Weather & Technical Diversions, Delays & Cancellations

[SierraHotel]

What sort of infrastructure would LBA require to be able to offer RNAV approaches?

 

[White Heather]

So given that MAN was closed earlier today due to 'heavy snowfall', and has now re-opened, presumably, it's ILS is out of action for the same reasons as here at LBA? And the other airports around the country that have been snow closed in the last 2 days at some point? If not, then why not?

I have to admit that this is an issue that has never before been mentioned at LBA Consultative Meetings despite plenty of snow events and the meetings being attended by the head of ATC. Given that the snow could take quite some time to thaw the prospects for this week at least seem bleak.

 

[quik123]

So basically all the big airports around the world that get a lot of snow get their ILS knocked out for as long a period as it takes for the snow to melt? So one would assume this could in some cases take months. That is how I am reading your explanation of the situation.

So all the big snow cities like Anchorage; Qubec; New York; Oslo; Stockholm; Moscow, they all operate through the winter without ILS then. This is standard and it's been going on for years? Please forgive me because I"m truly gobsmacked. I really had no idea hence all the probing.

I've no idea how all those airports deal with it. But it will certainly happen if they have a ILS system. Perhaps they don't need ILS all the time and have other approach aids to get them down to a decision height to land visually.

ILS being knocked out by snow sounds unusual - it is certainly not typical.

I can only assume that the NDB was unusable - or the conditions were out of limits for the NDB approaches.

It is a shame LBA doesn't have an RNAV approach.

RNAV is an approach aid as opposed to ILS which is a landing aid. RNAV would get them down to a decision height when another aid(ILS) or visual landing is required.

 

[paully]

So given that MAN was closed earlier today due to 'heavy snowfall', and has now re-opened, presumably, it's ILS is out of action for the same reasons as here at LBA? And the other airports around the country that have been snow closed in the last 2 days at some point? If not, then why not?

I have to admit that this is an issue that has never before been mentioned at LBA Consultative Meetings despite plenty of snow events and the meetings being attended by the head of ATC. Given that the snow could take quite some time to thaw the prospects for this week at least seem bleak.

In the old days, someone would have been required to resign....They haven't even got the approach roads to the car parks open yet.... We're there early tomorrow and I'm not looking forward to it...
Sadly I won't be using LBA in future in the winter, just too much of lottery

 

[quik123]

So given that MAN was closed earlier today due to 'heavy snowfall', and has now re-opened, presumably, it's ILS is out of action for the same reasons as here at LBA? And the other airports around the country that have been snow closed in the last 2 days at some point? If not, then why not?

I have to admit that this is an issue that has never before been mentioned at LBA Consultative Meetings despite plenty of snow events and the meetings being attended by the head of ATC. Given that the snow could take quite some time to thaw the prospects for this week at least seem bleak.

As I mentioned to Aviador, I've no idea how other airports deal with it, you'd have to ask them. Places like Man have DVOR/DME which can be used as an approach aid as can Loc/DME. Nor do I know why it is not mentioned in the meetings you've attended, again, you'd have to ask them. Perhaps our hill top location is the main reason. All I can tell you is that it does happen at LBA!

 

[White Heather]

In the old days, someone would have been required to resign....They haven't even got the approach roads to the car parks open yet.... We're there early tomorrow and I'm not looking forward to it...
Sadly I won't be using LBA in future in the winter, just too much of lottery

Flying from any airport in the depths of winter is a lottery. Are you certain that all the car park approach roads at MAN are open yet given it snowed again overnight there too?

 

[KARFA]

RNAV is an approach aid as opposed to ILS which is a landing aid. RNAV would get them down to a decision height when another aid(ILS) or visual landing is required.

I don’t know where you are getting this from. How do you think most landings are made at LBA and other major airports? The ILS also gets you down to a decision height and you transition to a manual landing at some point during that approach. This is true of most landings everyday, you use an approach method to get you to a point, but there is always a transition to a manual landing.

Where ILS is available, most landings are made like this under what’s called cat1 conditions. For airports, aircraft, and crew suitably equipped and qualified, auto landings under cat3 conditions can be made under low vis conditions, and if necessary the plane will land and roll out under the auto pilot. Auto lands are very much the exception and usually only happen when conditions dictate.

RNAV is just as much an approach as other non precision approaches like localiser only or ndb. RNAV has the advantage of not relying on ground navigation structures, but obviously has the disadvantage of higher minimums as a non precision. ILS as a precision approach has lower minimums even at cat1.

