Thursday, January 28, 2010

Cold and Macho

We meet at 6:30 for breakfast according to our strategy. The rental car can be returned at 7:00, and we've left ourselves a few hours leeway for contingencies so we can still get the airplane put away at destination (that's prearranged) and then get to the terminal and through southern airport security in time for our flights.

My boss texts as I'm gathering up my gear in my room. "Is it going to be too cold to fly?" There's a big bubble of arctic air over half the country. It's -32 here, actually a few degrees colder at destination, but as long as it's forecast to be over -35, we're okay. He doesn't want engines started below that. It takes too long for the oil to reach the moving parts at such low temperatures, and just turning over an engine could damage it.

It's always nice to have a "too cold to work" temperature that allows you to stay in bed, but usually the weather conspires to hover just above that temperature, always freezing your fingers but never allowing them to remain tucked in bed. Still, it's nice to know that it's there. I worked for a company once that had a too-hot-to-wear-a-tie uniform rule. I think the number was in the high 20s. Anything above that on the OAT and you could work in an open collar. Today I'm working in compression socks, two more pairs of heavy socks, leggings, long underwear, work pants, t-shirt, long sleeved shirt, sweater, and I think a sweatshirt over that, then my lined coat -- although not my wonderful parka. I thought we'd be going south before now. Plus a wool toque, a scarf, wool gloves and fleece-lined leather work mittens on top of that.

We unload everything on the apron next to the airplane and then I volunteer to load and secure it while he returns the car. We've done so little work this rotation, that I feel as if I have done less than my share. I had hoped to have everything ready to go when my co-worker returned, what with having to wait for paperwork and a cab and all, but I'm still securing gear when he's back already. The car rental place was all ready for the return and gave him a ride to the airport.

We untarp the airplane together. Everything is in good order, because we've been out shovelling and checking on it. There are a few patches of frozen-on ice where the tarps didn't cover properly, so I use some of the deicing fluid. I have a moment of "oh-no" when I realize that there is some old dilute fluid in the sprayer, but fortunately it hasn't frozen, and I manage to pour it out. Must remember to ... what? Rinse and dry? In the past I've kept deicing equipment in a heated hangar so I haven't encountered the problem of a frozen sprayer. Something to remember if I'm ever doing hot water deicing (works when the temperature is and will stay above freezing) and then stowing the sprayer in the plane. Everything takes more time and space to do in the cold. Anything that has to be folded or coiled actually takes up more space, because they won't bend. And the same goes for your hands. In heavy mitts they don't bend the way you are used to and if you take off the mitts and just work in gloves, pretty soon your fingers still won't bend, at least not without any strength.

My coworker is PIC so he straps into the left seat and I remove the cord from the engine block heater just before he starts. Fires up right away. We exchange delighted thumbs up and I pull the cord from the second engine. The cords are too cold to coil properly, so while he does post start checks I end up stuffing a tangled mess of electrical cords in the back of the airplane. I'm afraid I would break the plastic insulation--or even the wires inside--if I forced them to coil lightly to fit where they usually go.

I secure the rear door and then come up to the right seat. The right oil pressure is still indicating low, but the CHTs and oil temperatures are matched between the two engines. We turn on the heater and take off some of our layers of clothing as we wait for the oil to come up. It's moving--the gauge isn't dead--but really really slowly. After half an hour it still isn't registering enough for take-off. I know that as a student pilot you were taught to shut down an engine if it wasn't registering oil pressure in 30 seconds, maybe a minute if it was really cold, so why have we let it run for this long? We are almost certain we know what is going on in there.

The engine is out on the wing, a couple of metres away from me. It was kept warm enough electrically overnight to start and have oil circulating, which is why we see normal cylinder head and oil temperatures. The oil pressure gauge is on the panel in front of me. The oil pressure gauge works in the absolutely simplest way such a thing could work, and that is by having the actual oil pressure force oil through a line to the gauge. Simple is good. But now think about that line. It comes out of the engine, along the leading edge of the wing, into the fuselage and up to the instrument panel. Much of that path is unheated. We suspect that a little bit of moisture has condensed in that line and frozen solid, blocking the line. The oil coming out of the engine is warm, but cools quickly inside the narrow tube, so is not warm enough to melt the ice. If we thought there was any way that the actual oil pressure in our engine was as low as on that gauge, we wouldn't be running the engine.

Still, we're not going to take off with oil pressure in the red. We text the PRM about our predicament. He asks a bunch of questions, suggesting we do things we've already done, and adds one more. I get out and check the oil filter through the cowling vents. My coworker shuts the engine down so I can do this. I verify that the oil filter looks normal: in place, not swollen or leaking or anything. And the engine, bless its greasy soul, restarts perfectly. There wasn't really much risk of it not, as it was so warm and lubricated, but anytime you shut something down you risk not being able to restart it.

After a few more texts (we text because it's too difficult to talk on the phone in a running airplane) are exchanged the PRM concludes "I don't see that you're going to have any problems."

We text back, "We don't either. We just don't want to go without an ok from the PRM."

Understanding dawns. Now he understands we're not texting for help, we're texting to cover our butts. Butts duly covered, we fly. By the time we're in position on the runway the oil pressure is only a needle width below the green anyway, a situation one of my training manuals even accepts.

We launch and turn on course in good weather. There isn't often a lot of weather in temperatures this low. Almost all the moisture is already frozen. There's no energy to form the weather.

