PAPI and colour blindness

[Menen]

Just read a NTSB report where a Fedex B727 crashed well short of the runway during a night black hole approach. The F/O who was PF had a colour vision problem, and it was thought that not only the PAPI may have been affected by condensation on the lens system causing erroneous light signals, but that the pilot may not have picked up the red undershoot lights due his eye sight problem.

Any of you reading this post who may have slight colour vision deficiency ever had problems with PAPI colour discrimination? If so, what did the PAPI light signals look like to you?

[Bill Smith]

This has been done to death and proved that colour vision deficiency has no effect on piloting skills.

See Arthur Pape in the medical section.

It is not a "blindness" it is a sensitivity.
Chart has a descent profile published for cross checking.
Even if you are 3 reds and one white your aiming point/touchdown will still be the same albeit the glidepath will be lower.
The problem arises when you have 4 reds, then you lose any ability to assess where you are in relation to glidepath.
I have spoken to many pilots in regards to this and most "colour normals" agree that on a dark dirty night they have trouble with some of the papi approaches around the place.

The question has to be asked as to why both pilots failed to notice the deviation from the papi?

To answer the question it is impossible to tell a colour normal what you are seeing.
As long as the colour deficient is able to distinguish a difference and follow it accordingly, it doesn't matter what colour the lights are.

[Menen]

Bill Smith.

Thanks for the erudite reply. So from what you say, I take it that the NTSB report is all a horses arse? I do recall there was much criticism of colour blindness tests in Australian aviation circles many years ago. By the way, not all Australian instrument approach charts have a DME - Altitude scale - Mount Gambier for example, which is a well known black hole approach according to ATSB.

Now lets have a look at just one part of the NTSB horses arse report, shall we?
Quote in part:

"At the Safety Board's request, the first officer completed an extensive post-accident ophthalmic evaluation at the USAF School of Aerospace Medicine. During this evaluation, the F/O passed the FALANT (colour vision screen typically used by FAA medical examiners), but failed seven additional red/green colour vision tests.

The USAFAM report stated that the F/O had a severe congenital deuter-anomaly that could result in difficulties interpreting red-green and white signal lights. The report also stated that "we believe that he would definately have problems discriminating the PAPI's, because the red lights would appear not to be red at all, but more indistinguishable from white than red. Also, it would be extremely unlikely that he would be capable of seeing even the colour pink on the PAPI, more likely a combination of whites and yellows and perhaps not even that difference.

The USAFAM conclusions are supported by the results of an Australian study, which showed that individuals with colour vision deficiences similar to the first officer mistakenly identified the red light signal as white in up to 29 cases.

The Safety Board noted that this error could be especially dangerous when interpreting a PAPI signal because it might lead a pilot to descend lower when the aircraft is already too low.

The Safety Board concluded that the first officer suffered from a severe colour vision deficiency that made it difficult to correctly identify the colour of the PAPI signal during the below-glidepath approach to Runway 09 at TLH.

The Board added that current aviation medical certification standards for colour vision and related screening tests do not emphasise the full compexity of colour in modern operational situations, which include not only navigation lights, PAPI/VASIS displays and light gun signals, but may also involve cockpit displays, including weather radar, other flight instruments and gauges and annunciator panels.

Now, whats this about colour vision not having any effect on flight safety, Bill Smith?

[Bill Smith]

Colour Vision Standard in Aviation
by Arthur Pape MD

The colour vision standard in aviation has obstructed the aspirations of thousands of pilots and would-be pilots around the globe. Nowhere more than in Australia has the fight been more aggressively fought to remove restrictions on pilots with reduced (defective) colour vision. The author, an Australian commercial pilot, medical practitioner and colour defective, conducted two major court appeals against the standard in the late eighties, both of which succeeded in removing operational restrictions from colour defective pilots in that country.

Colour defectives have one and one only disability: they cannot accurately and reliably name certain colours when they see them. They fail colour vision tests, specifically designed to detect this disability. Supporters of colour vision standards argue that colour is used ubiquitously in aviation to code important information that pilots need to safely perform their duties as pilots. However, when testing their proposition, these supporters invariably make the naming of colours the end-point of the experimental task. Predictably, colour defectives perform less well than colour normals in this setting.

However when flying aeroplanes the accurate naming of colours is never an end-point in itself. It is the underlying information of operational significance that pilots need to access to make sound and safe operational decisions. A long list is easily drawn up of the many pieces of operationally significant information used by pilots. For example, pilots are intensely interested in navigational information, powerplant and airframe parameters, the occurrence of abnormal flight conditions and adverse weather, and so forth. Only by familiarity with the way in which pilots use this information, how each and every piece thereof translates into operational decision making, can the colour perception standard be properly appraised. It is a big task, and one with which the author has been involved for twenty years.

The extent to which colour plays a significant role in the provision of these many pieces of information is by no means established scientifically. The degree of disadvantage, therefore, that a colour defective pilot might experience is similarly not at all clear. The experience of the many thousands of colour defective pilots now flying with no restriction in the USA and Australia would suggest that there is no disadvantage at all. Likewise, careful analysis of the geometry of collision avoidance at night and of the information available in the state of the art EFIS display systems reveals that, on first principles, colour vision defectives should have no difficulty in performing all the tasks required in the "performance of their duties".