To emphasise again, the idea that the ILS infrastructure (localised and glideslope) normally break in snow conditions is frankly rubbish. Sure it can happen, but quite clearly many airports which had snow in the UK yesterday continued to have serviceable ILS.

 

[paully]

Flying from any airport in the depths of winter is a lottery. Are you certain that all the car park approach roads at MAN are open yet given it snowed again overnight there too?

Well just look at the degrees of yesterday, who got going faster?... When you're travelling I accept things happen in winter...but you need to look at who deals with it sooner....And that is rarely LBA...I have a friend who does daily airport runs, so I get fairly accurate updates....
But it's my money and I'll use Liverpool in future winter trips...... assuming we've got many left in us of course..

 

[SierraHotel]

LBA does have some mitigating factors being 680ft AMSL. Speaking of lotteries, travelling on the M62 to LPL is a fine example.

 

[gulftraveller]

So given that MAN was closed earlier today due to 'heavy snowfall', and has now re-opened, presumably, it's ILS is out of action for the same reasons as here at LBA? And the other airports around the country that have been snow closed in the last 2 days at some point? If not, then why not?

It is to do with the terrain around the airfield.

 

[paully]

LBA does have some mitigating factors being 680ft AMSL. Speaking of lotteries, travelling on the M62 to LPL is a fine example.

We usually go by train, stay over at the airport and visit the City, which we love, at the same time...Reduces the lottery a bit as a result.

 

[Finger66]

I am sure this is all a combination of snow, terrain and low visibility - all factors created by LBA's general geographical location. Other airports may lose their ILS in snow but probably then don't suffer the low Viz etc.

Considering the amount of snow that fell, overall I don't think losing a day and a bits worth of flights is actually all that bad, however frustrating we all find it.

We couldn't get out of our village yesterday so there definitely needs to be a sense of perspective kept in all this

 

[White Heather]

I am sure this is all a combination of snow, terrain and low visibility - all factors created by LBA's general geographical location. Other airports may lose their ILS in snow but probably then don't suffer the low Viz etc.

Considering the amount of snow that fell, overall I don't think losing a day and a bits worth of flights is actually all that bad, however frustrating we all find it.

We couldn't get out of our village yesterday so there definitely needs to be a sense of perspective kept in all this

Perspective is often in short supply. Trains are cancelled, buses are cancelled, the roads are treacherous, yet its expected that airports are cleared and flights operating in a matter of hours, with littie consideration as to the local geography and the severity of the weather because of that.

 

[quik123]

I don’t know where you are getting this from. How do you think most landings are made at LBA and other major airports? The ILS also gets you down to a decision height and you transition to a manual landing at some point during that approach. This is true of most landings everyday, you use an approach method to get you to a point, but there is always a transition to a manual landing.

Where ILS is available, most landings are made like this under what’s called cat1 conditions. For airports, aircraft, and crew suitably equipped and qualified, auto landings under cat3 conditions can be made under low vis conditions, and if necessary the plane will land and roll out under the auto pilot. Auto lands are very much the exception and usually only happen when conditions dictate.

RNAV is just as much an approach as other non precision approaches like localiser only or ndb. RNAV has the advantage of not relying on ground navigation structures, but obviously has the disadvantage of higher minimums as a non precision. ILS as a precision approach has lower minimums even at cat1.

To emphasise again, the idea that the ILS infrastructure (localised and glideslope) normally break in snow conditions is frankly rubbish. Sure it can happen, but quite clearly many airports which had snow in the UK yesterday continued to have serviceable ILS.

You've missed my point. RNAV cannot get you to the ground. ILS (CAT3) can. I never said the ILS 'normally' breaks in snow. I simply offered it as a reason for the recent problems. As for where I get this from, over 30 years working at airports including Manchester and LBA.

 

[KARFA]

You've missed my point. RNAV cannot get you to the ground. ILS (CAT3) can. I never said the ILS 'normally' breaks in snow. I simply offered it as a reason for the recent problems. As for where I get this from, over 30 years working at airports including Manchester and LBA.

thanks. so with your experience at MAN did their ILS fail everytime it snowed? Or is this a uniquely LBA issue?

