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Red, Green or White

Find out why colour vision is crucial for aviators, and if colour-blindness disquali­es all aspiring pilots.

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia, Color Blind, Inflight Magazine,CVD test,Colour Vision Deficiency

COLOUR BLINDNESS

As a general rule, airlines do not employ pilot aspirants with colour vision issues for obvious reasons. Safety is paramount and in some countries where rules have been relaxed, a pilot with a case of colour blindness may never be a commander.

     To begin with, a more politically correct term for colour blindness is colour vision deficiency (CVD). This is the inability or a decreased ability to see and interpret colour correctly.  About eight percent of men and 0.5 percent of women in the world are born colour-blind. That’s as high as one out of 12 men and one out of 200 women. 

     There are various degrees of colour blindness. Protans are people who have problems recognising red while deutans are those who find it hard to identify green. It is the latter category that makes up 99% of CVD cases. Red-green deficiency is the most common. Blue-yellow is next and is prevalent among three to six percent of the population. This deficiency can be acquired from chemical exposure, as well as the aging of the eye. 

     A person with colour deficiency is often slower to identify colours and more likely to misidentify them. This is why colour-blind people are restricted from becoming commercial pilots. 

     However, not all is lost if an aspiring pilot can pass a CVD test. 

CRUCIAL COLOUR RECOGNITION

Colour vision is essential to pilots especially when flying at night. Firstly, pilots must be able to recognise aircraft position lights. At night, it’s easy for pilots with good vision to know if they are flying headon towards another plane or safely in the same direction by merely looking at the lights on its wing tips. 

     This is possible because the navigation light on the left side of the wing tip is always red while the light on the right is green. So, if you see a red light on the right wing tip at night, this would mean that you are on a collision course with the plane ahead! 

     Additionally, a pilot must be able to identify colours of the light-gun signal in an emergency, airport beacon lights, approach–slope indicators and chart symbols. The light-gun signal is used by air traffic control to communicate with aircraft; different colours and flash patterns indicate specific directives. 

     But the most crucial signal to read is the approach-slope indicator, a light system on the side of an airport runway threshold that provides visual descent guidance during approach. Its lights indicate if a plane is well below the correct landing path (red) or too high (white) for a safe touchdown. 

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,Inflight Magazine,airport runway,light-gun signal,light system,flying at night

The runway is lit in a variety of colours, each performing a specific function like indicating the beginning and end of the runway, marking the edges of the runway and so forth.

RUNWAY LIGHTS & SAFETY 

A pilot must also be able to distinguish the colours of runway lights during landing. For example, the green threshold (from the beginning of the runway) lights are of considerable significance when a pilot is landing at night. A colour blind pilot might have difficulty perceiving a displaced threshold (part of the runway that cannot strictly be used for landing) and land in the danger zone. 

     In extremely poor visibility (about 100 metres), pilots, during an automatic landing are also trained to recognise the runway length by distinguishing the colours of the runway centre line lights and override the system by applying the brakes earlier than usual. Variable white lights denote lots of room to spare, alternate red and white light indicate 900 meters (3,000 feet) to go, and red lights mean the pilot will run out of runway in another 300 meters (1,000 feet)! 

     Safety regulations state that a pilot must have ‘the ability to perceive those colours necessary for the safe performance of airman duties’. An inability to satisfy this requirement may prohibit pilots to fly on grounds of colour deficiency. 

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,Inflight Magazine,Colour Blindness Test,colour vision test,Ishihara plate

Ishihara plate (Can you see the  figure ‘8’?)

COLOUR BLINDNESS TEST 

An aspiring pilot with a mild case of colour blindness will have to pass a colour vision test. If the candidate fails the colour blindness test, he or she will be given a second chance with a different colour vision deficiency check.

     Most pilots with colour vision deficiencies are only mildly affected and can easily perceive the colours necessary for the safe performance of a flight. A person who has a significant and potentially hazardous colour vision problem is likely to fail his or her colour vision examination.

 CHALLENGE BY CVD PILOT 

In 1987, a pilot applicant in Australia met all the requirements of his medical examination but was unable to meet the standards of the colour vision test. He was therefore granted a licence with a condition that he not fly an aircraft at night. However, he brought a case against the Civil Aviation Authority requesting that his licence not be subject to that condition. 

     After many presentations by experts, it was decided 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. However, that was an exception; this pilot would require the approval of the civil aviation authorities of foreign countries if he were to operate outside Australia.

 NOT THE END OF THE RUNWAY 

These restrictions are in place for the safety and protection of passengers, and aren’t merely a bureaucratic or flippant policy.  

     In fact, I know a pilot with colour blindness who is flying as a First Officer only because his medical test restricts him from exercising his privileges outside the Australian airspace or above his Commercial Pilot Licence level, thereby precluding him from obtaining a command position and becoming a Captain. 

     As you can see, an aspiring pilot with a mild case of CVD can still pursue his flying dream if he can satisfy some of the colour blindness tests as prescribed by aviation doctors.


