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Help with ILS Visabiltiy??

Old 28th Jun 2010, 10:33
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Help with ILS Visabiltiy??

Reaching the minima on the ILS how do you tell if you have 800m, 1.2k or 1.5k vis?
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Old 28th Jun 2010, 10:38
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well at the minima, if you're on slope you'll be at the prescribed distance from the runway which is published on the chart (in NM). So if you can see the start of the runway from the minima you have 'that' much viz.

Normally my guide is at minima to be able to see the TDZ.
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Old 28th Jun 2010, 10:54
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Have a look at the ERSA AD section on approach lighting- there are from memory 2 different types in use in Australia.

When getting visual, a quick count of the lights will give you a distance (or know beforehand how many you will need to see), and also don't forget the 500/1000/1500ft markers etc.


Cessna, some aircraft may not have the ability to measure the ILS dist. on the chart... And like you said, on slope...
But if you can get that measurement then that makes it somewhat easier to judge the visibility!
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Old 28th Jun 2010, 10:55
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The idea of the 1.2/1.5km viz for runways without HIALS is at the minima you will see at least see the threshold.

At the minima with 800m viz and the HIALS, you will see a substantial part of the HIALS, but not the threshold.

Last edited by Velikiye Luki; 28th Jun 2010 at 11:29.
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Old 28th Jun 2010, 10:57
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800m vis = Runway end lights

1.2k = PAPI/T-VASIS
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Old 28th Jun 2010, 12:35
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When getting visual, a quick count of the lights will give you a distance
Please tell me you are kidding...
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Old 28th Jun 2010, 13:40
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When getting visual, a quick count of the lights will give you a distance

...1..2..3..4....5...6..7...8...9..10..11..12...13... YES!!!
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Old 28th Jun 2010, 13:51
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No, not kidding.

I'm talking about the approach lighting, Icarus, which are very easy to recognise and judge.
Seeing as though they extend out to a known distance from the end of the runway (and depending on the type of approach lighting, the amount of perpendicular rows which are spaced at 150m), you can judge distance based off this. Look at ERSA AD to see the different types of approach lighting.
I expect that that is part of the purpose of the approach lighting.

For example if you are expecting that at the DA you will see all of the perpendicular rows of lights out your window but only seeing a couple, well you know instantly you do not have the required vis.


You wont be counting individual bloody bulbs on your fingers and toes!


The other 'measurements' people have mentioned here I presume are based off being on slope at the DA.


So, how do you do it Icarus? Got a good method to contribute?
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Old 28th Jun 2010, 14:08
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Imagine the discussions at 140kts at 300 feet at the minima - count the lights - I reakon it's 700 metres - ohh nah I reakon 900 - nah I reakon - ohh well doesn't matter now we've landed.

If anyone can with the naked eye tell the difference between 100 metres of vis at midnight at 300 feet at 140kts in pouring rain lit by landing lights their observation skills are wasted in flying an aircraft !
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Old 28th Jun 2010, 14:20
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Agree with MNII, you count the bars - simple, and done in a millisecond, providing you know what you need to see (i.e. the number of bars) and not have to do calculations - e.g. 4 bars X 150 mtrs = etc,etc.

Fatalbert/Velikiye Luki, pretty much it.

compylot/icarus, best better think your replies before posting.
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Old 28th Jun 2010, 14:45
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Anything which involves counting at the DA at around 120 knots and 600 feet per minute rod is doomed to fail. Really.

Others have already contributed the best solution with no counting required.

Counting is good when staionary at the end of the runway about to commence a take-off roll and you need to work out if you have 500 metres visibility.
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Old 28th Jun 2010, 16:08
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Zanzibar, exactly.

If you know you need X crossbars when coming down the slope, you know whether or not you have the required vis. It is just one method.


The approach lighting goes out to 900 metres. The crossbars (depending on what type of approach lights) are at 150m intervals stopping at 750m. It is very easy to pre-plan what you need to see.

If you are coming down the slope and all you are seeing is one or two crossbars then you know you (potentially) wont have the required vis and thus at the DA you wont be thinking "is this enough or not?"


The other situations mentioned do not account for being off-slope. If for example seeing the PAPI/VASIS when at the DA is the required vis, if you are high on slope you will meet that DA closer to the runway. You might JUST see the PAPI but in reality you are closer than actual with less than the required vis as the intersection of the GP and DA (which is where you need the required vis) would occur a little behind where you broke visual.

puff, the purpose of the crossbar lights is more than likely to aid the eye in determining the distances in the dark and rain! Otherwise, why have them at all? If there was no need then there may as well only be centreline lead-in lighting.

Like I said before, its not concentrating and counting individual bulbs on your fingers and toes. Its not rocket science.
Forward planning- just like working out your planned ROD to hold slope.


"Anything that involves counting..." you say...
What about realising you are too slow or fast and have to compensate? That's counting in a way.... Are you doomed to fail? No.

The "Best" solution? There's more than 1 way to skin a cat. Using all methods/information available to you is an ability some people lack.
Have you contributed your method Icarus? No.

Last edited by MyNameIsIs; 28th Jun 2010 at 16:20.
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Old 28th Jun 2010, 16:22
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Counting lights?

I have been instrument rated for 23 years - flown the odd ILS to minimas - NEVER have I counted lights, never even occurred to me.

Maybe I need to spend more time in Flight Sim?

Before you fly an ILS you need to have an understanding of what you will likely see at the minima with min vis. That depends on the published minimum vis - it might be the threshold or it more likely be the first bit of the HIALS for Cat 1.

