraft was travelling could be deduced by such an observer from the colours of the lights visible to him and their positions relative to one another. That knowledge was similar to what a pilot is required to acquire as part of his training. The subjects were then shown cards, each with a dot or several dots on it; each dot was either red, green or white. They were told that the dots represented the navigation lights of an aircraft and were required to state as quickly as possible, in respect of each card, the direction in which the aircraft was travelling. The research demonstrated that, where a person understood the significance of the relative positions and the colours of navigation lights of an aircraft, that person was able to know quickly the direction in which the aircraft was moving relative to his own position.

34. During the proceedings in Re Papea number of pilots gave evidence that they utilised their perception of the navigation lights of other aircraft, particularly when circling an aerodrome prior to landing, to acquire knowledge of the directions in which those aircraft were travelling. However, others said that they did not do so and that there were always ample other cues from which they could, and did, derive that information. Although in the course of their training a pilot is required to learn, in effect, the code which Professor Cole taught the subjects of his experiments, he will not derive from the perception of the air navigation lights of another aircraft in flight a quick appreciation of the direction in which it is travelling unless he has kept fresh his knowledge of that code. Although some pilots gave evidence that they had done so, others said that they had not. In these proceedings Dr Vingrys, who for several years was employed as an airline pilot, gave evidence that he was not aware of knowing the navigation code; he considered that it did not matter what colour the navigation lights were, as long as there were lights. That was sufficient to enable him to understand in which direction the other aircraft was travelling. We have, come to the same conclusion as we did in Re Pape that, even if a colour defective pilot saw all navigation lights as white, that would not pose any risk to his safe piloting of his aircraft.

35. In addition to information which navigation lights may provide as to the direction in which an aircraft is travelling, perception of them will also make the observer aware of its presence, if he is not already aware of that as a result of having seen for some time the aircraft's white strobe light or its red rotating beacon. In the proceedings in Re Pape one pilot gave evidence that, when his aircraft was cruising, he relied on the air navigation lights of other aircraft to provide him with information of their presence. However, both in that case and in this there was evidence that the white strobe light and the red rotating beacon are considerably brighter than the air navigation lights and consequently visible from a greater distance. Thus Dr Vingrys gave evidence that, although he looked for navigation lights, it did not matter if the light which he saw was a navigation light or a strobe light; whatever light on another aircraft he saw first enabled him to detect its presence. We have no doubt that that is so, and that colour plays no part in such detection. However, they are doubtless of value to an airport tower controller.

36. The research into the value of colour at airports was conducted by Dr R. K. McKelvey. Evidence of the results of that research was given to the Tribunal in the proceedings in Re Pape. The persons used by Dr McKelvey for his experiments were experienced pilots. He projected onto a screen a series of photographs of airports as seen by pilots approaching them. To one group of subjects he showed the photographs in colour and to the other in black and white. He found that the group to whom they were shown in black and white had no difficulty in quickly identifying what they saw. He concluded that the perception of colour was not vital to safe use of airport lighting as a source of information to pilots.

37. It appears that Dr McKelvey's photographs were taken when the visibility was good. In these proceedings Dr Vingrys expressed the view that the ability to distinguish the colours of runway lights, and in particular the green threshold lights, was of considerable significance when a pilot was landing in poor visibility. However, he also gave evidence that lenses of different colours permitted different amounts of light to pass. He said that a clear lens or a white lens permitted the most to pass, with the green, red and blue lenses in that order permitting less light to pass. We were able to observe the effect of this when viewing the video films made for Dr Clark's demonstration. As the aircraft from which the film was being taken approached an aerodrome, the white runway lights became visible well before the green threshold lights. We referred Dr Vingrys to that; he said in response that on approach the threshold lights were 200 ft closer than the runway lights; in conditions of poor visibility that was very important as in such conditions pilots acted a lot on expectation. One expectation was to see the green threshold lights.

38. Rarely, if ever, do the threshold lights become visible before the much brighter runway lights; we are not convinced that in that situation the perception of the lights as green is of any significance. The pilot knows from the compass bearing on which his aircraft is flying and from the fact that there is only a single line of lights, that they are not runway lights. He sees the line extending only as far as in each direction as the breadth of the runway and at right angles to the bearing on which his aircraft is heading. Simultaneously he sees the first lights of the runway. We have come to the conclusion, therefore, that the perception of the threshold lights as white and not as green does not impair the pilot's ability to fly his aircraft safely. Dr Vingrys considered that a pilot with defective colour vision might have difficulty perceiving a displaced threshold. However, we are satisfied that the unique shape of lights displayed when the threshold has been displaced is by itself an adequate cue. Further, the pilot will usually be aware of the displacement from NOTAMS or as the result of information given by air traffic control.

