Sky News : you 'avin a larf ?
I watched BBC news last night having got back to England as a pax for Christmas myself just 15 hours late. I think the explanation I saw was the Eric Moody Sky piece by the sound of it. It was simple, and accurate, explaining how extra spacing is needed to protect the ILS and that extra spacing is needed on the ground to avoid problems.
Interestingly when I tried to get out on tuesday (Londonderry-Stansted) we had thick fog (only one flight got in and out all day, apparently, but by wednesday morning we had a beautiful day in NI but the whole of the UK seemed to be covered. Seems I was lucky to get back so quickly, overall.
Interestingly when I tried to get out on tuesday (Londonderry-Stansted) we had thick fog (only one flight got in and out all day, apparently, but by wednesday morning we had a beautiful day in NI but the whole of the UK seemed to be covered. Seems I was lucky to get back so quickly, overall.
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As a humble SARBoy, whos solution to fog would be an internal radar letdown in the bay followed by a hover-taxi to the beach, I was going to ask what exactly is the problem. I'm perfectly aware that fog slows things up, but armed with Cat III autoland and ground positioning radar and all the other expensive toys in an airliner and a proper airport, where is the choke point?(and that's not rhetorical - I just don't know which bit(s) of the process it is that delay you guys). Having read the whole thread, I suspect the Eric Moody and Jock Lowe pieces would answer the question. Can anyone post a link?
BTW, if a professional in another branch of aviation with 26 yrs experience can't figure out exactly why fog screws things up (even though my own operation became an ops-only one-shot deal), what chance do the journos have?
Sven
BTW, if a professional in another branch of aviation with 26 yrs experience can't figure out exactly why fog screws things up (even though my own operation became an ops-only one-shot deal), what chance do the journos have?
Sven
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Cat I ops at LHR = 42-45 landings an hour (3 mile spacing, or vortex).
Cat III ops at LHR = 24-26 landings an hour (six mile spacing).
Normally when we go into LVPs it's only for the morning, and the fog clears by midday, allowing us to recover in the afternoon, and perhaps running on into the early hours.
When it's been constant LVPs for days on end, the effects get felt.
Cat III ops at LHR = 24-26 landings an hour (six mile spacing).
Normally when we go into LVPs it's only for the morning, and the fog clears by midday, allowing us to recover in the afternoon, and perhaps running on into the early hours.
When it's been constant LVPs for days on end, the effects get felt.
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Nobody has blamed Ops, crewing, de-icers, caterers, handlers, fuellers, bog service or the bus from the car park.
I think that if the staff wore more religious symbology we would never have got this fog to start with.
I think that if the staff wore more religious symbology we would never have got this fog to start with.
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Gonzo
Thanks for that, but
what is it that causes the cat to change, and why is it different for different cats? And is it the cat limits that actually slows the airport up, or is it something else, like ground movements?
Sven
Thanks for that, but
what is it that causes the cat to change, and why is it different for different cats? And is it the cat limits that actually slows the airport up, or is it something else, like ground movements?
Sven
Last edited by Sven Sixtoo; 22nd Dec 2006 at 20:33. Reason: not to appear a complete plonker
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When the vis gets below 600m we go into LVPs. The Localiser Sensitve Area (CAT III holding points) needs to be clear of the preceeding aircraft (as opposed to just the runway being clear in CAT I ops) by the time the next inbound gets to one mile from touchdown, otherwise ATC send it around. We aim to have the LSA clear when the next inbound hits 2 miles. That's why we need extra spacing, to ensure that occurs.
If anything is within the LSA, be it vehicle, a/c or anything else, the ILS Localiser signals might be compromised and the a/c receives fluctuations. Not A Good Thing when visibility is poor and it's an autoland!
Ref: Different CATs, yes it can get confusing, especially to us ATC types! That's why we've narrowed our procedures down to:
A) Low Visibility Procedures (Viz below 600m) - LSA is protected, 6 mile spacing, CAT III holdings points used.
B) All other times - LSA not protected, whatever spacing we can get away with (!), CAT I holding points (much nearer the runway) used.
If anything is within the LSA, be it vehicle, a/c or anything else, the ILS Localiser signals might be compromised and the a/c receives fluctuations. Not A Good Thing when visibility is poor and it's an autoland!
Ref: Different CATs, yes it can get confusing, especially to us ATC types! That's why we've narrowed our procedures down to:
A) Low Visibility Procedures (Viz below 600m) - LSA is protected, 6 mile spacing, CAT III holdings points used.
