Why does snow close runways?
Discussion
Theres about an inch of snow here in South Manchester and the airport has been closed for 2 hours. There are now 30 odd aircraft in the queue for departure and the runway has reopened even though its still snowing.
Why exactly does a bit of snow cause the closure and what is different between now and 2 hours ago?
Does this happen in "snowy" places too? It sounds like chaos on the radio.
Why exactly does a bit of snow cause the closure and what is different between now and 2 hours ago?
Does this happen in "snowy" places too? It sounds like chaos on the radio.
EINSIGN said:
I would like to know how it can effect Trains?
It wouldn't if we took after the Americans/Canadians http://www.youtube.com/watch?v=QenN5DVuLtwBut it sometimes goes wrong for them http://www.youtube.com/watch?v=tF2ZPRmocs4
Edited by xr287 on Sunday 20th December 12:51
Snow contaminated runways increase (significantly) take-off distance required, and substantially increase the distance required to stop, particularly in an aborted take-off, despite commercial aircraft having what is effectively ABS. The allowable crosswind limit is reduced, and there is a significant risk of turbine engines ingesting snow/ice and becoming damaged. Some turboprop engines are mounted 'backwards', with a u-bend intake which can be susceptible to snow ingestion and build-up.
Was reckoned that snow on the runway was the cause of the Munich air disaster in 1958.
http://en.wikipedia.org/wiki/Munich_air_disaster
http://en.wikipedia.org/wiki/Munich_air_disaster
Dogwatch said:
Was reckoned that snow on the runway was the cause of the Munich air disaster in 1958.
http://en.wikipedia.org/wiki/Munich_air_disaster
Not too relevant to today's aircraft. In fact, it was "slush" on the runway that was the main culprit.http://en.wikipedia.org/wiki/Munich_air_disaster
Have just received this from a mailing list that I am part of
I'm sure all of us share the frustration when watching flights divert away from Manchester. But we have to be realistic.
Xxx: your comment that the airport knew snow was coming and should therefore have been able to somehow pre-empt it is simply impractical in the real world. Indonesia knows that a volcano is going to erupt in the next few days but they can't prevent it from happening. And they can only clear up after the eruption has happened. The same applies to blizzards here: accurate weather forecasting is not enough to keep runways safe. You can only clear away snow after it has fallen.
De-icing. Runways are specially designed to drain efficiently. If you put (very expensive) de-icing fluid on the runway too soon - well, it all drains away and is totally ineffective. If you clear snow whilst a blizzard is still in progress, you have to repeat the job. And if you clear the snow after the blizzard has finished the job must then be done thoroughly (think safety and legal liability) ... this takes time. Completion estimates are issued on a best endeavour basis by the staff involved, but inaccuracy is inevitable in a dynamic situation. However much money the airport spends, however many extra hours the staff put in to keep traffic moving, they will be condemned by folks who cannot possibly understand the complex reality of the task required. They are fighting a force of nature!
Yyyyy - your question regarding the relatively small amount of snow is a good one. But my answer to it may not be what you are expecting. Avoiding getting too technical here, there are essentially two types of snow and they have very different properties. These are DRY SNOW and WET SNOW. Dry snow falls in temperatures well below freezing and is 'powdery'. It actually compacts into a very good braking surface and is relatively easy for airports to cope with. Firstly, it can be blown away (wet snow sticks, powder doesn't), then what remains can be compacted. So next time you hear a friend say, "Why can airports in Scandinavia cope with lots of snow and Manchester can't?", you will be able to explain the answer!
Because what Manchester gets is the dreaded WET SNOW. This falls at temperatures close to zero centigrade, it is wet and clingy (definitely not powdery) and readily turns to slush. For aircraft, this stuff is lethal. If an aircraft takes off from a runway covered in wet snow, this slushy substance is flicked up by the nosewheel on to the aircraft underside and wings where it freezes on contact with the cold metal surfaces and impairs the aircraft's airworthiness (dry powder snow blows away harmlessly). In extreme cases this can be fatal: think of the Manchester United crash in Munich, or 'Palm 90', the Air Florida Boeing 737 with ice-laden wings which stalled into Washington's Potomac River.
In answer to Yyyyy's question as to why cant we cope with two inches of this stuff, the answer is that this is a particularly dangerous amount for aircraft operations. Two inches is the perfect amount to produce slush to be flicked up and puddles which subsequently freeze into a hazardous braking surface. Those continental airports which cope so well are dealing with powder snow - not this stuff. And on those few days in early autumn and late spring when airports such as Copenhagen, Zurich, Moscow and Munich receive this close-to-zero-centigrade wet snow they suffer just as Manchester has today. But in mid winter they get DRY SNOW.
