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Help with ILS Visabiltiy??

Old 29th Jun 2010, 02:17
  #21 (permalink)  
 
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I get the distinct impression that this is going to go around in circles...
So I probably wont really bother much longer. Nobody seems open to discussion as such, more interested in disputing something without putting in much input themselves.
All I know is that it works and is just one method of helping determine your visibility

Seems like some seem to think the "count" is very literal- "oh, i can see now... lets see theres 1, theres 2...wait ive run out of fingers better use my other hand!".
It really isnt that hard to recognise something like the crossbars and to be able to determine how many there are. Even easier 2 crew as one of them looks out the window mostly!

I'm liking people saying "look for the HIALS" - Ok you might see it but what exactly are you looking for?
If you see half of it can you continue the approach or do you have to miss out because its not enough visibility?

Also, RVR is not visibility along the approach path.
RVR may not be representative of the visibility you are getting out of your window on approach.
However, it is another piece of information you can use to help make the decision at the DA- just like the crossbars! Yet nobody is knocking the RVR!
Also note that an RV assessment is not a substituite for a required RVR observation and cannot be used for precision approaches under certain conditions.
So if you have been basing your decision at the DA based on the RVR from the tower, what are you going to do when they cannot give one?


Maybe its not practical in all ops. Those rubbishing my method have not exactly said anything like "yeah I see where you are coming from, but that is actually a little impractical for us doing XXXXXX. We however use this......" All I see is "your kidding" "your joking"
We aren't all Maverick coming in at 120, 140 at the DA. Sounds more like some are trying to compare dick sizes.

Last edited by MyNameIsIs; 29th Jun 2010 at 02:33.
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Old 29th Jun 2010, 02:39
  #22 (permalink)  
 
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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.
Using the figures from the CNS approach vid previously posted by chuckles for an example, I'd interpret your method above as not getting visual and continuing the approach below DA.
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Old 29th Jun 2010, 03:45
  #23 (permalink)  
 
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Oh come on girls! Its not that hard - is it?

I have held an IR for 25 yrs and have flown a few ILS in that time (maybe 25 a year). In that time I have never missed in anger off the minima - OK, so I do live in paradise!

There are many in here who do this stuff for a living every day, in all sorts of crappy weather that I don't need to get out of bed for.

I bring the Bo down the ILS at 120 kts (Let's see ya do that in the Retard Vehicle Jaba and not run off the end of the runway at YBBN!).

Below 300' I am not counting noth'in! I am just looking to plonk it on the runway in one piece or bug out for another go.

I am a simple kind of guy and work in the big picture - not a lawyer who revels in the detail and fine print.

Vis is an issue in any approach but I guess it is maybe more of an issue when you are close to the weeds on an ILS.

Forkair SOPs state that at the minima you must be able identify enough on the ground to fly the aeroplane to safe touch down - or else you bug out. Start of the HIAL (I thought that was the purpose of HIAL ??), lead-in lights, PAPI/VASIS, whatever.

The DA at Townsville puts the HIAL right in front of you - if I could see the start of that it would never have occurred to me that I might not be legal to land.

I would like to hear from a Big Bird pilot - do you "miss" if you can only see the start of the HIAL from the DA?

Dr
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Old 29th Jun 2010, 04:30
  #24 (permalink)  
 
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Mynameisis:

Yes the Cairns plate is an exception with a higher DA and vis requirement than most CAT I installations. I accept your point. I didn't have the plate handy. However, on this approach at minima you're still not going to see the threshold or all the HIALS. Stick with me here!

We're agreed the ILS takes you to 1000' in to the runway. At the minima you'll be 1500m from the threshold. ((311'/Tan3 degrees) - 1000') converted into metres. The HIALS runs 900m from the threshold so you're still 600m short of the start of the HIALS and with only 1200m vis you will still only see the 600 metres to the start of the HIALS and then 600 metres beyond that which is the first three crossbars and part of the lights to the fourth.

OK so that's Cairns, which is a worst case scenario.

Compare with Sydney 16R or Melbourne. At the minima for Sydney 16R, you will be 4045' from where the glideslope intersects the runway. (212' @ 3 degrees). That puts you 930ish metres from the threshold. That's just short of the HIALS. You won't see the threshold in 800m. It's unlikely you'll see the first crossbar as it's going to be under the nose of whatever aircraft you're flying so that will leave you with the remaining 4 crossbars, and you may not quite see the 4th, closest to the runway, in 800m vis.

