Wednesday, November 04, 2009

Not Done After All

My Thanksgiving flight was supposed to be our last in the area, but a communications error between our customer and our customer's customer mean that we have to go back. A shame, as the weather was perfect on Thanksgiving and now it's ... not. The weather is good to the north, but is forecast here to come as low as 2000' broken and five miles visibility in snow. We head out to the airport anyway to try and get the job done.

The airport is on the edge of Watson Lake, with the approaches to two of the runways (one is closed, but you can still see the markings, it used to by runway 02) coming right over the water. If you slid off the end of the runway you would get wet. The air is cold, maybe minus ten or fifteen on the ground, but the lake is still open water, and thus warmer than the ambient air. The layer of air immediately over the lake water becomes warm (where one degree above freezing equals "warm") and saturated. Warm air rises, but as it does it cools by expansion and by contact with the sinking cold air. The water vapour it collected from the lake condenses into fine droplets, making plumes of fog appear all over the lake. This is called steam fog. You can see it over the ocean in the high arctic.

The fog is making a wall to the south, but we are headed north and decide to give it a try. I mark a waypoint in the GPS as my coworker climbs out, and mark it as 3 MILE FINAL 08. Five miles vis in snow is not a lot for setting up a visual approach, and it could end up being special VFR visibility on our return. We climb to about 4500' indicated and we've reached the misty beginnings of the cloud bases. It would be possible to sneak into the valley between the first two peaks we can see, but it would not be wise. It's fully possible that the clouds part after only a few miles of this, and we know it's high overcast at the destination camp, but there are too many rocks in these clouds for it to be worth pursuing. This isn't like on our way up when we were flying above the altitude of all terrain within miles and ducked under low cloud to access a gully leading off a flat plateau. These mountains get higher to the north, and we are already below the height of peaks within sight. We fly west a little ways in case there is a clearer route from that direction, but soon return to the airport and call it a day.

As we tent the engines and plug everything in one of the plug receptacles breaks. It was held against the inside of a hole in the nacelle by a plate. I can find the part with my fingers, but I can't pull it out. I can see that it was plastic, and it just snapped. Funny that something designed to withstand pressure in the cold would be made of plastic. It's cold enough overnight that the engine won't start if it is left to cool overnight. I have to find a way to plug it in.

This airplane is wired a little funny. Usually these heater plugs are on the inboard side of the nacelles, but on this one they are on the outboard. And it's the left side, such that the wing inspection light, the light I can turn on at night to see if ice is accumulating on the wing, is right above it. I could probably remove the screws all around the wing inspection light, as I would do to change the light bulb -- something I am authorized for in elementary work -- and while I was in there I could just happen to reach down and plug in the tanis heater. I'd do that if I were on my own, but it so happens that the AME who changed the mag is still here, so we assign him the problem instead.

He reports back that he managed to reattach what was left of the plastic plate to the inside of the receptacle, so as long as we are careful it should last until the next scheduled maintenance. "How did you get to it?" I ask. He says he went through the deicing light. I feel smart.

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