Starting a campaign to improve PAPI
Thread Starter
Starting a campaign to improve PAPI
I have no idea how to go about this and therefore seek advice from people who have dealt with aviation authorities such as ICAO, FAA, CASA (UK, AUS), etc.
The problem as I see it...
The white light of a white/red PAPI system is too close to the colour yellow/orange and this results in inadequate contrast with the red lights.
You know what I mean! If you are on the correct descent path with the PAPI indicating two reds and two whites, and then start descending below the correct path, the transition from two reds to three reds is very gradual and nebulous. It certainly does not attract your immediate attention!
Even if you are on the correct descent path with solid red and "white" light indications I often find due to particulate air polution such as smoke, smog, or dust, the white light isn't really white, but rather an orange hue.
I believe the problem lies in the fact that the PAPI specifications standards of ICAO, FAA, etc. allow the manufacturers to use halogen bulbs for the white lights. The problem with these lights is that they are not hot enough.
White light emitted by light bulbs can be defined in terms of temperature. The hotter the temperature the whiter the light (because as the temperature increases it includes more of the green, blue, and violet light spectrum (higher frequencies).
Apparently Halogen light is at 3200K whereas sunlight is 5250K.
(Kelvin (K) is a scale used to measures absolute temperature).
These days we can do much better than Halogen light bulbs and that is to use Xenon light bulbs.
Xenon light bulbs emit light at a much higher temperature (around 5000K) and therefore are much further away from the red/orange light and closer to pure white.
We've all seen Xenon headlights on cars. They look positively blue in comparison to the normal halogen headlights.
Another example of the hotter blue light is the (ironically) "cool white" compact fluorescent light bulbs as compared to the "warm white" variety. If you look at the box you will see that the "warm white" bulbs are described as emitting 3000K white light and the "cool white" bulbs are described as emitting 5000K white light.
Here is a web site that describes the contrast between Halogen and Xenon well.
Advantages of Xenon headlights
The blue Xenon light (by comparison to the halogen light) presents a much starker contrast to the red filtered lights used in the PAPI system. It would make the PAPI system a much more effective tool against the risk of inadvertently flying too low and short of the runway especially during visual/circling approaches.
So my question is, how do I go about putting this argument to the various authorities to the view of initiating the required changes?
Can someone describe the processes involved and how to get them started?
And yes I'm serious!!
The problem as I see it...
The white light of a white/red PAPI system is too close to the colour yellow/orange and this results in inadequate contrast with the red lights.
You know what I mean! If you are on the correct descent path with the PAPI indicating two reds and two whites, and then start descending below the correct path, the transition from two reds to three reds is very gradual and nebulous. It certainly does not attract your immediate attention!
Even if you are on the correct descent path with solid red and "white" light indications I often find due to particulate air polution such as smoke, smog, or dust, the white light isn't really white, but rather an orange hue.
I believe the problem lies in the fact that the PAPI specifications standards of ICAO, FAA, etc. allow the manufacturers to use halogen bulbs for the white lights. The problem with these lights is that they are not hot enough.
White light emitted by light bulbs can be defined in terms of temperature. The hotter the temperature the whiter the light (because as the temperature increases it includes more of the green, blue, and violet light spectrum (higher frequencies).
Apparently Halogen light is at 3200K whereas sunlight is 5250K.
(Kelvin (K) is a scale used to measures absolute temperature).
These days we can do much better than Halogen light bulbs and that is to use Xenon light bulbs.
Xenon light bulbs emit light at a much higher temperature (around 5000K) and therefore are much further away from the red/orange light and closer to pure white.
We've all seen Xenon headlights on cars. They look positively blue in comparison to the normal halogen headlights.
Another example of the hotter blue light is the (ironically) "cool white" compact fluorescent light bulbs as compared to the "warm white" variety. If you look at the box you will see that the "warm white" bulbs are described as emitting 3000K white light and the "cool white" bulbs are described as emitting 5000K white light.
Here is a web site that describes the contrast between Halogen and Xenon well.
Advantages of Xenon headlights
The blue Xenon light (by comparison to the halogen light) presents a much starker contrast to the red filtered lights used in the PAPI system. It would make the PAPI system a much more effective tool against the risk of inadvertently flying too low and short of the runway especially during visual/circling approaches.
So my question is, how do I go about putting this argument to the various authorities to the view of initiating the required changes?
Can someone describe the processes involved and how to get them started?
And yes I'm serious!!
G'day Blip,
I fully agree with you and think that the T VASIS system was vastly superior to the PAPI sytem which replaced it and I wonder why the T VASIS system ever went out of favour.