Typically I'm looking at 140-150 knots at minima. One pilot will have the ability to observe the developing visual segment. The other pilot will not. The other pilot will not have the time to count the crossbars, particularly if they're flying when they need to now deal with any crosswind and the tendency to turn towards the runway, and the tendency to duck low, both of which are best counteracted by a quick glance up to check the visual segment and then getting head down again.

Anyway, that's it from me. Hope the answers help the original poster. Like most of these things it's an interesting discussion.

Last edited by DirectAnywhere; 29th Jun 2010 at 06:05.
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Old 29th Jun 2010, 04:54
  #25 (permalink)  
 
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You won't see the threshold in 800m. It's unlikely you'll see the first crossbar as it's going to be under the nose of whatever aircraft you're flying so that will leave you with the remaining 4 crossbars, and you may not quite see the 4th, closest to the runway, in 800m vis.
That's as I was taught joining airlines and going on to jets many moons ago, and still practice it successfully. You don't have to "count", as such, the recognition that you have the vis or not is instantaneous aided by the number of bars you see.

It's simply a matter of KNOWING what you need to see at the DA respectively for 800m, 1200m or 1500m requirements which others have already been mentioned in previous post.

In a way I think that was what MyName etc was trying to say .........
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Old 29th Jun 2010, 05:41
  #26 (permalink)  
 
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You won't see the threshold in 800m. It's unlikely you'll see the first crossbar as it's going to be under the nose of whatever aircraft you're flying so that will leave you with the remaining 4 crossbars, and you may not quite see the 4th, closest to the runway, in 800m vis.
And thats basically what I've been on about.

Mentioned previously which I agreed with- "what you expect to see when visual".
If you are expecting to see what you describe above, and that's what you see, then you are ok.
But what happens if its blatantly obvious that you cannot see past only 1 or 2 bars? (You've 'counted' those bars havn't you?) Presumably one would deduce that they do not have the required vis and commence the missed approach.

Do any aircraft manuals state that you lose X metres of vis or that they hide a certain amount of approach lights under the nose for situations such as this?


The method of checking the crossbars is just one of the ways in assisting you in determining your visibility.
Don't know why I've copped so much flak about it. As seen in the "how to start a hot injected engine" thread there are many ways about going about things yet there doesn't appear to be any negativity such as this over there!


Forkair SOPs state that at the minima you must be able identify enough on the ground to fly the aeroplane to safe touch down - or else you bug out. Start of the HIAL (I thought that was the purpose of HIAL ??), lead-in lights, PAPI/VASIS, whatever.
I'm hoping that just because you see the start (and presumably not all) of the HIAL lights doesn't mean you think it's safe to continue.
Almost like saying "I can see a couple of edge lights, so i can take off" even though its actually below the takeoff minima.

The DA at Townsville puts the HIAL right in front of you - if I could see the start of that it would never have occurred to me that I might not be legal to land.
Herein lies my point with the amount of crossbars you can or cannot see!
If you only see 1 or 2 then thats not the required vis.


Its more recognition of what you are expected to and subsequently seeing that I'm on about, and recognising 3 or 4 rows of lights 150m apart is not difficult in a momentary half-second glance out the screen.
If you are looking out the window to identify something to to determine if you have the the required visibility (or not), be it the threshold lights PAPI/VASI or the 500/1000/1500ft markers, why is it inconcievable to some that the crossbar lights are also a valid way?



Direct, yes an interesting discussion and thanks for the input. The method I've mentioned might not be all that practical for you at your speeds, but I'm sure there are plenty of aircraft out there that can and do go slower, in which case they might find that the crossbar lights works for them.

I think the word "count" has brought about a bit of confusion to some, for which I apologise. But what other word can be used to describe recognising a numerical amount of things?
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Old 29th Jun 2010, 08:28
  #27 (permalink)  
 
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Yes, I can see the senario clearly now. After here we are in the Big Bird on the Rwy 16R ILS into Sydney after 14 hrs peddling from LA, Captain PF..........

Co-pilot: Visual (or whatever you guys say). (Happy now?)

Captain: Oh shoot! We only have 700 m vis, missed approach!

Yeah right!