39. So far as taxiway lights are concerned, if they are blue they are seen by protans and deutans without any difficulty or error. If they are green they are in a single line which starts in the middle of the runway, turns off it and then continues; as a runway is always marked by two lines of white lights, one on each side of the runway, the fact that there is only a single line is by itself an adequate cue that the lights mark a taxiway and not a runway. Red lights indicating holding points are at right angles to the taxiway; because of that, perception of them as lights is sufficient to indicate to a pilot that they mark a holding point. In the case of deuteranopes there is little chance that the lights will not be perceived as red, particularly when the aircraft is near to them. Furthermore, when a pilot comes upon them, his aircraft is not travelling fast and he is under the direction of an air traffic controller who can observe where his aircraft is and give him appropriate instructions. We have come to the conclusion that any diminution of the intensity of red light perceived by a protanope will not prevent him from seeing the lights in ample time to stop his aircraft at them and that any possible inability of a pilot who is a protan or a deutan to perceive holding point lights as red will not prevent a pilot being aware of their significance or prevent him from operating his aircraft safely on an aerodrome. Similarly we are satisfied that a pilot with defective colour vision will recognise the line of red or green lights at the end of a runway as what it is because of its direction relative to the runway lights.

40. We turn now to the VASIS lights. In these proceedings we received evidence that manufacturers of lights do not design them to have equal intensity for all colours unless that is specified as a requirement. Such a requirement increases the cost considerably and is not imposed unless there is a very great need for all the lights to be of equal intensity. As already noted, coloured lenses reduce the intensity emitted, some colours more than others. We are satisfied that, because of the size and brightness of the VASIS lights, changes from one colour to another will be perceived by pilots with defective colour vision as changes both in colour and in intensity. Deutans will almost certainly perceive the red light as such and any other colour as something different. Protans will see the red light as having significantly decreased intensity compared with the other colours. So there is no significant risk of protan or deutan pilots maintaining the incorrect height during their approach to an aerodrome because of inability to make proper use of the VASIS.

41. We come now to the one matter in respect of the pilot's perception of lights outside the aircraft which caused us concern in Re Pape, that is to say the significance, in terms of safe flying of an aircraft, of the possible inability of a pilot who is a protan or a deutan to perceive a red light as red, and of a pilot who is a protan to perceive it from a sufficient distance. The first point which we must make is that pilots who are deutans are likely to perceive red lights as such unless the size and intensity of the lights are both very small. Next, we consider that it is a matter of significance that red lights are displayed on the ground and on structures for purposes other than the marking of obstructions, so that perception of a red light does not of itself enable a pilot to know that he is seeing a particular obstruction or indeed any obstruction. That is to be contrasted with maritime navigation where lights of particular colours and having particular characteristics, e.g. intermittency, are part of a rigidly applied code, so that the precise position of the thing on which a light is displayed, in terms of map-reference and relationship to other things, can be ascertained by reference to the characteristics of the lights on it. In aviation a pilot cannot confidently decide on his position relative to known obstructions in the area and to the location of the aerodrome simply by perceiving a red light, or several red lights. As several witnesses pointed out, all that a pilot can safely depend on is that any artificial light which is not on another aircraft must be on the ground or on a structure above the ground; it must therefore be avoided. The third matter of significance is that not all obstructions have a light on them.

42. Professor Cole gave evidence that, if a light "pops out" from its surroundings, the attention of an observer is drawn to it more quickly. He said that red lights had the quality of "popping out". Professor Crassini disputed that; he said that there was nothing intrinsic in the colour red that caused it to "pop out". If it was displayed with a number of single lights of other colours all of equal intensity, it would not "pop out" from among them. If it was the only light that was red among a number of lights of another colour, that would cause it to "pop out"; but in the same way a single white light among a lot of red lights would "pop out". We accept Professor Crassini's evidence in that regard. However, we note that, although in an urban area there may well be red lights which are not lights displayed to mark obstructions, there will usually be many more white lights, so that the red lights will stand out from among them. If a light "pops out", attention is attracted to it; that increases the speed with which attention will be given to it if it is of significance.

43. In Re Pape we were concerned that Dr Pape would take longer than a pilot with normal colour vision to perceive red lights as such, particularly where he saw them against a background of other steady lights on the ground. We took the view that it might be unsafe for him to come below the normal meteorological minimum height set for an aerodrome unless there were clear visibility of the ground from a greater height so that, by the time he reached the meteorological minimum, he would have already had some time to identify obstruction lights. In the present proceedings a considerable amount of evidence, not presented in Re Pape was given about various types of visual stimuli to the retina and the manner in which such stimuli are processed in the retina and in the higher visual channels in order that the brain may receive information as a result of them. Because of that evidence we have found it necessary to reconsider the conclusion to which we came in Re Pape regarding the significance, in terms of the safe piloting of an aircraft, of the possible inability of deuteranopes to perceive some red obstruction lights as red.

44. Dr Samuel gave evidence that a person who had never had very precise colour vision was not going to be particularly reliant on the perception of colour. Consequently, such persons were less dependent on chromatic cues than those with normal colour vision. They might depend more on recognising shapes or changes in luminosity. He said that it was impossible to tell on the basis of clinical and laboratory tests what a person would do in the real world. He was unaware of any evidence published that protans or deutans had more difficulty passing flight tests than persons with normal colour vision. That appeared to indicate that, when they were tested on practical tasks, they had no difficulty in performing them and that their failure to pass colour-naming tests did not really have any correlation with how they could fly an aeroplane and perform the tasks required for doing so.

