As we approach Turkmenistan and the high country of Afghanistan the sun has risen (such a short night when heading west-to-east!). I peek out one of the blinds at the dry landscape below, and look down in wonder as the earthly tapestry slowly passes below. I am looking forward to seeing the high country.

Approaching Afghanistan (which is perfectly safe, by the way, with well defined airspace and excellent Air Traffic Controllers), our pilots will be thinking ahead, again playing the “what-if” game.

You may recall during the preflight safety demonstration that you all watched so carefully (right?), that oxygen masks will drop from the ceiling if the aircraft depressurises. I’d like to talk a little about that but, once again, DON’T FREAK OUT about it… it is just knowledge, and knowledge is a key part of being in control of yourself and your situation.

So, an airliner travels very high, but up at these levels (we’re at 37,000 feet at the moment) there is not enough air outside to breathe for any length of time. Luckily your airliner has 4 very effective airpumps (they’re called engines!). These engines power airconditioning machines which compress the thin air from outside and heat it (a natural side effect of compression, and useful because it’s danged cold outside too!).

That comfortably air-conditioned are is pumped in to the cabin to provide a nice environment for you. The air pressure is not at sea level pressure, more like the equivalent of standing on an 8000 foot (2500m) tall hill.

If (and like I said, pilots are always thinking “what-if”),… if there was a problem with the pressurisation system the simple solution is to descend the aircraft to a lower altitude where there is sufficient air to breathe. 10,000 feet is preferable, but 14,000 feet is acceptable.

Such a descent does take a little while, and while the pilots are doing that you would want some oxygen to breathe… thats when the masks come down… to cover the time between the depressurisation and getting to 14,000 feet.

However, over very high terrain such as Afghanistan you CAN’T descend immediately to 14,000 in some places because of the mountains. So, plans are made by the pilots for “escape routes” that allow avoidance of the highest terrain and minimise the time that you would have to wear those pesky masks.

Okay, I hope that doesn’t disturb you… it wasn’t meant to, but that simple example does highlight the fact that your pilots ARE doing stuff all the time, much of it about playing the game of “what-if” (so that YOU don’t have to!).

Having said all that, if you are sitting near a window seat you might like to take a peek outside as we go over Afghanistan… the terrain is AMAZING in it’s dry ruggedness, and it seems so close. In fact, the terrain will be around 16,000 feet in some parts we’ll fly over, so the Earth’s surface has been brought closer to you for your viewing pleasure!

Tags: afghanistan, deppressurization, depressurisation, high country