So all. Please note that I am not having a go at you. You are simply the ones asking the questions which most others wonder about. But the truth is that Manchester Airport is spending vast sums on de-icing/snow clearance and their staff are working flat out in miserable conditions. And those staff know that the general public and the media will rage and sneer at them despite their best efforts on the ultimate thankless task.
But if you are reading this you are an aviation enthusiast. And you know better than the general public. Many of those clearing this snow are aircraft enthusiasts too (some TAS members?). Some of them read these comments. They don't want Manchester flights to divert away any more than you or I, but they can't work miracles in conditions like this.
There are many uninformed people out there ready to label airport snow clearance staff as lazy, incompetent idiots. We TAS members should know better. Let's use these messages to THANK them for the effort they are putting in enabling ANY flights to move at Manchester on a day like this. Because the chances are they won't get recognition or thanks from anyone else.
I'm sure all of us share the frustration when watching flights divert away from Manchester. But we have to be realistic.
Xxx: your comment that the airport knew snow was coming and should therefore have been able to somehow pre-empt it is simply impractical in the real world. Indonesia knows that a volcano is going to erupt in the next few days but they can't prevent it from happening. And they can only clear up after the eruption has happened. The same applies to blizzards here: accurate weather forecasting is not enough to keep runways safe. You can only clear away snow after it has fallen.
De-icing. Runways are specially designed to drain efficiently. If you put (very expensive) de-icing fluid on the runway too soon - well, it all drains away and is totally ineffective. If you clear snow whilst a blizzard is still in progress, you have to repeat the job. And if you clear the snow after the blizzard has finished the job must then be done thoroughly (think safety and legal liability) ... this takes time. Completion estimates are issued on a best endeavour basis by the staff involved, but inaccuracy is inevitable in a dynamic situation. However much money the airport spends, however many extra hours the staff put in to keep traffic moving, they will be condemned by folks who cannot possibly understand the complex reality of the task required. They are fighting a force of nature!
Yyyyy - your question regarding the relatively small amount of snow is a good one. But my answer to it may not be what you are expecting. Avoiding getting too technical here, there are essentially two types of snow and they have very different properties. These are DRY SNOW and WET SNOW. Dry snow falls in temperatures well below freezing and is 'powdery'. It actually compacts into a very good braking surface and is relatively easy for airports to cope with. Firstly, it can be blown away (wet snow sticks, powder doesn't), then what remains can be compacted. So next time you hear a friend say, "Why can airports in Scandinavia cope with lots of snow and Manchester can't?", you will be able to explain the answer!
Because what Manchester gets is the dreaded WET SNOW. This falls at temperatures close to zero centigrade, it is wet and clingy (definitely not powdery) and readily turns to slush. For aircraft, this stuff is lethal. If an aircraft takes off from a runway covered in wet snow, this slushy substance is flicked up by the nosewheel on to the aircraft underside and wings where it freezes on contact with the cold metal surfaces and impairs the aircraft's airworthiness (dry powder snow blows away harmlessly). In extreme cases this can be fatal: think of the Manchester United crash in Munich, or 'Palm 90', the Air Florida Boeing 737 with ice-laden wings which stalled into Washington's Potomac River.
In answer to Yyyyy's question as to why cant we cope with two inches of this stuff, the answer is that this is a particularly dangerous amount for aircraft operations. Two inches is the perfect amount to produce slush to be flicked up and puddles which subsequently freeze into a hazardous braking surface. Those continental airports which cope so well are dealing with powder snow - not this stuff. And on those few days in early autumn and late spring when airports such as Copenhagen, Zurich, Moscow and Munich receive this close-to-zero-centigrade wet snow they suffer just as Manchester has today. But in mid winter they get DRY SNOW.
So all. Please note that I am not having a go at you. You are simply the ones asking the questions which most others wonder about. But the truth is that Manchester Airport is spending vast sums on de-icing/snow clearance and their staff are working flat out in miserable conditions. And those staff know that the general public and the media will rage and sneer at them despite their best efforts on the ultimate thankless task.
But if you are reading this you are an aviation enthusiast. And you know better than the general public. Many of those clearing this snow are aircraft enthusiasts too (some TAS members?). Some of them read these comments. They don't want Manchester flights to divert away any more than you or I, but they can't work miracles in conditions like this.
