Colour vision deficient pilots see red

While the topic of aberrant regulatory conduct dominates the nation’s aviation dialogue, we’re wondering whether a letter from CASA to all employers of pilots might represent a practical joke, an early example of a scorched earth strategy, or an act of rebellion against the ASRR’s erudite recommendations.

We’d speculate that such a bizarre missive could hardly have originated from the aviation medics, who would be well aware that when you want to quote medical research convincingly in support of a position, you need to provide a reference to the relevant original medical research papers that present the evidence referred to. (We’ve requested that reference from CASA and are still awaiting a response.)

It also seems unlikely that the letter got the nod from CASA’s legal office, because it seems to be asking AOC holders and/or pilots to make decisions which CASA’s not prepared to make itself.

No, it’s signed by the executive in charge of CASA’s” Permissions Centre,” sometimes referred to by disenchanted permission seekers as the “Sheltered Workshop.” But what on earth it hopes to achieve is difficult to discern. It tells employers that “the possibility exists that your pilot’s CVD may be of a type and/or severity that could adversely affect aviation safety to a degree greater than was believed to be the case when the medical certificates were issued,” and then it goes on to tell their employers to make decisions they are not equipped to make because CASA simply hasn’t told them what the hell it’s on about and it doesn’t tell them what the problem is and what it considers is an “appropriate” course to take.

Here’s the letter which all AOC holders received on June 5. We follow it with a commentary by Dr Arthur Pape, who is widely acknowledged as Australia’s leading expert on the issue of colour vision deficiency (CVD).

If you’re bewildered by the letter, you’ll find Dr Pape’s analysis enlightening by comparison, and indicative of a clear way forward for any responsible medical official seeking to develop intelligent and effective policies on this not-so-complex issue.

5 June 2014

Dear AOC holder,

Colour Vision Deficiency

I am writing to inform you of actions the Civil Aviation Safety Authority (CASA) has taken in relation to pilots with a recognised colour vision deficiency (CVD) in the light of recent medical research involving the assessment of CVD, and the possible implications of these developments for affected pilots and the operators who employ them.

A number of pilots have taken their medical certificates issued subject to a limiting condition because they do not meet the applicable medical standard for colour perception specified in the Civil Aviation Safety Regulations 1998 (CASR). You may employ one or more pilots whose medical certificates are subject to such a condition.

Recent medical research indicates that the safety-related implications of an individual’s CVD may be more significant than they were initially considered to be, and the possibility exists that your pilots CVD may be of a type and/or severity that could adversely affect aviation safety to a degree greater than was believed to be the case when the medical certificates were issued. CASA is reviewing the situation and will consider what further action, if any, may need to be taken on the basis of that review, at which time affected medical certificate holders will be notified accordingly.

In the meantime, CASA has written to all potentially affected pilots advising them to consider whether it is safe for them to continue to exercise their flight crew privileges subject only to the existing CVD-related condition, and encouraging them to seek the advice of their personal physician or designated aviation medical examiner about any adjustments that should be made to their flying practices, pending the outcome of CASA’s review.

As I told recipients of that advice I would be doing, I write to you now, as the holder of an air operator’s certificate (AOC) who may employ one or more affected pilots, to encourage you to consider whether it is safe to allow those pilots to continue to exercise flight crew privileges under your AOC, subject only to the existing condition, and what adjustments to those arrangements you may consider to be appropriate, in the interests of safety, pending CASA’s further determination of the matter.

For more information visit CASA’s website at:

For further details, please contact Dr Pooshan Navathe, principal medical officer, on 131757. Yours sincerely,


Peter Fereday

Executive Manager, Industry Permissions

Enlightenment from Dr Arthur Pape

The Aviation Colour Perception Standard[i] (ACPS), as specified by ICAO and replicated by practically all signatory states, requires that: “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.”

At its philosophical/scientific core, this so-called “standard” represents a conclusion (or argument) based on three implicit assumptions, as follows:

Assumption 1

There is extensive use of colour-coded information in the aviation environment.

Assumption 2

The “safe performance of duties” in the aviation environment is dependent on “the ability to perceive readily those colours necessary etc etc……..”.

Assumption 3

Without ‘the ability to perceive readily those colours, the perception of which is necessary for the safe performance of duties”, these duties will be performed unsafely.


The validity or “truth” of the ACPS relies entirely on the validity or “truth” of each of the three assumptions. In turn, the validity or “truth” of each of the assumptions relies on evidence, as opposed to opinion and/or established prejudice.

Let’s consider the first assumption. At the dawn of aviation, over a hundred years ago, colour coding was used solely in the form of signalling by means of coloured flags or lights, as the means of communication between people on the ground and in the air. It was suggested that people who could not readily perceive the colours of those signals might perform their duties “unsafely”, and that suggestion, under the circumstances of the day, would have had some merit. Out of this there arose the ACPS, whose wording has changed little from those heady days of cloth covered aeroplanes and simple instructions to pilots using simple coloured objects in a simple “code”.