Regards,
BH.
I fully agree with you and think that the T VASIS system was vastly superior to the PAPI sytem which replaced it and I wonder why the T VASIS system ever went out of favour.
Regards,
BH.
Bullethead, ever hear of the "not invented here" syndrome?
I agree with you 100%, T vasis is much better in dodgy conditions when there is fog etc. It is also a direct indication, ie you will land in the area of the r/w to which it points, hence very little thinking/interpretation required.
I agree with you 100%, T vasis is much better in dodgy conditions when there is fog etc. It is also a direct indication, ie you will land in the area of the r/w to which it points, hence very little thinking/interpretation required.
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
Gosh, T vasi, had almost forgotten about those.
First one I used was at Perth Australia circa 1978, in a 707.
Quite nifty, very accurate.
So, if they have been withdrawn...why?
Always enjoyed PER...really nice folks there.
First one I used was at Perth Australia circa 1978, in a 707.
Quite nifty, very accurate.
So, if they have been withdrawn...why?
Always enjoyed PER...really nice folks there.
Join Date: Apr 2007
Location: Europe
Posts: 114
Likes: 0
Received 0 Likes
on
0 Posts
Have to agree with Rainboe,
once you got to OZ after not beeing there for a while one had to really think about the indication, PAPI is for the stupid like me and if it is a bit orange there is still a difference between orange and red.
Maybe we could use whiter bulbs as they are available those days but please no unecessary complicated indication.
16
once you got to OZ after not beeing there for a while one had to really think about the indication, PAPI is for the stupid like me and if it is a bit orange there is still a difference between orange and red.
Maybe we could use whiter bulbs as they are available those days but please no unecessary complicated indication.
16
Guest
Posts: n/a
There is a reason they have taken over- it's because they are better.
A few days back, during a night approach on a non-standard 3.9° ILS in montainous terrain the lighting system was very much dimmed. The papi was dimmed that much that all four lights appeared to show red.
The problem as I see it...
The white light of a white/red PAPI system is too close to the colour yellow/orange and this results in inadequate contrast with the red lights.
The white light of a white/red PAPI system is too close to the colour yellow/orange and this results in inadequate contrast with the red lights.
A quick call to ATC to increase intensity will solve most, if not all, of the issues mentioned.
The problem is that a light pointed at you at high intensity, giving the correct and expected colour spectrum, may disturb you during the approach; a dimmed lighting, as perhaps requested by a previous aircraft, may give you the expected 2 white / 2 red only on short final.
and I wonder why the T VASIS system ever went out of favour.
Both T-VASIS and PAPI are subject to certain limitations (erroneous indications) in misty weather, one of the important safety aspects of T-VASIS is that in a gross undershoot situation at 1.9 degrees the lights go red.
With PAPI, the presence of all red lights means you could be slightly under the ideal glide path to where all lights go red but that proceeding lower still below the glide path the red lights stay as is - in other words no graduated below all reds slope. Put another way, with T-VASIS all lights red means you are in a dangerous undershooting situation. Papi all red could mean anywhere between a mild undershoot to scraping the terrain.
There is a reason they have taken over- it's because they are better.
Like a lot of Australian aviation: dumbing down to the lowest common denominator - the rest of the world! Hard to soar like an eagle when you're surrounded by turkeys...Still, PAPI makes stabilising our approaches much easier now: "hey Bloggs, you're going a bit low!" "ya reckon? They look mostly white, well pink, err orange to me!". "Yeh OK, press on!".
Useless system that works only at 300ft and below - too late to be of any value then.
You get what you pay for: cheap and nasty.
Changing the globes for better technology sounds like a great idea to me. I'm not sure CASA would get involved, depending on how tightly they define the system specs. How about approaching the Airports Association; the airport owners/operators make the decisions about what gear they use.
The white light of a white/red PAPI system is too close to the colour yellow/orange
VIE used to have T-vasis on 16/34. Fun part was that its crossbar was made of four lights. "Your PAPI is not working, it shows four whites on the glide" calls on gnd frequency vere pretty regular.
I've seen someone fly what they thought was an on-slope approach on T-VASIs, it was then pointed out to them that they were actually high on PAPIs. The lesson learned, brief the bloody lighting system!
Thread Starter
OK OK thanks for the inputs so far everyone.
I didn't want this thread to turn in to a PAPI vs T-VASIS debate but there you go it's happened.
For what it's worth I personally believe that the T-VASIS is superior to the PAPI because as has already been pointed out there is no colour perception required (which also eliminates the problem when the lights are dimmed for night operations), there can be multiple aiming points so that each set up can accommodate many different types of aircraft, and if you do see red lights? for goodness sake hit the TO/GA switch because you are about to hit mother earth!