Dr

Last edited by ForkTailedDrKiller; 30th Jun 2010 at 14:44.
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Old 29th Jun 2010, 09:50
  #28 (permalink)  
 
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The BOTTOM LINE= at the minima make a "Command Decision", is it safe to continue or do I go for option B(Go-around), doing all this while maintaining a safe flight profile i.e. on slope/speed etc. Remember in marginal conditions at the minima it is easy when hand flying to deviate significantly from the approach profile due to visual illusions of often being too high which can result in a "duck-under"......scan inside/outside.
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Old 30th Jun 2010, 04:51
  #29 (permalink)  
 
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Sh*t....who cares.....I ain't goin around......its scary up there!! Yep me too
25 odd renewals and REAL precision approaches ....only missed on some remote NDB's.
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Old 30th Jun 2010, 08:19
  #30 (permalink)  
 
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25+ years of ILS, I HAVE gone around on a number of occasions - due still in cloud. Visibility does not need to be assessed other than that you have an "expanding visual segment" and have enough vis for the approach. [for cat1]
Cat 2 see threshold, Cat3a see "something" Cat3b - land!
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Old 30th Jun 2010, 13:56
  #31 (permalink)  
 
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Yes, I can see the senario clearly now. After here we are in the Big Bird on the Rwy 16R ILS into Sydney after 14 hrs peddling from LA, Captain PF..........

Co-pilot: 220', I have the approach lights visible (or whatever you guys say).

Captain: Oh shoot! We only have 700 m vis, missed approach!

Yeah right!
Try:

PM: (at or approaching the minima) "visual" (or similar)
PF: "landing" (or similar)

Or

PM: (at the minima) "no contact" (or similar)
PF: "going around" (or similar)

Clinical, straightforward and simple. Not the rubbish otherwise suggested, there's not the time for that.
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Old 30th Jun 2010, 14:08
  #32 (permalink)  
 
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It were me in the vid which was taken by the third pilot with a hand held pocket digital camera in the video mode hence the relatively poor quality. The actual video file is around 30 megs and I believe when you upload a file to any of the hosting sites they are compressed and so lose some quality.

This is what our low vis ops manual has to say about what you need to be able to see at DH

"CAT I Minima (and above)
At DH the pilot is required to see an adequate portion of the threshold or approach lighting system to identify and assess the aircraft position and approach path, it is not a requirement to see the threshold or TDZ at DH.

Note: It is assumed that below DH the visual segment will continue to expand,
providing adequate visual reference to manually flare and rollout."

There is no counting of anything that close to the ground in poor vis, you either see what you expect to see and land or otherwise buggeroff!

If you have any queries about this fire away and I’ll try to give coherent answers.

Regards,
BH.
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Old 2nd Jul 2010, 06:35
  #33 (permalink)  
 
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G’day BL,

With the YMEN ILS DH at 351’ HAT and a 3deg G/S being 325’/nm I figure that on slope at DH you’ll be 1.08nm/1900yds/1740mtrs from the glideslope antenna. I think you used the DH altitude in your calculations instead of the HAT.

Now the glideslope antenna, or more specifically the glideslope ground intercept point, is usually around 300mtrs from the runway end so on slope at DH the runway end should be 1740-300 or 1440 mtrs in front of you in which case you should be able to clearly see the HIRL and threshold.

I hope this explains it and that I haven’t got my maths wrong.

Regards,
BH.
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Old 2nd Jul 2010, 08:38
  #34 (permalink)  
 
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I'm confused by this thread's seeming obsession with assessing the visibility at DA.

The only time you're interested in the numbers, be they met vis, corrected met vis or RVR is BEFORE the meat of the ILS is commenced, i.e. is the visibility at or above the minima required to make the approach? Answer 'No' = different approach, different vis (if you can hang around that long) or different airport/runway. Answer 'Yes' = conduct approach.

Most countries now have the Approach Ban Point (ABP). This is variously, depending on where in the World you are, at the FAF, OM or 1000'. If the vis is below minima at or before the ABP, discontinue the approach. Vis above minima, then continue the approach. Vis decision made......no more discussion....no light counting.

At DA the only decision that needs to be made is 'can I see the elements required of this type of approach'? These have obviously been designed such that a safe landing can be carried out and I won't insult your collective intelligence by listing them (as well as can't be arsed to list the 10 options of a CAT 1 ).

So, to the original question. At DA you don't decide if you have 800m etc visibility. That was done ages ago or you wouldn't have commenced the approach. At DA you either land or go-around.

(For the pedants; yes, I do realise there's no DA on a CAT IIIB/C, so no decision needs to be made )
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Old 2nd Jul 2010, 09:18
  #35 (permalink)  
 
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FTDK

Ever thought of doing a renewal in a different place/ship?

We never find out how many cobwebs we need to blow out until it is too late.

Last edited by Baldnfat; 5th Jul 2010 at 00:45.
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Old 2nd Jul 2010, 10:23
  #36 (permalink)  
 
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This is one of those "who cares" threads.