45. Dr Pape made the point that a pilot with normal colour vision who was unfamiliar with an airport could not say that, because a light was red, it necessarily marked an obstruction relative to his flight path; nor could he necessarily ignore white lights. All lights needed to be observed. Consequently, a pilot with defective colour vision was in very much the same position as a pilot with normal colour vision unfamiliar with the airport. He stressed that not all obstacles were lit by red lights.

46. Professor Crassini gave evidence that the simple perception of colour and intensity of a light were not the only factors contributing to the reception of knowledge in the brain and the brain's reaction to that knowledge. Many other factors were involved. An example was the part played by the rate of expansion of an image in the retina. That was believed to be involved in enabling the brain of a bird to acquire the information necessary for reactions to occur which would cause the bird to land accurately on a particular branch of a tree or, in the case of a gannet, to dive into water at a speed of 60 or 70 km an hour without injuring itself. The same factor played an important part in the human brain estimating the time to contact, which was critical in flying, as it was also, for instance, in sport. Consequently, to have regard only to the cones and rods of the retina was too simple an approach and quite inappropriate to an understanding of the totality of perception. Another example which he gave of a factor additional to the simple perception of the colour and intensity of a light was that of hyperacuity, that is to say the ability of humans to perceive detail smaller than the limit of visual acuity, which is normally taken to be the limit of a human being's visual resolution. Clearly, he said, something occurred at some higher level in the visual system that enabled that information to be received by the brain.

47. We received also evidence of studies carried out in the USA (where the testing procedures are such that many pilots with defective colour vision are granted licences free of conditions) into accident rates of pilots with defective colour vision. The research was carried out in respect of each of the years 1974, 1975 and 1976 by Dille and Booze. It was financed by the Federal Aviation Authority of the USA. Details of all accidents which occurred in the USA during each of those years were obtained, as were the reports of those who investigated them. Although initially it appeared from the raw data that pilots with defective colour vision had more accidents, by the end of the three years the authors had come to the conclusion that, when the number of flying hours of those pilots in a period of six months was taken into account, the accident rate was no greater than that for pilots with normal colour vision. Further, and most significantly for our present purposes, most of the accidents involving pilots with defective colour vision occurred when their aircraft were cruising, not when they were landing. In Australia, it appears, no statistics have been kept of accidents of pilots with defective colour vision; of course, unless any such pilot has somehow succeeded in passing the flight standard test, in which case it has not been known to the authorities that he has defective colour vision, such pilots have not been permitted to fly at night. So, even if any statistics had been kept, they would be of no assistance to us in determining whether such pilots are at significantly greater risk of accidents due to problems with obstruction lights.

48. After hearing many days of evidence from many witnesses in Re Pape and even more in these proceedings, it has become increasingly obvious to us that much of the evidence which we have received from pilots as to a pilot's reaction to various stimuli, and in particular coloured lights, has been merely accounts of their own personal experiences as understood and remembered by them and rationalizations made by them on the basis of those experiences as so understood and remembered. As they are experts in piloting aircraft, their opinions given as the result of those rationalizations would be valuable if there were any general consensus of them. We have no doubt that the opinion stated by each of them was one which he genuinely held and was based on his own experiences as understood and remembered by him. In the end, however, we find that, because of the variety of opinions expressed, their evidence has been of little help to us. This is an expert tribunal; we are ourselves well aware of the tasks of a pilot as he approaches an aerodrome at night with the intention of landing his aircraft there. Unlike the pilots who gave evidence we have had made available to us in these proceedings, and in Re Pape, much evidence relating to the nature of defective colour vision and to visual perception generally.

49. In reconsidering the conclusions to which we came in Re Pape, we have noted the rules set by and under the Civil Aviation Regulations for flying an aircraft at night and the meteorological minima set for individual aerodromes. We have concluded that their effect is that, except in an emergency, a pilot, whether he has normal or defective colour vision, has ample time to identify obstacles before descending to the height at which they will be encountered. An emergency can arise either because equipment of the aircraft has become defective during flight or because the aerodrome which is the intended destination and all alternative aerodromes are covered with cloud extending to below the meteorological minima for those aerodromes. It is, therefore, such emergency situations to which we have to turn our attention.

50. In regard to emergency situations during night operations we consider the following facts to be significant. First, the intensity of an obstruction light will be perceived similarly by a deutan pilot and by a pilot with normal colour vision; this is important as, because not all obstructions are marked by red lights, there is a need for all pilots to have regard to all lights, whatever their colour. Unless a light is very small and of very low intensity, the deutan will usually perceive its colour as red. A protan may not see a red light from the same distance as the deutan or the pilot with normal colour vision. We shall discuss separately the significance of that as, although in these proceedings we have been asked to reach conclusions applicable to protans, we are concerned primarily with the applicant, who is an extreme deuteranomal. The second fact which we consider significant, as already noted, is that a red light cannot safely be assumed to be an obstruction light; so a pilot who is able to perceive a red light as red is not able simply because of that to establish his aircraft's position in relation to it and other obstacles and to the aerodrome by identifying it as marking a particular obstacle. In training a pilot is taught - and a competent pilot always remembers - that, at least in civil aviation, he must not react to any information he receives until he has satisfied himself that it is correct. So a pilot who perceived a red light and thereafter proceeded on the erroneous assumption that it marked a particular obstruction might put his aircraft into greater danger than a pilot who did not see it as a red light.