A standard ILS brings you down at 320'/nm. At a typical DA of 220' (BN 19ILS) you will be 1270m from the touchdown zone - min vis, 800m, you MIGHT see the runway end lights but no way the VASI - you will see the the HIALS. Remember too the reported vis is not reported through a windscreen doing 90-120kts. If they say 800m in rain you will likely have less REAL visibility at the minima - shitty windscreen wipers not withstanding - doesn't mean you second guess them either - they say 800m you're good to go and use that command judgement you're payed so well to exercise from time to time.

Count lights - you gotta be kidding?

If you see anything vaguely resembling what you expect to see you're visual - you don't and you're not. You make an instant decision.

How much counting of lights you see happening here? This is the CNS Rwy 15 ILS - anyone know the minima, its been too long since I landed there.


Last edited by Chimbu chuckles; 28th Jun 2010 at 16:43.
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Old 28th Jun 2010, 16:39
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A standard ILS brings you down at 320'/nm. At a typical DA of 220' (BN 19ILS) you will be 1270m from the touchdown zone - min vis, 800m, you MIGHT see the runway end lights but no way the VASI - you will see the the HIALS.
The HIALS is exactly what I'm talking about.

Correct me if I am wrong, but doesnt the ILS/PAPI/VASI bring you down to the 1000ft markers? 1000ft is approx 300m into the runway- so from your figures at the 220' point you are 970m from the end of the runway. If you can see that you have 5 (4 is not quite enough) of the crossbars, you have over 800m vis from your current position.
If you only see 1 or 2 crossbars, well you don't have the required vis.

The above probably comes down to what you say here:
If you see anything vaguely resembling what you expect to see you're visual - you don't and you're not. You make an instant decision.
CNS is 320ft (311AGL)and 1.2k vis.
Which off your figures again would put them 1nm from the TDZ.
At the DA (1nm/1800m from the 1000ft markers; 1500m from the end of the runway) you would plan to be able to not see the runway end lights but to know you had the required vis you should see 4 of the crossbars. If not then you dont have the vis.

When I heard the minima call I can make out the approach lighting. Because the video quality is crap and the eyball has better clarity, I later paused the video at this point (yes I know you will tell us all that pausing cannot be done for a real approach!) and can definitively count at least 3 crossbars. Only half a second after the minima call I can make out the 4th crossbar.
Surely they wouldn't have continued the approach if they didn't have the required vis! And how do you propose they worked out that they had the vis? Can you hear someone calling "can you see the approach lights?" during the approach before they get to the minima?


NEVER have I counted lights, never even occurred to me.
Likewise.
Got it suggested from guys driving jets.

Last edited by MyNameIsIs; 28th Jun 2010 at 17:20.
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Old 28th Jun 2010, 17:17
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I'm with Chimbu. At minima in minimum vis:

CAT 1: 200' - vis 800m (550m RVR) - HIALS - you will NOT see the threshold.
CAT 2: 100' - RVR 400m - Threshold.
CAT 3: 20' - RVR 200 -Touchdown zone or RWY centreline lights.

If you can see that much, no counting of lights, you're OK. BRIEF what you expect to see. At minima PIC is an approved observer (refer AIP). If PIC sees enough, they see enough.
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Old 28th Jun 2010, 17:27
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I'm with Chimbu. At minima in minimum vis:

CAT 1: 200' - vis 800m (550m RVR) - HIALS - you will NOT see the threshold.

If you can see that much, no counting of lights, you're OK

My interpretation of what you have just said is that you wont see the threshold at the DA and thats OK to continue.
So how do YOU judge whether YOUR visibility is enough or not in such a situation?
Do you just continue on down the slope the rest of the way because you see part of the HIALS?
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Old 28th Jun 2010, 17:53
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Can I look up and see the crossbars? Yes.

Can I see 2.5 or 3.5? Who knows? I look up at minima. I can see two cross bars - maybe the outline of a third. I'm back down on the ADI before I can count the exact number of lights at minimum RVR.

I use the F/D or ILS from 200' to 100'ish then I'm heads up. For CAT II or III - it's as discussed.

If you can fly an ILS to CAT 1 and at 200', manually flown, be head up long enough to count the cross bars plus other lights well done, you're a better pilot than me.
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Old 28th Jun 2010, 21:51
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I don't know about you guys but I'm on the dials and approaching the DA while I'm waiting for the call "visual" or "not "visual go 'round"

I'm not counting lights doing 120 KIAS
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Old 28th Jun 2010, 22:17
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Possibly A.T.C. might give a VIS/RVR reading prior to the commencement of the approach, at the minima the P.I.C. will assess the visual environment and either continue or go-around depending if they have sufficient ground references i.e. approach lighting system or runway environment in sight, never counted lights myself in 30+ years of ILS ops........Cat 3B is easier!!
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Old 28th Jun 2010, 22:36
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I feel for 888 who just wanted a rough answer.

Mate. In Aus we use HIALS that are called British Calvert. They are the ones with the bars. They are spaced evenly. The minima normally is past all the lead in bars and is overhead a point called the descion bars, were they turn all red and are 1000' from the threshold.

As most people here are talking. We don't COUNT the bars or edge lighting.
Just know some simple rules :
800 m - gota see at least the threshold green lights and a few white edge lights
1200m - gota see the papi/vasi lights
1500m - gota see the touchdown markings clearly plus a little more

There ya go.

Oh and not everyone does 120 knots either @ Vat. So bear that in mind.

Cheers

PS found this great little article just now. Not much on HOW to calculate vis, but gives a great insight to approach lighting. From this, you can develope your own methods.
Calvert Cross Bar Lighting System

Last edited by mustangranch; 29th Jun 2010 at 00:54.
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