You get to DA, you are visual or you aren't. The prescribed visual reference is set out in the regs or your Ops Manual. If you have it and you are happy, you land. If you aren't, you go around. Simple. You don't need to know what the RVR/met vis actually is at that point.

RVR/met vis is only relevant before you commence the approach or when approaching FAF, whatever the rule is in Oz land. Our company minima for an approach ban was 1000' AGL in Europe.
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Old 2nd Jul 2010, 11:07
  #37 (permalink)  
 
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It were me in the vid which was taken by the third pilot with a hand held pocket digital camera in the video mode hence the relatively poor quality. The actual video file is around 30 megs and I believe when you upload a file to any of the hosting sites they are compressed and so lose some quality.

This is what our low vis ops manual has to say about what you need to be able to see at DH

"CAT I Minima (and above)
At DH the pilot is required to see an adequate portion of the threshold or approach lighting system to identify and assess the aircraft position and approach path, it is not a requirement to see the threshold or TDZ at DH.

Note: It is assumed that below DH the visual segment will continue to expand,
providing adequate visual reference to manually flare and rollout."

There is no counting of anything that close to the ground in poor vis, you either see what you expect to see and land or otherwise buggeroff!
Thanks Bullethead for your reply. Good to hear it from the person in a supplied example, thanks for the input.

However, some questions for you.
With regards to "At DH the pilot is required to see an adequate portion of the threshold or approach lighting system...." WHAT is deemed adequate? HOW do you deem it adequate?
I did post earlier that the word "count" has probably brought in a lot of confusion. I accept that. But is it not fair to say that if you only saw bugger all of the approach lights, for example only the 1st or maybe the 2nd bar if you are lucky, that that would be deemed inadequate?

I know it is more recognition of what you expect to see at the DA, and it appears to me at least (and I wont flog a dead horse much longer) that people seem to think that you actually need to physically count bars one by one. Thats not the case. You'll recognise pretty much instantly on a glance if you've got most or next to nothing....
I should have re-phrased my initial response to "well, if you see bugger all of the approach lighting you probably wont have the required vis. but if you see most of it, then you probably do".
However I think some people out there (whether they actively contribute here or not) may have learnt from this post, even though some contributers may not want to admit it, that the approach lights can be used to help one identify distance. It is just another tool. Other than a bit of assistance with lateral adjustment etc when breaking vis, why the hell else would the lights be spaced evenly apart to a standard for? They ain't christmas lights!


I also find it interesting that your ops manual states that you do not require the chart-stipulated (adjusted for other things HIAL U/S etc) visibility, just what you deem "adequate" ! No need to discuss that though.


"Count" - probably the wrong word. Shame so many people thought it was so literal.
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Old 2nd Jul 2010, 11:23
  #38 (permalink)  
 
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FTDK

Ever thought of doing a renewal in a different place/ship?
I have done IR renewals at Paraparaumu (NZ), Archerfield, Mackay, Townsville and Innisfail, in PA28, C172, C210, Bonanza, Apache, Aztec, C310, C402, Duchess and Baron aircraft.

......... and your point is?

Dr
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Old 2nd Jul 2010, 11:34
  #39 (permalink)  
 
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I also find it interesting that your ops manual states that you do not require the chart-stipulated (adjusted for other things HIAL U/S etc) visibility, just what you deem "adequate"
I know that wasn't directed at me but I thought it needed clarifying anyway. Re-read my bit above and you'll see that you don't need the visibility (adjusted for U/S equipment etc) at DA; you need it BEFORE you get to DA. If you don't have it before you get to the Approach Ban Point you cannot continue the approach, so you'll never get to DA.

The required elements required to be seen at DA depend on the type of ILS. CAT 1 has some fairly high requirements e.g. PAPIs OR Rwy markings OR edge lights OR Rwy end lights etc etc but has a high DA and, therefore, you are likely to see them. CAT 2 has a lesser requirement but includes a 'lateral element of the approach lighting system' to assist in your adjustment of line-up. CAT 3A has only a 'one light' requirement but you've got lots of back-up equipment being used now (fail operational etc) and there's no need for you to see much 'cos either the autopilot or HUD/Flight Directors are doing it for you and, almost certainly, you're going to autoland anyway. Cat 3B you're along for the ride and employed to make sure the kit behaves itself.

SO, in summary, you do have to allow for equipment being U/S and this will 'up' the visibility requirements. Not at DA but, more than likely, at the descent briefing.
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Old 2nd Jul 2010, 12:46
  #40 (permalink)  
 
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I have done IR renewals at Paraparaumu (NZ)
The finest NDB approach on the planet...
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