Airbus 320

Ladies and Gentleman, Boys and Girls:

After flying four times in two weeks, now I can finally say something about Cabin Pressures. Like any other essays, we'll start with some basic background knowledge. I am writing this because the Hard Disk Scan cannot be stopped and it takes seemingly forever.

Background:

At sea level, that is altitude 0m. We can breath normally, and the WATER boils at 100 celcius. That's actually how Celcius determined, the temperature where water becomes gas from liquid = 100 celcius and 0 celcius at when exactly water turns into solid from liquid. Neat, isn't it. All have something to do with water. -273.15 celcius is the absolute zero.. Anyhow, the water will boil much faster on moutains. During the two years in Canberra (about 1000m above sea level), the water always boils below 100 degree. I can still breath normally in Canberra, but when you reach some place (about 4000m above sea lvel), you start to feel difficulty because the air pressure goes low.

Another well known fact is that every 1000m you climb, you'd feel 6 degree colder. In the same city, at sea level it might be 18 degree. Say they have a 3000m mountain near by, the temp on top would be 0. how? 18 - 3*6 = 0. How about airplane? I think it flys much higher than the moutain, and yet, in the cabin, we don't feel cold or breathing difficult. The answer is that, air craft cabin is 'pressurized'. Yes, they add pressure to the cabin, or otherwise, we'll certainly not make it to the destination. Since at 10,000m, the air is really too thin to suruvie for too long.

BUT HOW MUCH EXACTLY they pressurize their cabin. Most of us would not really know. All we notice is that our EAR pop in and POP OUT. and sometimes, cause discomfort. If they really pressurize the cabin right, accurately, maintain the same pressure at sea level, THE EAR discomfort would never take place. It's happening, because they don't put the right pressure right. In fact, when they take off, they add too much pressure (more than at the sea level). Then when they flying high and smooth, they don't add enough.



With bit of help of the equipment, now I can tell you that for Boeing 717 and Airbus 320, when they fly on the top (that is flying flat, not climbing or decending), they make the cabin equivalent on a 2000m mountain (double canberra, that is), just below 800 hPa[mb]. So really, when you flying you feel like on top of a 2000m mountain. and when you landing... your ear starts to feel funny, esp when you try to swallow water.

WHY? We'll have to understand one concep, our BRAIN, our inner head is pretty much sealed. Don't believe me? We have mouth and nose, they are open constantly. That's true, but they are not connected, if the inner skull are somehow linked with mouth, or nose. then you'd see Brain Juice ( .. eel , some girl might not like it) come out from your nose, mouth and maybe your eyes. Nope, brain juice stay inside.

Good, with understanding of this, so you can see, we have a small concealed chamber. But it is somehow has a whole connected to the outside. THE EAR HOLE! Inside you can find some half sealed membrane... So when the fly take off. pressure goes thin, and inside your skull, sea level pressure are inside, thinner air are outside. Eventually through flying, that the air pressure would equal by air comes out from inside to the outside. Most people would not have problem in this stage. Sorry, have I being verbose here? I know I should cut it short, but disk scan is still on its way...

The problem is that most plain decending pretty damn - fast. Within 15 minutes, they can touch down. That simply means, it's like you climb down the moutain in 15 minutes. and in this duration, the pressure would DRAMTAICALLY INCREASE to match the sea level pressure, about 1010 hPa[mb] vs. below 800 (for 2000m moutain). With such increase of pressure, the outside air wants to get inside of your brain, and ear being the only open channel bears the pressure, and the memberane sometimes hurts. CHEWING gums helps, what it does is, loosen the membrane, CONTANTLY let some air in, gradually balance the pressure inside / outside your skull. (Smooth transition). Ear Plugs helps, but reducing the pressure, and evenly distribute it on the inside wall in the ear. Very bad English here, (prep), on, at, in, onto, into.. ... That's it from me.

ps: in case I haven't mentioned, JJ and I worked out really well after we had few 'talks.' ^_^