B) All other times - LSA not protected, whatever spacing we can get away with (!), CAT I holding points (much nearer the runway) used.
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What is important to state in addition to the previous poster. From the airport side to assure the quality of the radio signal to meet the reduced tolerance required of Cat111. Flow rate is decreased so that aircraft are not only clear of the runway but a distance away. To limit interference holding points are moved further away, in other words the exclusion zone around the glide and localiser transmitters is increased. Which also impacts aircraft ground movement as there are less holding points available for use, so aircraft have to remain on stand until space available. Giving yet further airfield delays.
oops someone has posted before me
oops someone has posted before me
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Gonzo and Paul W
Thank you. Learning has taken place.
Gonzo, if you are ever explaining this to an outsider (like me), start by saying what LVP stands for! Then you can go on to why.
May we never meet professionally
Sven
SARboy
Thank you. Learning has taken place.
Gonzo, if you are ever explaining this to an outsider (like me), start by saying what LVP stands for! Then you can go on to why.
May we never meet professionally
Sven
SARboy
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I'm very sorry, I did consider it, but you mentioned 'Cat III autoland' and I assumed a level of knowledge about the subject. My error. 
I'll take that to mean you hope you're never tasked to pick me up, not that you don't like me! 
Given that one of two escape routes to evacuate our new control tower is to climb through a hatch onto the roof and await SAR pick up, you never know!!!!
May we never meet professionally
Given that one of two escape routes to evacuate our new control tower is to climb through a hatch onto the roof and await SAR pick up, you never know!!!!
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I personally have no issue with the news reporting channels doing what they are paid for, but do we tell them how to report alleged stories, no, please do not tell us how to operate aircraft when the nearest you have ever come to it is is flightsim and wikipedia when you did not know how to wrok them correctly. 
PS The spelling error is intentional..............
PS The spelling error is intentional..............
CH3CH2OH
As Autoglide said - soma for the masses
From Wikipedia, the free encyclopedia
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Soma is a fictional, happiness-inducing drug in Aldous Huxley's novel Brave New World (1932). In the novel, soma is an "opiate of the masses" that replaces religion and alcohol in a peaceful, but morally controversial, high-tech society far in the future. Soma, a narcotic tranquilizer in tablet form, is regularly taken by all members of society in order to produce feelings of euphoric happiness. The name satirically refers to the revived interest in ancient Aryan culture at the time. Huxley's society is caste based, like that of Brahminical India.
The name of the drug in the story is based on Soma, the stimulant drink used in ancient Aryan (Indo-Iranian) rituals, in particular those of Vedic India.
Jump to: navigation, search
Soma is a fictional, happiness-inducing drug in Aldous Huxley's novel Brave New World (1932). In the novel, soma is an "opiate of the masses" that replaces religion and alcohol in a peaceful, but morally controversial, high-tech society far in the future. Soma, a narcotic tranquilizer in tablet form, is regularly taken by all members of society in order to produce feelings of euphoric happiness. The name satirically refers to the revived interest in ancient Aryan culture at the time. Huxley's society is caste based, like that of Brahminical India.
The name of the drug in the story is based on Soma, the stimulant drink used in ancient Aryan (Indo-Iranian) rituals, in particular those of Vedic India.
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The reason for reduced capacity in LVPs is due to the bit when pilots take control of their aircraft, rather than monitor the performance of the automatics. In particular, we are talking about clearing the runway. In good vis the crew can modulate their braking to achieve a sensible, but earliest turn off. These points are called High Speed Turnoffs(HSTs). In poor vis, the pilots cannot see the HSTs from afar so they have to get the aircraft down to a sensible taxy speed and then 'hunt' for the turnoff. It's just like driving in fog and looking for a road junction. So there you go then, approach spacing has to be increased to allow the human element to clear the runway. BTW, a year ago, I came into LHR as a passenger, mid afternoon and went round the hold 5 times. 1 hour later, departed, on a domestic flight. Blocks off to airbourne was 50 mins. At one point 'Captain Speaking' came on the PA to point out the new terminal 5. I thought 'this place can't handle the traffic it has, how will it cope with T5? Add some fog and it all goes horribly wrong. The bottom line is 'Mr Walsh, the airport won't take it' Best of luck to anyone who flies out of LHR in the future. It will, to be sure, go even more horribly wrong. Merry Christmas everybody, and the best of luck to those stuck at LHR!!