Everything you need to know if you are new to Colour Vision Regulations
Colour Vision (CV) is defined as the ability to distinguish colours amongst various wavelengths of light waves and to perceive the differences in hue. There are important questions for anybody wanting to understand colour vision in aviation. Why does CV matter in aviation? How is it regulated around the world? What about Europe? Can you become a pilot if you're colour vision deficient (commonly and wrongly defined as colourblind)? We're going to answer all these in the following article that will serve as an introduction to beginners and everyone, in general, interested in this specific matter.
1) Why does colour vision matter in aviation?
To reply to this one we have first to introduce a series of ICAO statements on the issue:
"Colour plays an important role in the transmission of information from the environment to aviation personnel. Color-coded information is found on instruments and displays, radar screens, charts and documents, and throughout the external airborne and terrestrial environment. Over time, aircraft systems and equipment have become increasingly complex. In many cases that complexity includes an increased use of colour-coded information."
"However, there remain questions and uncertainties about the aeromedical significance of needing to recognise specific colours in aviation and how to best test for these."
ICAO quotes that ‘the problem with colour vision standards for pilots and air traffic controllers is that there is very little information which shows the real, practical implications of colour vision defects on aviation safety’. (Manual of Civil Aviation Medicine, 2012)
"The manual (Manual of Civil Aviation Medicine (Doc 8984)) recognises that “precise physical and physiological criteria cannot be given because of the large number of variables in different viewing situations.” The challenge is to “determine exactly where the cut-off between ‘safe’ and ‘unsafe’ should be placed with respect to an initial applicant who chooses aviation as his career or hobby".”
There are various studies that tried to investigate where this cut-off between safe and unsafe really is, CAA UK 2009 study arrived at the conclusion that PAPI lights are the most safety critical colour-coded task in aviation and in collaboration with London City University developed a test called CAD Test (Colour Vision Assessment and Diagnosis), the DTA of New Zealand published in 2015 a detailed study that analyzed all the available literature and questioned a lot of facts previously presented within these studies and highlighted flaws within the CAD test and other lab-based methods.
"The evidence raises questions about the suitability of current clinical test regimes as a means of restricting or disqualifying applicants. Consistent with the finding of NATO and the practice of some regulators, it is instead recommended that a practical or operational check, to identify practical handicaps as a result of CVD, is a more relevant and fair method by which to determine whether an applicant can safely crew an aircraft."
At the time of writing there is no empirical evidence that demonstrates where this cut-off really lies, as CV is somewhat subjective and the deficiency presents itself in a wide range of severities, DTA suggested that the only way to judge whatever a candidate is really "safe for the job" is trough a comprehensive operational test and continuous monitoring of the performance of the candidate throughout his/her training.
2) How is CV regulated around the world?
As we discussed before, CV regulations are extremely variable among NAA but usually, they're all divided into at least two stages, a third stage is present only in some countries:
1) Pseudoisochromatic Plates:
This is a screening test, the most commonly used is the Ishihara Test, a series of plates are presented to the candidate who has to identify numbers or figures, it's employed for its easy, fast and economic setup. Generally, a pass on this one means that the candidate is Colour Normal so no further tests are carried out. Depending on the authority this test can be repeated during renewals or revalidations, this is because AMEs are aware of the availability of those tests to the general public and the relatively easy way to memorize the patterns. If instead, you failed this test it probably means that you could have a Colour Vision Deficiency that requires further investigations, this is carried out with a series of secondary tests. Even on the standard to define a pass, there are differences across authorities, UK CAA allows 0 errors where, for example, the US FAA allows up to 6 errors.
2) Secondary (Advanced) Tests:
If you have failed the screening test, generally a second-level test is carried out by the medical authority, this can be performed using various clinical tests such as Lantern Tests (Holmes-Wright, Beyne, Spectrolux, FALANT are the most common), Nagel's Anomaloscope Test, CAD Test or Farnsworth D15; in the above table are described the requirements in force in the main countries. At this point the problems start to emerge: every single authority can decide to administer different tests according to its regulation, the issue with this is that lot of variability is created, so no single standard is followed. You can be deemed as colour safe by one country and unfit by another, as you'll fly through a common sky shared by all the ICAO member states aircrafts this creates a situation where the standards actually in place have and should be questioned.
Figure 1 -The UK CAA Colour Vision Regulation – Truly A Grey Area!- Author Jordan Penning
3) Operational Colour Vision Assessment (OCVA)
In some countries like USA, Australia and New Zealand an operational in-flight test is performed in the case where the applicant failed both the screening examination and the advanced clinical test. The examination carried out by an authorized examiner chosen by the competent NAA, consists on a flight (day and night conditions) evaluating various aspects of the candidate readiness and ability to interpret colour coded signals, if the outcome is positive he/she will be deemed as colour safe and no further restrictions (except from flying without radio contact into a controlled aerodrome) will be imposed on his/her license. Some authorities, especially in Europe, don't agree on this testing method, saying that so much variables can't be considered or calculated and a decision can't be based on a single or a couple of flights, Jordan Penning in his "The UK CAA Colour Vision Regulation – Truly A Grey Area!" made this statement regarding this issue:
"There are some challenges to the OCVA stemming mainly from the UK CAA and in the 2014 Senator Fawcett vs CASA's Director of Aviation Safety and Principal Medical Officer hearing. The CASA director mentions that because a practical flight test happens on one day when the weather, conditions and flying situation are in one state it may not replicate the worst possible conditions the pilot will experience, therefore it can’t be used to
determine whether a respondent is colour safe or not as the NAA won’t be able to determine the safety in all different types of scenarios. Nevertheless, the counterargument to this in which the CVDPA and the Senator argued, was that any flight examination for licensing is based on the day that examiners asses an individual.
They decide on that day alone whether the candidate is safe to perform the duties of the licence entitlements. Furthermore, the UK CAA offers a medical flight test for respondents with a condition in one eye, so therefore this argument is an unnecessary barrier. (Rural & Regional Affairs and Transport Legislation Committee, 2014)"
ACRONYMS and TERMINOLOGY
AME: Aeromedical Examiner (Doctor conducting the medical examination)
CASA: Civil Aviation Safety Authority (Australian NAA)
CAA UK: Civil Aviation Authority of the United Kingdom
COLOUR NORMAL: A person possessing all of the three independent channels for conveying color information, derived from the three different types of cone cells in the eye and not having any abnormality within them.
COLOUR SAFE: The ability of an applicant to readily distinguish the colours used in air navigation and correctly identify aviation coloured lights.
CV: Colour Vision
CVD: Colour Vision Deficient
EASA: European Aviation Safety Agency
ENAC: Italian NAA
ICAO: International Civil Aviation Organization
NAA: National Aviation Authority
TCCA: Canadian NAA