Wednesday, September 24, 2014

Cold, Hypoxia and Spiders

From time to time a person stows away in the wheel well of an airliner. There's a big space up there, with room for all the hydraulics, a retracted wheel, and a person. Doors close over the opening to provide streamlining, but I don't know that they close tightly enough to prevent draughts. Mine certainly don't. My gear doors don't even cover the whole opening. There is no pressurization and no heating in that space. At altitude the proportion of oxygen in the air is the same as at sea level, but the total air pressure is less, so the partial pressure of oxygen is also less. This pressure is important. A person can't get sufficient oxygen just by breathing faster. The pressure of the oxygen is what allows oxygen to enter the bloodstream. If the pressure isn't high enough, there is insufficient oxygen for the brain to function. A person loses the ability to make decisions, passes out and if the deprivation is severe enough, eventually dies.

The air temperature decreases by two or three degrees for every thousand feet of altitude, down to about -56C. I've never seen one of these where the stowaway had sufficient knowledge--or resources--to wear a parka. I've been outdoors in temperatures down to about -40. Wearing a parka, and gloves, and a toque underneath my parka hood, and giant Sorel boots, and mittens, while physically active. If I had stopped and curled up for a few hours I know I would have become very very cold.

Most of the time the cold, lack of oxygen and sometimes falling out of the wheelwell kills the stowaway. But sometimes they make it, like this kid from California. Humans can be freaking tough. I find it hilarious, but not that surprising that an unhappy teenager successfully breached airfield security. There is trust involved in aviation. Many places we pay for fuel on the honour system. It takes no genius and rarely requires tools to breech an airport gate. There is also a trade off, mutual assistance among aviators is a tradition much older than airfield security. It's hard to stop people from helping one another. And absolutely any tool someone might need on an airport can literally fly over the fence.

I'm amused that the commenters on that CBC piece include someone who insists a wheelwell monitoring camera and pre-departure check thereof should be standard, someone who doesn't believe the incident happened at all, and someone who sees a conspiracy theory at work.

My airplane often carries little stowaways that seem to suffer no ill effect. Spiders crawl up in my wheel wells. I landed the other day, taxied a short distance off the runway, shut down and got out to clean the windshield. In that time, maybe five minutes since the propellers had stopped spinning, a spider had already strung silk from the propeller across to the fuselage, such that I had to break the web to access my forward cargo area, where the windshield cleaner is. I don't know that it was one of the spiders I carry with me, but I like to think the conditions are producing super spiders. I wonder if insects are attracted to the heat coming off the nacelles, making that a prime spot for web building.

1 comment:

Sarah said...

I sometimes give rides, inadvertently, to insects left inside my glider canopy. Moths, flies of various sorts, a couple of "lady bugs". Even a spider or two, though I try to keep my distance from arachnoids. Irrational, but they just have too many unsettling moves for me. I don't know why.

A couple weeks ago, it was a small green & yellow bee, like this pretty one. I thought I'd shooed it out, but it was still there when I was flying. So I thought peaceful thoughts and waited for the cold and altitude to sooth it. Which it did - bee spent most of the flight sitting still, looking out the window with me. It flew away when i landed, both of us enjoying probably my last soaring flight of 2014.