51. The third fact which we consider significant is that not all obstructions are marked by red lights. The presence of a hill, for example, may be revealed only by street lights on it. It is clear that a pilot cannot rely on the fact that a light is red, or on the fact that it is not red, to ascertain where obstructions are situated relative to the flight path of his aircraft as it approaches an aerodrome for landing. He must take into account all lights of all colours and their relative positions and rely on cues such as motion parallax and the rate of expansion of images on the retina. We have come to the conclusion, therefore, that, so far as the safe flying of his aircraft depends upon his perception of anything outside his aircraft, a pilot who is a deutan is at no significant disadvantage compared with a pilot who has normal colour vision.

52. There is no dispute that the intensity of lights other than red lights is perceived the same by protans, deutans and persons with normal colour vision. In respect of a red light, however, it is generally accepted that the intensity of the light perceived by a protan is less than that perceived by a person with normal colour vision and by a deutan. The degree of the diminution of the intensity perceived has been stated in a formula commonly known as Allard's law. According to that formula the diminution is such that the furthest distance at which a protan is able to see a red light is only approximately half of the furthest distance at which a person with normal colour vision can see it. Although the formula is stated to be applicable to protans generally, Dr Samuel cast doubt upon such general applicability. He said that there were two variables that had to be taken into account as contributory to the diminution in the perceived intensity. One was the nature of the red colour, that is to say whether it was a deep red or nearer to orange, and the other was whether the person suffered from protanopia or extreme protanomaly or only from mild protanopia.

53. He gave an account of a patient suffering from mild protanomaly with whom he had flown for the purpose of testing the patient's ability to see red lights from a distance. He had observed that the patient was able to recognize a type 2 red light at a distance of over 11 km in circumstances where the best for a person with normal colour vision was stated by Allard's law to be 9 km and for a protan 4.6 km. A type 2 red light is deep red. The patient had been able to see a type 1 light, that is to say a lighter red, at a distance of 25 km. Dr Samuel said that he had no doubt that the patient had been able to see the light; it flashed at a certain frequency and he had been able to check that the patient saw the flashes at that frequency. Dr Samuel acknowledged that Allard's law was an accepted formula in the ophthalmological world but said that like most empirical formulae it was not 100% accurate. It was our understanding of his evidence that the formula was substantially correct when it was applied to protanopes and extreme protanomals and that it was only when a person was suffering from mild protanomaly that it might not be applicable.

54. An interesting demonstration of the ability of a protanope with above average visual acuity to recognize very small red dots at a distance when a person without such good visual acuity did not see those dots at all was given by Captain R. Cronin. A number of photographs taken from an aircraft at night by Dr Pape were projected onto a screen. Captain Cronin stood about 10 ft from the screen and members of the Tribunal were nearer to the screen than he was. He identified the red dots, which in the scene photographed by Dr Pape were red lights, when they were not visible at all to some of us. Captain Cronin gave evidence that he was a protanope and that he had distant visual acuity of 6/5 without correcting lenses. It was apparent to us that, if the Allard's law formula were correct, the furthest distance at which a protanope with 6/6 distant visual acuity could see a red light would be approximately the same as the furthest distance at which a person with normal colour vision but a distant visual acuity of 6/12 could see it.

55. We note that Medical Standard No. 2, applicable to applicants for and holders of student pilot and private pilot licences includes distant visual acuity of 6/12 or better in each eye with or without the use of correcting lenses (ANO 47.1.3.13(c)) and that Medical Standard No. 1, which is applicable to applicants for and holders of commercial pilot licences includes distant visual acuity of 6/9 or better in each eye with or without the use of correcting lenses (ANO 47.1.2.13(c)). We can, therefore, see no justification whatsoever for the present total exclusion of all protans from night flying. It is our view that for the grant of a student pilot licence or a private pilot licence, so far as the safe flying of an aircraft depends on perception of things outside the aircraft, a protan will not be at a significant disadvantage compared with a pilot who has normal colour vision provided that his distant visual acuity is 6/6 or better in each eye with or without correcting lenses. Similarly, for the purpose of a commercial pilot licence a protan will not be at a significant disadvantage compared with a pilot with normal colour vision if, and for so long as, his distant visual acuity is 6/5 or better in each eye with or without the use of correcting lenses.

56. It seems likely from Dr Samuel's evidence that persons with only mild protanomaly, even if their distant visual acuity is not twice as good, are likely to be not significantly disadvantaged in comparison with persons with normal colour vision. We consider that protanomals should be tested individually to ascertain the degree of the diminution of their perception of the intensity of red lights. Indeed, it seems to us that a very mild protanomal, such as Dr Samuel's patient, ought not to be denied an opportunity to take the Farnsworth lantern test, and if he passes it to obtain an unconditional licence, simply because, as is required by the present colour vision standard, testing on the Nagel anomaloscope or the OSCAR has shown that he is a protan. However, we must emphasize that protanopes and extreme protanomals whose distant visual acuity is not twice as good as the standard set for persons with normal colour vision in relation to a particular class of licence are probably at a substantial disadvantage as the result of their inability to see red obstruction lights at the same distance as pilots with normal colour vision and the required distant visual acuity. On occasions that may adversely affect the ability of pilots in this class to fly their aircraft safely at night.

