Friday, November 13, 2009

Freezing or Sweltering

The morning's forecast calls for freezing fog over much of he area, and the town is already enveloped in fog. I go through it to get some groceries and a layer of ice doesn't form on me, but I don't know if that's because it's not freezing fog or because I'm not an airplane.

After a few hours the fog dissipates and we go flying. A guy tows the airplane out of the hangar for us with a little tractor. It's not one of the old agricultural tractors like on the prairies, but a smaller, newer, utility tractor. It does the job.

As I watch him towing out the airplane I see an enormous raven glide over the hangar. It pauses to perch on a fence, then swoops down out of sight behind the hangar. A moment later another worker yells at the guy on the tractor, "Hey, there's a raven after your lunch!" He runs off to shoo the bird and rescue his lunch. What I couldn't see was that the raven was in the back of his truck. I'm not sure whether it was opening his lunch box--they're certainly crafty enough to do that--or just tearing open shopping bags. I'm certain that birds like that understand the concept of swiping stuff as opposed to finding your own, because they steal from one another all the time and go chasing after the thief, gronking loudly. But do they know that the things in cars and trucks are ours? I bet they do. I think they know perfectly well that lunchboxes are not a naturally occurring phenomenon, and that they will annoy us by taking food from them, just as they annoy wolves by "sharing" their kills too. But that's what they do. My airplane takes 100LL. Ravens take your lunch. Local legend asserts that Raven stole the sun, so a few sandwiches constitute very petty larceny.

The engines are happy with their fresh oil and overnight hangar stay, so we're on our way after conditioning the new brake pads. We crank up the heat in the airplane for the computers in the back, but because some of the electronics are in the rear of the airplane, designed as a cargo compartment, we are sweltering in order to have enough heat back there to keep the computers going. I lay my arm against the cold exterior window and pour some of my drinking water into my bra in an attempt to cool off. It varies between -10 and -15 outside, and apparently it's only 15 degrees at the back, but it's like a sauna in the cockpit.

There is some fog still on the ground west of town. It gradually vanishes during the flight, but it's forecast to come in worse tonight, so we finish our day before dark and put the airplane back in the hangar.

Back at the hotel I'm ready for a delicious fresh salad, but a minor tragedy awaits me. My fridge is too cold. I have all the ingredients for a very very crisp salad. Everything is frozen. The lettuce is delicate crunchy like autumn leaves. I rinse it under the tap and the entire package reduces to a double handful of mush, like cooked spinach. The cucumber is so solid that at first I think it's okay, but it thaws to mush. I don't even think a raven would eat it.

Here's a weird accident report. Anyone familiar with CRJ systems have an idea how this could happen the way the pilot said it did?


Ward said...

We were sitting inside a cafe one time, next to a window and we could see the people sitting on benches outside. One guy got up off a bench and came inside to get something, leaving a muffin sitting on a plate on the bench. As soon as he was gone, a crow tried to grab the plate, knocking the muffin to the ground, where it tried to drag it farther away. The guy came back in a minute, then a minute later noticed his muffin was gone and started looking around. He finally noticed the remains on the ground, but by then the crow and a couple buddies had eaten most of it.

Anonymous said...

"... pour some of my drinking water into my bra..."

Well then it can truly be said that "your cup(s) runneth over!" ... hey - I had to say it before someone else did.

CanuckFlyer said...

I can honestly say that I've never heard of someone pouring water in their bra to cool off. Thats a new one for me. However, hats off to you for your ingenuity!

nicnacjak said...

That accident report was odd...maybe they hit the throttle by accident?

rw2 said...

What kind of computers require warmth? Most of them prefer the cold.

Sarah said...

Yes, crows & ravens are quite smart. I've heard amazing things about the social order and customs of the common crow.

@rw2: What kind of computers require warmth? Most of them prefer the cold.

Maybe ... computers with rotating disk drives? Heads flying low above platters in colder than standard air might crash.

dpierce said...

Computer components tend to heat up quickly. If they start out in a very cold state, the quick rise in temp can cause problems with thermal expansion. (And there may be other concerns -- I'm just familiar with this one.) I've seen cracked packaging on CPUs used in cold test rooms, and other such deviltry.

Worse is when the liquid crystal in an LCD freezes! [That's a joke.]

Matt said...

Strange accident. I have no idea what happened, but there's a discussion of it on the PPRUNE forum:

click here

Anonymous said...

During the Blitz of London in WWII - Ravens were thought to possess powers of prescience regarding the arrival of German bomber aircraft . Any occurrence of agitated behaviour was taken seriously as a possible harbinger .

mattheww50 said...

Computers and other equipment built with very high speed logic (Emitter coupled Logic, or ECL, although sometimes called CML) are quite temperature sensitive.
Most logic circuits operate with the transistor either fully on, or fully off. Emitter Coupled logic operates with the transistors in the active region at all times, so they are never fully on or fully off. This makes them much faster. The bad news is ambient temperature impacts the characteristics of these devices, so if the temperature is outside the range, they may go to a fully on or fully off state, which makes the logic state changes much slower.

The ECL logic is generally the fastest you can buy, but it isn't at all tolerant of substantial temperature excursions.

By contrast the logic used in automotive engine control applications needs to be very tolerant of temperature excursions because it has to be able to start the engine when it is -30 outside, and still run when the temperature under the hood is above 100C.

Icebound said...


"Freezing Fog": One of the things that fell through the cracks when North American hourly observations were converted from the "SA" format to METAR. (Are you old enough to remember SAs??)

In the original SA specification, you have "FOG" and "ICE FOG".

FOG was distinct from "ICE FOG" in that FOG was water droplets... "ICE FOG" was ice crystals.

Hence you knew that "ICE FOG" could never "freeze" onto your airframe, since it is already frozen. And you know that "FOG" at below-freezing temperatures was possibly dangerous, since it COULD accumulate on your airframe.

Along come METARS with no code for "ICE FOG". Therefore, when the temperature is below freezing, whether you code FG or FZFG really implies the same thing, since FG technically means water droplets and hence the potential for freezing.

SO.... for the sake of uniformity, (although NOT for the sake of useful information)... my understanding is that Canada will always code FZFG for fog in below-freezing temperatures... NO MATTER WHETHER IT IS LIQUID OR ICE-CRYSTALINE.

The added remark "FROIN" (frost on indicator) ... or absence thereof... is supposed to be your clue as to whether this is "REALLY" freezing fog or not.