From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,Inflight Magazine,AirAsia X Simulator Flight Instructor,Captain Lim Khoy Ling,AirAsia Airbus A320,AirAsia X A330/A340 pilot

     Captain Lim Khoy Hing is a former AirAsia Airbus A320 and AirAsia X A330/A340 pilot who also used to  fly the Boeing 777. He has logged a total of more than 25,500  flying hours and is now a Simulator Flight Instructor with AirAsia X. In his spare time, he shares his opinion on aviation issues with others. For more air travel and aviation stories, check out his website, ‘Just About Flying’ at  www.askcaptainlim.com.

From The Magazine, Pilot's Perspective, Captain Lim, Travel 3Sixty, AirAsia,Inflight Magazine,AirAsia X Simulator Flight Instructor,Captain Lim Khoy Ling,AirAsia Airbus A320,AirAsia X A330/A340 pilot,Life in the Skies,Just About Flying,AirAsia Megastore

     Capt. Lim’s first book, Life in the Skies, has just been released. You can purchase it on-board all AirAsia and AirAsia X flights, AirAsia Megastore kiosk at LCCT Sepang or on-line at AirAsia Megastore at www.airasiamegastore.com/life-in-the-skies.html. They are also available in all major book stores in Malaysia and Singapore Enjoy the great collection of articles, anecdotal stories and observations of this veteran aviator in this book.

RESOURCES:

  • Andy

    What a load of tosh! Mr Lim Khoy Hing is just reinforcing the common layman’s mistaken belief that colour recognition is crucial in aviation. It is not as colour coding in aviation is completely redundant as proven in a very long court process in Australia which was certainly the most thorough examination of the use of colour in aviation that the world has ever seen. Its conclusion was that all Deutans (green deficient) pose no threat to aviation safety and should not be restricted in any area of aviation, even captains of airliners. It did not come to exactly the same conclusion about Protans (red deficient) and the boat is still adrift on that one unfortunately. A protan pilot is currently getting his refusal for captaincy reviewed by the AAT and I suspect this is the person Lim Khoy Hing is referring to. Mr Lim Khoy Hing appears quite uninformed on this issue and makes the mistake of lending his weight in favour of the unjustly discriminatory behaviour of most aviation authorities on the colour vision [non-]issue. Only Australia has been brought to task on this unjust discrimination because it is lucky enough to have a review body called the AAT which is independent of the aviation authority and able to make its own mind up. Most other countries leave review of aviation medical decisions up to the aviation authority who made the decision in the first place – so they can play judge, jury and executioner without fear of recourse. Now Australia has hundred of colour deficient pilots including international airline pilots flying into cities near you, without incident and for the last 25 years proving they perform just as safely as the colour normal pilots. Please stop this unjust discrimination. Stop telling us we cant fly safely when it is so obvious we fly just as safely as anyone else. Show us the evidence – show the mistakes we have made – you cant because its just an old wife’s tale and yet it continues to destroy the dreams and potential careers of 8% of the male population.

    • Carl

      Hi, I am a private pilot in the uk who also has this restriction of no night flying. I have actually flown at night with my instructor with out incident. My instructor, who is also the chief flying instructor couldn’t fault my approach, landing or my identification of the airfield lights. I feel powerless to get this restriction removed as the CAA don’t want to know. I couldn’t pass their computer based exam that had no practical use. I’m just hoping that one day I may be able to progress through medical treatment as I don’t see the rules changing.
      There is actually no reported incidents of a colour blind pilot causing an accident. The fed ex flight that crashed had two other pilots on board, both had perfect colour vision so clearly not the reason that plane crashed.

      • http://www.airasia.com/travel3sixty Travel 3Sixty

        Hi Carl,

        As pointed out to Andy from Australia, the official view of the aviation authorities on colour vision deficiency worldwide is about the same. It appears that Australia is leading the world against this restriction (‘unjustly discriminatory behaviour’ as stated by him). Unless they can convince the authorities that, in the worst case scenario, protans (red deficient pilots) can safely operate a commercial airliner, then fine and good.

        Similarly, many people with colour blindness will still be able to get a car driver’s licence, but may not qualify for a commercial driver’s licence or may have restrictions that mean they cannot drive at night. This is what happens in the Australian aviation industry – there is a restriction that such category of pilots can operate only as a first officer but not as a captain.

        Lim Khoy Hing

    • http://www.airasia.com/travel3sixty Travel 3Sixty

      Hi Andy,

      My article was written without malice but merely on some general information about colors and the aviator. It naturally highlights the official view of the aviation authorities, especially CASA (Civil Aviation Safety Authority) on cases of color blindness. I fully support CVDPA (Color Vision Deficiency Pilot Association) objectives of promoting the legitimate and just aspirations of CVD pilots. As a former pilot, I empathized with all my fellow aviators and hope Australia will lead the way to eventually overcome these obstacles and prove to the world that CVD pilots are just as safe as normal pilots. I wish you all the best in your endeavor against the aviation authorities in Australia.

      Lim Khoy Hing