For those of you who don't understand how T-VASIS works you can think of it this way (although it is not strictly correct but the concept works very well). Think of the four horizontal lights as the centre (and most commonly used) aiming point which is usually at the 1000' markers at an angle of 3 degrees.
If you see a lights sticking out closer or further down the runway than those four horizontal white lights (that appear from your perspective to be below or above the four horizontal lights), that simply means that if you were to fly a 3 degree path from your current position to the runway, your eyes will meet the runway abeam that light which sticks out the most. So if the dots appear to make a T, a three degree path from your present position will have you arriving abeam the bottom of the T. The longer the T is (one, two, or three lights), the further short of the 1000' aiming point you will land. If you see an inverted T, a 3 degree path from your present position will have you landing beyond the 1000' aiming point abeam the top of the inverted T. No thinking required.
But any way I am resigned to the fact that PAPI seem to be cheaper to own and operate and that they comply with the minimum specifications required. I just think that they can (and should) be improved with the use of xenon bulbs.
So I've gota ask, how many pilots does it take to change a light bulb?
I didn't want this thread to turn in to a PAPI vs T-VASIS debate but there you go it's happened.
For what it's worth I personally believe that the T-VASIS is superior to the PAPI because as has already been pointed out there is no colour perception required (which also eliminates the problem when the lights are dimmed for night operations), there can be multiple aiming points so that each set up can accommodate many different types of aircraft, and if you do see red lights? for goodness sake hit the TO/GA switch because you are about to hit mother earth!
For those of you who don't understand how T-VASIS works you can think of it this way (although it is not strictly correct but the concept works very well). Think of the four horizontal lights as the centre (and most commonly used) aiming point which is usually at the 1000' markers at an angle of 3 degrees.
If you see a lights sticking out closer or further down the runway than those four horizontal white lights (that appear from your perspective to be below or above the four horizontal lights), that simply means that if you were to fly a 3 degree path from your current position to the runway, your eyes will meet the runway abeam that light which sticks out the most. So if the dots appear to make a T, a three degree path from your present position will have you arriving abeam the bottom of the T. The longer the T is (one, two, or three lights), the further short of the 1000' aiming point you will land. If you see an inverted T, a 3 degree path from your present position will have you landing beyond the 1000' aiming point abeam the top of the inverted T. No thinking required.
But any way I am resigned to the fact that PAPI seem to be cheaper to own and operate and that they comply with the minimum specifications required. I just think that they can (and should) be improved with the use of xenon bulbs.
So I've gota ask, how many pilots does it take to change a light bulb?
So I've gota ask, how many pilots does it take to change a light bulb?
The pilots will make use of a union to negotiate how much they get paid for programming the machine. The bigger the light bulb is, the easier the machine will be to program and, perversely, the more the pilots will get paid. The oldest pilot will look back fondly on the days when he used to change smaller light bulbs by hand with out the aid of any machines at all and may occasionally touch the light bulb himself just to "keep his hand in".
Every now and then the system of machine plus three pilots will fail completely and a light bulb will get broken. Posters on a light bulb changing internet forum will then discuss in great detail why the bulb got broken. At some stage it will be suggested that it was because the pilots don't get paid enough and are forced to change too many light bulbs each month.
Join Date: Jun 2006
Location: Europe
Posts: 716
Likes: 0
Received 0 Likes
on
0 Posts
While we're at it: anyone else used to fly on PLASI? I did my flight training in the US on PAPIs and VASIs, but to my surprise, most of the regional airports in Norway use PLASIs for visual vertical guidance. What's up with that? IMHO they are far inferior to the other systems, and if it's one place you could use a proper system, it's there 
Join Date: Feb 2000
Location: Pacific
Posts: 731
Likes: 0
Received 0 Likes
on
0 Posts
PLASI is really great. No interpretation and very accurate. I don't think it covers the quoted range though. I use one at Merrill Field in Anchorage. Even my students get it first time.
Registered User **
Join Date: Mar 2009
Location: USA
Age: 49
Posts: 480
Likes: 0
Received 0 Likes
on
0 Posts
When did you guys quit looking at the runway? Granted a valid point to promote a comfortable safe landing but this mindset as I see (and may be wrong) directs too much attention away from basic approach/landing skills.
One exemption I have experienced when the landing pilot was focused on the runway and the environment created an illusion MROC at night given it's situation in hills and runway height variance.
One exemption I have experienced when the landing pilot was focused on the runway and the environment created an illusion MROC at night given it's situation in hills and runway height variance.