EGGD this morning
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I have just read the latest CAA incident bulletins and there are 2 airfields now reporting a number of airlines/operators for approaches in low visibility. will not name here in case I get told off, but the names are there for all to read and the visibilities for each incident are stated.
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The whole issue of 'instant' IRVR can be a real pain in the ass.
The classic airfield for this is Birmingham, I believe their IRVR detectors are located in possibly the worst place on the airfield. I have lost count of the times we have seen the airfield from 20 miles out, they have, in the past, given the most ridiculous met of 10km, LVP's, IRVR 250,125,300 and we have maintained visual contact all the way down approach and rollout.
So, last night we were doubly inconvenienced as they have removed the centreline lights as part of the work in progress - hence, no CAT III, or CAT II below 550m
We did get in, legally, we had sufficient RVR up to the 4 mile point, we never lost sight of the runway even on short final where the alledged RVR dropped to unspeakable amounts.
So......................
Why can't the airport builders/maintainers and ATC people communicate and discuss such matters with 'the customers'. They would then appreciate that if you are going to use IRVR, it shouldn't be located in a boggy hollow that is the first place to fog out.
The classic airfield for this is Birmingham, I believe their IRVR detectors are located in possibly the worst place on the airfield. I have lost count of the times we have seen the airfield from 20 miles out, they have, in the past, given the most ridiculous met of 10km, LVP's, IRVR 250,125,300 and we have maintained visual contact all the way down approach and rollout.
So, last night we were doubly inconvenienced as they have removed the centreline lights as part of the work in progress - hence, no CAT III, or CAT II below 550m
We did get in, legally, we had sufficient RVR up to the 4 mile point, we never lost sight of the runway even on short final where the alledged RVR dropped to unspeakable amounts.
So......................
Why can't the airport builders/maintainers and ATC people communicate and discuss such matters with 'the customers'. They would then appreciate that if you are going to use IRVR, it shouldn't be located in a boggy hollow that is the first place to fog out.
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I don't think the incident bulletins are available on line but there's a CAA document that describes the absolute minimum.
A couple of other things, few airports with IRVR still have the ability to offer human observer RVR.
As I understand it, and I speak as a simple controller, unless the IRVR equipment is reported as faulty by the engineers or is giving an error from its own diagnostics (and ATC report to a/c that it is u/s), the pilot cannot use and factor the met vis.
The visual approach business is interesting. Never been faced with a pilot electing to do a visual approach and I thought it was not permitted because of accidents 20 or 30 years ago where the poor slant visibility caught some pilots out. I'm sure there used to be something in the controllers' documents about absolute minima for visual approaches but I can't find it now. In the UK though, the ANO (articles 38 and 39) say that the aircraft can't go through 1000ft if the wx is below the minimum for the approach. Presumably there are minima for visual approaches and whether the pilot can see the runway or not, if the wx is below the minimum, the approach cannot be continued - or am I way off the mark here?
A couple of other things, few airports with IRVR still have the ability to offer human observer RVR.
As I understand it, and I speak as a simple controller, unless the IRVR equipment is reported as faulty by the engineers or is giving an error from its own diagnostics (and ATC report to a/c that it is u/s), the pilot cannot use and factor the met vis.
The visual approach business is interesting. Never been faced with a pilot electing to do a visual approach and I thought it was not permitted because of accidents 20 or 30 years ago where the poor slant visibility caught some pilots out. I'm sure there used to be something in the controllers' documents about absolute minima for visual approaches but I can't find it now. In the UK though, the ANO (articles 38 and 39) say that the aircraft can't go through 1000ft if the wx is below the minimum for the approach. Presumably there are minima for visual approaches and whether the pilot can see the runway or not, if the wx is below the minimum, the approach cannot be continued - or am I way off the mark here?