There are many uninformed people out there ready to label airport snow clearance staff as lazy, incompetent idiots. We TAS members should know better. Let's use these messages to THANK them for the effort they are putting in enabling ANY flights to move at Manchester on a day like this. Because the chances are they won't get recognition or thanks from anyone else.
That post from Speedchick pretty much details it.
You can only clear the snow from the runway once it has fallen. I think (not 100% certain) there are some pretty strict restrictions (due to NIMBYs) on the second runway ops so you can't sweep one runway and switch ops to the other one.
Also it's not just the runways, you have to ensire that the taxiways are safe to use and that there are not snow banks piled up ready for jet engines to ingest. Then you've got to de-ice aircraft before they push back. This means the aircraft is sat on the stand longer. This means that inbounds have nowhere to park until the outbounds have been de-iced and gone. So that starts slowing the whole "airport machine".
It's not hard to see how things can very quickly grind to a halt.
You can only clear the snow from the runway once it has fallen. I think (not 100% certain) there are some pretty strict restrictions (due to NIMBYs) on the second runway ops so you can't sweep one runway and switch ops to the other one.
Also it's not just the runways, you have to ensire that the taxiways are safe to use and that there are not snow banks piled up ready for jet engines to ingest. Then you've got to de-ice aircraft before they push back. This means the aircraft is sat on the stand longer. This means that inbounds have nowhere to park until the outbounds have been de-iced and gone. So that starts slowing the whole "airport machine".
It's not hard to see how things can very quickly grind to a halt.
Thanks for the comprehensive reply Speedchick.
I had guessed that the "sloppy" kind of snow was key to the problems yesterday. However it wasn't coming down particularly heavily and staff had plenty of warning about likely conditions.
I understand that the ground staff were working flat out under difficult conditions and most people understand that. I think where Manchester let them selves down yesterday was in the sum of the parts. Communication was poor, with the director not been passed info on what was going on with the runway clearance or likely reopeing times. One pilot was complaining that he had been de-iced 5 times in preparation!
Also, I'm sure there is a reason (cost? byelaws?) but why wasn't 23L used as well? Could they not clear each in turn?
I know its not as simple as saying "pah! 2 inches, get it cleared!!" but the overall management of the situation could have been much better imo.
I had guessed that the "sloppy" kind of snow was key to the problems yesterday. However it wasn't coming down particularly heavily and staff had plenty of warning about likely conditions.
I understand that the ground staff were working flat out under difficult conditions and most people understand that. I think where Manchester let them selves down yesterday was in the sum of the parts. Communication was poor, with the director not been passed info on what was going on with the runway clearance or likely reopeing times. One pilot was complaining that he had been de-iced 5 times in preparation!
Also, I'm sure there is a reason (cost? byelaws?) but why wasn't 23L used as well? Could they not clear each in turn?
I know its not as simple as saying "pah! 2 inches, get it cleared!!" but the overall management of the situation could have been much better imo.
mattdaniels said:
That post from Speedchick pretty much details it.
You can only clear the snow from the runway once it has fallen. I think (not 100% certain) there are some pretty strict restrictions (due to NIMBYs) on the second runway ops so you can't sweep one runway and switch ops to the other one.
Also it's not just the runways, you have to ensire that the taxiways are safe to use and that there are not snow banks piled up ready for jet engines to ingest. Then you've got to de-ice aircraft before they push back. This means the aircraft is sat on the stand longer. This means that inbounds have nowhere to park until the outbounds have been de-iced and gone. So that starts slowing the whole "airport machine".
It's not hard to see how things can very quickly grind to a halt.
agree with all but the part about taxi-ways...You can only clear the snow from the runway once it has fallen. I think (not 100% certain) there are some pretty strict restrictions (due to NIMBYs) on the second runway ops so you can't sweep one runway and switch ops to the other one.
Also it's not just the runways, you have to ensire that the taxiways are safe to use and that there are not snow banks piled up ready for jet engines to ingest. Then you've got to de-ice aircraft before they push back. This means the aircraft is sat on the stand longer. This means that inbounds have nowhere to park until the outbounds have been de-iced and gone. So that starts slowing the whole "airport machine".
It's not hard to see how things can very quickly grind to a halt.
Farnborough was totally iced over yesterday - airport ran out of de-icer and our aircraft was told that its your call whether you go on not. Due to the low volume of de-icer they had left they were only de-icing the runway!
Ours has a film of water twixt tyre and snow/ice, which makes it much harder to deal with. 
no s
t sherlock springs to mind 
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