The author recently attended an ICAO working group in Warsaw, Poland, on behalf of IAOPA. At that meeting it was clear the European representatives were intent on increasing the stringency of their already very strict colour perception requirements. The prospect for a rational international standard is therefore slim. What appears will happen is that the USA and Australia, and possibly Canada, will progress to ever less restrictive colour vision standards, while Europe goes in the opposite direction. There is an underlying reason for this: the European states offer far less opportunity to appeal standards such as this one before the law. The standard is vulnerable to detailed examination, an exercise the protectors meticulously avoid.

This editorial as well as the following web page offer insight into the colour perception standard and its weaknesses. Perhaps it may stir some long overdue debate, particularly where the proponents of this standard stand so well shielded from critical scrutiny.

Arthur Pape MD

[Menen]

Thanks Bill Smith. The colour displays in the cockpit with good illumination probably compensate for colour vision problems to a certain degree. Arthur Pape is certainly the expert in his field I am sure.

Having said that it is also hard to disregard the NTSB evidence with regard to the serious doubts of the first officer to pick the PAPI reds. From the results of the Fedex B727 accident, it certainly seems his colour vision deficiency was a significant factor in the under-shoot accident.

I have always thought that T-VASIS was the best of VASIS systems because it does not rely on colour discrimination - keeping in mind of course that all VASIS systems can give erroneous indications in mist, fog or rain under certain combinations. At least with T-VASIS the 3 dots fly-up lights precede the final red lights which appear at 1.9 degrees.

[frangatang]

Everytime l fly into australia l have the same old arguments on the T vasi with my erstwhile first officer,who all insist on flying
it the wrong way,even tho there is a booklet on it.It helps,having flown in Oz for 6 years,so from now on l will tell them if it says T that means thrust you are low!

[Bill Smith]

Menen

Couldn't agree with you more the T Vasis is an excellent system which leaves very little ambiguity as to where you are on the profile.
I think that the NTSB would lean towards assuming that the Color deficient F/O incorrectly identified the PAPI rather than assuming that both crew has missed the fact that they were low.
I am not saying that it couldn't happen it just seems strange that 2 suppossedly fully functioning crew would fly low on profile without realising.
I guess we will never know what the crew were seeing unless it is on the Tape somewhere !!

Cheers:ok:

[Prop's ????]

Menen

Now, what’s this about colour vision not having any effect on flight safety


Are you saying pilots with colour deficiencies are unsafe?

I have a deficiency and have passed all CASA required tests. I fly both VASI and PAPI approaches regularly and have never had a problem distinguishing the red/white lights.

To be honest, I never had a problem with my colour vision until I sat my first medical. When they advised me I had a colour deficiency I was amassed, my first thought was I could see all colours.

Yes I have a problem reading the Ishihara colour test cards, but how relevant are they to aviation, an artist I will never be.

I don’t think generalising is totally fair. I fly with older pilots many in there 60’s, should I constantly assume they all have heart problems?

Going back to the report I also have to ask, if it was a colour deficiency that caused this incident. Then both pilots’ must have been affected.

[barleyhi]

I have a deficiency and have passed all CASA required tests. I fly both VASI and PAPI approaches regularly and have never had a problem distinguishing the red/green lights.

Bit of a worry if you're looking for green lights on the VASI & PAPI!!!

[Prop's ????]

barleyhi

Your right, I have corrected my mistake accordingly.

What I was referring to is that most colour deficient people have a red/green deficiency.

[OZAZTEC]

Prop's ????

With you - Like you I was found to have a deficiency at an aircrew medical (16 yo and devastated)- up to then no realisation of a problem. The T-Vasi is a great system and is sureley the best with or without a deficiency. Misreading on PAPI's have on numerous occasions been given as the reason for unstable approaches and in the worst case accidents/CFIT with 'Normal' colour vision pilots.

Menen, any pilot has the ability of stuffing up - We are human. Knowing that I have a coulour deficiency only sharpens my awareness of the situtaion. If I thought I was unsafe I would not fly!

Bill Smith - with you all the way.

If only my primary teacher had told me that tomatoes were red and peppers (green) were green! (now there is an interesting thought)

[Islander Jock]

For those who haven't done so yet, have a look at the colour defective thread in the Medical Issues forum.

We should all (us CVDs that is) feel pretty lucky that we can fly unrestricted in Australia. Although like me many perhaps have the CPL and Oz Airspace only restrictions on their medicals. All thanks to Dr Arthur Pape who took CASA to the AAT and at huge personal expense, won.

The poor guys in UK and Europe seem to be having a much harder time of it although some progress is being made.

Props,
Going back to the report I also have to ask, if it was a colour deficiency that caused this incident. Then both pilots’ must have been affected.
When I read the same report, I wondered the same thing. The CVD issue therefore might just be a convenient scapegoat in this case.

Of interest locally is that the job ads for CALM pilots now specify "normal colour vision". Probably something to do with identifying coloured ground markers