This airplane has two heaters, one that mainly keeps the back warm, and which runs off a heat exchanger with the exhaust gases and one that mainly warms the front, and which burns gasoline. We, obviously are in the front, but we're expecting that with the engines blasting at climb power, we'll start feeling more heat, as we won't be losing our front heat to the back of the plane. But we're feeling colder. We adjust a few knobs and hold our hand in various places before we accept the fact that the combustion heater has shut down. It is designed to run on the ground, but because of reduced airflow it is possible for the plenum to overheat and trip the circuit breaker. A reasonable precaution for a device that is literally on fire inside the fuselage. These heaters are affectionately known as "nose bombs." To prevent cold pilots from resetting the circuit breaker when there is a real problem, the circuit breaker is accessible only from the outside of the airplane.

We both know this. "This two hour flight just got a lot longer." Is that because we turned around, landed back at origin and reset the breaker? No. Is that because we landed halfway at a well-attended airport that was literally under our intended flight path and reset the breaker? No. You know from the post title. It was because two hours seems a lot longer when you are sitting still in subfreezing temperatures. We toughed it out to destination with only the rear heater, definitely not enough to keep us comfortable.

We took turns taking control while the other person reached back for and donned the outer jackets and sweaters set aside earlier. We swapped "what's the coldest you've ever been?" tales. And we laughed at ourselves. The two of us have only had one flight together where we were neither too hot nor too cold: that was the flight with the exploding moon. With passengers, obviously we would have stopped. Without airline tickets booked, perhaps we would have stopped. But whenever you stop you risk not being able to go again. You've seen on this blog how easy it is to be grounded by a stupid thing. And we know how much it costs an hour to run this thing. T land and take off again would add time and money to the cost of the trip. We can take a little discomfort in the name of efficiency. We did have cold weather gear and one heater working. (Notice that the working heater was the simple one: "run outside air past hot exhaust and duct heated air to cabin. Simple is good. We also have simple avionics without those LCD computer screens that seize up at minus five, so we don't need to worry about our radio controls freezing. I guess "liquid" crystal displays require a certain temperature to remain so.

A temperature inversion meant it was even colder on the ground than in flight, and to get there we needed to reduce engine power, drastically reducing the output of our one working heater. Brrrr. But we did it. We reached our destination, found the hangar, and got a ride to the terminal from someone who told us, "you look cold." True that.

funny graphs and charts
see more Funny Graphs


Aviatrix said...

Neener, got it written on time!

Sarah said...

Which approach did you fly on the sim first?

Blaine Beaven said...

I remember a time when I was on reading week from school, and I figured it would be a good idea to let the company's regular pilot (I flew summers) take a week off in February. So I got up there, and we do a couple circuits to make sure I remember what I am doing.

During the flight, I notice the heater wasn't putting out much heat (Janitrol). He told me - don't worry, just recycle it.

I spent the whole week, flying every day, in -25 or lower, with no heater... I had really good boots.

gmc said...

Minus 35? Real Ice Pilots fly down to minus 40. I saw it on the internet.

Stay warm!

Scoon said...

"I worked for a company once that had a too-hot-to-wear-a-tie uniform rule. I think the number was in the high 20s."

CELCIUS? Here in Brisbane Australia I went to a private highschool where we had to wear trousers and long sleeved shirts with ties no matter the heat. And I'm talking 35-40C in tropical humidity.

We brought it up with the headmaster but he just referred us back to the fact that things had been that way for the last 120 years, and they weren't about to change.

townmouse said...

@Scoon - We had the opposite problem - a Scottish boarding school where up to the age of 14, the boys had to wear shorts and the girls had to wear tunics with socks - weweren't allowed tights. Ok, so it never got to -30 but when you've got bare legs, even a little below freezing is challenging... Perhaps the uniform codes got confused with your Brisbane school?

zb said...

Yay avionics, yay electrical!

Liquid Crystal Displays use a liquid consisting of really long molecules between two screens that have polarizing filters. An electric field will align the molecules such that they will not twist the polarization of the light passing through both filters just right. Without an electric filed, a very fine structure on the inner surfaces of the filters will align the molecules such that they will twist the light in the correct way to pass.

When it gets too cold, the electric field will be unable to align the almost-solid molecules.

Too hot ain't doing no good either: The entire display will be black because the molecules will not care about the fine structure on the insides of the filters.

Captain Dave said...

Love that chart!!!

Jimmy said...

I had a Capt. that started out washing company aircraft for extra cash. As a result of lying on his back on wet pavement scrubbing exhaust tracks from the Janitrol off the belly, he hated them with a passion.

Despite the fact he had never washed a plane in over three years, we co-joes were forbidden from using the 'dirty' heater.

I hated pairings with that guy. Shivering your ass off at -15 just because he didn't like the 'filthy' heater. If you really pressed him on his hang-up and tried to use the heater, he would turn it off, claiming that 'we might need the gas'.

If I run into him again I'm going to give the guy a smack in the head...

Aviatrix said...

Ah ha, Jimmy, that's hilarious. Our planes duct the exhaust from the front Janitrol all the way to the tail. No sooty tracks!

Paul said...

Combustion heaters are a nightmare.

Almost every twin driver I know has a story of being freezing so bad they could barely fly the plane.

One of the few benefits of a single...