57. We have concentrated so far on the effect of defective colour vision on the ability of a pilot to fly his aircraft safely during the phase of the flight preceding the aircraft landing at an aerodrome. We have considered whether it may prevent him doing so on take-off or when the aircraft is cruising or when it is on the ground before take-off or after landing. We have come to the conclusion that it does not. On the aerodrome before take-off and after landing, we are satisfied, he is able to perceive correctly the aerodrome lights. Before taking-off he is able to take time to ascertain from his charts and by observation outside the aircraft where obstructions in the vicinity are located and to identify any lights marking them. He is also able to work out the headings that he must fly on take-off in order to avoid them. When cruising he will be as aware of the presence of other aircraft as quickly as pilots with normal colour vision. In spite of a reiteration by some witnesses of evidence given in the proceedings in Re Pape that the recognition of air navigation lights assists in the avoidance of collision in the air, we are satisfied that the view which we took in Re Pape is correct, namely that there are sufficient other cues from which a pilot can and does ascertain the direction in which other aircraft are travelling and that it would make no difference if all the navigation lights were white. Consequently, the inability of pilots with defective colour vision to see the green and red navigation lights as such does not increase the risk of their aircraft colliding with other aircraft in flight or indeed on the ground.

58. A matter which had not been raised in any proceedings in the Tribunal before Re Pape was the possible problems which a pilot with defective colour vision might have in flying an aircraft safely due to an inability to identify the colour of lights inside the cockpit or the colour of lines on maps. Over the past ten years or so colour coded instrument displays have been fitted in an increasingly large number of aircraft. Several years ago the Department became aware of the possible problem and provided funds for research to be carried out at the Victorian College of Optometry by Professor Cole and Dr Macdonald. In 1986 they prepared two articles for publication in specialist journals. In those articles they gave an account of their research and stated their conclusions. Copies of both those reports were tendered in evidence. Professor Cole and Dr Macdonald gave evidence at the hearing amplifying and explaining the manner in which they carried out the research, their reasons for carrying it out in that manner and the basis of their conclusions. The research was criticised by Dr Pape and Professor Crassini. A lengthy written statement of the latter's criticisms was tendered. He explained them in detail in oral evidence given at the hearing.

59. The respondent arranged for the Tribunal to see the reproduction of the cockpit of a Boeing 767 aircraft in a flight simulator and to have the use of the instruments demonstrated to us in simulated flight by Captain J. R. Rhind. Characteristics of modern aircraft instrumentation were described to us by Mr Chatfield. He showed a number of photographic slides which demonstrated the general lack of colour in the cockpits of older aircraft and the increasing use of colour, and the greater sophistication of that use, in more modern aircraft. He said that, although initially the new instrumentation had been used principally in larger passenger transport aircraft, lighter aircraft were now being equipped with sophisticated Electronic Flight Instrument Systems ("EFIS"). He believed that eventually all aircraft would be equipped with them when manufactured. He said that the patterns and symbols on the various instruments and the colours used were all computer-generated, so that they could be changed simply by altering the computer software. One of the instruments of which he showed slides and which we considered of interest and significance in relation to the issue with which we are now dealing was the weather radar. It was significant because it was the only instrument in which, he said, colour was the only cue used. He subsequently agreed that the luminosity of the various colours differed, so that there were luminosity cues; however, he considered that degrees of luminosity on their own were difficult to perceive as representing particular colours.

60. In Re Pape we pointed out that, if the problems caused to protanope and deuteranope pilots by the introduction of the new colour coded instrumentation were such as to impair significantly their ability to fly their aircraft safely, it was necessary to consider whether they should be permitted to fly an aircraft equipped with such instrumentation either by day or by night, that is to say at all. To date pilots with defective colour vision have been permitted to fly by day provided that they have met the medical standards in all other respects. Such problems might, we thought, be worse by day than by night because in strong daylight the colours of the instruments might not show up as vividly as they would at night. There was, therefore, the possibility that pilots who were permitted at present to fly by day might have to be prohibited from flying at all. Consequently, it was an issue which we regarded as most important. So did the parties; consequently they provided us with a great deal of expert evidence and we have given it very careful consideration.

61. The research conducted by Professor Cole and Dr Macdonald was designed to ascertain whether the response time taken by a person with defective colour vision to obtain information from EFIS displays was longer than that taken by persons with normal colour vision. In order to carry out that research they took photographs of part of the EFIS instrumentation in a simulator, namely the Horizontal Situation Indicator ("HSI"); different photographs were taken of the HSI as it was at various stages of a simulated flight. On the HSI were lines, symbols, words and numbers displayed in white, light blue, green and magenta. They made slides of the photographs in both colour and black and white. There were five groups of subjects. None of them were pilots; their ages and educational attainments varied between one group and the other groups. Those in two of the groups had normal colour vision. Those in the third group were deuteranomals, those in the fourth group deuteranopes and those in the fifth group protanopes.