(Edit: just to add I didn’t see any notams detailing failure of ILS at at MAN yesterday and today, and they have had significant snow fall)

 

[Statto]

There was a live stream from MAN yesterday morning - available on YouTube. The accumulation of snow was nothing like those at LBA. At MAN, even early yesterday morning, you could still see the grass at the side of the runway and in front of the Glideslope antenna. At LBA the accumulation was about 8 inches. It’s not comparable. A dusting on the grass won’t cause distortions with the ILS signal, whereas 8 inches will; not because the equipment broke or failed, but because the extent of the snow covering will cause the signal to reflect and scatter.

 

[gulftraveller]

But that does not explain why it was not working even once the runway was cleared.

 

[Statto]

But that does not explain why it was not working even once the runway was cleared.

yes it does. The glideslope antenna is not on the runway, it’s on the grass, about 100m to the side of the runway centreline. Therefore its an issue with the condition of the ground in front of the antenna, not the condition of the runway. If suddenly that ground is 8 inches higher and is white snow rather than green grass, the signal can give inaccuarate readings.

I asked Chat GPT to summarise as it can do a better job than me:

=======

The issue of signal reflection and scattering caused by snowfall is influenced by both factors, but in different ways:



1. Increased Ground Height


• Impact: Snowfall effectively raises the “height” of the ground surface as snow accumulates. The glide slope system depends on precise reflections from the ground to create its guidance signal. When snow changes the height of this reflective surface, it can disrupt the careful calibration of the glide slope system, causing errors or irregularities in the signal.


• Result: This change can alter the angle or shape of the glide slope, potentially leading to deviations from the intended approach path.





2. Reflective Nature of Snow


• Impact: Snow’s reflective properties can scatter the radio signals emitted by the glide slope antenna. Unlike a flat, consistent surface like asphalt or grass, snow tends to reflect signals in multiple directions, particularly when the surface is uneven (e.g., wind-formed snowdrifts or melting patches).


• Result: This scattering and multi-path interference can create “false signals” or degrade the integrity of the original signal, impacting the precision of the guidance provided to aircraft.





Which Factor is More Critical?


The relative importance of these factors depends on the severity of the snowfall:


• Heavy snow accumulation: The increased ground height is the primary concern, as it directly affects the geometry of the signal’s reflection.


• Light or fresh snowfall: The reflective and scattering nature of snow can have a more pronounced effect, particularly if the snow surface is irregular or partially melted.

==========

 

[White Heather]

yes it does. The glideslope antenna is not on the runway, it’s on the grass, about 100m to the side of the runway centreline. Therefore its an issue with the condition of the ground in front of the antenna, not the condition of the runway. If suddenly that ground is 8 inches higher and is white snow rather than green grass, the signal can give inaccuarate readings.

I asked Chat GPT to summarise as it can do a better job than me:

=======

The issue of signal reflection and scattering caused by snowfall is influenced by both factors, but in different ways:



1. Increased Ground Height


• Impact: Snowfall effectively raises the “height” of the ground surface as snow accumulates. The glide slope system depends on precise reflections from the ground to create its guidance signal. When snow changes the height of this reflective surface, it can disrupt the careful calibration of the glide slope system, causing errors or irregularities in the signal.


• Result: This change can alter the angle or shape of the glide slope, potentially leading to deviations from the intended approach path.





2. Reflective Nature of Snow


• Impact: Snow’s reflective properties can scatter the radio signals emitted by the glide slope antenna. Unlike a flat, consistent surface like asphalt or grass, snow tends to reflect signals in multiple directions, particularly when the surface is uneven (e.g., wind-formed snowdrifts or melting patches).


• Result: This scattering and multi-path interference can create “false signals” or degrade the integrity of the original signal, impacting the precision of the guidance provided to aircraft.





Which Factor is More Critical?


The relative importance of these factors depends on the severity of the snowfall:


• Heavy snow accumulation: The increased ground height is the primary concern, as it directly affects the geometry of the signal’s reflection.


• Light or fresh snowfall: The reflective and scattering nature of snow can have a more pronounced effect, particularly if the snow surface is irregular or partially melted.

==========

Many thanks. All very helpful in understanding the problem.

 

[quik123]

thanks. so with your experience at MAN did their ILS fail everytime it snowed? Or is this a uniquely LBA issue?

(Edit: just to add I didn’t see any notams detailing failure of ILS at at MAN yesterday and today, and they have had significant snow fall)

No it did not fail 'everytime it snowed'