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salavation
the difficulty is that the transmitometers need to be alongside the runway-one in each third, yet clear of the strip-for obstacle clearance, putting them over grass-leading to problems with overreading-human observer method of course reads over the runway itself looking at the runway lights, much more likely to be accurate if the fireman is awake!-do not see any way round this problem, we suffer from both spiders in the lenses and moisture-but have to give the readings unless tels take it out of service
the difficulty is that the transmitometers need to be alongside the runway-one in each third, yet clear of the strip-for obstacle clearance, putting them over grass-leading to problems with overreading-human observer method of course reads over the runway itself looking at the runway lights, much more likely to be accurate if the fireman is awake!-do not see any way round this problem, we suffer from both spiders in the lenses and moisture-but have to give the readings unless tels take it out of service
>Presumably there are minima for visual approaches and whether the pilot can see the runway or not, if the wx is below the minimum, the approach cannot be continued - or am I way off the mark here?>
Spitoon - you are quite right. Most company Ops Manuals specify that the touchdown RVR for the landing runway most be at least the (CAT I) RVR required for the instrument approach onto that runway if there is one. Also there are requirements for In Flight Vis whilst conducting the visual circuit depending on a/c Cat (eg C is, I believe, IFV 3,700 metres). Only the pilot can assess this latter aspect!
Spitoon - you are quite right. Most company Ops Manuals specify that the touchdown RVR for the landing runway most be at least the (CAT I) RVR required for the instrument approach onto that runway if there is one. Also there are requirements for In Flight Vis whilst conducting the visual circuit depending on a/c Cat (eg C is, I believe, IFV 3,700 metres). Only the pilot can assess this latter aspect!
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The point about SRA is also interesting. The approach to LGW's Northern runway (08L/26R) is via an SRA initially, which is to 2 miles. Now, when conditions are marginal, it appears some companies aren't allowed to start an approach if reported conditions are below their minima, others are allowed to fly down to these and continue if they can see the approach lights. Thus, we lose some traffic but not all.
We do try to base our decision upon whether or not to cancel a night's maintenance and keep the main runway open on whether or not we're going to lose traffic, but obviosly we can't cater for just one operator when everyone else can make it in. It's interesting how these things can vary between operators, even of the same a/c type. However, in all cases, ATC will offer the SRA to whowever wants to make an approach.
BTW, when things are marginal, we study the short & long TAFs, have long conversations with the Aerodrome forecaster at Exeter (very helpful & knowledgable) but in the end it quite often comes down to our local knowledge and experience - cloud ceiling 700' or 900'? vis 2,500m or 3,000m? You're damned if you do, damned if you don't! It's great when you guess right, Yellow Pages down the trousers the following morning if you don't!!!
Cheers,
TheOddOne
We do try to base our decision upon whether or not to cancel a night's maintenance and keep the main runway open on whether or not we're going to lose traffic, but obviosly we can't cater for just one operator when everyone else can make it in. It's interesting how these things can vary between operators, even of the same a/c type. However, in all cases, ATC will offer the SRA to whowever wants to make an approach.
BTW, when things are marginal, we study the short & long TAFs, have long conversations with the Aerodrome forecaster at Exeter (very helpful & knowledgable) but in the end it quite often comes down to our local knowledge and experience - cloud ceiling 700' or 900'? vis 2,500m or 3,000m? You're damned if you do, damned if you don't! It's great when you guess right, Yellow Pages down the trousers the following morning if you don't!!!
Cheers,
TheOddOne
I'm sure there used to be something in the controllers' documents about absolute minima for visual approaches but I can't find it now. In the UK though, the ANO (articles 38 and 39) say that the aircraft can't go through 1000ft if the wx is below the minimum for the approach. Presumably there are minima for visual approaches and whether the pilot can see the runway or not, if the wx is below the minimum, the approach cannot be continued - or am I way off the mark here?
If you scroll down to the last page of the CAA Document link that you posted earlier, para 6 reads:-
"A value of 800 metres RVR is to be used at all airports as the Absolute Minimum for visual approaches"
Per Ardua ad Astraeus
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I'm not really sorry I dragged this away from where it started. (Tks Rwy in sight, BTW).
May I summarise my enquiry? It appears that no-one can over-rule an errant pair of 'daleks' UNLESS the Tels people can be persuaded to withdraw them, and they would, presumably, only do this if they were 'broken'? So we appear stuck with it.
May I summarise my enquiry? It appears that no-one can over-rule an errant pair of 'daleks' UNLESS the Tels people can be persuaded to withdraw them, and they would, presumably, only do this if they were 'broken'? So we appear stuck with it.
