Thursday, November 6, 2008

Compartmentalization

One of the worst things we do in aviation is putting our experience into little compartments that stay on the shelf until the exact circumstance repeats itself. One example is the pilot who has been flying twins and forgets to keep a landing spot in mind when flying a single. It's a form of complacency.

This came up the other night while flying with a student. We had been scheduled for the night before, but a strong cold front came through, attacking us with ceilings around 1500' and lots and lots of wind. Gusting to 30 wind. The ceiling was too low for a first night flight and the wind was too strong for a student. So we cancelled.

Now we had clear skies and light winds on the ground, although the winds were around 20 knots 1500' above the airport. I gave him the Introduction to Night Flying lesson, and off we went.

I wanted to take him over the city and its reassuring lights first. The winds were favoring runway 21, and the city is east of the airport, so the natural thing is a left downwind departure. But that's where the hills are, too, and I convinced him that it would not be prudent to take off toward high terrain at night with a big tailwind: every hesitation in the turn to downwind and in setting up a crab into the wind would take us toward the mountains. Google Cory Lidle, the Yankee pitcher who hit a building in Manhattan, for a reminder of what happens when you ignore obstacles in high wind.

In the picture, the left downwind departure is red, and the right downwind departure is in green. Each has a crosswind turn, then a distorted downwind leg. The left downwind departure goes directly through a tower 1700 feet above the airport and only about 4 miles away. A 172 can't outclimb that.

The tower approved the right downwind departure to cross overhead, and soon we were over the city. The city is in a triangular valley, and I told him to fly closer to one side so that we would have room to turn around. There was a long cloud over the city, surprisingly low, but not low enough to prevent VFR. Just one long cloud, running parallel to the valley, illuminated by the lights below.


Any glider pilot would recognize the cloud, but my glider knowledge was in a compartment back home, not in the airplane. It was a rotor cloud, sometimes called a roll cloud. The picture to the right, from the FAA's Glider Flying Handbook, shows what was happening. The strong wind from the west -- the same wind we had just discussed -- passed over the mountains at the edge of the valley producing a strong downdraft (we found it), a rotor, and a strong updraft (we found that, too).

The thing is, the rotor can be really turbulent, and this one was. So our smooth introduction to night flight became an object lesson in the positive and negative effects of mountain wave. In the end it was fun, but for a few seconds there I could that my student had that uncomfortable feeling in the pit of his stomach, the one that comes up when there is unexpected turbulence.




I've written about complacency before: see Missing the Signs, back in September, or How Far Can You Go? in August. Writing about complacency is a weak way of avoiding complacency, better than nothing. But avoiding complacency takes more; checklists help some, but it almost takes minute-by-minute vigilance to guarantee success. Do you daydream while your student checks the magnetos, or do you watch carefully to make sure that both are on before takeoff? Do you believe that your student looked outside during the clearing turn, or do you look, too? Do you yawn through the pretakeoff checklist, or do you sit there with a smile plastered on your face reciting "Controls Instruments Gas Attitude Runup" to yourself while you verify that each has been done?

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