62. The subjects were taught what information was conveyed by the various lines, symbols, words and numbers displayed on the HSI. They were then set seven tasks. In each task they saw a slide of the HSI projected on a screen. One of the two groups of persons with normal colour vision was shown the slides in black and white. The remaining groups were shown the coloured slides. In respect of each slide the subjects were told the nature of the information which they were to derive from the HSI; the time which they took to obtain that information and the accuracy with which they did so was then recorded by Dr Macdonald. Professor Cole and Dr Macdonald noted that the older and less educated subjects were generally slower and gave less accurate responses to multicolour visual displays. Overall, they concluded, in respect of the most complex colour coded visual display utilised the subjects with defective colour vision had been shown to have slower response times and to make more errors than those with normal colour vision.

63. However, perusal of graphs contained in the articles reveals that, where the colour coding of a display was less complex, there was no significant difference in the response times of persons with defective colour vision and those with normal colour vision. Furthermore, the graph in respect of the fourth task, which had three quite significantly different levels of complexity, produced a result which must put in doubt some of the conclusions drawn by the authors. The task was to search for and to count way points; the search was by reference to shape and colour. The graph shows that the response time of the protanope group to the display at its most complex level was considerably better than that of the group of persons with normal colour vision.

64. There is one major reason for querying generally whether the research justified any conclusion being drawn in respect of the task of piloting an aircraft. That is that the subjects were not experienced pilots and were shown still photographs not sequentially related to one another. During the flight of an aircraft the pilot is constantly scanning his instruments; he does not suddenly come upon an instrument displaying certain information. He has been seeing that instrument at frequent intervals for however long the flight has lasted. Consequently, whenever he sees it, he does so in the context of the flight. He knows what has gone before and if, as is usual, the flight is being conducted in accordance with a flight plan, what he can reasonably expect to come next. The greater his experience as a pilot using such instrumentation, the greater will be his understanding of its display and consequently his ability to derive from it in the context of the flight the information which he requires in order to fly the aircraft safely.

65. However, the fact that the research conducted by Professor Cole and Dr Macdonald does not by its nature satisfy us that a pilot suffering from defective colour vision will respond more slowly to information displayed in the HSI part of the EFIS does not necessarily mean that a pilot with defective colour vision will not have difficulties with other parts of the display or with the colour coded electronic Engine Indicating and Crew Alerting System ("EICAS") which relates to the engines and other ancillaries of the aircraft. In the course of the hearing we heard a considerable amount of evidence about the colour coding of that instrumentation, about the other ways in which it conveys information and also about aural warnings which accompany instrumentation displays indicating equipment malfunctions which may be serious. We also heard a good deal of evidence about the weather radar part of the EFIS.

66. In a large passenger transport aircraft the number of different instruments which were required before the introduction of EFIS was such that they could not all be placed in front of the pilots; a third cockpit crew member, a flight engineer, had to be employed to watch a group of the instruments located behind the pilots. The introduction of EFIS and EICAS has reduced the space required for instruments. Many different pieces of information can be displayed on the same screen, either simultaneously or sequentially. As a result all of the instrumentation is now located in front of the pilots, either all of it below the windscreen or part of it below and part of it above the windscreen. When there is any malfunction a red or amber warning light comes on immediately in front of each of the pilots. The appropriate part of the instrumentation panel turns red or amber and a written message stating which piece of equipment has malfunctioned appears on a small screen in front of the pilot. If the malfunction requires immediate action to be taken because of it, the warning light is red, the written message is displayed in red and an aural warning sounds.

67. The aural warning varies in sound according to which piece of equipment has malfunctioned. The only time when it does not sound for a malfunction requiring immediate attention is on take-off, in the short interval between the time when the aircraft has reached the critical, or decision, speed and the time it reaches a set height, usually about 400 ft. When the aircraft reaches that height the warning sounds. The reason for the warning not sounding during the short interval is that, once the aircraft has reached the critical, or decision, speed, it may be more dangerous to try to abort the take-off than to take off; during take-off the pilot must concentrate entirely on control of the aircraft. It might endanger the aircraft if his attention were distracted by an aural warning of a malfunction. We are satisfied that, because of the aural warning, a pilot with defective colour vision is not going to take significantly longer to obtain from the EFIS or EICAS display the information necessary for him to identify the nature of any serious malfunction.

68. Where the malfunction is less serious, so that immediate action is not required, the warning light is amber; the written message is also in amber colour. No aural warning sounds. However, we are satisfied that a pilot with defective colour vision will become aware of the amber light as quickly as a pilot with normal colour vision. Further, because it is amber and is quite large and not far from the pilot's eye, he will see it as amber. He can then read the message on the screen; if there are two messages one relating to a malfunction requiring immediate attention and the other relating to a malfunction which does not require such urgent attention the letters of the words and the message will be coloured red or amber respectively. Again, if they are amber, a colour defective pilot is very likely to be able to perceive the fact. In any event, having read the messages he can immediately look at the part of the instrumentation display which relates specifically to that equipment and, as the information is provided by that instrumentation both by colour code and by a dial or other similar non-colour coded method, he can very quickly obtain the information which he needs. It is possible that he may acquire it marginally less quickly than a pilot with normal colour vision. It was suggested by some witnesses that that could be significant in an emergency situation. In our view the difference in response time would not be significant, certainly not as great as the differences in the reaction times of different pilots with normal colour vision. We refer once again to the fundamental instruction given to pilots in the course of their training that, at least in civilian aviation, an automatic response to particular information is not safe and that information should be evaluated before action is taken upon it.

