Monday, April 19, 2010

Winds Aloft

So what's all the fuss of Airplanes and Volcano's anyway. One can understand the idea of a big ole jet motor ingesting something big and the affects that has. It is hard to imagine that something so small as dust can do the same amount of damage. Well, it does and frankly I am kind of glad the government officials who deemed it necessary to stop all air traffic did so. Most of the aircraft that ply the trans-oceanic airways are twin engine aircraft. It's one thing to be in a B747 or an Airbus A340 and loose one or two of your motors, you have others, but if you are in a B777 or A330 you lose one motor and you have officially half screwed. And on top of that, you have to worry about the health of that other motor. Not a good think in a twin jet.

The way it works is that this material which has been described as glass-like is actually near pure carbon. And at high tempratures it bonds to surfaces which would normally be resistant to such thinks. You pass through a small cloud of the stuff and your motor especially the Rotors and Stators get a little bit of fouling. Pass through a lot of it and it builds up like a new layer or lamination on the hot parts of your average turbo fan. And trust me, there are a lot of hot parts in your average turbo fan. The best you can expect is that it reduces the performace of your engine, robbing you $$$ in fuel costs and average engine life. The worst is that the motor stops functioning altogether and your aircraft becomes a glider. That is a lot to worry about.

Then there begs the question about how did all this stuff get up and distributed so quickly and over such a large area. Simply put, it was the Jet Stream.

You see, the jet stream maneuvered into an unusual position almost two weeks ago, and that is what has brought all this Icelandic hell upon northern Europe. When I flew over here the Pilot announced shortly after takeoff that he was predicting an early arrival into Frankfurt. By more than an hour which when you are strapped into those small things they call 'seats' in Economy class that hour less is certainly welcome. The Pilot claimed it was because we would be crossing the Jet Stream an unusual 4 times as we fly east. Usually they hit is once and get a 15 or 20 minute gain (a boost of airspeed of around 100 knots). Crossing it 4 times meant a gain of more than an hour and true to his words we were almost 90 minutes early into Frankfurt.

But that same unusual pattern is what allowed that plume of ash to get distributed to completely and quickly. It turns out Volcano eruptions happen many times a year in Iceland but their plumes rarely make it to altitude and if there is no jet stream it simply disperses harmlessly.

But not this time. Note below in this capture of the NOAA jet stream forecast showing the shape of the stream as it works it way east, it goes right over Iceland. I doctored it a bit to show all the salient points.

There are several forecasting sites that show what the projected jet steam will be on various dates. I shows how the jet stream shape will change for the better during the week and by Wednesday it might open up enough to allow airliner traffic through. There will still be a cloud by it will have maneuvered away to the south and east. Here is the forecast chart for Wednesday.
I doctored it a bit to show the normal great circle route flight path that the Airliners take on their way across the north Atlantic. Remember, these are for the most part two engine aircraft and they have to say close enough to make it to an airport and that the Circle flight path is the shortest distance between two points on a sphere, you know the earth.
Ah well, its time for a Beer and some goulash. There is a place round the corner that has a "southwestern" goulash, a spicy brew with chili peppers. Closest thing to chili one is apt to see here and it's high time I went over and tried some out.

BT: Jimmy T sends.


Bag Blog said...

Southwestern goulash sounds pretty darn good. I wonder if they use red or green.

Buck said...

Better safe than sorry certainly applies here. The various Euro gub'mints are catching ALL kinds o' flack on the shut-down but I'm glad they're erring on the side of caution. Like you said: it's hard to motor long distances on just one engine. Or none.