January Snow Watch

I don't wish to defend Heathrow as I think they are pretty inefficient at the best of times but I watched an interesting interview with an aviation expert.

Apparently, from an airport point of view, there is really the wrong type of snow! He was explaining the difference between airports in the UK and Scandinavia. Although Scandinavia get considerably heavier snowfall their snow is the dry stuff. Their snow ploughs can clear it with no trouble and leave a dry surface. With the wet type snow we have and sub zero temperatures there is a thin layer of ice left on the runway surface. Snow ploughs can't clear ice.

No matter how many times they run the ploughs over the runway, with sub zero temperature, the surface will ice up. That, in itself can be coped with to a certain extent.

Unfortunately they have other problems because of icing up. The docking areas for the planes also get iced up and the snow ploughs can't get to them because the planes are there. Therefore, moving the planes in and out takes much longer.

Also, because Heathrow's timetable always works to capacity there becomes considerably delays and cancellations due to the very much greater time it takes for the planes to manoeuvre in and out of docking and the extra time need to be allowed for taxiing on the icy ground.

The other, very important, problem because of ice is that the wings ice up. Ice on wings is a very serious problem as it alters the aerodynamics of the plane and it needs to reach higher speeds to take off. The wet snow freezes on the wings whilst the plane is docked. Just before pull-back time the deicing sprayers clear the wings.


Then the plane pulls back and taxis to the runway. As Heathrow is such a large airport it takes quite a long time to pull back, taxi and take off - as any of you that have flown out of there would know. If it is still snowing and still freezing the ice starts to build up again. The maximum time allowed between deicing and take off is 20 minutes. Otherwise the wings may have too much ice on them.

So, we really do have 'the wrong type of snow'!!!

Most of the time, although our snow is usually the wet type, we don't get sub zero temperatures as well. Then it's easier to get timings right and the wings don't need deicing.

 

I don't know what happened at Heathrow, all I know is conditions can vary tremendously within a few hundred yards. On Friday I was able to drive home from work some 20 miles without too much trouble until I got into my village. Then I had to abandon my car and walk the last couple of roads. Even now we are not clear, it's not the depth of snow just that it's turned into compacted ice and the slightest incline makes it impossible to get a grip. People with 4X4s are fine. Someone has been and gritted the little slope I got stuck on and I've managed to retrieve my car now. This is our road yesterday:



In the past I have worked in a couple of airports (not Heathow but quite close) and for some reason they always seem to attract the worst weather. I think it's because they are flat and open and the wind can howl across.

 

Been the same sort falling here all day since around 8 - frozen drizzle;

Shiney - I agree that some disruption is going to be inevitable at Heathrow, and I am quite sure that they are quite often 'up against it' for want of a better expression; however, Gatwick is operating normally today with minor delays, and being subjected to the same (if not worse) weather.

I also understand that Heathrow is a busier airport than Gatwick - however, I also believe that they are somewhat over-egging the pudding by using the 'stuffed to capacity' excuse in this case; the cynic in me says that they are simplyusing this as a tool to get their way in the third runway argument.

Besides anything else, this being a Sunday, there will be fewer flights in and out of Heathrow today than there would be on a weekday.

 

Go careful Zigs

 

The normal flight rate at Heathrow is 80 per hour (every 90 seconds for each of the two runways) so any delay because of the weather is going to have a serious effect on throughput. Gatwick also has a similar per hour rate for its one runway but has approx 11% more aircraft stands. This only makes a significant difference when there are difficulties, like now.

This is one of the inefficiencies (bad planning) that I referred to. They should have been building many more stands and then they would be much better able to cope with deicing them. That's why planes have been left with passengers on board and unable to get to a stand .

You get a similar back-up problem when there aren't sufficient customs/immigration officers or enough baggage handlers.

 

Maybe an animal peed in it!

 

Well, it's obviously an algae, Peter, if it's not a leak from anything artificial. There are a lot of algae that like cold and you can tell where it's found nutrients by the thicker green. I must admit I've not seen something like that before. Has anything, fish or some thing small died in the pond??