69. The one part of the instrumentation which is not redundantly colour coded, that is to say where it is intended that the information should be conveyed entirely by colour, is the weather radar. At present eight different colours may be used to denote different weather conditions. Evidence was given that consideration is being given to increasing EFIS colours to sixteen. That prompted Dr Macdonald to comment that such an increase would result in unnecessary colour cluttering of the screen and to query whether the manufacturers were concerned with providing more information that was usable or with making the screen more visually attractive to potential buyers. In coming to a conclusion on this aspect of the issue of colour inside the cockpit, we again note that, at whatever time the pilot looks at the weather radar screen after take-off, it is not the first occasion on which he has looked at it in the course of that flight. Before commencing the flight he has obtained meteorological information and has prepared his flight plan accordingly. The weather situation which he sees displayed on the weather radar develops as the flight progresses. While unexpected meteorological conditions may be encountered, the screen will change gradually as the changes in the weather develop. Some of the colours used are colours that a protanope or a deuteranope has little trouble in identifying. Those which he does have trouble with will usually be displayed in sufficient quantity and with sufficient brightness,that, with the screen so near to his eyes, his retina will be so suffused with them that the mechanism within the retina to which we have referred above, whatever it is, will respond to the stimuli sufficiently for him to perceive the colour differences. That process is doubtless aided by the different luminance of the various colours, to which Mr Chatfield referred. Additionally the boundaries of different colours representing on the radar screen different precipitation rates are clearly defined; those shapes will be available to the pilot with defective colour vision. Consequently, we have come to the conclusion that a pilot who is a protanope or a deuteranope is able to obtain readily from the weather radar screen the information about the weather which he needs in order to fly his aircraft safely. It accords with evidence given at the hearing by pilots with defective colour vision, including the applicant.

70. On aircraft with pre-EFIS instrumentation many instrument dials have segments or lines coloured differently, usually with the segment in which the needle should remain when the aircraft and equipment are operating normally coloured green, a segment coloured yellow or amber to indicate that caution needs to be exercised to prevent the equipment becoming overstressed and a third segment or line coloured red to indicate that the safe limit of the equipment has been reached or exceeded. Further, such a dial is also marked with numbers, which all are of the same colour, usually white. Captain K. B. Englesman gave evidence that, as a test pilot, his duties required him continually to fly many different types of aircraft, so that he had no opportunity to become sufficiently conversant with every instrument in every aircraft to be able to tell by reference to the numbers whether the equipment to which it relates was functioning correctly; consequently he relied on reference to the coloured segments. However, a pilot who is a protanope or a deuteranope can see that there are segments and knows that they are placed sequentially in relation to the information they convey. Similarly, where there is a coloured line on a dial marking the limit to which the needle should be allowed to go, a pilot who is a protanope or a deuteranope can see the line, even if he cannot identify its colour. He knows its significance from its position on the dial.

71. Before the introduction of EFIS, no-one apparently questioned the ability of pilots who were protanopes or deuteranopes to obtain information from the instruments of aircraft correctly and with sufficient expedition for them to be able to fly aircraft safely in the day time. We are satisfied that they were, and are, able to do so. Captain Englesman gave evidence of the instrumentation in the cockpits of helicopters. We are satisfied from his evidence that there is no difference between the instrumentation of helicopters and that of fixed wing aircraft which is significant in relation to the issues with which we are concerned in these proceedings.

72. Another instrument on which the colours of the lights displayed may be confused by a deutan or a protan is the autopilot function display. When a radio navigation input is selected on stand-by, the light displayed is amber; when the autopilot engages this input, the light is green. If the input becomes invalid, the green light is replaced by the amber light. A dangerous situation could arise if a pilot were unaware that the autopilot was no longer controlled by the selected input. However, not only is the green light replaced by the amber light, but in that situation the amber light flashes. It does so to draw the pilot's attention to the change. We are satisfied that it would draw the attention of a pilot who was a protan or deutan as quickly and effectively as it would that of a pilot with normal colour vision. So no additional risk results from the pilot having defective colour vision.

73. The maps carried by pilots for use in flight are frequently marked with coloured lines. A pilot who is a protan or a deutan probably has difficulty identifying the colours of lines, particularly red, in the subdued light of a cockpit at night. However, so too does a pilot with normal colour vision if, as is permitted, the colour of the cockpit lighting is red. In such a situation a pilot with defective colour vision may actually be at an advantage since, as Dr Samuel pointed out, a person who has never had very precise colour vision habitually seeks non-chromatic cues. On a map there are many cues in addition to the colours of particular lines. We have come to the conclusion that the inability of a pilot who is a protan or a deutan to identify quickly and accurately the colours of lines on maps does not result in a risk of his not being able to pilot his aircraft safely.