Since then there has been an exponential increase in the use of colour throughout the aviation environment, both in the aviation physical environment and in and on aeroplanes. The list of uses of colour is enormous, and the validity of the first assumption is self-evident to anyone with even a minimal knowledge of the aviation environment.

Result: Assumption 1 is “True”.

Assumption 2 is, however, problematic. For this assumption to be valid, it needs to be demonstrated that the perception of the colour(s) is sufficient and necessary to see the information that is required for the “safe performance of duties”. In other words, “see the colour” equals “see the information”, which results in “safe performance of duties”. This assumption could be tested empirically, but this type of work has never been done in respect to the aviation environment.

Result: Assumption 2 remains an unproven assumption

To paraphrase assumption 3, would go like this: “see no (or different) colour” equals “see no (or wrong) information” which results in “unsafe performance”. To digress briefly, let me state that the existence of individuals with colour vision deficiencies (CVD) is a proven reality. That 8 to 9 percent of the male population and just less than 1 percent of the female population have one or other of the various types of CVD is beyond any doubt. Further, there are numerous reliable and proven tests available to detect and classify the severity of any particular CVD condition. Let me add also that the CAD test is an excellent test to diagnose and quantify CVD conditions.

So, in short, the ACPS, via the implicit Assumption 3 would predict that people with CVD should perform the duties (involved in flying an aeroplane) unsafely. This proposition could be tested empirically (i.e., by measurement, observation and analysis). No formal empirical testing of assumption 3 has ever been conducted.

Result: Assumption 3 is also problematic.

It is a fact that pilots with CVD have been around for a very long time and in considerable numbers. For almost a century, the FAA has applied a wide variety of colour vision tests and practical tests, whereby tens of thousands of CVD pilots either passed the ACPS or were granted waivers against the standard. Since 1989, a few thousand Australian CVD pilots have enjoyed the freedom to fly at night and many hundreds have achieved successful careers in airline operations. If Assumption 3 were “true” one would expect there to be evidence of “unsafe performance of duties” by these pilots. This should be particularly evident in the incident and accident records kept by the aviation authorities of the USA and Australia. A landmark study in the mid 1970s by two researchers (Dille and Booze) working for the FAA examined the accident records of the large group of CVD pilots with a “waiver” and found not even one accident where the existence of a colour vision defect could have contributed to the cause. Furthermore, the accident rate for this group was no different than that of the general pilot population (accidents per 100,000 hrs of recent experience). Until 2002, the FAA had no record of any accident attributed to CVD, and since 2002 there have been none. The significance of 2002 is that in that year a Fedex B727 crashed while on a PAPI-guided night visual approach, and the CVD status of the flying FO was attributed a causal role in the crash. However, two other crew had normal colour vision and also did not see what the PAPI should have been showing them. The relationship between this crash and the significance of CVD is highly contentious. The ATSB and CASA have admitted they have no record of any accident attributed to CVD.

The Australian experience since the Denison case in 1989 has provided excellent positive evidence against the “truth” of Assumption 3. There are estimated to have been several thousand CVD pilots operating with either no restriction or minimal restriction in the period in question, and a significant number at the highest level of airline operations. I can say with confidence that we have examples of even the most severe kinds of CVD working as captains and FOs on the full range of airline type aircraft. These pilots are surveilled, trained, tested and examined in exactly the same way that pilots with normal colour vision are handled. They pass and keep on meeting all requirements “necessary” for the “safe performance of their duties”, and these assessments are made by duly qualified examiners of airmen, as opposed to aviation medical doctors or optometrists. This is taken by many informed commentators as evidence that Assumption 3 is “false”, and raises the question as to whether the ACPS serves any useful role in modern aviation.

It is abundantly evident that the appeal by John O’Brien [A pilot with CVD] and the unprecedented interrogation of CASA on this topic in the Australian Senate has triggered a tsunami of hysterical and irrational activity within CASA. It is my view that CASA’s actions and the responses by the Director and the Principal Medical Officer to the Senate Estimates Hearings reflect an absurd and indefensible position. Claims of “medical evidence” by both in support of their stance cannot be substantiated because such evidence does not exist.

There is no “rocket science” in any aspect of this saga.



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About Paul Phelan

Paul Phelan flew for over 50 years in private, charter, corporate and regional aviation, worked in senior management roles with a major regional airline, and retains his license. In parallel he has been writing for Australian and international aviation journals for well over 20 years on all aspects of aviation including aircraft evaluation, flying, industry affairs, infrastructure, manufacture, regulatory affairs, safety, technologies and training. He has won three separate National Aviation Press Club awards for "best technical aviation story of the year."

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