74. It was suggested to us that, while we might find that no single difficulty which pilots with defective colour vision might encounter in acquiring information from colour-coded displays would result on its own in a significant risk to the safety of air navigation, the combination of several difficulties experienced together would have that result, as it reduced their ability to take appropriate action sufficiently quickly in a situation of emergency. The delay in acquiring any one piece of information and, therefore, in responding to the situation to which it relates might itself be insignificant. But, if a number of pieces of information had to be acquired and responded to at the same time, the total delay might be significant. Having regard to the nature of emergencies which may arise during the flight of an aircraft, we have come to the conclusion that in practical terms the total delay, if any, will itself be insignificant and that the risk to the safety of air navigation will still not be significant or unacceptable.

75. Having given consideration to all of the very considerable amount of evidence presented during these proceedings and with our knowledge of the evidence which was presented in the proceedings in Re Pape, we have come to the conclusion that a pilot who is a deutan does not, simply because of his defective colour vision, pose a significant and unacceptable risk to the public by flying an aircraft at all or at night or by flying an aircraft equipped with EFIS and EICAS instrumentation. During the course of these proceedings and those in Re Pape we received evidence which makes it clear that, although a country may be a signatory of the Convention on International Civil Aviation and a member of the ICAO, different countries have effectively set different standards of the colour vision required for the grant of a pilot licence in those countries by varying the method of testing. In some countries the standard and the tests imposed are more strict than those in Australia. In some other countries they are less strict or less strictly applied or both. Although the pilots who are accepted by one of those countries as having attained the requisite colour standard are granted unconditional licences which enable them to fly anywhere an aircraft registered in that country provided that their licences are endorsed for aircraft of that type, we consider that the comity of nations requires that, where a licence is granted under the provisions of regulation 63, that is to say where the medical standard set by regulation 62 has not been met, the licence should be granted subject to a condition that the pilot is not to fly an aircraft in any country other than Australia except with the express approval of the civil aviation authority of that country.

76. The licence should also be subject to a condition that the aircraft is equipped with adequate radio equipment maintained in working order suitable to enable him to be in voice radio communication with air traffic control while flying in a control zone. Those are the only two conditions to which, in our view, a licence granted to a deutan under regulation 63 should be made subject. Accordingly, we have set aside the decision under review and in substitution for it decided that a commercial pilot licence is to be granted to the applicant subject to the conditions to which we have just referred.

77. As the respondent has requested us to do so, we have stated our views in relation to pilots who are protans. In summary, we are satisfied that, so far as the instrumentation of aircraft is concerned, a pilot who is a protan will not be at a significant disadvantage compared with a pilot with normal colour vision. However, some protans may be significantly disadvantaged by an inability to see red obstruction lights at the same distance as pilots with normal colour vision. Whether a particular pilot will be disadvantaged to the extent that the granting of a licence without a condition prohibiting him from flying at night would be likely to affect the safety of air navigation depends on two factors, his distant visual acuity and, if he is not a protanope, the degree of his protanomaly. We recommend that in certain circumstances pilot licences should be issued to protans under regulation 63 and be subject to only the same two conditions as those to which we have made the applicant's licence subject. Those circumstances are that, for the licences for which Medical Standard No. 1 is required, the pilot has distant visual acuity of 6/5, while meeting the other requirements of ANO 47.1.2.13, and for the licences for which Medical Standard No. 2 is required, he has distant visual acuity of 6/6 while meeting the other requirements of ANO 47.1.3.13. Otherwise, a licence granted to a protan under section 63 should be subject to the additional condition that he does not fly an aircraft at night.

78. We recommend that suitable practical tests should be devised so that a protan can be tested individually, if he wishes, at his own expense to ascertain the extent of the loss of his ability to perceive the intensity of red lights. If his distant visual acuity is such that, when allowance is made for the loss of ability to perceive the intensity of red lights, he is able to see red lights at the furthest distance that they can be seen by persons who have normal colour vision and the distant acuity required by ANO 47.1.2.13 or ANO 47.1.3.13, as appropriate to the type of licence sought, a licence should be granted to him under regulation 63 subject to only the two conditions referred to above. If a change in his visual acuity is detected thereafter in the course of any routine medical examination, he should be required to undergo the practical test again. Otherwise a licence granted to a protan under regulation 63 should be subject to the additional condition that the pilot does not fly an aircraft at night.

79. Finally, while recognising that the Tribunal has no power to review decisions of the Authority to set medical standards under regulation 62, we suggest that protanomals ought not to be totally prevented, as they are at present, from meeting the colour vision standard. It appears from Dr Samuel's evidence that some persons with mild protanomaly are able to perceive the existence of red lights at a distance which is as great as, or greater than, the furthest distance at which a person with normal colour vision and distant visual acuity of 6/6 can do so. We suggest that the colour vision standard be altered so as to permit such mild protanomals to take the Farnsworth Lantern test and, if they pass it, to meet the standard and so be qualified, so far as colour vision is concerned, for the grant of an unconditional licence.